($40 GPSDO working well now, my mistake) - Page 1
Forum section: electronics / projects

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2017, 02:15:11 pm
content: Edit: Old title was: GPSDO loss of satellites+fix troubleshootingNew title: True Position GPSDO working well nowOriginal post:What would you look for as broken/fixable in a GPSDO that:1.) fails to lock on more than 1-3 satellites at a time, and that with extreme difficulty.2.) wanders in terms of temperature and seems very hot (upper 40s C.)The antenna and signals are known to be good, so its not that. It currently has around a 50% sky view.Note: I should have known better.The GPSDO was never broken, it was my dumb mistake, its a semi old GPSDO, and it needed to have a big and expansive sky view to be happy, which it wasnt getting in my windowsill. Moved to the middle of the back yard, it got seven sats.its happy and working well now (and these GPSDOs, which were used in cellphone E911 radiolocation, are a great value.)

author: ConKbot
author_rank: Super Contributor
timestamp: August 12, 2017, 02:33:27 pm
content: What the c/n numbers (signal strength or SNR potentially) for the 3 satellites you do lock? A good antenna/lna/rx should pull C/N numbers in the high 30s to low 40s for satellites in good positions, and in the 30s for the rest of a reasonable constellation, with a few satellites (maybe on the horizon) in the high 20s.If you're only getting lock on 3 or so and they are in the 20s, something is potentially wrong with your antenna/lna/cable/rx front end.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 12, 2017, 04:43:52 pm
content: Cdev, you know better than this! We can only give vague general suggestions when you give us vague general info. What type of GPSDO is it? Can you talk to it? Any error messages?Ed

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2017, 05:35:28 pm
content: Its a True Positioncellphone radiolocation board. Telecom surplus, apparently.It looked like too good of a deal to pass up.And now its working better, much better.So, (crossing fingers) maybe that was it!Wow, nowsevensatellites.. things are looking good..Thank you!

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2017, 06:09:45 pm
content: Its a telecom surplus unit that was made in 2008. It contains a Bliley OCXO and Furuno GT-8031 timing GPS.It cost me around $40!What do you get?The bare board. It requires 12 volts of power and you need to talk to it via 3.3 volt UART or RS-232. When it boots, you have to enter in $PROCEED and then it starts receiving.There are a number of commands that are possible which are detailed in a PDF at packratvhf.com There was a thread in May mostly about them on the Time-Nuts mailing list.Now the fun part starts, building a device around it.There is an "$EXTSTATUS" message which is not documented in the PDF which contains the number of satellites tracked.Quote from: edpalmer42 onTodayat 10:43:52

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: August 12, 2017, 06:16:19 pm
content: I'm considering to buy one of this also, to check my 2 Trimble units, and to round all also a NEC one just to check the others

author: ConKbot
author_rank: Super Contributor
timestamp: August 12, 2017, 07:21:48 pm
content: I've seen receivers that are off for a while take 15-20 minutes to lock up while almanac data is updated, and some time receivers take well past 20 minutes to be happy and enable output. Not too unusual for a unit powered off for an unknown but probably long period of time. I wouldn't be too worried.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 12, 2017, 08:39:34 pm
content: Many (most?) GPS receivers remember where they last were. If you move the receiver, it starts looking for where the satellites are supposed to be and they're not there. They also don't know what time of day it is. This can result in a *very* long time to find satellites and download the current almanac and ephemeris. If the receiver allows it, you can drastically speed up this process by manually entering the approximate time/date/location. It doesn't have to be perfect, just close.Ed

author: ConKbot
author_rank: Super Contributor
timestamp: August 13, 2017, 02:43:16 am
content: Quote from: edpalmer42 on August 12, 2017, 08:39:34 pmTangentially related, but still related. Some time receivers have a fixed position mode. If you have a surveyed in accurate antenna location, or let the receiver self survey (averages location for 24+ hours) and record the location. With location fixed, you no longer need 4 satellites for a fix (1 for time, 3 for triangulation) so you have an "extra" 3 satellites adding to precision of the time fix.

author: cdev
author_rank: Super Contributor
timestamp: August 13, 2017, 03:18:45 am
content: After letting it have its antenna outdoors to do its survey now its chugging away indoors - I don't know how accurate it is in this mode yet. I think my GPS timing antenna is getting mounted outdoors fairly soon.Quote from: ConKbot onTodayat 20:43:16>Quote from: edpalmer42 onTodayat 14:39:34Tangentially related, but still related. Some time receivers have a fixed position mode. If you have a surveyed in accurate antenna location, or let the receiver self survey (averages location for 24+ hours) and record the location. With location fixed, you no longer need 4 satellites for a fix (1 for time, 3 for triangulation) so you have an "extra" 3 satellites adding to precision of the time fix.

author: metrologist
author_rank: Super Contributor
timestamp: August 14, 2017, 07:30:36 pm
content: Quote from: edpalmer42 on August 12, 2017, 08:39:34 pmIt always intrigued me on how these receivers can look for SV's where it thinks they should be. It's easier to understand not know the time and then not knowing which SV's to expect to hear.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 14, 2017, 08:37:32 pm
content: Quote from: metrologist on August 14, 2017, 07:30:36 pmIt always amazes me that GPS works at all! A receiver starts off knowing nothing. Somehow, it listens for multiple signals on the same frequency, finds one, gets the date and time, then downloads the almanac and ephemeris that tells it what else to look for and then calculates its location based on triangulating those signals. It makes my head hurt to think about it!Arthur C. Clarke said that "Any sufficiently advanced technology is indistinguishable from magic." For me, GPS is proof of that statement!Ed

author: cdev
author_rank: Super Contributor
timestamp: August 14, 2017, 09:07:35 pm
content: GPS is an incredible example of a great many different scientific disciplines being used together to solve an age old problem.Anybody interested in how GPS works should check out RTKLib.Which you can learn about athttp://rtklib.comit's author'shome page, and his github.Here isa tutorial..

author: cdev
author_rank: Super Contributor
timestamp: August 14, 2017, 09:15:26 pm
content: A little update: You totally nailed it in this post, ConKbot.Now that it was able to download its survey info, and has been running for awhile, its now running okay with even an indoor antenna, and tracking between 2 or 3 and 7 sats. In other words, its managing using an indoor patch antenna. Freeing up my other antenna for other stuff.It seems to me that at the beginning, having its location reset, thinking it was back in Japan, really impacted its ability to function.Quote from: ConKbot on 2017-08-12, 20:43:16>Quote from: edpalmer42 on 2017-08-12, 14:39:34Tangentially related, but still related. Some time receivers have a fixed position mode. If you have a surveyed in accurate antenna location, or let the receiver self survey (averages location for 24+ hours) and record the location. With location fixed, you no longer need 4 satellites for a fix (1 for time, 3 for triangulation) so you have an "extra" 3 satellites adding to precision of the time fix.

author: CJay
author_rank: Super Contributor
timestamp: August 15, 2017, 05:12:54 am
content: I picked one of these receivers up too and have just received a cheap patch antenna with the correct connector:http://www.ebay.co.uk/itm/3M-28dB-LNA1575-42MHz-RP-SMB-GPS-Signal-Active-Antenna-Aerial-Connector-Cable-FE/252329705481?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649Is this similar to the patch you're using cdev?

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 06:17:55 am
content: don't forget the RF forum. I get paranoid thinking about how many responses I don't get posting my threads there!!!

author: cdev
author_rank: Super Contributor
timestamp: August 15, 2017, 02:03:36 pm
content: Cjay,That's good to know about- thank you!I am using a home-made adapter from SMB to SMA. Both of the powered antennas Ive used with the True Position (one is a Lucent/Max-Rad/PCtel, that runs off almost everything you throw at it, the other is a Motorola SMA patch antenna that runs off 3.3 or 5 volts) have 'worked' i.e. registered as being there.Isn't the True Position a great deal?Have you put it into a case yet? I'm looking for an inexpensive case.I think this project deserves something a bit nicer than my usual cases. (I often use recycled cases from other devices or even cardboard boxes.. that's what it's in now)

author: cdev
author_rank: Super Contributor
timestamp: August 15, 2017, 02:10:22 pm
content: That would depend on downloading an ephemeris and almanac, which they can do usually within 15 minutes if they have a decent antenna and even a marginal sky view. However, it still had to deal with the configuration which was telling it it was in Kyoto, Japan. Not being in California, or Hawaii or Alaska, I suspect that NONE of the SVs visible from there were visible at my QTH at the times they were supposed to be above.Quote from: metrologist onYesterdayat 13:30:36

author: CJay
author_rank: Super Contributor
timestamp: August 15, 2017, 02:17:45 pm
content: Quote from: cdev on August 15, 2017, 02:03:36 pmSo far, I've not let it run a full survey with that antenna so hold off buying one of that particular type, especially as the PackRat document seems to say it won't work. The True Position does seem to recognise it has an antenna and the serial output does seem to indicate it can see sats but I've no idea if it's working properly as yet, for the price it's worth a try but I can lay hands on a timing 'bullet' if need be.I've got a lovely anodised aluminium rack case complete with LCD cutout and bezel that it will go into I think, there's already cutouts for BNCs on the rear so adding a distribution amp will be simple, as always it's a 'when I get to it' job.I reckon the True Position is a lovely little board, a bargain if it all works (so far so good).

author: cdev
author_rank: Super Contributor
timestamp: August 15, 2017, 04:43:11 pm
content: Does it ever show a 1 in the third field (I think) of the $STATUS sentence? If not you are good to go as far as it being recognized.$EXSTATUS shows number of sats being tracked.Why havent you done a survey?If you can- just for a few moments- get that antenna into an optimal position with a decent ground plane under it.. and type in $SURVEYa CD size, even, would likely do wonders over no ground plane, but bigger is better.. and do the survey which once it starts running, may even complete fasterIdeally, either find a piece of flat steel and place it outside just to get the first survey done, or find some large appliance - say a refrigerator, thats near a window or south facing wall, and try placing the antenna on top of that.A magnetic antennas optimal placement is on top of a car.Without the ground plane, indoors or out, it won't work well.Quote from: CJay onTodayat 08:17:45

author: pigrew
author_rank: Frequent Contributor
timestamp: August 16, 2017, 06:20:51 am
content: I just bought a three of these boards from Taobao. I'm running them at 12VDC input (which had been suggested on the time-nuts list), though the board seemed OK at 9V, too. The oven uses 5V, and I couldn't find any regulated voltages above 5V. Someone had written 9V on the power input connector.Example GETVER strings:$GETVEROCXOGPSNote$GETVER 12.0.1 0.4850266.0.1 19 fbde 7437 06162200B0000A2004183ACCBliley NV47A1282GT-8031AMy board #1$GETVER 12.0.1 0.4850266.0.2 19 fbde 7437 06162200C1000A200442A35FBliley NV47A1282GT-8031BMy board #2$GETVER 12.0.1 0.4850266.0.5 19 fbde 7437 06162200C2000A2009350093CTS 1960017GT-8031FMy board #3$GETVER 10.1.2 BOOT 10 9e05 7437 06162200C1000A2005411C55Bliley NV47A1282GT-8031FPackrat BoardI put together a quick control program for Windows, for ease of debugging. I thought that I should post the commands that I've discovered, as I've not seen any list other than the PackRat PPT which was for older firmware.// Based on FW 12.0.1// Commands://// $PROCEED [Send at startup to get past the bootloader]//// $FACT [Factory preset]// $GETBDELAY [returns board delay, nanoseconds]// $GETDELAY [returns cable delay, nanoseconds]// $GETPOS [return position ]// $GETSCALEFACTOR [Returns a float, such as 3.742106e-3]// $GETVER [returns version info]// $KALDBG <0|1> [Enable reporting of Kalman filter parameters]// $PPSDBG <0|1> [Enable or disable timing information every second]// $RESET [Unit software reset]// $SETBDELAY <n> [-32 <= n <= 32, Set board delay, PPS4 units (roughly 5 or 6 ns). PPS4 is controlled to equal this value]// $SETDELAY <n> [-32768 <= n <= 32767Set cable delay, nanoseconds]// $SETPOS <n> <n> <n> [set position to Lat/Long/Elevation_MSL, send value returned by survey]// $SURVEY <n> [survey for n hours, default is 8]// $TRAINOXCO [Start OXCO Training. This restarts the board ($PROCEED needed), and measures freq// change with 500 ADC count]// $UPDATE FLASH [update flash memory settings]//// Other unknown commands:// $GETA [returns -1; Attenuator?]// $GETP [returns -1 255; Potentiometer?]// $SET1PPS ["$SET1PPS 0"/"$SET1PPS 1"] seems to go to a manual holdover mode, and status changes to 3]// [Seems to return to normal a few minutes after "$SET1PPS 1 1"(Status goes 8,16,17,18,0]//// Messages:// $STATUS// 1: (Maybe 10 MHz bad, based on packrat docs)// 2: (Maybe PPS bad, based on packrat docs)// 3: Antenna is bad? 0=good// 4: Holdover duration (secs)// 5: Number of sats tracked (different than, but within 2 of $EXTSTATUS, perhaps only counts channels 0-7???, range is 0-8)// Status [Locked = 0, Recovery = 1, (Forced holdover?)=3, Train OXCO=7, Holdover = 8,// [Startup A/B/C/D = 10/11/2/19 ]// [ (transition from 1 to 0) = (14,15,16,17,18) ] Wait states when transitioning// [ (transition from 0 to 1) = (20,21,22) ] Wait states when transitioning// (6 = locked, but unknown location?)//// $PPSDBG 1187153266 3 25.28081e3 -253 -6 2 2 0.0// 1: same as clock (GPS Time)// 2: Same as $STATUS status, but updates much more often (and seems to skip states less often)// 3: Floating point number. Output voltage. Tends towards 29e3 on my board. Proportional to the DAC voltage// On my RevC CTS board, Vbias ~= 6.25e-5*PPS3. This may make sense for a 4.096 V reference: 4.096/2^16=6.25e-5// During startup, it is not put in the result string (this field is blank, so two sequential space characters are in the string)// 4: Measured phase offset? Units seem something like 6.5*ns// 5: Looks like a saw-tooth between -15 and 15 (or so). Perhaps the quantization error reported by the GPS module?// 6: Normally 0, but sometimes 2 (related to holdover/startup?)// 7: Normally 0, but sometimes 1 or 2 (related to holdover/startup?)// 8: Always 0.0?//// $EXTSTATUS// 1: SurveyStatus [0=normal, 1=surveying]// 2: Number of sats (different than, but within 2 of $STATUS, perhaps only counts channels 0-9, range is 0-10)// 3: DOP (maybe TDOP?)// 4: Temperature (close to FPGA? close to oven?) (my board reads about 45C)//// $GETPOS (sent after setting position, or requesting position// Latitude// Longitude// Elevation_MSL// Correction to MSL to get WGS elevation (add this value to MSL to get WGS ellipsoid)// Status flag [(Normal?)=0 on 196 board or =2 on Bliley board, Surveying=3], or maybe a FOM?//// $SURVEY 40448488 -86915296 225 -34 7129// [sent during a survey]// 1: Latitude// 2: Longitude// 3: Elevation_MSL// 4: Correction to MSL to get WGS elevation (add this value to MSL to get WGS ellipsoid)// 5: Number of seconds remaining//// $SAT// Channel # (0-based, seems to only return channel 0 through 7)// GPS Sattelite number// Elevation (degree)// Azimuth (degree)// SNR (dB*Hz)//// $CLOCK 1187156731 18 3// GPS UNIX-timestamp (secs since 1970), but my board is off by 10 years (reporting 2007 while it is 2017)// Count of leap-seconds// Time figure-of-merit (1=good, 7=bad)//// $GETVER 12.0.1 BOOT 10 fbde 7437 06162200B0000A2004183ACC// $GETVER 12.0.1 0.4850266.0.1 19 fbde 7437 06162200B0000A2004183ACC// [version information, I used this to know if I need to send the PROCEED command, String contains BOOT when in bootloader mode]// [During boot, only terminated with LF but not CR(or maybe other-way around?)]// 1: Bootloader version?// 2: ("BOOT" during boot) or (software or perhaps GPS version info?)// 3: Status code (same as $STATUS)// 4: CRC of something?// 5: Always 7437?// 6: (Part number: 06162200)(Board Rev: B)(Assembly version: 0000)(Delimeter: A)(Year: 2004)(Week?: 18)(SN?: 3ACC)//// $WSAT 4 138 209 38 0// [WAAS Satellite info, same format as $SAT]//// $SET1PPS// [Sent at boot, but also in response to a $SET1PPS command. Sent every 20 seconds.]//// $KALDBG 1187203779 0.08 29.59241e3 0.120e-3 0.568 0 0// [Only be sent when reference is locked (state=0)]// 1: GPS UNIX-timestamp (secs since 1970), but my board is off by 10 years (reporting 2007 while it is 2017)// 2: Floating point number.// Resets to 0 at time of lock (and at end of holdover).// 3: Floating point number. Magnitude is similar to PPS3, but does not track it so well.// 4: Floating point.// Resets to 0 at time of lock (and at end of holdover).// 5: Floating point. Smoothed version of PPS3, seems like ~6.5*(PPS phase in ns)?// Resets to 0 at time of lock (and at end of holdover).// 6: Flag, always zero?// 7: Flag, always zero?

author: CJay
author_rank: Super Contributor
timestamp: August 17, 2017, 08:43:09 am
content: Mine seems to be working just fine, an absolute bargain.Despite not having a timing antenna (I may or may not order one now) it's tracking 7-8 satellites and the OCXO is stable, one counter tells me it's ~0.2Hz low, the other tells me it's 0.7Hz low, which pleases me an awful lot, neither counter has been calibrated since 2006 so those option 04b Racal High Stability OCXOs really live up to their billing.Next task is to build it into a case and try to make sense of the data that comes out of the board, I've gotten really rather confused by some of the messages from it and at one point thought I was in the middle of the Atlantic because I'd misplaced a decimal point...Pictures to follow as long as CDEV doesn't mind a minor thread hijack?

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 02:57:24 pm
content: I have had good luck with a Maxrad "GPS-TMG-26N", which I paid around $20 for. (its often sold as Lucent or PCTel too)It was a very good investment because it "always works", for GPS, it will also accept and run on any voltage delivered by a GPS, anywhere from 3 volts to >12v.It has a built in SAW filter so I don't know how well it works with Glonass, (1.6 GHz) it may not work at all there. But for use with a timing GPS its perfect.---Would love to see photos of your GPSDO, and the case you're planning to put it into.Pigrew,thank youfor posting your command list!There are a lot of intermediate status settings that look useful for understanding how it works.I definitely want to incorporate some way of tracking that process into my own device, however it turns out.Quote from: CJay onTodayat 02:43:09

author: pigrew
author_rank: Frequent Contributor
timestamp: August 17, 2017, 03:15:16 pm
content: Quote from: cdev on August 17, 2017, 02:57:24 pmIt was a combination of trying random commands, looking at the packrat PPT file, and trying to write a controller program. I have my laptop outputting a log message when it receives an unknown command or status.One guy (Mark Sims) posted on time-nuts that he had extracted the firmware image from the flash, but I don't think that it has been posted, yet.I'll try to continue editing my post with what I learn. (I just noticed a "$GETA" command, but I don't know what it does).

