OCXO frequency dividers and PLL multipliers - Page 1
Forum section: electronics / projects

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 19, 2020, 11:18:58 am
content: After going of topic in other boards I follow the suggestion and open a new board.It should be used for discussions around unusal frequency dividing schematics neededto reach useful frequencies for PLL synch with GPS time bases as example.In my case I try this with an 65 MHz OCXO and some NOS schottky Flip-Flops. Since I‘m notan expert but doing this as hobbyist I hope for hints and examples from others.

author: Labrat101
author_rank: Unknown
timestamp: July 19, 2020, 01:06:02 pm
content: You saw my method which works fine for me, divide 20Mhz by 2 .. as my maths Deg. is not good enoughto go more.There is something else I noticed about the jitter but I am not sure I should mention my theory as It willopen a bag of worms .. that i will do by PM

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 20, 2020, 05:32:38 pm
content: As mentioned to some of you earlier I got a 65 MHz VCOCXO from a cable television provider.To use it for a GPSDO I need to divide the frequency down to 1 or 5 MHz.I have a bunch of NOS schottky IC by the hand and my quest is to design a workingdivider with them.I simulated some designs in Multisim and to be clear, it is no problem to design a working by-13-divider(4-digit-counter with some gates and reset) that work. But I have only a few ICs by the hand.So I found a fancy design with 5 flip-flops and I simulated it in Multisim. (attached the schematics)It uses 74S112. These are specified up to 120 MHz and we used them in the 80ies to build digital frequency displays forour FM radios. This were the fastest dividers you could get in the eastern bloc at this time.(there were some soviet ECL ICs for the military complex - but this was out of my universe)Unfortunately the attached simulation reaches only 50 MHz and I haven't "breadboarded" it since real life is demanding these days.I will bring up the real life test asap to this board.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: July 20, 2020, 07:23:52 pm
content: Quote from: Bad_Driver on July 19, 2020, 11:18:58 amWell, becoming an "expert" is essentially down to gathering plenty of "experience".Do enough 'experimental' solderless breadboard builds and you'll become an "expert" soon enough!Still and all, there's no harm in reading up on other experts' experience to better prepare yourself in trying out various ideas and avoiding the pitfalls in breadboarding such circuits whether on solderless or vero(strip) boards (or even deadbug style on copper clad board layouts).Since, despite being "off topic", those circuit drawings I'd attached in the SDS2000X+ topic thread had attracted sufficient enough interest to be viewed 94 and 78 times to date, I've decided to attach them here for easy reference.The first shows the circuit for the mark one with its 13MHz OCXO and all the TTL jiggery pokery required to turn it into a 10MHz reference. I don't think adding U1 helped very much, if at all since the 3n502 clock multiplier doesn't require a perfect square wave input clock to provide an ultra low jitter (20ps pk-pk) square wave output.As for dividing the OCXO's output down to 32.5MHz, I wasn't sure whether 74S74s actually existed but I tracked down an entry for one in my TI TTL data book (75MHz min, 110MHz typ clock inputs speed). If you find an equivalent to this in your collection, you're in with a chance (provided you can select a 74193 that's fast enough for the job).If you can find a 74S169 or equivalent, you can use this to divide by 13 straight from the 65MHz input (count up clock input speed is given as 70MHz typical). the '169 isn't identical in function to the '193 (it uses a single up/down control input and a ripple carry output with T and P enables versus separate clock inputs to determine count direction and borrow out/in and carry out/in connections of the '193). Both are programmable input synchronous counters but whether this means the '169 can also be used for modulo N counting isn't too clear from the notes.On the other hand, you can probably find a modern multipurpose programmable divider (PIC?) to do this with a single 8 pin chip (assuming you can find one that can deal with a 65MHz clock input). In my case, I was lucky enough to be dealing with a low enough starting frequency (26MHz) to drive the clock input on my selected 74193 making it easier for me to do what you're proposing to do with your own collection of ancient TTL.One thing worth checking if that OCXO is a sine wave output type, is to verify whether it needs a 50 to 100 ohm loading to turn a soft sawtooth wave into an undistorted sine wave as I had to do with my CQE branded 12v 10MHz OCXO when I spotted a peculiar 2ns jitter on the falling edge of the square wave output of my 74HC14 sine to square wave converter/buffer circuit in the mark two build. How typical a requirement this might be for sine wave output OCXOs in general, I just don't know but if it can be a problem for one brand of OCXO, it's just possible it might also be a problem with other brands.I'll leave you to peruse those hand drawn circuit diagram sketches for now before turning this contribution into yet another monster missive.JBG

