Lady Heather & HP 58540a - Page 1
Forum section: electronics / projects

author: mojoe
author_rank: Frequent Contributor
timestamp: February 19, 2024, 04:30:51 am
content: I have LH working with my BG7TBL unit, but am having problems with the HP unit. I am using the /rx5 command.Most of the time, LH starts up and seems to be communicating on Com1, but I get no data display. After running LH multiple times, I did get a display a couple of times. The communication with the HP is slow (fault of the unit), but when it does work, after a bit the basic information (model, SN, time, timezone, etc) is displayed. I know that this unit doesn't report PPS or OCXO parameters, so that area is blank.Edit: the rollover is also displayed.When I do get a display, there is one area that should display data, but doesn't. The unit does report satellite data, using the command ":GPS:SAT:TRAC:DET?". See the image below.I assume that the 58540A must be different than the other "5" models that LH supports. The manual is also attached.

author: cncjerry
author_rank: Unknown
timestamp: February 19, 2024, 06:02:24 am
content: what version of LH are you running? Try pressing the 'g' key and then the key for constellation and take the default after that.I had the same problem recently and it seems like it didn't report the sats ( in the middle, upper left) until it had finished the survey. So if that unit initializes with a survey, that could be the problem but I don't know. My GPSDO started reporting after the survey completed. Texaspyro, Mark, wrote V6. he's a good guy, I drilled some heatsinks for him for the X72 Rb unit. I'm sure he gets a lot of questions, though.The other thing to try is putting in the longitude, latitude and altitude. That seemed to make a difference. It also looks sometime like the GPS is tracking the sats but not getting a signal at all. I started to wonder if the sat track was somehow stored in the GPS. again, once I put the accurate long, lat, alt, in I started to see the correct sats as I have two Symmetricom units side by side sharing one antenna. If one can see a sat, the other should too. I have to upgrade the sat receiver in one of the units, I bought the little card that has like a 10 pin header on it that sticks into the motherboard, but the Symmetricom unit has more little screws than I can count.Anyway, try some ideas above.One other, put it in trace mode (NMEA or SCPI) and wait for it to present the status screen every minute or so. That should jive with what the GPS is should be seeing.JerryJerry

author: mojoe
author_rank: Frequent Contributor
timestamp: February 19, 2024, 06:17:40 am
content: LH 5. I'll try 6.I took it out of suvery on powerup and set lat/lon/alt to what was reported by my BG7TBL, after LH ran a precision survey. Since it has a newer, u-blox GPS, I figured that it would be more accurate than having the HP do a survey.This model doesn't have a status screen.I don't know why LH showed data only a few times. Most runs, it shows nothing, even after running for hours.

author: mojoe
author_rank: Frequent Contributor
timestamp: February 19, 2024, 07:01:16 am
content: I had to delete and repost, as I forgot to blank my location on the screenshot.LH 6 is misinterpreting what it reads and shows garbage. I went back to LH 5. This is one of the few times when LH is showing data from the HP, so I'm leaving it running. As you can see in the screenshot, this model is limited in what commands it supports, and what data it reports. However, as mentioned above, it does report satellite data, so I don't know why LH doesn't show it.The coordinates are the ones I entered. They don't change on the display.

author: mojoe
author_rank: Frequent Contributor
timestamp: February 19, 2024, 07:07:48 am
content: While I'm on the subject, I do have a question as to LH and my BG7TBL unit. A few days ago, I did a SP survey. I wasn't sure if the coordinates were saved, so I did EE. Later, I went into u-center and set the GPS to Static, and under NAV3 (I think that's where it was), I entered the same survey coordinates. When I again run LH with this unit, it doesn't appear that LH is using those static coordinates. I says 2D/3D and the coordinates are constantly changing. Shouldn't I see unchanging coordinates, like I do on the HP unit?

author: cncjerry
author_rank: Unknown
timestamp: February 20, 2024, 01:31:21 pm
content: Did you try looking at the constellation map? If LH sees sats it will show up on the map. Did you try going into terminal mode and watch the commands come in as text? I have a feeling they are somehow turned off in the 58540a or not reporting correctly. Later ublox can turn on or off very selectively, I don't know what is in the 58540a. In terminal mode LH acts like an ascii terminal and you should see all the commands coming from the 58540a, or not if they are disabled.On the other topic, If the location is changing then the survey might have finished but didn't take or be locked in. On the ublox after the survey runs, I always told it to write it to its eprom. You have a time length and a minimum location goal on ublox receivers. I think the location goal is the important one. We found you have to run the survey to a location of .1meters to have the least variability in the output. If the location is changing then you need to rerun the survey and not move the antenna, of course, duh, <-that is meant for me. Then write it.I was thinking though that without sawtooth your pps output from the 58540a, if it has it, will be moving around. You can always use a tapr tadd-2 or one of the picdiv chips to recover the pps from the 10mhz output. Depends on where and how it presents its PPS. One other thing, I don't know a lot about this, I am more of a user, but I found many GPSDO used a common small rectangular daughter card that can be easily upgraded. I upgraded my symmetricom units that way.Jerry

author: cncjerry
author_rank: Unknown
timestamp: February 20, 2024, 01:37:13 pm
content: By the way. On your bg7 unit, can you hook it directly to the unlox software? Can't remember the name of the software. Sounds like you can because you can see the sections. The software will tell you if the survey is finished with a survey status message you might have to turn on. The manual on the later chips is like 350 pages.