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 03:26:52 pm
content: So now its possible the optimum voltage may be lower than 12 volts.If it does well with a well-regulated 9 volt supply that would mean I can use a decent transformer containing well-regulated linear wall wart that I have.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 17, 2017, 04:22:10 pm
content: Quote from: cdev on August 17, 2017, 03:26:52 pmThe two regulators (LT1963 and LT1765) on the board both list 25V as their maximum input voltage. I'm not sure about the LDO (LT1963A), but my guess is that it's powered by the other regulators.... I expect that it'll be happy with anything between 8V and 14V, but I've been running it at either 9V or 12V, and it seems OK. I've been running mine off of a bench supply (66309D) until I get around to making a case.But, I'm very unsure about a case. How much ventilation should it have? I don't want the board to cook, but I don't want to expose it to air conditioning, either.For the commands, one confusing thing is the number of satellites. Both $STATUS and $EXTSTATUS return a count. However, sometimes one is higher, and other times the other is higher. I'm not sure about the difference. The one in $STATUS is usually larger.Another interesting thing is that when parsing commands, it doesn't look at all of the characters. For example "$GETAB" and "$GETA" both return the "$GETA" message. It seems to only look at the first few characters of the command name.

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 04:35:46 pm
content: One count of tracked SVs may include the tracked SBAS satellite(s), one may not?At one point I also saw a "$WSTATUS" or similar. Have you see that?Quote from: pigrew on August 17, 2017, 04:22:10 pm

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 04:46:32 pm
content: Were it not for the shipping costs, some old servers (in rackmount cases) sell for really little now because of their power consumption to performance ratio. If one lived near the seller, it would likely be possible to get a 19" rack case, perhaps even with an LCD, by buying some old server and removing the server part to leave the case.The problem is, the shipping cost likely makes that uneconomical with ebay.I think I may put it in a PCB box or even just a plain white cardboard box lined with copper and soldered, (that makes it easy to cut out the hole for the LCD - making it the right size) to get it out of harms way, for now.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 17, 2017, 05:14:47 pm
content: Yes, the photos of cases I've seen online rarely have ventilation, though I can't believe that this is a good idea. They must run quite hot. I'm tempted to 3D print a case with ABS. I don't have other sensitive things running, so I don't think that it'd be so useful for me to shield the case. As for a power supply, I'm torn between using a DC wall-adapter and buying a AC->DC converter off of eBay.If I hold my hand on the trueposition board's OCXO to cool it down, it will sometimes go into holdover mode, so it does need some insulation. My guess is that a case with a small number of holes would work well (just enough of a case to prevent drafts). Even then, I think that it is likely drifting less than my Racal 1992 04E counter does (I see a shift in it of a few ppb with a day->night temperature swing).I've never seen the $WSTATUS message. My above post documents all of the commands and messages that I know of. Do you have a different firmware version than I do?[I also got a Trimble UCCM module, but it's receiver seems quite deaf. I only get 2-4 satellites with it. It could be aged too much. The trueposition boards have better reception, but confusingly only report 8 channels even though the receiver should support 12.]

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 05:28:45 pm
content: The receiver may be using some/all of those channels for its local SBAS system. Many receivers also have another config switch where they can be told to use the SBAS sat(s) in resolving the position as if it was a GPS satellite.Two PDFs I found on the Furuno GT8031 (if you don't already have them) are attached.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 17, 2017, 06:32:41 pm
content: Quote from: cdev on August 17, 2017, 05:28:45 pmThe docs say that it should be able to have 12 normal channels + 2 SBAS, so it doesn't make sense that the GPSDO processor only reports 8. Though it's possible that it is actually using more and just not reporting them. We could sniff the GPS module's TX pin to see what it's saying, and try to decode it's messages, though I'm not planning on doing that unless we can find a GPSDO command to directly send messages to the GPS module (at which point the GPS module communication could become useful).

author: cdev
author_rank: Super Contributor
timestamp: August 17, 2017, 07:04:59 pm
content: The long rows of contacts might hold some additional signals?This was also interesting, I thought.https://blog.regehr.org/archives/794There probably are better ways, I would think, though, to measure timing down to the individual cycles.. with GPIO-containing hardware.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 18, 2017, 03:23:40 pm
content: My command list has been slightly updated:I finally received a $WSAT response. I'm assuming it's for WAAS satellites used for SBAS. It's very rare that I receive that message.My guess is that $STATUS is a count of tracked satellites in channel 0-7, and $EXTSTATUS reports channels 0-9. $STATUS had a max value of 8 last night, and $EXTSTATUS had a max value of 10. Sometimes one is higher than the other, but always within two counts.The unit seems to only process one command per second. If more than that are sent, it'll ignore most of them.I don't know the meaning of $GETP [returns -1 255] and $GETA [returns -1]. I'm not planning on trying to set those variables without knowing what they are.

author: cdev
author_rank: Super Contributor
timestamp: August 18, 2017, 03:53:06 pm
content: "almanac" maybe for "$GETA"?Many GPS's let you download the almanac from their memory.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 18, 2017, 09:51:29 pm
content: Is it just my board, or do all of them have a huge reverse-biased diode (D9, SMCJ5.0A-TR) beneath the antenna port? At -5V, it should be about ~5nF. Shouldn't that nearly completely short out the RF signal? I'm confused, very confused.I'm tempted to remove it, and see if signal strengths increase. How is it even working? What am I missing?EDIT: And I did remove it. The C/N0 did not significantly change, and it seems that the reported signal statistics are very imprecise. Every time I power it on, the reported signal statistics have change by a few dB*Hz. Perhaps the diode has so much inductance that it doesn't matter to RF?

author: texaspyro
author_rank: Super Contributor
timestamp: August 19, 2017, 01:54:31 am
content: Here is a list of (most of) the Trueposition commands (besides the ones sent automaticallY. Lady Heather now implements these. There are a couple of others... not recommended you mess with them. I managed to blow away my unit serial number.send_true_cmd("$RESET"); // warm reset unitsend_true_cmd("$FACT"); // factory reset unitsend_true_cmd("$GETVER"); // get receiver versionsend_true_cmd("$GETA"); // get attenuator valuesend_true_cmd(out); // $SETA %d - set attenuator valuesend_true_cmd("$GETPOS"); // get positionsend_true_cmd(out); // $SETPOS %ld %ld %ld - set position (lat lon alt in same format as $GETPOS)send_true_cmd("$GETDELAY"); // get gps delaysend_true_cmd("$GETBDELAY"); // get board delaysend_true_cmd("$GETP"); // get pot values (also has a $SETP command)send_true_cmd(out); // $SETDELAY %d - cable delaysend_true_cmd(out); // $SETBDELAY %d - rf delay?send_true_cmd("$UPDATE FLASH"); // update flash memory settingssend_true_cmd("$PROCEED"); // get out of boot modesend_true_cmd("$GETVER"); // get receiver version infosend_true_cmd("$PPSDBG"); // gives temperature at 1Hz (alss, value only updates every 5 secs)send_true_cmd("$KALDBG"); // Kalman filter debug messages - gives temperature at 1Hz// but value only updated every 5 seconds.send_true_cmd(out); // $SURVEY %ld - do a self survey for %d hourssend_true_cmd("$PROCEED"); // get out of boot mode

author: pigrew
author_rank: Frequent Contributor
timestamp: August 19, 2017, 05:40:54 am
content: Quote from: texaspyro on August 19, 2017, 01:54:31 am$PPSDBG is very useful, but I've not been able to convince myself that it outputs a temperature. It outputs, for example, "$PPSDBG 1187155826 1 29.87666e3 30 5 0 0 0.0".Yes, the value is around 25-29, but I've found it seems very dependent on the timing state. I've been using $SETDELAY to adjust the time-offset, it has a very large effect on the various parameters. I'm not sure about the exact meanings, but I don't think that my unit is returning a temperature for any of these parameters. The floating point number seems to be a roughly proportional to the frequency offset in parts-per-trillion. It seems to trend towards about 29e3 on my unit. My current thinking is that it's the OCXO tune voltage.Another thing to note is that this also contains the status-state (same as in $STATUS), but it updates much more frequently, so I'll use this status instead of the $STATUS status. The meanings of the numbers are the same.I'm in process of updating my earlier post with some of these details.

author: cdev
author_rank: Super Contributor
timestamp: August 19, 2017, 01:53:27 pm
content: $PPSDBG 0 turns PPS debug offAlso the float numbers on mine (however just turned it on now, so still warming up) are around 37... flag after it is 0-3, then an integer, neg or positive, then two single digit integers, then at the end a short float.Going to bring the output into a spreadsheet program when I have a bit more time later to make graphing the various flags easier.I am hoping there are some more signals on the unit to use, a 10 MHz square wave would be useful, also a pp2s if it has one..There may be other UARTS..Uploading image which shows location of potential test points on my unit

author: cdev
author_rank: Super Contributor
timestamp: August 19, 2017, 05:17:19 pm
content: With the sentence based stream of data coming out of the GPSDO every second or less, it might make the most sense to simply save each of the command outputs into their own tables in a database (a different table for each type of data) and queries made against it every second to determine what gets written to the display, LEDs, whatever. The tables would be maintained in a temporary storage and once they reached a certain size, which wouldnt have to be very large, but it could be configurable, the older entries would be purged. Only the most recent entries would be displayed.This would lend itself well to a platform like the Raspberry Pi that has a bit more power than Arduino.Since so little old data really needs to be saved the database would be tiny in terms of RAM.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 20, 2017, 03:07:59 pm
content: The OCXO control voltage is reported as part of $PPSDBG. The big floating point number seems to be the ADC count, in units of 6.25e-5 V. This may make sense if Vref=4.096 since 4.096/2^16=6.25e-5.V ~=6.25e-5*floor(PPS3-0.045)The $KALDBG parameters seem unintelligible to me. KAL3 somewhat tracks the OCXO control voltage, but not always. Many of the parameters reset to 0 when the GPSDO locks (at startup or the end of holdover). Kal5 may be the time derivative of Kal3. Kal5 looks like a smoothed version of PPS4.I was also having trouble with my CTS board maintaining lock. The PPS4 (PPS phase?) parameter would drift upwards away from zero and eventually it would go into holdover. I ended up executing a $FACT command, and it started working properly. Perhaps with my screwing with the board, it got a bad gain value somewhere. I have not tried sending the $UPDATE FLASH command, as it seems like it automatically writes settings to flash occasionally?

author: texaspyro
author_rank: Super Contributor
timestamp: August 20, 2017, 03:57:44 pm
content: Quote from: cdev on August 19, 2017, 05:17:19 pmLady Heather basically does that. It has a circular buffer plot queue (defaults to 3 days at 1 second per entry). The plot queue supports up to 14 different values. Most of the interesting data from the device gets saved in the plot queue (and written to a log file). The plot queue can also be dumped to a log file. The plot queue view can be adjusted, scrolled, filtered, etc. You can display various statistics (min, max, span, average, RMS value, etc) and display a linear regression trend line or remove a trend line from a plot. Also display the derivative of a plot.And it runs on a PI.

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 04:58:56 pm
content: Is LadyHeather on the TruePosition ready for release?Lady Heather is really pretty amazing and I would love to be able to use it on the TP.I just am poor and can't afford to run even cheap color screens all the time (since it seems to get more accurate the longer its on, I plan to do something like that with the TP.)Can one run LH in some kind of text mode where it could work with small displays and read from/write to some push buttons and LEDs?---also, sort of an unrelated question.. It seems as if so far I have never seen it give me a "time figure of merit" of 1 and I have only seen it get to 2 briefly. Its actually getting better, 2 is new, for a while it only had gotten to 3.I am guessing that being in a case will likely be helpful to improving that figure.. that the effect of a real case around the board would make it more immune to (dramatic) changes in ambient air temps stable and improve that TFOM. Its a bit less than a meter away from an air conditioning unit whose top is also serving as the ground plane for its antenna. Its also close to a fan which runs much of the time.The GPSDO is not currently in a case at all, its just bare.Also, with the eclipse coming up I wanted to point you tohttp://abelian.org/vlfrx-tools/which is a VLF receiver for PCs that runs on linux and it contains a host of different functionality which I need to spend some time with to figure out.It includes some timing-related programs including one which presents a novel method for getting data from the PPS pulse using the audio card input which might work with almost all hardware and give you a way to use the pps "pops" with LH that would not be dependent on running on RPI or a machine with a real serial port.I don't know. But it might be worth trying.

author: texaspyro
author_rank: Super Contributor
timestamp: August 20, 2017, 05:07:07 pm
content: If run Linux/RPI/macOS compiling from source is easy. Most Windoze users have problems (well, duh). If you can build the current v5.0 distro from ke5fx.com, you just need to copy the *.c* files from the X11 .ZIP and do a make.No well in hell will Heather ever run on a screen smaller than 640x400.

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 05:51:59 pm
content: Yes, LH works quite well now with my Venus GPS's- thank you!So I am sure it will compile.On my desktop I could use the RS232 to hook the GPSDO up to my PC directly, including sending it PPS via the DCD pin. (currently I am using an arduino's built in FTDI USB-UART chip to connect to it.)

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 06:08:06 pm
content: LH would be the ideal UI for it, I agree.There is a lot of data that doesn't lend itself so well to a tiny text display, or even a tiny graphic display.

author: texaspyro
author_rank: Super Contributor
timestamp: August 20, 2017, 08:19:48 pm
content: It works well with the RPI 800x480 touchscreen. It's still a little small for my tastes... more, yeah more, that's what I want... more. I tweaked up the display code to work better on smaller screens. And added a touchscreen keyboard.I've been thinking about having some instrument cases built that would have space for the RPI screen and enough extra front panel space for connectors, etc. Rear panel would have a cutout for an IEC power plug and maybe a small fan. Maybe some cutouts for some panel mount USBs and ethernet. You can build a lot of useful stuff with a RPI and a touchscreen. I'm surprised nobody seems to sell a similar RPI box.

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 08:33:37 pm
content: You should mock it up in a cardboard box and that way you can try out a bunch of different layouts.A good selling point would be if you internally had the mounting particulars set up so it would be compatible with a bunch of different popular SBCs. Not just the RPI.Spend some time with it and use it and change your mockup a cople of times to see if you might prefer it some other way. Once you find it works best for you then go for it.I think the only way to do something like that is as a labor of love where you say to yourself upfront that you are unlikely to make any money and might even lose money.That enables you to do it the way you want it and only then you oftendomake money.If you can accept upfront that you may not, then you can do it and have fun with it.But its a jungle out there as far as profitability.Very few businesses are so inherently profitable that luck doesn't play a very large part in their success.

author: texaspyro
author_rank: Super Contributor
timestamp: August 20, 2017, 09:19:02 pm
content: I'm thinking about a place like Front Panel Express. They CNC custom panels and have a line of modular cases where they have corner/side rails with slide in panels that set the enclosure size. They have a nice designer program that lets you layout the panel / enclosure. They can engrave, etc the panels and paint the enclosure to your tastes. Their panels are fairly reasonable, but I don't expect a decent setup would be less than $100.Another company like that is Cam Expert. They don't have the fancy designer program, but are cheaper.

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 09:37:08 pm
content: The RPI definitely has a place in industrial settings. People save so much on the computer they might be willing to spend more on a case. But once they spend a certain amount, then they will start thinking, why not just buy an industrial computer in a rack. Thats not such intelligent thinking because the Pi has a great many advantages but, its the way most people think. That said, you still likely have a lot of room there. I am particularly cautious when it comes to money these days. People always need computers, though, and there again, compelling arguments can be made for Pis.Now if they could only make it work with SATA drives and have gigabit ethernet capability!

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2017, 09:40:06 pm
content: How does one get it into $KALDBG ?Quote from: pigrew onTodayat 09:07:59

author: pigrew
author_rank: Frequent Contributor
timestamp: August 21, 2017, 03:53:55 am
content: Quote from: cdev on August 20, 2017, 09:40:06 pmSend "$KALDBG 1", and it'll output the $KALDBG message every 20 seconds. Seemy other postfor details....It seems that KAL1 is GPS time. KAL3 is of similar magnitude to the output ADC counts, but doesn't exactly track the ADC. KAL5 is a smoothed version of the phase error (roughly in units of 6ns). I'm unsure of the rest of the meanings.To get the ADC counts, you have to look at the PPSDBG string.

author: texaspyro
author_rank: Super Contributor
timestamp: August 21, 2017, 04:49:40 am
content: Some more command are in this list (leading $ not shown):if (!strcmp(msg_field, "CLOCK")) parse_true_clock();else if(!strcmp(msg_field, "DISCARD")) parse_true_discard();else if(!strcmp(msg_field, "ESN")) parse_true_esn();else if(!strcmp(msg_field, "EXTSTATUS")) parse_true_extstatus();else if(!strcmp(msg_field, "GETA")) parse_true_geta();else if(!strcmp(msg_field, "GETBDELAY")) parse_true_getbdelay();else if(!strcmp(msg_field, "GETDELAY")) parse_true_getdelay();else if(!strcmp(msg_field, "GETPOS")) parse_true_getpos(0);else if(!strcmp(msg_field, "GETP")) parse_true_getp();else if(!strcmp(msg_field, "GETSCALEFACTOR")) parse_true_scale();else if(!strcmp(msg_field, "GETVER")) parse_true_getver();else if(!strcmp(msg_field, "KALDBG")) parse_true_kaldbg();else if(!strcmp(msg_field, "LEAVE")) parse_true_leave();else if(!strcmp(msg_field, "PPSDBG")) parse_true_ppsdbg();else if(!strcmp(msg_field, "PROCEED")) ;else if(!strcmp(msg_field, "SAT")) parse_true_sat();else if(!strcmp(msg_field, "SET1PPS")) parse_true_set1pps();else if(!strcmp(msg_field, "SPIW")) parse_true_spiw();else if(!strcmp(msg_field, "STATUS")) parse_true_status();else if(!strcmp(msg_field, "SURVEY")) parse_true_getpos(1);else if(!strcmp(msg_field, "TRAIM")) parse_true_traim();else if(!strcmp(msg_field, "UPDATE")) parse_true_update();else if(!strcmp(msg_field, "WSAT")) parse_true_wsat();Also firmware dump attached...

author: nuno
author_rank: Frequent Contributor
timestamp: August 21, 2017, 11:57:32 am
content: At the top center there's an inductor with the ferrite broken.

author: CJay
author_rank: Super Contributor
timestamp: August 24, 2017, 09:12:54 am
content: Just a quick post, the case I intend to repurpose for my GPSDO:

author: cdev
author_rank: Super Contributor
timestamp: August 24, 2017, 01:58:57 pm
content: Nice! I've been scouring the sites looking for something similar for not too much.That's (re-purposing an existing case) definitely the way to go.Something with BNCs, buttons, and an LCD ideally.