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: July 20, 2020, 07:37:06 pm
content: Correct me if I'm wrong but that circuit seems to be a mix of ripple and synchronous counter stages. This might explain the 50MHz issues you're seeing.JBG

author: Benta
author_rank: Super Contributor
timestamp: July 20, 2020, 08:49:00 pm
content: Quote from: Johnny B Good on July 20, 2020, 07:37:06 pmAgreed, an absolutely terrible design. 74AC161 would do the trick (divide-by-13), but with a much better result.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 21, 2020, 09:15:29 am
content: Yes, this design I found elsewhere in the web is strange but seems to work anyway but I coudn‘d explain whyI give it a try since I have the ICs by the hand but I ordered as suggested a dozen of 74AC161, seemsmuch easier to handle but unfortunately Mouser has no PDIP on stock, it‘s in backorder.Thanks for your advice!John, do you have some results with your new Neo m8t?

author: Labrat101
author_rank: Unknown
timestamp: July 21, 2020, 01:09:53 pm
content: That good you have found a solution .. If you are going to order parts for a divide by 13 .. I would some how look at the CTS ocxo 20mhzas they are cheaper than the 10Mhz .. Have no idea why but the 20Mhz have a better ratings .Also some thing completely different my Siglent 1152CML+ 150Mhz ( that was a Precision 2190E 100mhz ) that's now 3 yrs old had somefunny sinx problem so I striped down thinking it was a PSU problem . 1 cap a little dodgy. There was no screening between the psu and thevideo chip and cables that ran under the PSU . Screened them all . and also the plastic case near the main socket it's made so it closes off allthe air vents on the PSU .So opening the vents the whole scope runs 30 degrees cooler .And also Magicly my Jitter is also less .. Not Gone .. so the cpu etc must also have been over heating .The case Is really badly designed but it is out of warranty a few extra holes in the plastic ..When I replace this scope I will convert it into a pizza Oven .

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 21, 2020, 07:56:46 pm
content: Good to hear that you found the reason for the problems. It seems that Siglent has done a big leap forwardduring the last 3 years with their scopes. I‘m pretty happy with my and if you are interested watch Dave‘steardown of the SDS2000x+.Today I found some time to work on the OCXO-10 MHz reference strip board for my Feeltech 6900 sinceI decided to finalize the efforts a last time.I discovered that my new selfmade scope probes perform much better than the Siglent one which came withmy scope. I will show details in the next days. Photos will follow.

author: Labrat101
author_rank: Unknown
timestamp: July 21, 2020, 09:43:42 pm
content: It looks pretty but I notice that the screen resolution is not all that good . compared to the keysight scope.I don't think I would get another Siglent . and as Dave mentioned those heat sinks get really hot .If you hack it and run it faster I have a feeling it will also increase the heating.I don't think that there cooling is enough and having the fan in the middle and 2 side vents will cause crossflow turbulence . There are no cooling slots on the Bottom to cool the M/Brd.At least they opened the vent holes and made them a bit bigger.The Linux seems to be a lot new .I don't think that this is a scope that one can say it will last me 10 years trouble free ...Those knobs will fall off in a year.I am sure its better than what I have now for sure . 3 years and started to show ageing.I think any way I am going to wait awhile I am sure something will appear in the next yearit like everything today by the time you open the box its become obsolete .My BNC's were getting so hot I could not touch them . Now after my cooling mode they are mere warm.But I still prefer my Boat anchor The screen res is far better . Colour yes .. GreenRNS

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: July 23, 2020, 06:02:45 am
content: Quote from: Bad_Driver on July 21, 2020, 09:15:29 amI've had rather confusing results which aren't helped by the lack of an antenna splitter to feed the MKs I & II gpsdos from one good common antenna (I've got the M8T attached to the partly built MK II).My homebrewed resistive antenna splitter with a DC blocking cap on one port and a dc bypass inductor (1uH ferrite bead inductor) on the other to keep the GPS receivers fighting each other to power the active antenna, seems to confuse the MK I and not too surprisingly, reduces the signal by an extra dB or two over the normal 6dB insertion loss figure (not too surprising 'cos I cheated on a third resistor and just used two 33 ohm resistor going straight to the antenna port instead of a triad of 16.7 or 50 ohm resistors (star or delta arrangement respectively).I've just placed an order for a pack of three low loss 100 to 2700MHz 25W rated RF power splitter/combiners with BangGood. They were actually slightly cheaper than the resistive DC-5GHz signal splitters I'd been considering until I clicked on the "See more items like this" hidden pop up and stumbled upon those low loss splitters.This business of having to trawl through pages of barely relevant items on BG's site just to eventually stumble upon what you're actually looking for, really annoys the Hell out of me.It's a waste of time searching for a "GPS antenna splitter" on BG's site since their own search engine is such total and utter shite (if you'll pardon the Anglo-Saxon). Sadly this time, there wasn't a UK warehouse ordering option so instead of the goods arriving just 5 days later with my last order, it's back to the usual 2 to 5 weeks delay (assuming they hadn't suddenly run out of stock just as I'd placed my order).In the meantime, I'll have a go at reconfiguring my homebrewed antenna splitter into a proper resistive delta network (51 or 47 ohm resistors are easier to find than 15 ohm ones, especially if I'm scavenging smd types off of my collection of broken PC motherboards, plus it's a more do-able arrangement in the rather cramped space I'd left myself with - one of the reasons I cheated on the resistor count in the 1st place).I suspect that 1uH ferrite bead inductor was the problem with my MK I gpsdo so I'll remove that and hope the resulting 240mV drop across the 33 ohms worth allows my external active antenna to continue functioning as before which I do believe there's a very good chance it will.One way or another, when I finally start to make some sense out of what I'm seeing on my new 4 channel 'scope (two gpsdo reference outputs plus the 10MHz Sinc pulse out of my FY6600 that's standing in for a Rubidium sanity checking reference), I'll offer some further observations on that M8T module.It would be rather handy if the SDS2000X+ series could be set up to automatically take screen shots every minute or two. For all I know, perhaps it can? I just haven't gotten round to trawling through the user guide I'd downloaded a few months back. I've just been too preoccupied with trying to fathom out what's going on to spare any time to read user guidesNever mind, I'll make that my next priorityJBG