author: mojoe
author_rank: Frequent Contributor
timestamp: February 20, 2024, 10:14:24 pm
content: Quote from: cncjerry on February 20, 2024, 01:37:13 pmBy default, LH sees it as a NMEA GPS, because that is how it is configured. If you use the /rxu command, it sees it as a u-blox GPS, and shows more data. I already did a precision survey using the SP command, then used EE to save to the GPS. I even went into u-center and set those same coordinates.

author: cncjerry
author_rank: Unknown
timestamp: February 22, 2024, 07:59:58 am
content: When you do a survey on the Ublox software, or initiate it with the GPSDO app in our case, we tell it two hurdles. One is the .1meters and the second is the number of samples or hours, can't remember, to run. I remember they changed the software to cm from meters or the reverse and that caused some confusion. But it is showing survey complete when you poll that message? And you have the satstat message enabled in the correct section? If you have one of the modes turned off, then it doesnt help to enable satstat for that mode. I'm sure you know what I mean. I haven't done any development on this since before covid. Do you have a rubidium or other standard? I'd be curious to see what the GPSDO is doing by comparing it against another standard. What is its discipline status? It sounds like maybe the satstat message might be enabled for the wrong mode possibly, that's the last thing I can think off. Some of this i barely remember. I am playing with it again and have my two symmetricom modules up and running. I'm testing them against each other as well as against two Rubidium standards. I am going to pull out the GPSDO that has an lea8t In it and see if i can get running again as that has sawtooth compensation in it. I am going to replace the oscillator with a Rubidium that is set by the PPS. Then i am going to use a phase detector to lock a high quality, ultra-low phase noise oscillator against the rubidium. It has a switch so i can phase lock it or let it run free for phase noise testing.Were you ever able to get the signal sky map displayed?Jerry

author: cncjerry
author_rank: Unknown
timestamp: February 22, 2024, 04:24:48 pm
content: I keep thinking about how to get another view of what is going on with your box. What does it report for TFOM and FFMO? I pulled this from an earlier post (earlier being 9yrs ago).TFOM (Time Figure of Merit) is the accuracy of the 1 PPS signal, with 0 < 1ns, 1= 1 to 10 ns, 2 = 10 to 100 ns, 3 = 100ns to 1us, ... 9 > 1msFFOM (Frequency Figure of Merit) is the stability of the 10MHz signal. 0 = PLL stable, 1 = stabilizing, 2 = holdover, 3 = unlocked (do not use as 10MHz out of spec)My units were built by HP but I think they either built them for Symmetricom or Lucent or the other way around. Neither of my units ever reported TFOM < 3 that I remember. For FFOM they report 'lock'.

author: mojoe
author_rank: Frequent Contributor
timestamp: February 22, 2024, 06:30:22 pm
content: I'm going to put aside the data screen issue for now. There is an underlying issue with LH not communicating with the HP GPSDO that needs to be solved first. As I said previously, most of the time when I start LH for this GPSDO, it comes up with a blank screen. Rarely, it starts displaying some data from the GPSDO, as shown in a previous posting. I have some new screen captures which show what's going on.The GPSDO was previously set to not continuously output a string with time/date, etc., so LH would have to use SCPI to ask for it, as shown in a previous post. I just changed that to continuously output the data, to see if that made a difference in what was displayed on the screen. It doesn't made any difference, but does allow me to see that something is not right with the serial port communication.Note: as I've said previously, this model GPSDO does not output a status screen. The only regular output it does is what you see in the fourth pic, below. If you want satellite data, you use SCPI to ask for it.The first pic is what I usually get from LH when connecting to Comm1, which is the HP. The second pic shows what I get in the LH terminal (garbage). The third pic shows the command string used to start the program. The fourth pic is Tera Term, showing the correct data from the GPSDO. The fifth pic shows the Tera Term serial port settings.Why LH only talks to the HP GPSDO correctly once in a while, I don't know. The BG7TBL GPSDO and LH work every time.

author: cncjerry
author_rank: Unknown
timestamp: February 23, 2024, 03:30:16 am
content: I have noticed that sometimes LH, or the GPSDO, takes time to get going. But all the GPSDOs will talk to terminal emulators like Putty, etc. I mentioned satstat, that was around for a while, don't know if it still is, I have a copy. Other program is uCenter for ublox gps modules. That is what I use because if formats the messages, and is well integrated with the hardware. It has problems because certain versions are made for later ublox models. You can read NMEA text but ublox messages are only binary that have to be decoded.I don't know if you've tried this, but go into the PC settings, find the port and set the baud, etc to the correct values. Then do the same on the properties page, looks like you have them correct. this will make sure that the baud rate isn't changing for some reason. The fact that the HP unit is slow sort of bugs me. Maybe the max chip, or whatever they use inside, probably bit banging a I/O port, is off. You can check it with a scope of course, better if you have one that decodes ascii.The overall problem is, and I've battled with it on 4 GPSDOs and two Rubidium units that use external GPS units, everything has to be right, duh. You have to have the messages turned on and the right baud rate. And the messages have to be enabled for the right GPS system. As soon at the GPSDO starts up, you should see it start spitting out NMEA, SCPI or both or a proprietary encoding (unlikely). I don't know if LH polls or expects the unit to run asynchronously. You only need a couple messages and then sawtooth if the receiver support its. But it also has to send it to the PC and not just process it internally.Other than that, I guess I give up, but it should work. I guess you checked the voltages in it?Jerry