author: cdev
author_rank: Super Contributor
timestamp: August 25, 2017, 01:54:09 am
content: Attached is what I got from running the Linux strings command on the file!(27k) of strings. Unedited.Quote from: texaspyro on 2017-08-20, 22:49:40

author: cdev
author_rank: Super Contributor
timestamp: August 25, 2017, 02:09:15 am
content: Hmm.. in there it says "Hello from Nios II"Nios II is an OS that runs on the Altera FPGA platform.https://en.wikipedia.org/wiki/Nios_IIhttps://people.ece.cornell.edu/land/courses/ece5760/DE2/tut_nios2_introduction.pdfhttps://www.altera.com/en_US/pdfs/literature/hb/nios2/n2cpu_nii5v1.pdfIt appears you talk to it via a USB Blaster cable.. (implemented with another Altera FPGA)This is I'm sure what one of those headers is.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: August 26, 2017, 08:48:10 pm
content: Quote from: cdev on August 24, 2017, 01:58:57 pmThe Extron are good boxes for this propose they have lot(s) of BNC(s) with the RGB channels for the 10MHz distribution amplifier, and the H/V channels for the PPS, some models are tall enough to put an LCD, see this box Extron ADA6 300MXhttps://gerrysweeney.com/tag/extron/

author: cdev
author_rank: Super Contributor
timestamp: August 27, 2017, 04:01:03 am
content: You really are right about extron.I have to say after reading all the problems some people have had buying other comparable GPSDO units - (Symmetricom, Trimble UCCM, etc) which were also removed from telecom service, I feel extremely lucky to have gotten a solid unit that works well. I'm not in any rush to do this, I just want to have a solid enclosure for it that protects it from harm and feeds it clean power and displays the basic facts about its operation.I will use Lady Heather is for visual display of the more complex quantitative information..

author: pigrew
author_rank: Frequent Contributor
timestamp: September 04, 2017, 07:55:52 pm
content: I've stared trying implement a microcontroller-control program.I settled on the stm32f103 as my target platform (using the blue-pill board). I have it working, along with one of the I2C 0.96" OLED displays. BOM cost is less than US$10 (board is $2.50, OLED is about $2.50, plus some wire and surface-mount resistors).Current features:* Sends $PROCEED when needed.* Sends $PPSDBG 1 when needed.* Displays UTC time of day, satellite count (from $EXTSTATUS), OXCO/board temperature, and lock status.* Acts as USB serial-port, which forwards data the computer (I don't have data going the other way, yet).I still have a few things left to do, but it's a good start.Code athttps://github.com/pigrew/trueposctrl.I probably should add a button or two in order to be able to start a self survey, display satellite info, display lat/long info, etc.

author: cdev
author_rank: Super Contributor
timestamp: September 05, 2017, 03:57:14 am
content: I actually have a board exactly like yours - that is a very lucky coincidence.. So now I am looking at the display I have and I think it also should be adaptable.. but to make sure I am not making some kind of mistake, I'm going to post two photos I've taken of it.Total newbie to using any kind of bitmapped display here.This displays cost, like yours, around $2-3I think I bought it based on the argument that it was so cheap, I knew it would come in use, and even if it took me some time to use, I would use it.That was around two weeks ago. I guess there is a first time for everything.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 05, 2017, 05:00:08 am
content: Quote from: cdev on September 05, 2017, 03:57:14 amI think that my code, as is, would work with any SSD1306-based 128x64 OLED with the internal DC-DC converter. Some boards will have a big inductor on the them for a DC-DC, and the display initialization routine would need to be changed to use that external voltage source.I'd rather use a SPI3 interface, but I bought the I2C version. SPI3 would be faster.Perhaps I should order the SPI3 version, and change my code to use it....

author: cdev
author_rank: Super Contributor
timestamp: September 05, 2017, 07:09:02 am
content: I was looking at the libraries for it, its a bit faster and perhaps better for drawing graphs

author: medical-nerd
author_rank: Regular Contributor
timestamp: September 05, 2017, 11:09:56 am
content: HiyaI've been doing a search and looking on the packratvhf site - where do you get these particular GPSDO beasties?I've already got a FRS-C rubidium, a FEI custom rubidium and a couple of Z3801a's and want to play some more!!Cheers

author: CJay
author_rank: Super Contributor
timestamp: September 05, 2017, 11:22:06 am
content: Got mine from Fluke.I on eBay, untested $40 but it works, as far as I can see, perfectly after a few minor hiccups (one of which was me misplacing a decimal point and misunderstanding the $STATUS sentence, thought it was a bit odd that I was in the middle of the Atlantic)

author: pigrew
author_rank: Frequent Contributor
timestamp: September 05, 2017, 03:09:29 pm
content: Quote from: pigrew on September 04, 2017, 07:55:52 pmThe program is more complete now. Bi-directional USB seems to work. Still no button-inputs. Perhaps there is little need for button input (except maybe a display on/off feature?)I posted somephotos of the hardware reconfigurations of the microcontroller, if you'd like to play along.

author: cdev
author_rank: Super Contributor
timestamp: September 05, 2017, 07:26:13 pm
content: So, I am about to try to see if I can get it running on my breadboard in as simple a way as possible (just to verify its operating)first without the TruePosition online, to verify the display works, and then with the GPSDO.I've changed the pull-ups. Here is my problem, I didn't have any SMD resistors that were both appropriate values and small enough. The ones I have are probably two sizes too large so I couldn't use them. So, what I did is I moved the 4.7k resistor on R3 down to R4, and bridged r8 with a 1k (approximately) smd resistor I had which was too big but it's bridging them, and it will hopefully stay there. Both sides look solidly soldered.Dealing with these small SMD parts without the proper tools (working on that now) is a lot harder than dealing with larger ones for me.Hopefully 1k on R8 wont be too small.In the image it shows which resistors need to get changed.What do you think? My SMD resistor situation is not so great. I thought that I had more somewhere. I think I do, actually, a little ziplock bag with assorted SMD parts from a store that sells them in little random packages, goldmine electronics.Unless I can find that bag my only alternative to this that I can think of is attempting to remove resistors from junk boards.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 05, 2017, 07:30:19 pm
content: New command: $TRAINOXCOIt'll restart the unit ($PROCEED needed), wait a little bit for things to warm up, and then do OXCO training. During training, status is 7.It measures the oscillator frequency at two points separated by 500 ADC counts.Once it's done, status will go 9,10,11,12,13,0,19,20,21,22,1,0.Edit: It's also good to note that the DAC voltage changes every second when status=1. It changes only every five seconds when status=0.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 07, 2017, 12:47:38 am
content: Quote from: medical-nerd on September 05, 2017, 11:09:56 amHow I wish I had a Z3801a... I'd imagine they are better than this board?I got mine for about 120 RMB on Taobao. The seller says that he only guarantees the OCXO works, not the entire GPSDO. I should have bought a few more from him.There's also another seller in the PRC on eBay (or maybe the same person?) who sells them for a bit more, but says that the GPSDO will work.I bought three boards (one had been crushed a bit), all different vintages. I'm not sure if the Bliley or the CTS crystal is better. The revisions of the GPS chipset are also different in different boards.In terms of setting up boards, you should do a survey first ($SURVEY #), and write down the location where it says you are. I _think_ that it stores it in EEPROM automatically. You can set your location later with the $SETLOC command. Finally after it's warmed up for a while (>1 hour in an enclosure like a cardboard box), you should run $TRAINOCXO.I have some personal software that I've written to make plots of the GPSDO status (windows-only, not published). I've also been working on a STM32-based controller which will automatically start up the board, and display status info on an OLED screen.

author: texaspyro
author_rank: Super Contributor
timestamp: September 07, 2017, 12:55:13 am
content: Where did you find the $TRAINOCXO command? I did not see in my strings dump.

author: cdev
author_rank: Super Contributor
timestamp: September 07, 2017, 02:20:04 am
content: Indeed.. Entering $TRAINOCXO kicked it back into Boot mode.. so now its training the OCXO?(trying to figure out what's different)

author: pigrew
author_rank: Frequent Contributor
timestamp: September 07, 2017, 02:32:26 am
content: Quote from: cdev on September 07, 2017, 02:20:04 amThat's what mine does, too. Look carefully at my post from yesterday. After it boots, it'll measure the frequency at two DAC values (separated by 500). Things seem slightly more stable after running the training (though I just noticed that it went into holdover for a moment).I need to check if that sets the $GETSCALEFACTOR.... I'm not sure what scale factor it is.Quote from: texaspyro on September 07, 2017, 12:55:13 amI was trying random permutations of gain, train, tune, traim, and ocxo. I knew there must be some command like that, based on the packrat PPT (it lists a training mode). (I don't know what $TRAIM does). It was scary when I saw it reboot the first time, but it seems to be normal.I think that the software must use a complicated tree of if statements to decode the commands, so I think that they are not listed in the strings.We'd need to decompile the binary in order to get the command list, I think. The strings only show the output of the unit, not the input.

author: texaspyro
author_rank: Super Contributor
timestamp: September 07, 2017, 02:55:28 am
content: Actually the strings do show the input commands (see things like $GETPOS. $GETA, $GETP, $SETPOS, etc).TRAIM is time receiver autonomous integrity monitoring. TRAIM modes basically check that the satellite data is consistent between all the sats and rejects sats that don't agree with the majority.

author: texaspyro
author_rank: Super Contributor
timestamp: September 07, 2017, 02:58:10 am
content: SCALEFACTOR probably maps the desired frequency control word to the EFC DAC setting... basically the "P" term in a PID controller.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 07, 2017, 03:10:50 am
content: Quote from: texaspyro on September 07, 2017, 02:55:28 amThe ones you mentioned are also all part of the responses that it sends. I was thinking that only responses are sent (but it usually responds with the same command ID as it was sent). The string list is also missing all of the responses/commands that I expected that it would be sending the GPS module.Quote from: texaspyro on September 07, 2017, 02:55:28 amSo, maybe it reports a $TRAIM message when it detects inconsistent satellites? I saw $TRAIM in the string listing, but I've never seen that message.

author: texaspyro
author_rank: Super Contributor
timestamp: September 07, 2017, 03:16:43 am
content: It has the GPS control messages in the strings... they are the $PFEC sort of things. There is also $XXGLL messages... I bet the XX gets patched to match the NMEA GLL messages.

author: cdev
author_rank: Super Contributor
timestamp: September 07, 2017, 03:48:19 am
content: The embedded OS is something called Nios II that runs on the Altera FPGA

author: CJay
author_rank: Super Contributor
timestamp: September 07, 2017, 05:53:54 am
content: Quote from: cdev on September 07, 2017, 03:48:19 amDid a little looking around and NIOS appears to be a softcore RISC CPU design, not an OS as such, there's a few references to disassemblers which may be useful if we have a ROM dump from the TruePosition board?https://www.adveda.com/https://github.com/KarmaQueen/Nios-II-DisassemblerThere are also tools in the Altera toolchain that might e useful, I *think* the toolchain includes a C/C++ compiler with the NIOS core but I'm far from an FPGA expert (I can usually recognise an FPGA from a few paces but that's about it)

author: cdev
author_rank: Super Contributor
timestamp: September 07, 2017, 02:30:02 pm
content: I am hoping to use a UG-2864HSWEG01 OLED display I have.Its quite popular. Its display is controlled by an embedded controller chip, the SSD1306,Below are the documentation on the Furuno GPS receiver used in it, and the OCXO in my board.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 07, 2017, 08:47:19 pm
content: Quote from: CJay on September 07, 2017, 05:53:54 amRight. There are actually two Altera PLDs on the board. An Altera MAX EPM3064ATC100-10. This IC has an internal EEPROM, and its firmware likely cannot be read-back out of the device. This is what I'd consider a CPLD, with a reasonable number of macrocells, each of which is effectively big lookup table.The second is a Altera APEX EP20K160ETC144-2X, which is a FPGA. It has a large number 6400 tiny logic elements. This is where the soft-processor would live. It loads its configuration from an external EEPROM or flash. Generally the soft-core's programming will be loaded from FPGA's RAM which would have been previously set by the configuration RAM.I'm not sure exactly what the structure of the ROM is in the altera binary. We may need to extract it somehow before decompiling it. As far as I know, the binary configuration format is not published.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 07, 2017, 09:06:24 pm
content: Quote from: texaspyro on September 07, 2017, 02:58:10 amThe value makes sense if it is Hz/mV. The training tunes the OCXO by 500*(4.096 V)/2^16=31.25 mV. and I measured a frequency shift of about 0.12 Hz. My Bliley OCXO gives a value of about 3.663019e-3. This is within its datasheet specification of 2.5 Hz/V Min to 5.5 Hz/V Max.

author: cdev
author_rank: Super Contributor
timestamp: September 09, 2017, 12:41:31 am
content: I think the $TRAINOCXO may have significantly sped up my TP's time interval from power on/cold start to first attainment of GPS lock and 1pps.Also, I like the Z3801A's LED layout (below)

author: pigrew
author_rank: Frequent Contributor
timestamp: September 09, 2017, 05:17:38 am
content: Quote from: cdev on September 09, 2017, 12:41:31 amI'm still getting occasional unlocked events, even after the OCXO tuning, anecdotally every five hours or so.I've started playing with the $SETGAIN parameter. It seems to be in units of hundreths. Sending "$GAIN 95" will echo back with $GAIN 0.95. It seems like the gain can be set to both positive and negative values, and the values can be in the thousands. Setting too large (positive) of a value will cause a loss-of-lock (-10.00 or 10.00), and the tuning voltage will go haywire. Sending "$SETGAIN" will return a value, but I'm not convinced that it'll return the current value. I think that it'll just set the value to whatever happens to be in some memory location at that moment.Setting the gain to be -1.00 does seem to make the system unstable (As I'd expect if it were a multiplier of the P in a PID controller).I think gain is only applied when status=0.I've also been seeing slight oscillations in the system response of the GPSDO. PPSDBG:4 (phase?) would always stick at around +4 or -4, and rarely settle on 0. I'm going to set my gain to 0.25, and see if I can maintain a lock all night.I never found a way to set the SCALINGFACTOR to a value, it seems to only be settable via OCXO training, but the GAIN is likely multiplied by the SCALINGFACTOR, so that's good enough.In other news, I found (and fixed) a bug in my display-controller causing the USB serial port to screw up. The controller is pretty stable now. It also shows the duration of the current lock. It's convenient that it automatically sends the $PROCEED and $PPSDBG commands when needed.Quote from: cdev on September 09, 2017, 12:41:31 amFeel free to edit the display controller's code and do whichever setup you'd like. It'd be fairly easy to set GPIO ports based on the GPSDO state (unless you wanted more complicated logic?).

author: cdev
author_rank: Super Contributor
timestamp: September 09, 2017, 02:34:32 pm
content: Thats what I was thinking I might try to do.If I can figure out how the process works! I have an ST-link 2 coming soon so I should be working with the IDE verson and not your released binary.You shouldn't feel bad about your criticism of the STM32 Blue Pill's USB setup. You are by no means the only person making those complaints, I have read them quite a few times now.SO now I have two more BPs coming also in the mail so I will be a little more adventuresome. I am just quite cautious about damaging things sometimes.Economists would call it "risk aversion".I have to start thinking about which of my many wall warts, etc. I should use for the power supply. I think the $TRAINOCXO is meant to entrain the board to specific case environments and power supply conditions, so the more stable that is the better.So what are folks feelings on case ventilation? Closed case with no ventilation holes seems to be common in commercial units.My unit came shipped to me with some nice closed cell polyethelene foam that had a square hole the size of the oven already cut in it. So I trimmed that a bit and put a little top on it with scotch tape and tried putting it around the oven to see if it increased stability. It was hard for me to tell because right now I am not parsing the output in any way.It is clear though that when I have my little desk fan going and the cardboard box my GPSDO is currently in is open the board seems to go out of lock more.Antenna placement is still everything. When I am using an outdoor antenna (stuck in the middle of my back yard because that the best place for sky view) the GPSDO almost never goes out of lock. When the antenna is indoors, even next to the window (like it is now) every once in awhile it will lose lock and go into holdover and start counting seconds.So any ability to adjust the gain might be helpful when the antenna is indoors.So, just turned it on, after it being off for the night, it is starting to get much cooler here, fall weather and the ambient temperature was around 20 C even though its sitting in a sunny window area. I wonder if the scalingfactor also takes the ambient temperature into account? If it only has one temperature sensor I guess it really cannot, except at the very beginning of being on.I've read elsewhere that the typical OCXO is influenced somewhat by both barometric pressure and humidity - more so than I had realized.I recently ordered two barometric pressure sensors that also measure temperature and one that measures all three, temperature, pressure and humidity.I would like to have some means of allowing all of the various parameters to be captured and recorded on my only always on computer, a Raspberry Pi. One way of doing it is by parsing a UART stream - console-like.. another way is by saving the data to a file in some delimited format and then grabbing it somehow at regular intervals.. that can also be done with HTTP and often thats the easiest way. (My old school means of doing it is by using any command line program that can accept and fetch a URL- encoding the parameters in the one line request. So thats a good excuse to give the GPSDO some basic network capabilities.. if its possible. (No security is needed as it would just be requesting a public web page) Any of dozens of methods just about would work.Telling it about what to expect from small voltage shifts as far as frequency based on past performance under similar conditions is probably what the entrainment is all about.I'm attaching a image I saved of a nice case implementation.. simple, seems to balance cost of case and size of display and LEDs well. This one uses an LCD.Something even more informative in a small space could be done with a graphics OLED with icons or very small graphs.. perhaps..Dont really need to know location as much as other parameters - but thats easy to change.Quote from: pigrew onYesterdayat 23:17:38>Quote from: cdev onYesterdayat 18:41:31I'm still getting occasional unlocked events, even after the OCXO tuning, anecdotally every five hours or so.I've started playing with the $SETGAIN parameter. It seems to be in units of hundreths. Sending "$GAIN 95" will echo back with $GAIN 0.95. It seems like the gain can be set to both positive and negative values, and the values can be in the thousands. Setting too large (positive) of a value will cause a loss-of-lock (-10.00 or 10.00), and the tuning voltage will go haywire. Sending "$SETGAIN" will return a value, but I'm not convinced that it'll return the current value. I think that it'll just set the value to whatever happens to be in some memory location at that moment.Setting the gain to be -1.00 does seem to make the system unstable (As I'd expect if it were a multiplier of the P in a PID controller).I think gain is only applied when status=0.I've also been seeing slight oscillations in the system response of the GPSDO. PPSDBG:4 (phase?) would always stick at around +4 or -4, and rarely settle on 0. I'm going to set my gain to 0.25, and see if I can maintain a lock all night.I never found a way to set the SCALINGFACTOR to a value, it seems to only be settable via OCXO training, but the GAIN is likely multiplied by the SCALINGFACTOR, so that's good enough.In other news, I found (and fixed) a bug in my display-controller causing the USB serial port to screw up. The controller is pretty stable now. It also shows the duration of the current lock. It's convenient that it automatically sends the $PROCEED and $PPSDBG commands when needed.Quote from: cdev onYesterdayat 18:41:31Feel free to edit the display controller's code and do whichever setup you'd like. It'd be fairly easy to set GPIO ports based on the GPSDO state (unless you wanted more complicated logic?).