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 25, 2020, 08:50:07 am
content: I have to acknowledge that Multisim did a good job.Yesterday I found some time to breadboard the strange looking by-13-divider.And as simulated it works well up to 44 MHz with higher frequencies the divider „looses“on step and works as by-12 divider up to 90 MHz.Since 65 (MHz) is the result of multiplying two prime numbers (5 and 13) the otherpossible solution is dividing by-5. I also breadboarded a synchronus counter with 3 74S74 D-Flipflops and twoS-NAND-gates but it alsostops working short before 63 MHz (as simulated before with Multisim)It seems that the delay with the additional gates reduces the f-limits of the divider.Good thing I‘m now very confident in the reliability of Multisim.The bad one is, that the simple quest to design a working solution with my NOS schottky ICsisn‘t that easy as expected.

author: jpb
author_rank: Super Contributor
timestamp: July 25, 2020, 08:58:02 am
content: Have you looked at this Wenzel paper:http://www.wenzel.com/wp-content/uploads/dividers.pdfYou can increase the effective frequency of dividers by adding analogue circuit bits (to put it crudely).Look at the section : Getting More Speed from a Logic Family

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 25, 2020, 09:28:58 am
content: This is a cool paper! I will read it carefully this weekend.It remembers me to the (not so) good old times in East Germany in the early eighthies werewe used such techniques to get more out of the limited available stuff.On my shelf are a lot of 74LS circuits (also 74LS90,93,192,193 which should do the job up to 32 Mhz)but unfortunately only 74S03, 74S04, S10, S37, S74, S112 and a strange russian K531LAP1 = S20.As suggested I ordered a bunch of 74AC161. This seems the easy way. But I will rethink my designand try once again a 3-flip-flop divider with reset.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 28, 2020, 04:45:15 pm
content: After trying different versions of non working dividers for my 65 MHz OCXO I found a working solution.I use a modified Johnson-counter as you see attached to divide 65 MHz down to 13 MHz andthan with a simple 74LS193 down to 1 MHz.I simulated it first in Multisim and put it then on the breadboard.Attached you see on the scope the 1 MHz signal on top and on channel 2 the 1 MHz synched GPS signal of my Neo m8n.At this time I have a deviation of 20mHz (0.02 Hz)During the hours of rethinking of my divider design a tested a very simply VC for the OCXO with use of a TL431A.Before starting I tested the "interesting" Ref-Voltage for 65.000.000 Hz with a bench PSU (it's around 1.4 V)There is also a photo of my wild breadboard wireing. Left the divider starting with a 74S04 to get a sharp signal formthe sine of the OCXO, than the 2x 74S112 and my soviet 74S20 followed by the 74LS193 stage.In the middle the Neo m8n und a Neo m6n (the m6n synchronizes on the bread board with the simple ceramic antenna,the m8n needs an active antenna outside)You see also a reading of the counter in my SDG2042 of the OCXO - not to bad!

author: Labrat101
author_rank: Unknown
timestamp: July 28, 2020, 05:38:29 pm
content: Well done I glade you got it . Finely figured out .I just love your breadboard. you can sell that as an Art master piece .RNS

author: BrianHG
author_rank: Super Contributor
timestamp: July 28, 2020, 06:00:38 pm
content: Except for the op-amps driving the tuning voltage, I wonder if it is possible to re-create this entire project with a cheap crystal and this 1 IC with the right configuration stored in it's EEPROM:https://www.ti.com/product/CDCE925?keyMatch=CDCE925&tisearch=Search-EN-everything&usecase=GPNorhttps://www.ti.com/product/CDCE913?keyMatch=CDCE913&tisearch=Search-EN-everything&usecase=GPN

author: Benta
author_rank: Super Contributor
timestamp: July 28, 2020, 06:06:21 pm
content: If it's divide-by-65 that you want, two cascaded 74AC161s will do that in one go.