author: pigrew
author_rank: Frequent Contributor
timestamp: September 09, 2017, 03:29:55 pm
content: Quote from: pigrew on September 09, 2017, 05:17:38 amAt gain=0.25, I did lose lock once over-night, but the tuning voltage didn't change much at all during the unlocked period. I still saw oscillations with a period of about 5000s and a tuning voltage amplitude of 200 uV. At 3 V per Hz, this would be about 0.6 mHz. The oscillations are in most of the reported in multiple parameters (both tuning voltage and phase). This is "Good Enough" for all of the uses I have for a frequency standard (I only want need 0.5 ppm accuracy).Oddly (at least to me), using a larger gain (such as 2.00) has removed the oscillations I see in the tuning voltage. Of coarse, I don't want to make the gain to high, as the OCXO should have better performance than the PPS signal in the short term. If I didn't see it adjusting the tuning voltage, I would have figured that it was just due to GPS inaccuracies, however the voltage oscillation seems to imply that something is wrong.Re: Thermal environments and case:The crystal seems to want a very stable temperature, though it should be able to hold temperature steady best if it isn't too well insulated. I'm still working on a case, I have it in a cardboard box for a moment. I would tend to not provide vents in the can, as I've noticed that drafts will cause frequency shifts.I stole a power input section from a wireless router board which used 12VDC input. It provides a LC filter, fuse, and a 3.3V DC-DC converter.

author: cdev
author_rank: Super Contributor
timestamp: September 09, 2017, 08:00:12 pm
content: Does this mean that USB-to-serial using the USB micro connector on the Blue Pill can be used along with the display controller?If so that would be absolutely great.

author: pigrew
author_rank: Frequent Contributor
timestamp: September 09, 2017, 08:30:14 pm
content: Quote from: cdev on September 09, 2017, 08:00:12 pmExactly.The stm32 is programmed to a usb-serial converter, but also display the status and send $proceed and $ppsdbg when needed.

author: cdev
author_rank: Super Contributor
timestamp: September 11, 2017, 12:09:53 pm
content: Reading Time-nuts about GPSDOS, seems this may be what some of the settings incremental states and gain, delay, etc. are about. "Microtonal" adjustments in phase and frequency back towards exact lock during recovery? Similar to how NTP adjusts time when there is a correction needed. Slowly.https://www.febo.com/pipermail/time-nuts/2012-December/072265.html[time-nuts] GPSDO recovery from holdoverSaid Jackson saidjack at aol.comSat Dec 1 17:42:58 UTC 2012Hi Hal, We selected 10 steps upon customer request.The counter resolution is 16.667ns on the FF-IIA boards, so we end up pretty close to UTC. "Slowly" is determined by the PLL parameter serv:phaseco.By default we add very little frequency error, so drifting say 100ns can take a couple of hours if the ocxo is stable ( not warming up anymore). The settings vary per oscillator type, and are more aggressive for single oven units than SC cut DOCXO units. The user can "crank up" the gain and thus reduce the adjustment time, by increasing that parameter, all the way until the loop becomes unstable. We made it so slow for two reasons: one we wanted the best frequency accuracy, and drifting the phase requires adding a frequency error, so we want to keep that error as small as possible. Two: we indicate this phase offset via pushed or polled software command with 0.1ns resolution, so the customer can adjust for it if desired bydelay lineor via software calculation.Or the customer can simply set thegainhigher for faster phase corrections.. Bye, Said Sent from my iPad On Nov 30, 2012, at 8:36 PM, Hal Murray <hmurray at megapathdsl.net> wrote: > >saidjack at aol.comsaid: >> New JLT GPSDOs step back in 10 Steps over 10 seconds if more than 250ns off, >> then adjust the last ns slowly. > > Thanks/interesting. > > How/why did you pick 10? > >> If within 250ns, they just slowly slew back. > > How fast is "slowly"? >

author: cdev
author_rank: Super Contributor
timestamp: September 11, 2017, 04:56:42 pm
content: Current status:It was running for a bit - but the display had missing pixels. Then it froze.Its possible I may have damaged the display when attempting to move some resistors at the beginning.Or maybe its just connected improperly. It took some experimentation with resistor and capacitor values to get it to show up as an i2c device..Do you think its the i2c frequency? Pigrew, as far as I can tell, my specific display does not have a large inductor on it..So, its possible it doesnt have an internal DC-DC converter.Here is a web page I just found on archive.org about it..https://web.archive.org/web/20140812013022/http://geekonfire.com/wiki/index.php?title=I2C_OLED_Panel%28128x64%29

author: cdev
author_rank: Super Contributor
timestamp: September 13, 2017, 09:30:02 pm
content: This project is making me realize just how little I know about programming and microcontrollers. Basically almost nothing. But hopefully that will change.Thanks to Pigrew I've been introduced to an incredibly affordable little board and development tools. He's been very helpful in answering my often I suspect very stupid questions.The GPS controller works, and its quite inexpensive to build. Under $10 in parts, apart from the GPSDO and its stuff.I will take some pictures in a bit of my build which so far has used an unmodified Blue Pill board. (although I think I may also modify it because I'm phobic about USB power problems) I am going to use a new blue pill board I have because this one is set up for fooling around and "dupont cables" and thats not how I want a permanent device to be. Wires will fall off unless they are anchored more securely.

author: cdev
author_rank: Super Contributor
timestamp: September 14, 2017, 03:28:56 pm
content: Works!

author: don.r
author_rank: Frequent Contributor
timestamp: October 04, 2017, 11:36:13 pm
content: So I just wanted to make a nice little 10MHz distribution box with a little OCXO and now.... I have a TruePosition unit up and running waiting to go in to my enclosure.... works like a charm on as little as 9.3V. The project rabbit hole gets deeper as I'm thinking of using one of my newly acquired ESP32 units and have a WiFi accessible GPSDO. Why oh why can't things be simple?

author: texaspyro
author_rank: Super Contributor
timestamp: October 04, 2017, 11:40:43 pm
content: Precision thingies like a GPSDO seldom get along well with nearby transmitty thingines... It doesn't take much to influence/degrade a device trying to operate in the sub part-per-billion to part-per-trillion range.

author: cdev
author_rank: Super Contributor
timestamp: October 04, 2017, 11:53:37 pm
content: My GPSDO is running well but it still does not have a good case. I'm trying to make up my mind on the case.

author: cdev
author_rank: Super Contributor
timestamp: October 05, 2017, 12:00:04 am
content: Latency wifi adds would seem to me to make it much less accurate...If you can use real ethernet cards, and wired ethernet you could perhaps use PTP if the hardware is supported by ethtool. or its equivalent on whatever platform you use.Simplex radio PPS.Raspberry pi supports PTP for receiving (software PTP) but not transmitting.....Quote from: don.r on October 04, 2017, 11:36:13 pmIf you sent a pps signal via RF to preserve the rise time it would have to be simplex CW or FSK, not packetized.

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 12:10:47 am
content: I would simply use it for control/monitor purposes. It will be hardwired to the distribution box. I have a case (an old set top box) that has a shield wall before the front panel so I could stick the ESP32 behind the front panel and maybe put the GPDSO in a separate can as well. Not sure it it would affect the timing circuits of the GPSDO but we'll find out!

author: cdev
author_rank: Super Contributor
timestamp: October 05, 2017, 01:07:10 am
content: for the shell, sure, that makes sense..

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 02:09:43 am
content: It has a nice Delta PSU with half a dozen different outputs including a 9V 1A output which should be OK with a slight boost to 9.5V. Comes with a front panel with buttons and a seven segment display. Not bad for $5 from the thrift store. I've finally found a use for it.

author: cdev
author_rank: Super Contributor
timestamp: October 05, 2017, 02:16:41 am
content: How did you determine that 9.5 volts was your unit's optimal voltage?

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 02:44:00 am
content: I kept testing it from a cold start at lower and lower voltages. At 9.4V the unit starts no problem but the 10MHz waveform starts to become distorted. No issues at 9.5V. The digital portion works fine down into the 8V range but the OCXO is not working.

author: texaspyro
author_rank: Super Contributor
timestamp: October 05, 2017, 03:29:36 am
content: Quote from: don.r on October 05, 2017, 02:44:00 amIt's designed for 12V... USE IT! It's rather stupid to expect it to work properly at such a low voltage. It might start at 9.5V today but you know it's 0.1V away from failure. How do you know how well it is working at such a bogus voltage? OCXOs are temperamental and fussy little beasties.

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 03:42:22 am
content: Quote from: texaspyro on October 05, 2017, 03:29:36 amActually, the GPS module is designed for 13-15V supply. The OCXO actually has a 5V working voltage. Don't worry, I'll measure it over a few days at different voltages to find the lowest stable point. There appears to be a buck regulator at the input which supplies the board with its power so input voltage is not too important, as long as it works and is stable over time. I also have to test inrush current at turn on to make sure the PSU can handle that.

author: texaspyro
author_rank: Super Contributor
timestamp: October 05, 2017, 03:52:39 am
content: The system these were pulled out of run it at 12V... not 13V... not 15V... but 12V Ignore what the Packrat docs say.Just because it powers up does not mean it is working properly. You would need to measure phase noise and ADEVs across a reasonable temperature range to verify it is OK... and something tells me you don't have the equipment to do that.

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 04:33:33 am
content: I have access to a spectrum analyzer and enviro chamber but that's a waste of time. There is a buck regulator and an LDO precision linear regulator between the supply input and the OCXO. Input voltage is a non-issue.

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 09:24:18 pm
content: Worked great with a sub-$10 GPS antenna from China. Picked up half a dozen satellites in the space of a few minutes. The only worry is that the OCXO control voltage is already sitting at 4.00V and has a max of 5V. Hopefully she doesn't drift too much anymore. Looking at the specs of the Bliley, the power requirements are 5V +- 5% and the freq error due to supply is less than 1X10^-9 per %. Given that the LM1965 has a load regulation of around 0.1% should be no problem.

author: cdev
author_rank: Super Contributor
timestamp: October 05, 2017, 10:40:02 pm
content: The performance of a GPS-DO should be substantially better than that of the base OCXO its disciplining..My main concerns are - 1. is the 12v voltage optimal and 2. will putting it in a closed or semi closed case which may involve additional voltage regulation perturb the thermal characteristics in a negative manner.

author: don.r
author_rank: Frequent Contributor
timestamp: October 05, 2017, 11:06:27 pm
content: Quote from: cdev on October 05, 2017, 10:40:02 pmI would check out the specs of the two regulators involved with the OCXO. The first one is an LT1765 set to provide 5.78V to the next regulator. The input voltage goes anywhere up to the low 20V range, which is probably why we are seeing people destroy their GPS units with more than 22V. Here is the datasheet:http://cds.linear.com/docs/en/datasheet/1765fd.pdfThe next regulator is the LT1963 set to provide 5V to the OCXO from the 5.78V given to it from the LT1765. This output does not change regardless of input voltage to the unit. The LT1963 is very stable (0.1% regulation) and has only 40uV of noise. The OCXO has further power filtering inside (per Bliley website). Here is the LT1963 datasheet:http://cds.linear.com/docs/en/datasheet/1963fc.pdfAs for temp, look at the OCXO datasheet here:http://www.bliley.com/pdfs/Bliley_N47X_NV47X_OCXO.pdfand check out the best, good and easy figures for 10MHz for the various ranges. Even at 70C (remember the oven is temp controlled) the easy figure is +- 3X10^-8 The OCXO can take a +-5% variation in the power supply. I would not worry about it.

author: don.r
author_rank: Frequent Contributor
timestamp: October 13, 2017, 05:24:14 pm
content: A few questions for the more experienced:1. My survey time as returned by the $SURVEY response never changes from the set time. Is that supposed to happen?Works now. Just needed to wait for the right conditions.2. Anyone know what state 19 is? It appears to be some form of wait state.3. Mine also has a 10 year lag on the time. Can I simply add a 10 yr fudge factor to the time?4. Will I experience much signal loss if I add an antenna extension cable?5. What is the command to save location, satellites, training, etc? or is saving done by default?WiFi works a treat, at least for monitor purposes. ESP32 is an incredible little MCU for $7. Webserver and GPS control code takes up about 640kb so far. About 3.5MB to spare...

author: pigrew
author_rank: Frequent Contributor
timestamp: October 15, 2017, 07:24:49 pm
content: Quote from: don.r on October 13, 2017, 05:24:14 pmIt's part of a series of wait states 19->20->21->22, that I call "Wait B". I think this sequence happens when entering state 1 (not completely sure). There is another series of wait states 15->16->17->18 that happens while entering state 0.Look at the start ofhttps://github.com/pigrew/trueposctrl/blob/master/trueposctrl/Src/displayTask.cto see what I've reasoned, based on guess and check.Quote from: don.r on October 13, 2017, 05:24:14 pmThat's what I did.Quote from: don.r on October 13, 2017, 05:24:14 pmIt depends on what sort of cable you add. I saw that uBlox suggests using 75-ohm cables. The mismatch isn't too bad for reasonable cable lengths. If super-long, you'd need to add another line-amplifier (preferably at the start or middle of the cable).Quote from: don.r on October 13, 2017, 05:24:14 pmIt seems that my unit saves them automatically. texaspyro had written that "$UPDATE FLASH" would store something, though I've never used it. Use at your own risk.Quote from: don.r on October 13, 2017, 05:24:14 pmGood to hear. I have mixed feelings about the ESP32. I'm disappointed by its ESP-IDF, ADC linearity, and documentation.Would you post your code somewhere? I'm curious about how it compares against my control program for STM32. Is your goal to run a NTP server?

author: don.r
author_rank: Frequent Contributor
timestamp: October 16, 2017, 09:02:02 pm
content: Thanks for the reply. I'll probably need no more than 6 feet of extra cable. I have yet to play with the gain so it may not be an issue. Currently finding 7 satellites with the antenna sitting on my window sill but lock keeps drifting in and out. I'm not going to risk anything by running the flash command yet. I'll post some code when its ready but it will be ugly, very ugly.I'm OK with the IDF. I use Eclipse so much is hidden. C++ integration is lacking so I'm using C. Documentation is a rather sore point but I'm using Kolban's book as a guide. Its only been out a year so hopefully time will improve the software and docs. I have yet to characterize RF emissions so that may also be an issue. Haven't looked at the linearity of the ADC yet. Is it consistent enough to be corrected in software? A dual core 240MHz 4GB WiFi and BT enabled ucontroller with OTA update capability for less than $7 (less if you just need the module) is still impressive to me. For the cheap stuff there is always the STM32 or PICs for therealcheap stuff.Not planning on a time server, maybe?, but just don't want to have to hook a computer up to control and check things since the unit will sit high up on a shelf and somewhat inaccessible. I'll bring the RS232 out so I can hook up a PC if need be. My lab is in an outbuilding from my house so its also handy to check things out while in the house.... plus its excellent experience programming the ESP32.

author: don.r
author_rank: Frequent Contributor
timestamp: October 17, 2017, 01:50:20 am
content: Here is a sample screen shot of the info window. I have a separate window for commands.

author: don.r
author_rank: Frequent Contributor
timestamp: October 20, 2017, 04:00:53 am
content: Code now on github:https://github.com/don-r/TruePosition-GPS

author: cdev
author_rank: Super Contributor
timestamp: October 20, 2017, 02:30:10 pm
content: If I use appropriate 'magnetics' is it possible to use a compatible ESP32 device or at least access its web server via TCP/IP via conventional wired Ethernet (and not via Wifi?)(Or, maybe it could be ported to a Linux SBC that did have Ethernet?)

author: pigrew
author_rank: Frequent Contributor
timestamp: October 20, 2017, 02:36:11 pm
content: Quote from: cdev on October 20, 2017, 02:30:10 pmYeah, it'll work. It's the same principle I used to connect the UART to USB (just the coding is trickier since you'd want to support multiple streams).You'll have to pair the ESP32 with a PHY and transformer.You likely can find a prototyping board which already has the PHY and Ethernet connector on it, which could be connected to ESP32.

author: cdev
author_rank: Super Contributor
timestamp: October 20, 2017, 02:47:19 pm
content: That's good to know.

author: don.r
author_rank: Frequent Contributor
timestamp: October 20, 2017, 06:43:00 pm
content: I added the WebServer code. If you want to use ethernet, you should just have to change the ws_init and the wifi_event_handler routines. I tried to use SSL at first but its so slow (like 4 - 5 seconds to respond) that I just ended up with plain unsecured sockets. Not an issue for me as no one lives near enough to me to tap into my wifi but for others SSL may be required. All the code uses FreeRTOS as the OS which comes with ESP-IDF.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: November 10, 2017, 01:52:32 am
content: arduino, use arduino mini to send $PROCEEDneed a library alt soft serial ...Code:#include "AltSoftSerial.h"AltSoftSerial altSerial;// TX: PIN - 9 (connected to pin 2 GPS)// RX: PIN - 8 (connected to pin 4 GPS)void setup(){altSerial.begin(9600);}void loop(){char buf=0;char Nbuf=0;char c=" ";int i=0;int c_r=0;Nbuf = altSerial.available();if( Nbuf != 0){while(i < Nbuf){c=altSerial.read();delay(1);i++;}c_r=1;}if( c_r != 0){if( c = "R" ){altSerial.write("$PROCEED");}}}

author: cdev
author_rank: Super Contributor
timestamp: November 10, 2017, 04:06:04 am
content: That's simple!Must be the simplest interface out thereQuote from: GigaJoe on November 10, 2017, 01:52:32 am

author: GigaJoe
author_rank: Frequent Contributor
timestamp: November 11, 2017, 04:52:59 am
content: well , I need to start it, if no any fenzy thingi needs, then the code may acceptable; run it as standalone ....will add: 2-line display, +6 pins ; + 2 LED +2 pinsand buttons will do an analog way, each button send a specific voltage to ADC port, when you measure it you know the button ...

author: cdev
author_rank: Super Contributor
timestamp: November 11, 2017, 01:53:53 pm
content: Great!> if no any fenzy thingi needs, then the code may acceptable; run it as standalone ....Yes, that sounds very good. SoftSerial=no USB-UART chip needed.... So any MCU that runs Arduino code is okay.>"will add: 2-line display, +6 pins ; + 2 LED +2 pins "Just displaying the stream as it emerges? That will work fine!

author: GigaJoe
author_rank: Frequent Contributor
timestamp: November 11, 2017, 04:10:04 pm
content: Alt soft serial works well ( seems a bit differ comparing to original soft-serial) , 2 com ports - very easy to debug, FW upload and so ... I dont have MEGA that has more HW ports ...