author: BrianHG
author_rank: Super Contributor
timestamp: July 28, 2020, 06:08:45 pm
content: Quote from: Johnny B Good on July 20, 2020, 07:23:52 pmI've always had noise issues with 74HC14. 74HC04 is generally near perfect. 74HC14 is generally good for cleaning up slow noisy transition signals below 1MHz where jitter is not a critical factor.

author: Benta
author_rank: Super Contributor
timestamp: July 28, 2020, 07:57:34 pm
content: Quote from: BrianHG on July 28, 2020, 06:08:45 pmFor squaring up sine wave signals (or other "soft" waveform signals), my absolute favorite is cascading two or three 74HCU04 inverters.No jitter or noise, it's pure amplification/limiting.Unfortunately, 74ACU04 doesn't exist

author: BrianHG
author_rank: Super Contributor
timestamp: July 28, 2020, 08:16:04 pm
content: Quote from: Benta on July 28, 2020, 07:57:34 pmForgot about that guy. Just a single N & P channel push-pull switch mosfets from in to out... The 74AC04 is still works well in a lot of designs as well.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 28, 2020, 09:15:24 pm
content: Yes I know that there are much simpler ways to come to the same or a better result.But my quest was to get the job done with the 30....40 years old treasures from my shelf.And if you compare the datas, the 74S04 is not so bad.Would be worth comparing some 04 from different families with our high end scopes and generators.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: July 28, 2020, 09:46:29 pm
content: My bread board housing came from all the trouble with a single breadboard allone on the desk.That never worked for me.I found in the garage a piece of 30 year old pcb board in terrible condition..I sanded it and cut it with my table saw. The reason for the housing with this pcb board was not shieldingbut the approach to have a good grounding.Unfortunately I also used 40 years older solder thatswhy I‘m unhappy with the quality of the solderings.So I built this three chamber box with all possible connectors (bnc and banana) and connected all blue grounding lines at least with 4 or 5 wires to the copper walls.Because I measured a voltage loss from the bench PSU to the counters I add 2 cheap chinese voltage/current displays for fine adjustments. (5 V and 12 V)

author: Benta
author_rank: Super Contributor
timestamp: July 28, 2020, 11:44:28 pm
content: Quote from: BrianHG on July 28, 2020, 08:16:04 pmAre you referring to me? I always had the impression that canadians are polite and friendly. Well...

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2020, 12:01:20 am
content: I took the opportunity of this thread to design a divide-by-65 circuit.Not because I do designs for free (I don't), but because it gave me an opportunity to try out KiCAD as design software, and a reasonably well defined specification was just the thing.The KiCAD experience was disappointing, to say the least, kludgy library handling and other issues.The upside is: here's your :65 counter/divider, and as you have 74AC161s arriving, I wish you success

author: jpb
author_rank: Super Contributor
timestamp: July 29, 2020, 09:34:35 am
content: Quote from: Benta on July 28, 2020, 11:44:28 pmI think he was referring to the chip not a person - but perhaps you knew that, I'm sorry to take you literally if you were only joking.

author: BrianHG
author_rank: Super Contributor
timestamp: July 29, 2020, 03:13:53 pm
content: Quote from: jpb on July 29, 2020, 09:34:35 amBenta was playing with me. Right after the line, I described the internal structure of the 74HCU04, it was understood when he deliberately erased that part of my answer in his quote of me.

author: Benta
author_rank: Super Contributor
timestamp: July 29, 2020, 05:14:50 pm
content: @BrianHG: yes, I confess, I was winding you up a bit...

author: Benta
author_rank: Super Contributor
timestamp: July 31, 2020, 09:56:58 pm
content: Played around a bit more with KiCAD and have a better feeling about it now.But that's beside the point:I now have the simplest divide-by-65 circuit for the OP.Setting it up is simple using the equation 256 - N where N is the division ratio. In this case 256 - 65 = 191.The counters are loaded with 191 (binary 10111111, but any division ratio can be selected using the Px inputs.Cheers.

author: Labrat101
author_rank: Unknown
timestamp: July 31, 2020, 10:31:37 pm
content: Hi I have a questionI have a very strong 3rd harmonic from my 50Mhz out from my PLL 3n502 which is multiplying by 2.5 from OCXO 20MHzso the third @ 150Mhz should I try killing it with a filter will it smooth out some of the jitter.?and if so how would I just kill this harmonic .The easy way if that's possibleRNS

author: Benta
author_rank: Super Contributor
timestamp: July 31, 2020, 11:39:58 pm
content: It's better to start your own thread for this.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: August 01, 2020, 12:42:55 am
content: That's entirely normal for a clock pulse output with nice fast clock edges. There's absolutely no need to add a filter which, in any case will either aggravate jitter or cause a complete clock pulse failure elsewhere in the FPGA.JBG

author: Labrat101
author_rank: Unknown
timestamp: August 01, 2020, 08:50:49 am
content: Quote from: Benta on July 31, 2020, 11:39:58 pmWHY . its within the scope of "" OCXO frequency dividers and PLL multipliers ""

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: August 13, 2020, 08:15:50 am
content: Quote from: BrianHG on July 28, 2020, 06:08:45 pmSorry for the delayed reply, Brian.I was reviewing these posts and realised I should have responded to this one. Better late than never and to set the record straight, here's what I'd have said at the time.I don't doubt that the 74HC04 may have been a better choice in this case but I just went with what I had (and Inowhave a rather large collection of HC14s to burn through) but in this case, the peculiar 2ns jitter on the falling edge (triggering the 'scope on the rising edge) was entirely down to the distorted sine wave from the OCXO.After trying other component changes, I eventually cured the distortion using a 100 ohm resistor directly across the OCXO's output before the 1nF coupling cap and the 1K series resistor (now a 160 ohm resistor - which, as it turned out, was not a critical change) going to the 'HC14's input pin.As it happens, getting the 'mid point' bias adjustment just right is critical to nulling out 2nd order harmonics (the lpf does a better job when it only has to deal with odd harmonics starting at 30MHz rather than also having to deal with even harmonics starting at 20MHz).In hindsight, I should have padded that 5K trimpot with a couple of 2k2 resistors to make the adjustment more stable and easier to achieve. I'd had to readjust it again a few days later which need had me worried that perhaps it wouldn't remain stable for very long. However, it seems to be stable enough since that final adjustment but I'll keep the padding option in mind for any similar 'bias trimming circuits' I might need in future projects.JBG

author: Labrat101
author_rank: Unknown
timestamp: August 16, 2020, 04:40:51 pm
content: Hi Bad_Driver & JBGThings seem to have gone very quite. I am very much going to buy the UTG962 Function Signal GeneratorI know that the Square wave rise time is a bit slower than the FY68 .. But it works out the box .And all the time and effort I have put into this . its showing sign of failure the Jitter is not stable any morethe sine has started to show weird rounding at the top. I should have some how binned it when the PSUwent up in smoke after an hour of use .The Specs on the UNI-T are good and they do have after sales support .. some what.And it has some really nice features that are really missing on the FY...I read the manual from UNI website.it has really a lot more functions and a real sync output for scope this is a plus .And even in this forum I can't find any one who has said anything bad about it.Still waiting for my Leo Bodnar GPSDO to turn up .How was London?Have fun stay safe

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 19, 2020, 11:30:21 am
content: Hi Friends,sorry, unfortunately I was not available during the last weeks since I was in London (really strange during Covid-19!!!) and got some housekeeping problems at home with my water tubes.So there was no free time beside my family and my job for sitting on my deskIndependent form Brena I came to the same solution with the divide-by-65 counter (load the value =256-65 into the registers of a 8 bit counter). In my simulation it seems that the firstsuggested schematics of Brena doesn't work but may be I made an error.After finding some working solutions I came to the KISS conclusion . Keep it simple and short. The 65 MHz OCXO can rest for further investigations a while.So I found two cheap Trimble 34310-T 10 MHz OCXO in China and I'm hoping that they are on a fast boat to EuropeDuring my vacation I read a lot about frequency, time, noise/Jitter and I got the feeling to become a time-nutbut why not? I got the strong feeling thatI need a very good counter or a new device for further improvementsBecause there was only little time I have found only 2 hours for the following experiment (may be useful for our GPS friends) to get a feeling on GPS accuracy.I checked the 1 pps pulse of my 4 GPS receivers again each other in a simple setup. You can see (or better believe that they are there) all 3 Neo n6m and my Neo m8n on the bread board.The n6m's are connected to local ceramic antennas nearby (not perfect) but the n8m has an external antenna on the roof (3m away).Thanks to my SDS2000X Plus I measured the pulses for more than an hour. You can see the statistics in the screen shot. Track 1 (yellow) is from Neo m8n.15...20 ns may be caused by the distance of the roof antenna to my breadboard. The other neo's may be suffer from reflection and bad signals on my bench.I ordered 3 new external GPS antennas and will repeat the experiment asap. I keep you informed!Johnny, I found an information that it's possible to read out from the UBlox Neos helpfull informations regarding the absolut error that can be used for corrections.You need an Andruino setup for that.