author: Ernie
author_rank: Newbie
timestamp: February 11, 2018, 09:20:46 am
content: After power-up it starts to sending via the RS-232 port the $GETVER msg almost for ever and unable to stop and make the $PROCEED msg to enter..... is there any way to sop and enter some other msg..like $SURVEY and so on??? After several hrs the little green LED on the motherboard does not lit.Please advise

author: UglySteve
author_rank: Contributor
timestamp: February 11, 2018, 02:03:15 pm
content: Quote from: Ernie on February 11, 2018, 09:20:46 amWhen I had this problem, I had to change some settings in Hyperterminal. I believe these settings fixed it for me.ASCII set up." Local Echo" on, "append line feeds to incoming line ends" checked, "Wrap lines that exceed terminal width" checked.Steve

author: Ernie
author_rank: Newbie
timestamp: February 11, 2018, 02:51:02 pm
content: Hi Steve,Thanks a lot for the quick reply ...I had the same Hyperterminal set-up but unable to stop the incoming $GETVER msg..... what is the keyboard entry to stop the $GETVER msg...?pleas note I am not a PC/software guru so need detailed info.....Thanks.

author: UglySteve
author_rank: Contributor
timestamp: February 11, 2018, 05:02:36 pm
content: Quote from: Ernie on February 11, 2018, 02:51:02 pmAs far as I know, $PROCEED should do it. I think that if you type it, even if it doesn't show up on your screen, it should work. Just type over the incoming data. Do you have the serial data port wired correctly?I don't have the rs-232 wired to mine at the moment, I used the Packrat software on a micro controller, and made it a stand alone unit with a distribution amp, made from a modified RGB video distribution amp. I need to cut a hole in the box to mount a db9 connector for the rs-232.Steve

author: UglySteve
author_rank: Contributor
timestamp: February 11, 2018, 05:06:33 pm
content: Do you have pins 4-5 connected to allow serial data input?Steve

author: Ernie
author_rank: Newbie
timestamp: February 11, 2018, 07:26:01 pm
content: Thanks for the new tip.....Yes I have the correct " NULL-MODEM " cable.... works well with FURY GPSDO and other unit...... but I will try your tip only tomorrow.....pins 4-5 connected together....Ernie

author: Ernie
author_rank: Newbie
timestamp: February 12, 2018, 02:56:15 pm
content: Hi Steve,chked out your tip ..... to enter the $PROCEED msg.... in between the $GETVER boot msg and finally I had success....!!!!the very same time the motherboard small greeen LED was on and the current consumption was about a good 30mA higher....total 270mA @ +12Volt... also entered the $SURVEY command and the unit started to find its position......It is quite tricky the timing when you want to enter a new command....!!!The unit is doing the SELFSURVEY for a good 8 hrs....right now ....... and the 10MHz RF output seems to me also OK compared to my Rubi GPSDO. / True-Time XL-DC / but need more time to chk the ADEV plot.What other input command is important to enter in order to obtain the max precision from this little gadgetI want to use the unit only as a board the same location and just starting from a PC via RS-232 port and let is run for the next 200 years....Is it any chance to use a PIC to this unit and after power-up the PIC going to load the $PROCEED msg and then it,s going to work.....Sorry about the to many question .......Cheers, Ernie.

author: UglySteve
author_rank: Contributor
timestamp: February 12, 2018, 03:52:24 pm
content: Ernie,Here is a link to the Packrat page for this GPS. I used this as a guide, along with this page, and used the software from the page. Look at the PDF file.http://www.packratvhf.com/index.php/technical-articles/160-gps-receiver-projectAlso, you should not have to try and type a command between data lines coming from the gpsdo. just type the command. The command can look broken up on your screen, the complete command still gets to the gpsdo.Steve

author: Ernie
author_rank: Newbie
timestamp: February 12, 2018, 07:15:03 pm
content: Steve,Many thanks.....Brgds Ernie.

author: Squiddaddy
author_rank: Regular Contributor
timestamp: February 17, 2018, 10:18:04 pm
content: I finally got an antenna and got it hooked up to mine. Mine was stuck in wait state 19 for the longest time. I finally typed in $SETPOS with coordinates I got while playing around with a NEO-7M, and got it into state 1, recovery. Then it locked in state 0. Running a $SURVEY now.Man, the 10MHz on my Racal Dana 1992 says it's 10,000,000.009! That counter is very accurate for it's age, and I haven't touched it!Can't wait until I get an accurate survey and get it settled in.Now, like the rest of you, I need to get a case and a micro to control it.

author: texaspyro
author_rank: Super Contributor
timestamp: February 23, 2018, 03:59:58 am
content: Lady Heather v6.0 Beta for Windows is here. It talks TruePosition...https://www.eevblog.com/forum/metrology/lady-heather-v6-beta-for-windows-exe/msg1434005/#msg1434005

author: Squiddaddy
author_rank: Regular Contributor
timestamp: February 24, 2018, 04:51:56 am
content: Has anyone else tried to use a USB-TTL adapter to talk to the trueposition??I could not get it to accept the $PROCEED from the TTL port. I can see the TX led blink on the adapter.Works fine from the RS232, but when I disconnect that and connect TTL to the 15 pin header, no luck.Connected TX on the adapter to pin 3, GND to pin 5, and RX to pin 7. Just get the BOOT message.In order to use an arduino, I guess it will need to be 3.3v also?? The board is probably not 5v tolerant.I would like to control the board from an arduino and an lcd.

author: LazyJack
author_rank: Frequent Contributor
timestamp: March 27, 2018, 04:01:51 pm
content: Yeah, I just tested my new TruePosition with my Racal Dana 1992, amazing performance from that counter. Mine has the highest precision oven oscillator option, and it was off by 0.23Hz. God knows when it was last calibrated and what happened to it until i got it on ebay.The GPSDO works a treat, I simply used a TTL-USB serial adapter to talk to it and a $2 GPS antenna on my window sill. However, not the most sensitive GPS receiver it has. Needs some time to lock. I will need to find a better view to the sky.

author: BravoV
author_rank: Super Contributor
timestamp: April 17, 2018, 01:58:35 am
content: What is the antenna supply voltage for this board ? I assume its the standard 5 Volts ?

author: bingo600
author_rank: Super Contributor
timestamp: April 22, 2018, 07:13:48 am
content: I just got one of the "Old" boards , Bliley osc.Wanting to add NTP to it , i need to find 1-PPS to route to my Linux board for NTP 1-PPS.I'd prefer to get it before the conversion adaptation to 50Ohm on the coax out.Anyone having some info about that .... Before i start to poke around./Bingo

author: cdev
author_rank: Super Contributor
timestamp: April 29, 2018, 03:22:10 am
content: LazyJack, you need to get one training session (at its final location) with a really good sky view and then it seems to improve after that. First time attempting to train it as you can see from the beginning of this thread, I thought it was broken. Other GPSs often act that way too. Now, post training, mine works fine with an indoor antenna on my window sill.

author: BravoV
author_rank: Super Contributor
timestamp: April 29, 2018, 09:05:22 am
content: Quote from: texaspyro on October 05, 2017, 03:52:39 amJust noticed this note, so this one should be fine at 12Volt instead of 15Volt mentioned by Packrat's documentation ? As it mentioned there are two board types, 12Volt and 15Volt.

author: CJay
author_rank: Super Contributor
timestamp: May 03, 2018, 08:28:51 pm
content: Quote from: texaspyro on February 23, 2018, 03:59:58 amJust wanted to say thanks John, it's working really nicely here with my Trueposition but wow, what a lot of information it provides, time to sit down in a quiet corner and do some reading...

author: JamesWillis
author_rank: Newbie
timestamp: May 04, 2018, 05:10:58 pm
content: I have two of the Trimble boards, one each of the two boards on the pakrat blog. Both have been working using the Arduino software with the display option. Two problems however. 1. I cannot seem to command a survey, thru either the arduino TTL hookup or the RS 232 port and 2. While the longitude is output correctly when the GPS is running, the latitude is not correct, being off by .6 (90.6 vs actual 90.0).Any help would be appreciated.

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 05:21:21 pm
content: Quote from: JamesWillis on May 04, 2018, 05:10:58 pmJamesWillis, sorry, I can not offer any help.Its just you said you have both types, what voltage do you use to power them both ?Is it 15V for older and 12V for newer one as Packrat document stated ? or both at 12V ?

author: texaspyro
author_rank: Super Contributor
timestamp: May 04, 2018, 05:29:50 pm
content: Quote from: BravoV on May 04, 2018, 05:21:21 pmAs far as I know they are all 12V boards, not 15V. This has been measured in the original equipment the devices were pulled from. I have 3 different versions of the board and they all run on 12V. Where did this 15V value come from?I suspect it was pulled out of a flying monkey's butt.

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 05:48:03 pm
content: Quote from: texaspyro on May 04, 2018, 05:29:50 pmAh ... thank you.More like rat's butt I guess, as its came from the popular Packrat documentThis photo is from this Packrat PDF doc ->http://www.packratvhf.com/attachments/article/160/A-Packrat-GPS-Receiver-Project.pdf

author: texaspyro
author_rank: Super Contributor
timestamp: May 04, 2018, 05:56:40 pm
content: I do know that 20V will kill the thing...I had a 12V power supply crap out in the middle of a run and start shoving 20V into the beastie. Pop, fizz, magic smoke.

author: BravoV
author_rank: Super Contributor
timestamp: May 04, 2018, 06:02:18 pm
content: Quote from: texaspyro on May 04, 2018, 05:56:40 pmOk, good to know.All this time I've been running it at 12V, its just I'm curious as why they put that 15V for the older version while 12V for newer one , typo maybe ?Btw, you said you have 3 versions, how much different on the board and components among them ?My board according to Packrat is older one (my board photo attached few post counts back), but has 2016 date code at few ICs.

author: texaspyro
author_rank: Super Contributor
timestamp: May 04, 2018, 06:05:43 pm
content: I didn't look at the parts on the odd-ball board in detail, but the power connector was a different style.

author: JamesWillis
author_rank: Newbie
timestamp: May 04, 2018, 08:18:23 pm
content: Both boards have been on 12V. Could someone please describe what I should be seeing on the LCD packrat Ardunio display when I ground the #3 input on the arduino to command a survey? I do not see anything happen when I do this. Grounding the #3 input toggles the display between several different pages. Both boards also give the same incorrect latitude 39.68 N when my other devices (iphone, Garmin) give the same correct 39.00 N. Do not know if this is an error in the Packrat Arduino firmware or if it is a "feature" of the Trimble GPS board. One other issue is related to the RS232 input/output port. I tried using a USB to RS232 dongle and the computer, using a terminal program, could read the output from the GPS board, but I could not get the RS232 output to command the GPS. When checked with a scope, the dongle was outputting the correct levels and serial data, but these were damped way down when the RS232 output was connected to the GPS RS232 input pin #3. Yes pins 4 and 5 were jumped at the time. Any ideas would be appreciated.

author: BravoV
author_rank: Super Contributor
timestamp: May 05, 2018, 06:29:00 am
content: Mine works straight away without problem once I hook up with RS232 from my PC, although I used PCIE serial port card, not thru USB.Are both boards behave like that ?Btw, did I miss anything as you keep mention Trimble GPS board instead TruePosition, I thought they're different products ? CMIIW

author: mark03
author_rank: Frequent Contributor
timestamp: May 19, 2018, 12:37:38 am
content: Does anyone know offhand what the 12V power consumption is on these boards? I have one I'd like to mount inside an Extron 6 300MX, and I'm wondering if I can piggyback onto the existing power supply (with a linear regulator for 17->12 volts).EDIT: Answering my own question, about 0.5A at cold start, and 0.25A after OCXO warm-up. This is with nothing connected to the board except power. I have the older (Bliley) design.

author: Squiddaddy
author_rank: Regular Contributor
timestamp: May 23, 2018, 12:38:39 am
content: Yes, mine draws .5 at startup, and about .190 all warmed up.

author: mark03
author_rank: Frequent Contributor
timestamp: May 23, 2018, 02:31:33 am
content: I decided to replace the built-in supply with a Mean Well (that name cracks me up every time) unit, 15W. Load testing the original supply with an HP 6632B, the voltage sank to ~ 11V @ 0.75A and switching noise also increased markedly. The new supply is nominally 15V, adjustable to 16.5V, which will provide enough headroom for some RC filtering followed by linear post-regulation.Edit: Oops, just noticed (two months late!) that I posted this in the wrong thread. Should have been here:https://www.eevblog.com/forum/testgear/diy-10-mhz-distribution-amplifier-requirements-gathering/which is the chassis I'm planning to use for my Trueposition GPSDO.

author: mark03
author_rank: Frequent Contributor
timestamp: July 16, 2018, 12:05:46 am
content: I just fired up my Trueposition board this weekend. Like someone else reported, I could not get mine to leave wait state 19 and start picking up satellites until I issued a $SETPOS command with my lat/lon/elevation obtained from another GPS. At least, it wasn't making any progress after 1-2 hours with a good antenna. It's likely that some kind of factory reset would have worked also, but I was too chicken to try that.Now it is seeing between 4 and 8 satellites pretty consistently with one of those bullet-shaped timing antennas placed next to a window. Next step is to mount the antenna permanently in the attic.It does seem to bounce between status 0 (normal) and 1 ("acquire"?) quite frequently. Not sure if this is something that can be resolved with a better signal.I also have the Lady Heather beta version v6.05 running with it (thank you texaspyro!). It does not seem to track the EFC tuning voltage by default, or maybe I just need to read the manual? Anyway, this has me leaning away from the STM32 controller option and towards a Raspberry Pi + LCD display running LH instead. Is the touchscreen functionality of LH documented anywhere? I am trying to decide whether I really need a touchscreen on the LCD for this project...

author: mark03
author_rank: Frequent Contributor
timestamp: July 16, 2018, 08:47:01 pm
content: Do we know what the difference is between status 0 (normal) and 1 (recovery or acquire)? In Lady Heather, when the board bounces into status 1 it is not clear whether this is considered holdover or not. Here's an example where it was in status 1 for the middle part of the plot, corresponding to the wild swings in the EFC voltage (green trace):I can't imagine the 10 MHz remained locked during this time, with the huge EFC spike, although LH considers the total holdover time to be zero seconds. Possibly a bug?In any case, I had ~ 5 hours of solid lock before this happened, and nothing obvious to explain why it happened when it did. I.e. plenty of satellites, good CNR values, ...

author: texaspyro
author_rank: Super Contributor
timestamp: July 16, 2018, 09:04:54 pm
content: Quote from: mark03 on July 16, 2018, 08:47:01 pmAnt time the state is not 0 (normal) , Heather flags that with the red line at the top of the plot. State 1 is not an actual holdover. There is a message that shows the holdover time during actual holodver events. There is no documentation that elaborates on what the states actually mean. Most of the info on these receivers comes from what limited manufacturer data is available and from reverse engineering and scientific wild ass guesses.The EVAL values comes from the EXTSTATUS message. Again, no documentation what it means. It seems to be noisy during surveys and fairly stable during normal operation.

author: mark03
author_rank: Frequent Contributor
timestamp: July 16, 2018, 09:32:37 pm
content: Quote from: texaspyro on July 16, 2018, 09:04:54 pmHmmm. If the EFC voltage trace is correct, then state 1 may be considerably worse than a brief holdover... because in the latter case you'd expect the controller to keep the OCXO on a fairly even keel while the GPS timing is missing, whereas here it seems probable that there is a major frequency deviation at the 0->1 state transition. This assumes there is no other mechanism to explain why a sudden jump in EFC voltage would be needed---I can't think of one. Unless the OCXO itself is "hiccuping"... for lack of a better term?I guess it's a good reason for running >1 unit, to investigate questions like this.

author: RoadRunner
author_rank: Frequent Contributor
timestamp: July 18, 2018, 04:45:24 pm
content: My distribtion Board and Enclosurehttps://www.eevblog.com/forum/oshw/open-source-trueposition-gpsdo-isolated-distribution-board-and-enclosure/

author: texaspyro
author_rank: Super Contributor
timestamp: September 16, 2018, 06:03:10 am
content: Quote from: texaspyro on August 20, 2017, 05:07:07 pmWell, hell may have left the gate open and Heather got in and did some tweaking. Heather has a feature to draw text using scaled vector fonts (instead of the normal fixed sized dot matrix fonts). Vector fonts were originally added so that if you had a very big screen and the largest dot matrix fonts were too small... they can be scaled up to 500%. But they can also be scaled down as low as 50%.Sparkfun now sells a 3.5" 480x320 LCD touchscreen hat for the Ras PI ($25), so I tweaked up the screen formatting some and added 480x320 and 320x480 modes and also added an option for rotating the drawing 90 degrees. This seems to work better than expected. I have the Sparkfun board on order... I'm a bit worried that the 16 MHz SPI interface might be a bottleneck.

author: mark03
author_rank: Frequent Contributor
timestamp: September 17, 2018, 01:13:49 am
content: Cool! Please post again and let us know how it works once you've had a chance to test. I was tentatively planning to mount a Pi running Heather in my distribution amp enclosure, but was put off by the choice between an ugly HDMI connection, or the parallel connection which uses up every last GPIO pin on the header. SPI would be much more tolerable if it works.

author: texaspyro
author_rank: Super Contributor
timestamp: September 17, 2018, 01:27:31 am
content: Quote from: mark03 on September 17, 2018, 01:13:49 amThe official PI 800x480 screen uses it's own LCD interface connector and works quite well.

author: Towger
author_rank: Super Contributor
timestamp: September 17, 2018, 07:20:38 pm
content: Have you looked at the ability to generate timecode (LTC/SMPTE) from Lady Heather?I believe there are already libraries for the Pi. It could be used for driving studio clocks, giving a nice clean/large time display.

author: texaspyro
author_rank: Super Contributor
timestamp: September 17, 2018, 07:52:55 pm
content: Quote from: Towger on September 17, 2018, 07:20:38 pmI looked into generating IRIG time codes, but there is too much system dependent stuff to make it practical. It could possibly be done for a specific system / configuration, but doing it in a generic way is not really practical.Heather's full screen clock displays (ZC or ZW commands) makes for a nice wall clock display.

author: cdev
author_rank: Super Contributor
timestamp: September 21, 2018, 01:24:13 am
content: You people who are using it with LH absolutely must use its nice stabilized 1PPS as the PPS for a locally running copy of chrony, NTPD etc. Its nuts not to. The GPSDO has the potential to be substantially more stable PPS than a plain old GPS. A GPS is likely to stairstep within a range of around 25 or 30 nsecs. A very short amount of time but still it matters if you are doing scientific experiments right on your Pi. (Anywhere else it wont matter, however, the network latency will eat up a small but significant chunk of that accuracy, because of the way RPI's network card is done-to shave off a few bucks, via its USB bus.) Other slightly less inexpensive SBCs with "real" ethernet cards that pair them with the nice fast GPIOs would be a better choice for REALLY precise timing use with a network because of the USB latency of the Pi's network card issue. Other users here probably know a lot more about this than I do.However, we're splitting hairs here because all the differences usually only amount to less than a millisecond at most on a lightly loaded machine thats adjusted to minimize its network latency. You will still have a Stratum 1 time server either way. Switching from a generic GPS PPS (some are quite good) to a GPSDO ('smoothed out') PPS matters a lotbut only to other applications running right on the same machine or via some very low latency link (direct connections or fiber optics - light would be two ways to do it) that can take advantage of it accuracy directly.You can see the jitter and the effect of different changes using the 'ntpq' command.