author: Benta
author_rank: Super Contributor
timestamp: August 19, 2020, 03:22:30 pm
content: Quote from: Bad_Driver on August 19, 2020, 11:30:21 amMy apologies! In the meantime I've done an exact timing analysis of the programmable counter using 74AC161. It will only operate at up to around 35 MHz.Sorry for wasting your time

author: Benta
author_rank: Super Contributor
timestamp: August 19, 2020, 04:26:15 pm
content: Actually, the ideal solution would be the ON/NXP prescalers MC12034, MC12052, MC12053, MC12054 that are in SIOC-8 and capable of dividing by 64/65.Downside: they're all obsolete.

author: Labrat101
author_rank: Unknown
timestamp: August 19, 2020, 06:45:54 pm
content: QuoteHi . I might be wrong but if you are using all 4 channels on your scope there will be a slight difference due to the way the scopedivides the triggers (shares) the trigger levels .Try to use the alternative mode where you can set the trigger reference to each channel independently .you will find that c4 will be nearer to the others .Also did you read my post a few up . There is a Bug in the cyclone chip its self and its not the software .The input of the cyclone chip is failing on the xtal input . as per the manual the chip has an internal counter that's meant to control theinternal DACs stability and I think (know) these are NOT originals and putting a fast rise pulse instead of the cheap xtal that they used with a slower rise time was also just on the max .The cyclone can be run with a 100mhz xtal on the other pin .. (forgot the number off hand) .You can see the distortion from the pins going to the dac inputs Left & right of the cyclone .The jitter is caused but the second internal timing dac being out of phase by 1.5deg . this was on my chip and varies as much as 5deg.so there are 2 pulse overlaying It is also visible on the sine as well but harder to see as the rising edge of a sine is much slower thanA square or pulse . So it appears to be jitter but its not because I can see it as low as 2mhz . its hard to see as its within the widthof the scope line . Set the scope to Dots and Persistence 1s all becomes clear.This maybe just on my FY68 and I got the Big Lemon instead of a small Lemon.If your interested I found that Ali Express is shipping supper fast I order some stuff and it has arrive within8 days (working) I could not believe how fast.My Uni-T UTG962 should be here next week .. I have had it with FY . and I was not going to chance there BS Data sheet again.I might do a comparison .. but I have a feeling it will be like comparing aUpdate attached photo of the overlay that comes ns after . ..if its not an echo that would mean the jitter is negative in time .. and so far, that's not possible yetThe dots are a tracer that I put to show the neg pulseThe second trace is appearing a few ns after the first trace out of phase . giving the appearance that's it a negativeThis also visible from the cyclone output pins .Have Fun

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 20, 2020, 08:27:06 am
content: Sorry Benta for misspelling you nicknameAs I learned with this synchronous counter simulations it seems that the reset or load pulses are to short or coming to late for the first counter stage.Attached my (in the simulation) working by-65-divider with 74XX161, unfortunately I found only the 74AS161 in the database (not the AC), therefor I'm not sure that it will work at 65 MHz. (sim only with 26 MHz)My first described 65 MHz by-5 solution worked only by accident - I forgot in my first design the connection to the first flip/flop, the "original" Johnson counterdidn't work

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 20, 2020, 11:01:07 am
content: Hi Labrat,hope you are doing well!You are wrong with your assumption regarding the 4-channel-setup. Attached you find a screen shot with the same setting but with all 4 channels connected to the output of the Neo m8n.Yes there can be a slight difference between channels (what can be fixed with the skew settings) but these are measured in ps and not the ns as you can see. (1ns = 20 cm)Because I own a Leo Bodnar-pulser I will do this skew testings later and will show the results (yes, it's the Leo Bodnar you ordered the GPSDO from), the pulse from the Neo is not sharp enough.Regarding the Feeltec stuff it's really a pity. But I learned a lot from that improvement experiment and my FY works for me with all the little weaknesses.And now the (not VC)OCXO drifts into the right ballparkAnd I learned that I will not do the same mistake twice. It's better to spend more money than to jump to short. I'm happy with my SDG2042 (now 2122)I hope you will become happy with your new purchase!I'm keeping looking around for a HP 53131A but at EBay they are to expensive for me (or are located oversea with risky TAX issues) and it's hard to finda device here in Germany.If I find the time I come back with a PM.regards V

author: Labrat101
author_rank: Unknown
timestamp: August 20, 2020, 01:16:54 pm
content: Hi. I did say I might be wrong .I forgot you had the pulser.sorry I missed the pshad to much& BeerI am still waiting for my goodies to arrive . Looking on worst case scenario. It can't be any worse.than a FY.

author: Benta
author_rank: Super Contributor
timestamp: August 20, 2020, 05:10:23 pm
content: Quote from: Bad_Driver on August 20, 2020, 08:27:06 amUnfortunately it won't be much faster than the 74AC161 version, perhaps 40 MHz.Correction: the 74AS161 will actually be slower than the 74AC161.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 20, 2020, 05:28:35 pm
content: Yes I think any asynchronous counter with reset or set logic will be to slow.My Johnson counter solution only works because of my mistake with "forgetting" the reset-connection to the first stage.Later I connected it to Vcc. But a lot of great invention were done by accident

author: cdev
author_rank: Super Contributor
timestamp: August 20, 2020, 11:40:09 pm
content: You guys have got to see the homebuilt GPS-timekeeping device one of the users here uploaded pics of a couple of years ago, it was just totally over the top. And it worked. It llooked like something out of Doctor Who.This guy could have made a living designing one-of-a-kind art like that.I vaguely remember that his GPS used a handmade quadrifilar helix antenna sticking out of its top.Search for it, its worth looking for.Quote from: Labrat101 on July 28, 2020, 05:38:29 pm

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 21, 2020, 10:01:23 am
content: I belief this unseen. There a thousands of posts reagarding GPS time solutions. At the end you catch the atomic standards with your effortsYesterday I found a cool well thought solution and I couldn't hesitate to buy it.Unfortunately only in germanhttp://dl0wh.de/wp-content/uploads/2015/02/DF4IAH-10MHzRefOsc_V2_UKW60-Skriptum_20150901.pdfbut there is a english GitHub sourcehttps://github.com/DF4IAH/avr_DF4IAH_10MHz_ReferenceI'm not sure if the source of all the chinese GPSDO's is this project.And I love what is possible with my new Siglent SDS2000X+, another run with my GPS-receivers.You can see very well the gausian distribution of the time differences between the triggered Neo m8n und the 3 Neo m6n.Display persisting infinit. Run abaut 4h.

author: Benta
author_rank: Super Contributor
timestamp: August 21, 2020, 08:01:47 pm
content: @Bad_Driver, I think I might have solved your issue.Remember that I mentioned some obsolete Motorola/ON Semi parts?Well, it turns out that a company in Arizona is still making them. Lansdale Semiconductor seems to have specialized in obsolete RF parts and is producing them using a foundry.Here's your part, SO-8, divide-by-65 (and 64, 128, 129). You'll probably need to level shift its output. Don't pay attention to the minimum input frequency, that's only an issue with sine-wave input; if you provide a square-wave it'll work fine. Otherwise ML12017 is an option.http://www.lansdale.com/datasheets/ml12052_reva.pdfCheers

author: cdev
author_rank: Super Contributor
timestamp: August 23, 2020, 01:02:09 pm
content: Wenzel also has written on diode frequency doublers.Very easy to make.Also, TVB has made his PicPets and PicDivs as well as source for them athttp://www.leapsecond.com/pic/made from PIC microprocessors so verifiably accurate and inexpensive.Quote from: jpb on July 25, 2020, 08:58:02 am

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 24, 2020, 07:10:24 am
content: Thanks Benta for the link, seems an interesting business to provide military facilities with genuin new old parts! I went trough the websites - worth reading!@ CDEV:I know that diode frequency doubling is used in RF for decades, it was for a long time the only way to do that (before we got PLL and synthesizers).But the hint with the simple PICs is interesting! Much easier than programming Arduino or Raspi. (and I wish to have 3 cesium clocks to drive into the hillsand prove Einstein - follow CDEVs link)I think I give it a try. Programmers are available for about 12 € and the PICs for about 1€/p.And with some shaking of my brain my old assembler programming capabilities will show up againBut I run short of time for hobby these dayswill take a while.

author: cdev
author_rank: Super Contributor
timestamp: August 26, 2020, 12:41:26 am
content: Quote from: Bad_Driver on August 24, 2020, 07:10:24 amI am not a programmer and am the kind of guy who prefers not to reinvent the wheel if I can avoid it, that said, I really want to learn how to program PICs because TVB's code does look accessible, he's annotated it well, and it just looks SO very useful.So, I bought a bunch of 12F675s and they are sitting right here, I will probably burn two of them within the next couple of days to help me with my build of LARS's GPSDO which I am just beginning. A picpet and a GPSDO paired up makes a VERY good, but also very affordable timer.