author: texaspyro
author_rank: Super Contributor
timestamp: October 04, 2018, 05:42:48 am
content: I got in the Sparkfun LCD. It does work, but has some nasty gotchas that make it very difficult to use with a PI. The main issue is that dialog boxes do NOT scale to the small screen size. That means whatever is towards the bottom of the dialog box (like CANCEL / ACCEPT) cannot be accessed! Also once the terminal window gets more than a few lines on it, you cannot see any more output or what you are typing.Finally, the touchscreen hardly works with user / X11 programs. Maybe if you tap an item a couple dozen times it will register a click. Not sure what is going on here, the touchscreen seems to work OK with Raspbian generated stuff. If using a mouse, the mouse pointer lags behind mouse movement quite a bit.That said, except for the touchscreen issues, it does work with Heather. No real issues with the screen update rate.

author: texaspyro
author_rank: Super Contributor
timestamp: October 04, 2018, 06:12:55 am
content: I did some more testing with the touchscreen... if you hold the stylus down on an item for around 2-3 seconds it registers the click... makes typing on Heather's on-screen keyboard painfully slow, though.

author: tkamiya
author_rank: Super Contributor
timestamp: November 17, 2018, 04:55:26 am
content: Just bought 3 TruePosition board for cheap. I'm joining this thread. My current goal is to have it boxed up with Adouino and display, and add distribution amp to it at later date.Has anyone tested its frequency stability short and long term? I do not have an ability to test for this myself.

author: tkamiya
author_rank: Super Contributor
timestamp: November 17, 2018, 05:05:58 am
content: I'd like to modularize (is that a word?) my construction. But something like this is an unknown territory for me. Being self-controlled ovenized oscillator (that heats up), how do I manage cooling and venting?I've seen commercially made unit with vent holes only. Its manual specifically says convection provides enough cooling that install it vertically and NOT to have direct fan air.I've also seen DIYer install boards into a case with various insulation materials, and pretty much seal it.Any advise here from experience would be great.

author: texaspyro
author_rank: Super Contributor
timestamp: November 17, 2018, 05:22:17 am
content: Quote from: tkamiya on November 17, 2018, 04:55:26 amNote that for tau<50 secs the readings are dominated by the TICC's 60 ps resolution.Also, the plots have a (52 second) display averaging filter applied. The actual reading span values are around twice what is shown in the plot labels.

author: cdev
author_rank: Super Contributor
timestamp: November 17, 2018, 04:28:53 pm
content: This is a new one, and it looks quite a bit better !Is that right?Quote from: texaspyro on November 17, 2018, 05:22:17 am

author: tkamiya
author_rank: Super Contributor
timestamp: November 17, 2018, 04:36:36 pm
content: Is it true that this particular GPS lacks sensitivity compared to more modern ones? While I can get all 8 satellites with GPSTM, I am getting 5 to 8 on this.I am little concerned that we don't know what status 1 mean.... Mine flips between 0 and 1 fairly often. If it means locking and synchronizing is compromised, it is unusable. I read TexasPro commenting it probably doesn't mean fully unlocked.

author: cdev
author_rank: Super Contributor
timestamp: November 17, 2018, 04:58:38 pm
content: Tkamiya,Mine was only 'really' insensitive at the beginning when it was still figuring out that it was in the US rather than in Japan. After a bit of time running off of an outdoor antenna it stored the data and got a minimum of five or six sats fairly consistently after that, which is enough to maintain the time with a high level of precision. Thats why they picked the Furuno timing unit which is known for that ability.Now my GPSDO (when its on) is running off of an antenna slapped on top of an AC unit, outside but underneath an overhanging roof with its metal gutter. It works fine there. It also works okay (not great, but it maintains lock) with the antenna indoors as long as the antenna has a good ground plane.No, its not as sensitive as my Skytraq GPS which is much newer. That never loses lock even with a passive indoor antenna. Its incredibly sensitive.Nor is it as sensitive as my ublox GPS which is also quite new.Its probably around the same as my Mio with sirfstar III chip, a PND, a car GPS.It likes to have a good sky view if possible.Its gotten better with time, likely because it trains itself as to its surroundings, case, position, etc.I should leave it on all the time, but haven't been because mine is still not in a permanent case.I am probably going to encase it in an extron case I have, sharing the inside of my video distribution amplifier's case.That seems like the best plan for now.---------------There are some TruePosition GPSDO videos on YouTube now!The first one is by YouTube user CircuitValley who also is a user here.

author: tkamiya
author_rank: Super Contributor
timestamp: November 17, 2018, 11:15:14 pm
content: I am kind of recalling GPSTM took a while to lock first few times. So hopefully, this one will "learn" and stays locked.I have an 1U case I can use. I just have to decide if I want to keep GPS and distribution amp together or separate. Right now, I only have 5 equipment that need external sync. But this is expected to grow. I thought an ability to remember the last location was generic to all GPS....I actually have an ability to have an outside antenna but Kind of figured with shortened cable length will cancel out attenuation by going the attic route. Also, my 4 way splitter has a built-in amp to compensate for the loss.My setup is on desk and not in case. Because the OCXO gets quite hot, I didn't want to keep it running unattended. Just a bit scary. I hope to encase them in next few days. Then, I will probably interface it with Lady Heather and keep it running. I want to ultimately rack mount all of them and keep "house clock" all together.Thanks for the video. I thought the first video was yours.... no?

author: cdev
author_rank: Super Contributor
timestamp: November 17, 2018, 11:21:08 pm
content: GPSDOs have ovens so they all get warm.They have to. Mine gets toasty warm, but not really hot. Not painful to touch. If its working properly it should have a stable frequency. Its going to keep the oven at whatever temperature it needs to to keep that frequency where it needs to be. It has to be hotter than any normal ambient temperature, otherwise it wouldn't have any ability to go lower below that even if it turned the oven off. So it has to be quite warm.As far as sensitivity, if you are using a patch antenna, make sure it is on a flat, horizontal conductive ground plane, as large as is practical.A CD/DVD is around the minimum size that I think is enough. But a little bit larger than that is even better.

author: tkamiya
author_rank: Super Contributor
timestamp: November 17, 2018, 11:45:16 pm
content: No, but I don't think this kind of "Bullet" antenna depends on ground plane.

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 12:28:43 am
content: Do you know what's inside that particular bullet? If it uses a quadrifilar helix, no it doesn't need a ground plane and perhaps could even be mounted sideways and still 'work' kinda sorta. Thats a big advantage of them. They work in any direction. They will reject the first order (odd) reflections coming from any direction.Your photo looks like it should be rotated 90 degrees to the right.You can mount it to the inside wall but your GPSDO would likely work much better if you put it outdoors and away from metal things.Wood also will attenuate the signals a fair amount in that direction and you likely will be able to see it in the pattern built up over time, All the satellite in that direction, a good chunk of the sky, will be weaker.if you use software (like rtklib or lady heather) that records SNR in a manner you will see this- Both will show you the polar plot with signal strength.QFH antennas can be surrounded with metal junk and still work okay. But they do best just on a pole that supports them from below.If you use a 90 degree elbow, if you don't put a common mode choke ferrite bead right where the feedline leaves the antenna you may get a lumpy pattern from the transmission line going off to the side.This is a useful resource to see what happens:http://gpspp.sakura.ne.jp/anteva/anteva.htm

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 12:32:17 am
content: Would you or someone else tell me what I2C address Pakrat code is expecting? Not all LCD boards use same address and source is not available.

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 12:38:42 am
content: It is mounted up-right. For some reason, when uploaded, it looks sideways.I have no idea what is inside..... I was curious but it is glued shut. I doubt it is a kind that references earth as none of the metal screws touch the inside.

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 12:46:36 am
content: Your camera must have attached the wrong metadata to the image, if you could rotate it and re-upload it that would be good.Don't worry, if you can find a spot where your GPSDO can simply get three or more sats 90% of the time you should be more than okay as far as time and frequency accuracy. Even less than that will almost certainly work okay, once its gotten a decent start.The beauty of a good GPSDO is that it should be able to maintain a good time and 10 MHz signal even with a fairly sketchy signal if it needs to, once its had an opportunity to do its survey and it knows its stationary.

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 12:49:17 am
content: I hope my house doesn't move.... I am in Florida USA where it is not that uncommon for sink hole to develop under your house!

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 12:55:50 am
content: Everything on Earth is moving, and its complicated.Lots of different things are going on. Where I live, there was a huge glacier which finished melting around 10,000 years ago and because land farther to my northwest is now going up, freed of all that weight, where I live is now apparently going down, just a little bit. And of course, 'sea level' is rising too, an arbitrary water level of the oceans, not meaning that mountains are getting shorter, just the water level is rising. And of course there is plate tectonics.Sinkholes might be happening because of removal of a supply of water or pumping of water out of an aquifer? Ingress of fresh water likely keeps the ground up to some extent, even though that sounds a bit strange. If the ground is porous and the water that supported its volume was removed, some parts of it might get smaller. Just a guess.I'm sorry, I don't know what i2c address the Packrat Arduino code wants for its LCD display because Ive never used that code personally.

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 01:13:48 am
content: I will probably end up writing my own code anyway, but I thought I'll give Pakrat a try. It seem to be well received.There is a location not too far from my house where a HUGE sink hole showed up in front of a house. It swallowed a Porche that was parked there. Florida is basically a mound of sand. Pumping of ground water and torrential rain washes off sand and the result is a big hole.Eventually, I'd like to have a small LCD on GPSDO to monitor and have a connection to a PC with Lady Heather. That will be ideal. Anyway, thinks for sharing information. That university website was kind of interesting. (I read Japanese)

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 02:12:06 am
content: Now, I have Lady Heather version 6.0x talking to it.Other than yellow line is increasing, (OCXO temperature?), blue and green are horizontal lines. Some column shows number but they are unchanged. When "D mode" was 1, there was a red line in graph. (I think Texas Pro mentioned this earlier?) Is this supposed to be this way?Edit: Blue changed later on but green was still straight line.

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 04:31:52 am
content: You just turned it on. You have to let it run for quite a while. Have you done a survey? You should ask texaspyro questions about his software because I have not used it with the TP. I'm on Linux and although I have a controller its still caseless.So I have mostly spoken to my GPSDO via the command line.

author: mark03
author_rank: Frequent Contributor
timestamp: November 18, 2018, 05:16:02 am
content: Quote from: tkamiya on November 17, 2018, 04:36:36 pmI'm still concerned by this as well. In LH I have a trace (green in the screen grab I attached on the previous page) which purports to show the OCXO EFC voltage. We don't know if that is what it is, but it does stay relatively flat until one of these status 1/0 events happens, whereupon it makes a huge step and oscillates like crazy as it settles back down. Whether this is holdover or something else, it looks pretty serious to me, but I don't have a second unit, nor a TICC, that I could use to evaluate the effect on the output.I haven't built my board into an enclosure yet either. I have an Extron dist amp for this purpose but mine is a slightly less tall version (ADA 6 300MX) with essentially no room on the back panel to place the GPS antenna connection. (The rear PCB occupies the entire back panel---no room to sneak past it---and there aren't any unused portions of the PCB either.) So that is a bit of a hassle... I will get around to it, once some higher-priority projects settle down

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 12:59:54 pm
content: The signal quality is much more important in the timing and surveying contexts than it is for locating oneself within the typical non-RTK GPS spec's level of accuracy.One good way to analyze the quality of a signal from your antenna is to get any RTKlib-capable GPS (there are Ublox M8N copies on ebay for under $20 which work with it) and attempt to do either RTK with a stream of local, free base station data (such as a station on the CORS network of stationary receivers of known locations) if one is available or one of the several kinds of PPP. (accurate positioning using asinglereceiver over time to resolve the ambiguities)Doing this one can get a fairly good idea of how good in terms of multipath any given GPS signal is. (so you are really testing the antenna/location combination)Also, although LH's polar SNR display is not quite as much data as RTKlib with its chart of signals and residuals and cycle slips, its still a huge help, because one can see in one glance where in the sky the problems are. If a portion of the sky that would normally have arcs going across it has none or just a few sketchy ones after a day or so of capturing data, you'll know that your antenna could be moved - to get a better sky view, and should be.For example, a tree or building blocking satellites can often be seen in the polar plot as an area without signals.Ublox's-ucenter also can give you a similar body of info.Despite the lack of manufacturer data, when one looks at the large number of settings and configuration parameters we already do know about, its a fairly rich set of info.

author: pigrew
author_rank: Frequent Contributor
timestamp: November 18, 2018, 01:14:08 pm
content: When in state 1, I have noticed the reported control voltage to vary more than when in state 0. I have my antenna indoors, so only get 4 or 5 SV normally. I don't know if it is the lack of good reception, or an issue with the control loop, that causes it to go into state 1. I don't have time to check the data presently, but you should be able to calculate the frequency deviation during state 1 by multiplying the control voltage shift by the OCXO gain.

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 01:47:53 pm
content: Timing antennas have a pattern thats optimized for the higher satellites, (typically the ones with less multipath).If one is put outdoors with a good sky view it should do well with the TP.tkamiya, you definitely would have far better results if you put your antenna outdoors. Or even just moved it away from that beam to the side. Assuming the outdoors is behind and above where its now, that beam is between it and almost the whole sky in that direction.Its a miracle that you're getting a fix at all with it like that.

author: tkamiya
author_rank: Super Contributor
timestamp: November 18, 2018, 02:37:04 pm
content: I don't have a data to show you, but my current antenna works well feeding a pair of Nortel GPSTM. I get full lock and decent SNR covering most of the sky. I get a thin occluded area. I can put up an outside antenna but didn't have a need up until now. I might just do it for purpose of testing this board.Once I put it in a case, I can run 24x7 and get a decent survey. I don't want a heat source running unattended.

author: cdev
author_rank: Super Contributor
timestamp: November 18, 2018, 02:41:46 pm
content: If you don't feel its safe by all means, wait until you do.Get a good case for it. Its worth the time and energy putting it into a nice case. I would also either use a separate power supply or take care to not have the heat producing voltage regulators inside the case with the OCXO.Their heatsinks if they need them should be mounted on the outside.Take care to put it somewhere thats thermally stable. My GPSDO is not being used right now because i haven't put it in a permanent case yet.I plan to use an Extron video distribution amp which I have which is ideal. It has a big case and lots of room which has additional cutouts which can support four more BNC connectors. This particular video distribution amp also has a "TTL" channel which appears to work fine with the 1PPS. So I should end up with two devices in one case, the GPSDO and the VDA, which will give me an additional 9 10 MHz outputs and 3 1pps outputs that can either be switched on or left off.You should post the temperatures its giving you. There are a range of different boards, if your temperatures are abnormal somebody here could probably tell you. Mine (with a Bliley NVG47A1282 are usually in the 40s-centigrade) but as the ambient temps can be higher with the oven still remaining functional, the oven's operation is likely over a pretty wide range of temps. Some people here have had temps that are more than 10 degrees higher.

author: rbm
author_rank: Regular Contributor
timestamp: November 19, 2018, 09:09:45 am
content: Quote from: tkamiya on November 18, 2018, 12:32:17 amThe Packrat software is expecting a PCF8574AT-based I2C display at 0x3F. A Sainsmart LCD will work; a Ywrobot display will not because it and many other 16 x 2 LCDs use the PCF8574T backpack instead. They listen at 0x27. If you have an I2C LCD which you can swap the backpack for the right one, you should be good to go with Packrat SW.

author: rbm
author_rank: Regular Contributor
timestamp: November 19, 2018, 09:19:42 am
content: Quote from: tkamiya on November 18, 2018, 01:13:48 amI am working on modifying code that was published by Ben Hall, KD5BYB over on time-nuts. He distributesthrough his web site. His code depends on a 20 x 4 LCD, rather than a 16 x 2 one. I have the same aspirations as you, to have RS-232 connection for LH as well as an Arduino-based controller, and to build it into a box containing a distribution amp.

author: tkamiya
author_rank: Super Contributor
timestamp: November 19, 2018, 03:05:47 pm
content: Thank you! That is very helpful.I have 20x4 but the case intend to use is 1U. So I just ordered 2x16.I'll probably roll my own knowing nothing out there fits my need exactly. My plan is to make my GPSDO independent with minimal control and display to boot. Then for the rest, use LadyHeather. I am not sure now, if I want to include distribution amp. Making it in a separate box will allow me to change just the timing device and not remake the whole thing. I'll sit on this idea and see what else comes up.We should keep in touch then.

author: tkamiya
author_rank: Super Contributor
timestamp: November 21, 2018, 01:38:33 am
content: I decided to start with a minimalist system.The TruePosition board and Aduino (the smallest one) on a raw PCBMeanwell power supply and 16x2 LCD. (the one on photo is NOT)Antenna input10Mhz output1pps outputEnough coding in Aduino to generate "$PROCEED"Serial portThis should be a nice development setup.This case is some kind of telecom equipment and had a long haul interface in it. All of that was stripped out. I often visit surplus dealers and buy cases when re-usable ones show up.

author: cdev
author_rank: Super Contributor
timestamp: November 25, 2018, 03:23:23 am
content: Does anybody know the manufacturer and part number of the plugs that connect to the large two rowed connectors on the True Position and UCCM GPSDO boards?In the pic below: I mean the two big multiple connectors on the left.UCCM GPSDOs typically have one, the TruePosition board has two.

author: cdev
author_rank: Super Contributor
timestamp: November 26, 2018, 02:47:54 am
content: Found this while looking for videos about the GPSDO

author: tkamiya
author_rank: Super Contributor
timestamp: November 27, 2018, 05:31:00 am
content: I am a bit confused of existence of RS232C and TTL ports. As I understand it, they are either-or proposition controlled by a jumper between pin 4 and 5. When jumped, it enables RS232C. When open, it enables TTL ports.My initial plan was to use both simultaneously. I wanted the unit to start up and run. When needs arise, hook up a PC via RS232C. I guess this is not possible.Pin 6 is curious. RX only??

author: Miti
author_rank: Super Contributor
timestamp: November 29, 2018, 12:50:11 am
content: Where do you buy one of these?

author: tkamiya
author_rank: Super Contributor
timestamp: November 30, 2018, 04:06:57 pm
content: Some progress.....Put one of my board into a metal case with its own power supply, and added an Arduino (for future use). The case was some kind of telco equipment in its former role.As is, it works nicely with Lady Heather but does not have an ability to work independently. I have not decided how much stand-alone capability to build and how much UI to use.

author: tkamiya
author_rank: Super Contributor
timestamp: December 02, 2018, 07:46:46 pm
content: OK, now that it has been running for a few days, it is starting to stabilize.Since I have 3 of these boards, I wonder if it is possible to somehow take an average? Of course not because there is such need, but because I might be able to complicate it unnecessary a bit more?Right now, Arduino is there but not hooked up. Lady Heather actually sends "$PROCEED". I really don't feel like writing a software so I might keep it like this for a while.Writing software - feels too much like work....

author: cdev
author_rank: Super Contributor
timestamp: December 02, 2018, 07:57:02 pm
content: 'Average' of what? Compared against what?

author: cdev
author_rank: Super Contributor
timestamp: December 02, 2018, 07:59:21 pm
content: The usual suspects.Quote from: Miti on November 29, 2018, 12:50:11 am

author: tkamiya
author_rank: Super Contributor
timestamp: December 02, 2018, 08:38:23 pm
content: Quote from: cdev on December 02, 2018, 07:57:02 pmWith two, I can show which one is running faster than the other. There is nothing to base my decision on which one is more accurate. With three, I can average. Unless one is an obvious out-lyre truth is likely to be in the middle somewhere. It's average of all 3. Compared against each other.

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 02:17:10 am
content: How could one show if one is running 'faster'? How do you derive that info? (Lady Heather? But it connects to the GPSDO via the UART?)There are still major gaps in my knowledge here.Even the largest excursions of jitter that I know must be occurring are still so small I haven't figured out how to visualize or measure them yet.Maybe get a really really good free running oscillator like a rubidium frequency standard that had recently been calibrated - using a better frequency standard than itself, and compare them to that?I would need some hardware which I don't currently have, plus the oscillator, to do that.

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 03:14:11 am
content: I had both GPSDO connected to a scope. Synch was on channel 2. Over few hours, it moved with some recognizable amount. Since Channel 2 was steady (trigger) and channel1 was moving to the left, I could deduce frequency on channel 1 was lower.This "just trust us. it's accurate" thing bothers me. I want to quantify it.I know there is a way to do this on counters, and I have one that is capable. I have a significant lack of knowledge. This is an interesting challenge. I have a few "signal analyzer" type equipment and pen chart (really pen and paper). My goal is to keep logging short term changes for long term.I understand rubidium does NOT do better than OCXO on short term drift. Maybe we just have to buy us Cesium clock for Christmas.

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 03:52:50 am
content: How long has they been on, and were they both connected to the same antenna?How do you divide the signals?Do you mean one 10 MHz output shifted it's phase relative to another?

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 04:07:10 am
content: Antenna is in attic. Short Andrew Helix connects it to 4 channel Spectracom distribution unity gain amp. (so basically no signal loss) Port 1 goes to Nortel GPSTM. Port 2 goes to another GPSTM. Port 3 goes to this board in discussion. Port 4 is terminated. Earlier, I posted pictures of my setup.Yes that's exactly what I mean. Since signal 1 is a triggering signal, it is always on the same spot. Signal 2 is what the signal was happened to be doing when 1 got triggered. That signal moves to left. Wavelength is shortening := frequency is higher.My local cal lab is not able to cal the time standard. I'm going to have to find a way to get this done. With too many assumptions and supposed-to-bes, I am getting confused.

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 04:40:26 am
content: It should become stable after the GPSDO has been on for a while. I would connect one to Y and one to y, so you had lissajous figures. Since both are getting the same signal the phase shouldn't shift after its finished warming up. This may take a day or so but if you are getting a decent signal not that long.Thats a nice power supply you are using in your unit. Do you mind if I asked where you got it and also if it generates a lot of heat? I want a dial 12v 5 volt unit in a low form factor.

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 06:03:54 am
content: Problem with Lissajous is you can't tell which one is ahead. So I briefly tried it and switched back to y(t).The power supply is a little unit I bought on Amazon. "Mean Well" RS25-12. 12V 2Amp unit and voltage is actually adjustable. 8 dollars I think. I think the meaning of the words kind of got lost in translation though. In the box, I also have DC/DC converter from Amazon for 6 bucks. I did this with intention of feeding as little voltage as possible to the Arduino board. It has a 3 terminal onboard regulator and it and the CPU gets pretty hot if you feed 12v directly. I might just take that out because I don't need it with Lady Heather.It's hard to tell from from images but Mean Well directly attached to the bottom cover which is 1.5mm aluminum. With few hours of running I could not tell location of the power supply by touch alone.Funny you are asking me these question because I was JUST thinking about the same thing. I don't like external power supply solution, so that was OUT. But my Oven is running 50 degrees C. I doubt very little external heat reaches the element.What I'm going to do is to purchase a very short rack, in size of foot rest, and stick it under the desk. I can see quite a bit of activity when I open my door and when A/C kicks in. So its current location is not ideal.

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 01:27:46 pm
content: I left the comparison running overnight. Phase shifted for about 60 degrees and stopped. Lock seems to be solid as well. Total of 121 seconds of hold over, which I think happened in earlier part of test.Few nights ago, I've found a symmetricon distribution amp with redundant input on eBay. Port A is a master, and if it fails, switches to port B. Bought that. I think it will be a very nice overkill for my top secret government lab.

author: LapTop006
author_rank: Unknown
timestamp: December 03, 2018, 02:01:50 pm
content: Quote from: tkamiya on December 03, 2018, 01:27:46 pmI saw that one go past.Quote from: tkamiya on December 03, 2018, 01:27:46 pmThat sort of thinking is why I'm building my own custom pods for the Spectracom 8140 distribution system.

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 02:07:29 pm
content: That's what I'm using now: Symmetricon 8140. What kind of customization did you do on remote modules?

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 02:15:38 pm
content: The Extron video distribution amps will amplify 3x10 Mhz (R,G+B) per output as well as a sync "TTL" (1PPS) signal.Mine works well with the GPSDO 10 Mhz fed into one of the three channels and the PPS fed into the "S" So that gives me three 10 MHz outputs and three 1PPS outputs.I have not tried splitting the 10 MHz to send to all three channels (I will probably use a CATV splitter to do that) at the same time although I don't see any reasons it would not work except maybe the output being lower.Its cheap, built well and it does what's required of the job so far.------I still am undecided about how I want to handle the power for my TruePosition.The problem as I see it is the thermal influence on the GPSDO of additional heat sources in the same box.The GPSDO's own voltage regulation is supposed to be quite good. But because its a valuable and fun piece of gear for me, I want my case implementation to protect it as best as I can and provide an optimum thermal environment for it as far as stability goes. Certainly a far better one than a metal box sitting on a telephone pole.I want to use a 12v voltage regulator to protect it from overvoltage. Normally this will likely be working with just slightly over 12v so I am not expecting it to get hot, but I still want it's heatsink to be oversized and separated from the GPSDO thermally as best as I can. Ideally the heatsink would be on the outside of the box but another alternative is putting the gpsdo in a box inside of the case and doing the same with the power supply and experimenting with what fan setup would give the best balance between the various thermal factors. Having a horizontally oriented case where there isnt much convection would seem to indicate a need for venting for intake somewhere and a small exhaust fan on the power supply side.My house probably varies more in temperature throughout the year than most, intentionally, but its still nothing near as extreme as a metal box on a pole so I think I will be okay, as long as the temperature variations are within reason and consistent, I think the TP should be able to handle it with its learning algorithms.I just don't want to confuse it with additional heat.

author: CJay
author_rank: Super Contributor
timestamp: December 03, 2018, 02:36:34 pm
content: Quote from: tkamiya on December 03, 2018, 03:14:11 amI think what you need is this:http://www.wriley.com/3-CornHat.htmTexaspyro will know better than I do.However, if you want to buy me a Cesium clock, I can PM my address for delivery

author: metrologist
author_rank: Super Contributor
timestamp: December 03, 2018, 02:55:17 pm
content: Quote from: tkamiya on December 03, 2018, 04:07:10 amThis is my experience with my two UCCM units, only the drift was systematic. I do not recall now if the cycle was twice/day or every two hours... Over a period of a few minutes, one wave would shift ~+180° and then track back to ~-180° and then go back in phase until the cycle would repeat. Since I only have two units, I could not determine which one is moving, if they are both doing some sort of fix at the same time. I'm on a quest just to verify that, but one of my units does not show the same oscillator info and lock indicator in LH. I am planning on building two more units based on Lars DIY GPSDO.

author: LapTop006
author_rank: Unknown
timestamp: December 03, 2018, 03:17:52 pm
content: Quote from: tkamiya on December 03, 2018, 02:07:29 pmSpectracom, not Symmetricom.Haven't built them yet, ongoing project.The TL;DR is I'm building some multi-output pods using modern components, since I have a few pieces of kit that do nasty things on their reference input (ex, permanently terminated, or the ref is combo in/out and may reset unexpectedly) and while the pods are cheap, by the time you add shipping to Australia they stop being so.If I had a working kicad I'd have already ordered some test boards for the bias tees for circuit testing.

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 04:55:19 pm
content: I wonder what the expected lifetime of a telecom GPSDO is, and whether some GPSDO units are removed from service because of failing, or appearing to soon be in danger of failing, some calibration tests?They could probably tell exactly how much aging has occurred and how much longer they will remain in spec.Once they go outside of the range they are designed to correct I would suspect that one might need to replace the OCXO in them with an identical newer unit to get them working again.Quote from: metrologist on December 03, 2018, 02:55:17 pm

author: tkamiya
author_rank: Super Contributor
timestamp: December 03, 2018, 05:26:02 pm
content: I'd imagine our type of use and environment is not what designer had in mind. I'm sure we won't survive long in a telecom cabinet.

author: edpalmer42
author_rank: Super Contributor
timestamp: December 04, 2018, 10:13:11 pm
content: Quote from: cdev on December 03, 2018, 04:55:19 pmIf you look at the OCXO tuning voltage, you can get an idea of how much 'life' remains in the OCXO. Measure it - either with a DMM or by talking to the unit and plot it on a graph vs. time. Maybe once a day for a few weeks. Do curve-fitting and see approx. how long it will take to get to the limit.QuoteIf your GPSDO lets you change the PLL parameters you can 'tune' it to support a wide variety of OCXOs. Most don't have this ability. One I know of that does is the Trimble Thunderbolt.Quote from: metrologist on December 03, 2018, 02:55:17 pmAs mentioned by CJay, the Three-Cornered Hat measurement will help to determine what's really going on. However, to get usable data, you have to make three measurements simultaneously. That's okay. You wanted to buy more hardware didn't you?

author: cdev
author_rank: Super Contributor
timestamp: December 04, 2018, 10:33:46 pm
content: It seems from what I have read about the unique properties of the PIC on leapsecond.com that this could be done in a very affordable manner for almost nothing - using the synchronous timing function of the PIC without introducing any additional error.Caveat is I am considering a PIC hardware solution that runs using one clock (like a 10MHz GPSDO reference) and then can compare it to two additional devices. So total of three. Am I correct in that that is enough? (reference oscillator and two additional DUTs)Quote from: edpalmer42 on December 04, 2018, 10:13:11 pm

author: edpalmer42
author_rank: Super Contributor
timestamp: December 04, 2018, 11:13:44 pm
content: Quote from: cdev on December 04, 2018, 10:33:46 pmThat wouldn't give you enough data. Normally, you'd use three TICs to measure time intervals between units A-B, B-C, and A-C and then process the results. You need all three comparisons to solve the equations. One (or two) units could be a Rb standard or a good, stable OCXO.I'd be looking at something inexpensive like a PICTIC II or an updated version of it. Even that would cost $150 - $200 for three units. Anything beyond that is likely > $500. Of course, if you have or can borrow one or more commercial TICs, that makes it easier to get the three units. Higher performance is nice, but I wouldn't worry too much about that. The PICTIC II has a resolution of < 1ns. You can make some nice measurements at that level.

author: cdev
author_rank: Super Contributor
timestamp: December 05, 2018, 01:41:49 am
content: Thanks!Why is the PIC based hardware so expensive?

author: edpalmer42
author_rank: Super Contributor
timestamp: December 05, 2018, 02:14:07 am
content: Quote from: cdev on December 05, 2018, 01:41:49 amYou mean for the PICTIC II? The cost of $150 - $200 is for all three units. When it was originally designed, the goal was to keep the price <=$50 per unit, but that was back in 2010/2011. Recently the concept was updated with the creation of the TICC from TAPR. But the performance was also improved. End result is a very nice unit with a minimum resolution of 60 ps and a cost of $190 each.

author: cdev
author_rank: Super Contributor
timestamp: December 05, 2018, 02:23:50 am
content: Quote from: LapTop006 on December 03, 2018, 03:17:52 pmIf you can make a delicate conical inductor out of thin enameled wire and gently attach the wire coming out of its tip to the signal path trace you can make a great bias tee that can handle a very wide range of frequencies in less than half an hour. Because a conical inductor is not resonant at any single frequency. Try it!

author: cdev
author_rank: Super Contributor
timestamp: December 05, 2018, 02:28:52 am
content: Thats great and I'm sure its competitive with pro gear and support TAPR etc. But what if I wanted to make the exact same thing using my own PCB that I had made at OSH or similar. What would all the parts cost if I bought them from LCSC when appropriate or here, and put a lot of energy intonot spending even an extra penny that wasnt needed?And used my own Arduino clone from ebay. Or something else. Whatever worked.Quote from: edpalmer42 on December 05, 2018, 02:14:07 am

author: edpalmer42
author_rank: Super Contributor
timestamp: December 05, 2018, 03:13:34 am
content: Quote from: cdev on December 05, 2018, 02:28:52 amI'm getting confused about which unit you're talking about. But I don't know how much it would cost to build either from scratch. All the info is available for the PICTIC II. It's just jelly bean components.Most of the info is available for the TICC. I looked around, but didn't find the board layout. Maybe I didn't look far enough.You'll have to figure out your costs.For anyone playing along at home, here are the links to the PICTIC II and the TAPR TICC.http://www.ko4bb.com/doku2015/doku.php?id=precision_timing:picticNOTE: This page includes info on the PICTIC and the improved PICTIC II. Make sure you're looking at the right info.https://www.tapr.org/kits_ticc.html

author: cdev
author_rank: Super Contributor
timestamp: December 05, 2018, 04:29:57 am
content: Major cost reductions in as many essential or game changing things as possible - as well as the basics, shouldn't just be an obsession or a target, it should become a principle we promote and implement with a fervor- like we implement aggressive cost inflation now.Our goal should be making it possible for everybody to have a decent standard of living and security on as little money as possible. Not make poor peopledie earlier from stress.How many lives does it save to make taxpayer developed cancer drugs that don't actually improve on existing ones at all, more expensive by evergreening patents and eliminating alternatives? None. It kills poor people. It steals away lives and children's educations.

author: Miti
author_rank: Super Contributor
timestamp: December 13, 2018, 05:36:59 pm
content: Quote from: cdev on December 05, 2018, 04:29:57 amYoooouuuu pooooor idealistic dreamer ! That's your (our) goal but not "their" goal.

author: cdev
author_rank: Super Contributor
timestamp: December 13, 2018, 06:26:13 pm
content: I shouldn't have complained about those examples, they are NOT particularly expensive. Also, TAPR certainly, being a nonprofit, deserves to make enough money back on their projects to pay for them.So please let me apologize.

author: mark03
author_rank: Frequent Contributor
timestamp: January 26, 2019, 03:37:19 am
content: QuoteQuote from: cdev on August 15, 2017, 04:43:11 pmI realize this is old now, but it might be useful for someone googling the thread. My Trueposition is connected through a 2-port GPS splitter (Instock PD5120). The TP is on the port with the DC block, while another GPS receiver is supplying DC bias to the antenna through the other, unblocked port. My $STATUS messages always have a 1 in the third field, but so far the board appears to be working fine. I tested with Lady Heather for a few days last fall, and have now reconnected it through the splitter with a QFH timing antenna in the attic. Currently doing a 24-hour survey just in case, although it was already locked.

author: cdev
author_rank: Super Contributor
timestamp: January 26, 2019, 03:52:16 am
content: It sees that no current is being drawn so it registers 1 for that reason. In this case, telling you your DC block is working properly

author: Towger
author_rank: Super Contributor
timestamp: January 26, 2019, 06:47:48 am
content: Yes. Some GPS splitters have a '200 Ohm Dummy Load' on each output to simulate an antenna, keeping the receiver happy. The downside is they also require external power.

author: cdev
author_rank: Super Contributor
timestamp: January 26, 2019, 05:03:39 pm
content: A GPS distribution amp wouldn't need much gain, just very low noise, so could probably have a number of diodes to pull it from any of the GPSs that were on.Quote from: Towger on January 26, 2019, 06:47:48 am

author: mark03
author_rank: Frequent Contributor
timestamp: February 06, 2019, 02:15:56 am
content: Has anyone tried running their Trueposition board through gpsd, then pointing Lady Heather at gpsd instead of the serial port? I read somewhere that gpsd was read-only for clients, which I'm assuming would be a problem because LH needs to issue commands to the board. But I don't know that for sure. LH supports gpsd as one of its connection options, I just don't know if that will work for the Trueposition boards.Reason for doing this is that I'd like to use the same Raspberry Pi as an NTP or PTP server, besides running the LH front-panel status display.If the gpsd route doesn't work, it should still be possible to use the PPS signal as a reference clock, but use public NTP servers on the Internet to get "in the ballpark." Once the time is known +/- 0.2 seconds or so, NMEA is no longer required, only PPS. Still, it would be kind of nice for this to keep working during a network outage.BTW, I'm running LH at 800x480 on this 4.3" LCD with the Adafruit adapter and it works great:https://www.buydisplay.com/default/4-3-800x480-ips-tft-lcd-module-all-viewing-optl-touchscreen-display(The 5" display was too big for the front panel of the Extron distribution amp I'm building my GPSDO into.)

author: texaspyro
author_rank: Super Contributor
timestamp: February 06, 2019, 02:39:02 am
content: Heather has the ability to echo the device data to a serial port as NMEA format messages. Check out the /ek command line option.I doubt GPSD knows how to talk to the Truposition GPSDO, but have not checked.

author: mark03
author_rank: Frequent Contributor
timestamp: February 06, 2019, 02:58:20 am
content: Aha, even better! If I can abuse the /ek option to have Heather dump the NMEA messages into a named pipe instead of a serial device, I should be able to get gpsd to read from there.It would be nice to get rid of gpsd altogether, but I was planning to use chrony for NTP and it looks like chrony needs gpsd via a Unix-domain socket, or a shared-memory segment.

author: mark03
author_rank: Frequent Contributor
timestamp: February 10, 2019, 11:20:42 pm
content: Does anyone know the optimum load impedance for the Trueposition's 10-MHz and PPS outputs? 50 ohms? I suppose the fact that they're brought out to coaxial connectors would imply this, but I wanted to make sure before connecting to my modified Extron distribution amp.

author: cdev
author_rank: Super Contributor
timestamp: February 14, 2019, 05:47:59 am
content: That worked fine for me. I found I didn't even need to modify it at all. The TTL also works for 1pps.I use el-cheapo 50 ohm terminators from ebay.YMMV.

author: tkamiya
author_rank: Super Contributor
timestamp: February 14, 2019, 12:55:56 pm
content: It was also supplied with a short piece of 50 ohm coax. That implies 50 ohm also.

author: cdev
author_rank: Super Contributor
timestamp: February 14, 2019, 03:00:57 pm
content: GPS equipment is standardized on 50 ohm but since 75 ohm UHF-friendly coax (RG-6) is so much more widely available and cheaper, at least one manufacturer suggests its use in antenna installations. Since the typical GPS antenna has an LNA the coax doesn't matter so much, as long as its not really bad coax. One thing though, adding at least one ferrite bead at the antenna side sometimes improves the quality of the pattern in RTKlib markedly especially with patch antennas.

author: mark03
author_rank: Frequent Contributor
timestamp: February 14, 2019, 08:40:43 pm
content: I'm using 50-ohm input termination now and it works fine. I had removed the 75-ohm input resistors, set the project aside, then forgot I still needed to replace them. Without a load the 2x gain of the Extron amps caused clipping.@cdev when you say "cheap 50-ohm terminators from Ebay" do you mean the unused Extron inputs? I'm feeding mine internal to the box, so no need for BNC terminations. If you meant the outputs... beware that a 50-ohm load on all three outputs of a single CLC409 may load it beyond the datasheet recommendation.I had hoped to post pictures of my finished Extron GPSDO box this week but somehow in the shuffling around I managed to zap my Raspberry Pi's LCD panel. Now waiting on another from China

author: cdev
author_rank: Super Contributor
timestamp: February 19, 2019, 03:55:36 am
content: To date I've only used a single channel and actually, I have put them on the unused Extron outputs of the channel I am using. I haven't looked at the waveform doing that, I guess it would be a problem because of the CW nature of a 10 MHz carrier? (as opposed to video signal) That totally makes sense, thank you will need to check.I actually don't have any instruments yet that use the 10 MHz properly. I may use PicDiv and PicPet in a modular fashion to give me a few other frequencies, thats basically my plan right now, when I have the time to do it.

author: db5fp
author_rank: Newbie
timestamp: March 17, 2019, 02:57:12 pm
content: Hi,maybe I didi not understand the cammands of this device or I fill in the wrong commands.I'm trying to save my location to FLASH to get a quick startup.But after $UPDATE FLASH or dubble "EE" in Lady Haether the Position ist still $SURVEY 34733333 135350000 0 36 28800Any hints?Best regards

author: Squiddaddy
author_rank: Regular Contributor
timestamp: March 18, 2019, 01:26:24 am
content: Use $SETPOS with your correct coordinates. Or just run a $SURVEY for at least 8 hours.

author: db5fp
author_rank: Newbie
timestamp: March 18, 2019, 08:31:37 am
content: Hi,Thanks! Along survey and afterwarts $UPDATE FLASH solved the problem.best regadsFrank

author: Dek
author_rank: Regular Contributor
timestamp: March 28, 2019, 06:59:12 pm
content: Hi,I've just received my ebay source trueposition GPSDO and are trying to assimilate the various sources of info including ratpack info and this thread.I can't decide if the TTL serial requires 3.3v to 5v level conversion, so will have to scope the data lines to find out but before I do that, what have others done?Thanks,Dek.

author: Towger
author_rank: Super Contributor
timestamp: March 28, 2019, 09:09:14 pm
content: Quote from: Dek on March 28, 2019, 06:59:12 pmhttps://www.eevblog.com/forum/index.php?topic=174531.msg2288070.msg#2288070

author: db5fp
author_rank: Newbie
timestamp: March 30, 2019, 09:04:48 am
content: Sorry,but still same problem. Position is not updated at startup.It is still $SURVEY 34733333 135350000 0 36 28800best regardsFrank

author: Towger
author_rank: Super Contributor
timestamp: March 30, 2019, 09:13:28 am
content: When you start a survey it needs to finish before the position is updated. I think the default time is 8 hours.

author: CJay
author_rank: Super Contributor
timestamp: March 31, 2019, 06:25:11 pm
content: And when the survey is complete, wow accurate.It placed my cheap (very cheap) patch antenna to within a metre of the *indoor* windowsill it was sat on.

author: GNRFreak69
author_rank: Newbie
timestamp: April 12, 2019, 01:17:01 am
content: Ran across this thread a while back. Has anyone written a sketch for this other than the packrats hex file? Just don't wanna recreate the wheel.-Jeff

author: rbm
author_rank: Regular Contributor
timestamp: April 12, 2019, 01:27:27 am
content: There are several:https://www.eevblog.com/forum/metrology/lady-heather-v6-beta-for-windows-exe/?allhttps://github.com/pigrew/trueposctrlhttp://lists.febo.com/pipermail/time-nuts_lists.febo.com/2018-October/094480.html

author: tkamiya
author_rank: Super Contributor
timestamp: May 23, 2019, 05:50:06 pm
content: This is getting old but I started playing with it again.On Pakrat documentation, RS232 port has 1 as ground. This is CD (Carrier Detect) line. Ground is pin 5. Oddly enough, it worked either way. Corrected mine to the right pin.

author: tkamiya
author_rank: Super Contributor
timestamp: May 25, 2019, 09:28:22 pm
content: I got it to work stably now. No random disconnects!Key was temperature variations. Before, I was testing it with cover open. It takes forever to heat up and it never actually reached equilibrium. As temperature slowly rise, DAC value will jump and wobble and causes unlock. (or at least status other than zero). I found this while staring at LH display for hours.I closed the case. It went up to 55 degrees C or so fairly quickly and stabilized. At this point, lock is solid.I'm surprised how much OVEN XCO got affected by ambient change. My house is air-conditioned, so variation is like 2C at maximum.

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 01:49:29 am
content: I just finished my GPSDO project too:With the Extron case closed I also get ambient  temperature ~ 50-55 C. I was worried it could be much higher. I think this is safe for everything inside.It would be nice to know the ADEV performance of the finished unit, but this is my only GPSDO and I'm not sufficiently motivated [yet?] to purchase another standard for comparison purposes. The system integration brings in a lot of noise sources: switching power supplies, Raspberry Pi, etc. (Interestingly the RPi Zero W connects to my wifi access point just fine with the case sealed)For anyone who wants to use the Extron analog distribution amps as a GPSDO enclosure, I strongly recommend going with the taller unit which has an extra row of connectors at the bottom, which live on their own strip of PCB. On mine there was literally nowhere to put the antenna connector in the back. I finally gave up and made a big hole in the main PCB where one of the input BNC connectors used to be. This necessitated some PCB rework to reconnect a couple of traces passing through that demolition zone.

author: tkamiya
author_rank: Super Contributor
timestamp: May 26, 2019, 02:41:05 am
content: That is a very nice integration of all that is necessary! I like the idea of using Pi and having LH built in. I have a question for you. I'd guess you are using Linux for OS. How do you manage proper shutdown? Can't just yank the power, correct?I am also a bit concerned with switching power supplies right next to the GPSDO board. I have it in my plan to actually do a comparison between linear supply and switcher along with GPSDO.

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 03:03:21 am
content: Generally it is fine to pull the plug on Linux systems unless they are in the middle of some heavy activity, and even then, proper journaling filesystems have become the norm. RPi used to be infamous for filesystem corruption on improper shutdown due to some hardware issues, but I think those have been solved. That being said... I still log in manually and perform a remote shutdown if I remember; I may as well, since wifi is there.The Extron distribution amp shipped with two switching supplies, one on the "roof" of the case supplying +15V, and another, inverting buck, on its main PCB to supply the CLC409 op amps' negative rail. The Trueposition board has a switcher on its PCB as well. At least I am not introducing anything completely new. I have two Meanwell switchers, +15 and +5. The 15 volts replaces the original switcher, and is also RC filtered and post-regulated to 12 volts for the Trueposition board. The 5 volts is cranked to 5.5 and supplies the Raspberry Pi, plus the Extron positive rail through an RC filter and 5V LDO regulator, bypassing the on-board 7805.No doubt there is still plenty of room for mischief and EMI issues. The integration of GPSDO, distribution amp, and RPi sounded straightforward before I got into the detailsIt was a LOT more work than I imagined.

author: tkamiya
author_rank: Super Contributor
timestamp: May 26, 2019, 03:18:54 am
content: Thanks.My unit only has the GPSDO board and a small MeanWell power supply. (Switching type) My plan is to either replace it with linear supply or work on filtering output. I haven't gotten that far yet. My case is 1U rack mount, so what I can do is really limited.As far as front panel goes, I intend to have a few LEDs only. Maybe POWER, LOCK, and PPS. I should be able to do this with a smallest Aduino. Anything further, I'll do it remotely via RS232C connection. Rear panel has Antenna, 10MHz out, 1 pps out, and power. That's it. Very simple.While your oven is warming up, do you see frequent UNLOCKs? (shown as red-line on top of LH graph) and status other than zero? I kept having that problem for long time until I closed the lid and let it warm up quickly.I bought a bunch of Extron 3 output unit. I intend to take it out of case and use it as modules. These are really nice and cheap. Performance is pretty good, too. For general distribution in my lab, I already have two 12 channel distribution box.

author: texaspyro
author_rank: Super Contributor
timestamp: May 26, 2019, 03:32:12 am
content: With the small RPI screen, if you turn off the digital clock display (GZ) then you can see the satellite information table...Also, touching the upper left corner of the screen will bring up the touchscreen keyboard.

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 03:46:24 am
content: Quote from: tkamiya on May 26, 2019, 03:18:54 amMine was locking OK when I tested the board in the open, although it was a long time before it got happy. A long self-survey, and then the DAC recalibration routine (or whatever it's called) may, or may not, have helped this along. On power up with the box closed, mine takes something like 15-30 minutes before it hits "mode 0" which is the first time the red line goes away and the digital clock turns cyan. I don't think anyone knows what all it is doing. There are other odd behaviors, like constantly bouncing between 8 and 9 satellites on quite a regular pattern (about once a minute).

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 03:57:29 am
content: Quote from: texaspyro on May 26, 2019, 03:32:12 amThanks, I'll try this. Actually, I was going to ask if anyone had an optimized set of graphing options for Heather+TruePosition. What are the three plots people find most useful? RIght now I have # satellites, temperature, and DAC voltage which is not actually DAC voltage (just a flatline). With satellites listed elsewhere only the temperature is really compelling. That leaves one or two curves open for anything else that might be useful to see at a glance. It would be great to have the DAC on there but AFAIK this info is not available?(Edit: Maybe TFOM, and zooming out the time axis to ~ 6 or 12 hours, would be helpful. I am always curious if and for how long it has hit TFOM=2, my record thus far.)Unfortunately I do not have a touchscreen! None of the "normal" LCD options would fit on my Extron front panel, because the HDMI protrusion. I ended up with a 4.3" diagonal, 800x480 display from China (buydisplay.com) with an Adafruit parallel display adapter. This uses every pin on the GPIO header so the serial port is over USB. There is only one USB port on the Pi, so no touchscreen (also, there's no more room in there). All of this could have been avoided with a larger case, but once I had the little Extron, I was committed

author: KE5FX
author_rank: Super Contributor
timestamp: May 26, 2019, 04:48:18 am
content: Brier, huh? That's my old stomping ground (I used to live in Lake Forest Park.)

author: texaspyro
author_rank: Super Contributor
timestamp: May 26, 2019, 06:47:51 am
content: Hmmm... you should be seeing a DAC voltage response. Maybe you have some weird firmware that does not output the $PPSDBG message?

author: Towger
author_rank: Super Contributor
timestamp: May 26, 2019, 02:59:12 pm
content: There is bug in the newer version of Lady Heather. It appears to be in the installation strings. If you start the GPSDO with and older version and switch the latest version the DAC voltage is displayed/not flatlined.

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 04:49:07 pm
content: Quote from: Towger on May 26, 2019, 02:59:12 pmHmm, first I've heard of this. I'm running 6.14 beta with the following config:Code:# set com port to use (note the 'u' USB option is ignored for Windows since# Windows treats USB com devices the same as hardware serial ports). For Linux# and macOS, use a number 1 greater than the operating system device id (e.g.# -1u says to to use /dev/ttyUSB0) or use the -id= option to set the linux# device name. The -ip= command line option can set the TCP/IP address of# a remote decice on the network (local or internet)-1u# force the baud rate to use here (if not set, a default value depending uoon# the receiver type is used)# -br=9600:8:N:1# set the receiver type to use (-rx says to auto-detect)# If you did not first set the baud rate, auto-detect tries 9600:8:N:1,# 115200:8:N:1, 57600:8:N:1 and, 19200:7:E:1 in that order.-rxo# set your local time zone to use. You can use Linux standard format: CDT6CST-tz=-8pst/pdt# enable the digital clock display-gz1# enable the analog watch display-gw1# enable the satellite position map display-gm1# enable the satellite signal level display in the plot area-gq1-gb1# enable the sun info display, official rise/set horizon, with sound effects# Note: in order to make room for this display, this will restrict the# satellite info display to an abbreviated format. You can use the /si=# command line or SI keyboard command to adjust the satellite info display format-sr=o*# allow ESC ESC to exit the program# -ke# enable the singing clock (-th=4h for cuckoo clock, -th=1b for ships bells clock)# -th=4s# 800x480 screen resolution-vpIt does seem like I've seen a DAC curve in the past, although after the basic Trueposition checkout I've been so focused on the hardware that I really haven't paid attention again until now.Edit: Adding an explicit -gd1 to my cfg file, I do get the DAC curve. Maybe part of the confusion is a typo in the PDF version of the manual (http://www.ke5fx.com/heather/heather.pdf) where it lists GO twice; I think one of those is supposed to be GD.

author: mark03
author_rank: Frequent Contributor
timestamp: May 26, 2019, 04:51:14 pm
content: Quote from: KE5FX on May 26, 2019, 04:48:18 amHa... small world! I did wonder if I should blur that out, but I don't have any enemies with cruise missiles

author: LazyJack
author_rank: Frequent Contributor
timestamp: February 23, 2021, 07:18:48 am
content: I'm resurrecting this topic, as this one seems to be with the most details and most knowledgeable people on the TruePosition board.I have just finished my implementation of a TruePosition based GPSD, detailed inhttps://www.eevblog.com/forum/projects/yet-another-trueposition-gpsdo/.However, I have some unanswered questions that came up during the build. Maybe someone can answer them.1 - the 10MHz and 1PPS good parameters in the $STATUS. All documentation I have seem mentions it as an indicator that the 10MHz and the 1PPS output is valid and every implementation that cares about it, reports them. So does my implementation. However, I have never seen any of these to indicate that these signals are not good. My TP board always reports both as good. Under what circumstances are they not good? Is it worth bothering reporting them? I spent so much time creating the small icons, would hate to throw them away2 - It appears to me that the TruePosition actually saves the position after a successful fix, without any additional command. At least right after powering up, it was able to report the correct position before any acquisition. Is this true, or am I being tricked with something? I have implemented the reload of the previous position with the $SETPOS command, but it may be unnecessary.3 - The board acquires a fix without a $SURVEY command. But I don't know if running the survey will stop further fixes? That is, once the survey has run for whatever hours and got an accurate fix after averaging etc. will it stop acquiring new fixes as those will be most likely less accurate that what was accumulated during the survey.

author: cdev
author_rank: Super Contributor
timestamp: February 23, 2021, 05:28:10 pm
content: It needs to successfully complete the survey at least once in order to work properly. This can take hours or even days. I wasn't able to get it to complete with my PCTEL (Lucent) GPS-TMG-26 antenna indoors, only when I moved it to the middle of the back yard was it happy. Then it completed in just a few hours.Once that had been done then it was able to acquire a new fix fairly quickly. I think it only needs to know the general area its in and the date to figure the solution out.Until then it isn't happy, basically it doesn't work as it should at all.I recently aquired another GPSDO and it acts similarly. (But is much more sensitive) I wonder if the TP would get its initial position fix faster with my (passive) log spiral antenna which has a much larger receiving area. Thats definitely something to test out soon. That would give me much more flexibility in where I put it.

author: LazyJack
author_rank: Frequent Contributor
timestamp: February 24, 2021, 09:27:39 am
content: Yes, that was my experience too. Survey mode is quite sensitive to having a good signal. If it has then progresses quickly, otherwise it can stop for minutes or even hours. Once it does the survey it looks to me that it actually saves it to some non volatile memory, because if I power it down and up again, and use the $GETPOS command, it will report the same position, even before tracking any satellites. So I'm guessing that there isn't really any need for the controlling software to save and load positions. If the antenna is well positioned it will acquire a fix quickly, if it is not then it doesn't really matter if I enter a location. It my speed up the time to fix, but I don't think it matters in the case of a GPSDO anyway, when you'll need some time after poweron anyway to stabilize.

author: cdev
author_rank: Super Contributor
timestamp: February 26, 2021, 01:34:07 am
content: I wonder what hangs

author: CJay
author_rank: Super Contributor
timestamp: February 26, 2021, 08:42:12 am
content: Quote from: LazyJack on February 24, 2021, 09:27:39 amThe information from survey mode is indeed stored in flash on many commercial GPSDO.I think because the GPS antenna shouldn't have moved between power down modes and the receiver doesn't need to work out speed, direction of travel or any 'rate of change' it can hit the ground running and maintain an accurate PPS or whatever output it provided for oscillator discipline as soon as it acquires satellites because one of the major variables is already known with a high degree of precision.The satellites provide the other high precision information required to 'solve' for the last variable, I.E. the oscillator output.

author: tabajaralabs
author_rank: Regular Contributor
timestamp: March 06, 2021, 09:46:38 pm
content: 11 pages, what a LOT of messages! =DBut I still have a question, sorry for being so n00b about the subject:I have an E8285A spectrum analyser, and a 53131A frequency counter. What is the best way to use them?Use the internal High Resolution OCXO from the E8285A to give 10MHz signal to frequency counter?Use my home made OCXO time base inside the frequency counter to give 10MHz signal to E8285A?Use a GPSDO (just got a trueposition board) to give 10MHz to bothThanks! =)

author: cdev
author_rank: Super Contributor
timestamp: March 07, 2021, 03:32:45 am
content: Once you know the precise position you can solve the time and frequency with consistancy.

author: CJay
author_rank: Super Contributor
timestamp: March 07, 2021, 08:36:33 am
content: Quote from: tabajaralabs on March 06, 2021, 09:46:38 pmWhich one do you think is most accurate?The problem is fairly neatly summarised by Segal's law:"A man with a watch knows what time it is. A man with two watches is never sure."If you have three watches, choose the two that agree with each other most closely and disregard the third, but in your situaton I'd set up the Trueposition, connect it to Lady Heather and when Heather shows it to be working correctly, use that.

author: cdev
author_rank: Super Contributor
timestamp: March 08, 2021, 12:52:25 am
content: When I connect my trueposition to my huge tindie sourced RHCP log spiral antenna I get six SVs on my TP GPSDO. No LNA just bare antenna. Will have to investigate what quality the signal is (perhaps with rtklib if that is possible) somehow later. It looks to me like the spiral is probably a pretty decent GPS antenna as navigation goes.It's the bigger of the two that are being sold. Does anybody know why one now cannot buy it in the US?