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 26, 2020, 08:59:09 am
content: Hi CDEV,can you give me a hint which programmer you bought (and hopefully works)?PICs seem to be very easy to work with for a lot of simple and not so simple stuff.Thanks in advance!

author: cdev
author_rank: Super Contributor
timestamp: August 26, 2020, 07:25:47 pm
content: It's an old chip so old software and hardware seem more likely than their newer offerings to support it.It seems their newest "PicKit 4" didnt support this chip as of two years ago (when I collected what I have) It may now.My gut impulse is to install an older version, but come to think of it the code itself has headers and in that header I think the version of MPLab TVB used to write the files is I think recorded. I cant lose if I use the same version, or close to it, right..Tell you what, there is no time like the present. I'm going to give it a try installing the MPLAB software and writing one of the binaries that I have to a one of my 12F675 chips now. I am a rank beginner, but at times, a real expert in making stupid mistakes!I wonder which of the binary files I should attempt to write first? So many of them look useful, its hard to PIC. So I am going to have to take a bit of time to look through the code and his web pages again.Please don't laugh at me if I screw it up, okay? I am being so stupid to encourage people, if I can do it, most certainly all of them can.---------------The source files are inwww.leapsecond.com/pic/srcThey are little frequency dividing gems, basically.. For example: (from leapsecond.com/pic )The pic divs are dividers, the picpets are timers of various kinds..VariationsWhen a programmable synchronous microcontroller is clocked from an accurate frequency reference, manyinteresting, practical, one-chip solutions come to mind. The initial 10 MHz to 1 Hz divider evolved into dozens ofuseful devices.Powers of ten dividersPD3 divides by one thousand (10 3 ), e.g., 10 MHz→10 kHzPD4 divides by ten thousand (10 4 ), e.g., 10 MHz→1 kHzPD5 divides by hundred thousand (10 5 ), e.g., 10 MHz→100 HzPD6 divides by one million (10 6 ), e.g., 10 MHz→10 Hz or 1 MHz→1 HzPD7 divides by ten million (10 7 ), e.g., 10 MHz→1 HzPD8 divides by five million, e.g., 5 MHz→1 HzNote: there is no requirement to always drive these dividers with 10 MHz. A PD3 will divide by 1000 regardless ofthe input frequency; the output frequency is always 1000 times less than the input. The PIC clock operates fromDC to 20 MHz.Quite a few of them perform multiple tasks.

author: Labrat101
author_rank: Unknown
timestamp: August 26, 2020, 10:16:47 pm
content: Hi this looks nice I was wondering if the 12F1822 would also work as I have whole bunch of them . they have the same pinout . we bought a whole bunch a few years back for a projectthat the customer back out of .. So they are mine now ..I might try one and see what happens . I guess it will ether work or notThe only trouble the code is in HEX so I have no idea what the internal fuses are .If some has the original open source code but I guess this maybe the owners protection.to the code ..Thanks this is a cool timing project to get my teeth in. for fun ..

author: cdev
author_rank: Super Contributor
timestamp: August 26, 2020, 11:10:18 pm
content: The header for picdiv27 has the following - The author who is also a user here, tvb pubishes both the hex and the mpasm code - is that what you mean?; ------------------------------------------------------------------------;; Title:;; PD27 -- PIC 10 MHz to 1PPS divider, with sync and milli-step;; Function:;; This PIC program implements a digital frequency divider: the external; 10 MHz input clock is divided by ten million to produce a 1PPS output.;; - The 1PPS pulse width is 10 ms (1% duty cycle).;; - Two Step inputs are checked once a second:; to advance 1PPS by 1 ms, hold StepA low; to retard 1PPS by 10 ms, hold StepB low; to advance 1PPS by 100 ms, hold both StepA and StepB low;; - Two inputs support optional manual 1PPS synchronization. Pull Arm; pin low for a second to stop divider. The output will synchronize; to next rising edge of Sync pin (within one instruction cycle).;; Diagram:; ---__---; 5V (Vdd) +++++|1 8|===== Ground (Vss); 10 MHz clock in ---->|2 pD 7|<+--- StepA; 1PPS out <----|3 27 6|<+--- StepB; Arm o--->|4 5|<+--- Sync; --------; Notes:;; o External pull-up required on Arm input (pin4/GP3).; + Step and Sync inputs have internal WPU.; Output frequency accuracy is the same as clock input accuracy.; Output drive current is 25 mA maximum per pin.; Coded for Microchip 12F675 but any '609 '615 '629 '635 '675 '683 works.;; Version:;; 07-Feb-2013 Tom Van Baak (tvb)www.LeapSecond.com/pic;; ------------------------------------------------------------------------; Microchip MPLAB IDE assembler code (mpasm).

author: cdev
author_rank: Super Contributor
timestamp: August 26, 2020, 11:21:30 pm
content: I think they still have free tools available but it seems they charge for their compiler and recently changed to a yearly fee model. Some of their software may also phone home.I had heard about this problem- not specific to them, it was again and again described to me over the years as the thing that drove so many makers to Linux late in the last century.Quote from: Bad_Driver on August 26, 2020, 08:59:09 amI don't know, but there is a thread on the issue in the Microchip forum. Maybe they will have a change of heart. It makes me less inclined to use Atmel too.

author: Labrat101
author_rank: Unknown
timestamp: August 27, 2020, 11:26:02 am
content: Hi I cant find the code for the PICPET is what interested me I followed all the instruction on how to.for the life of me the codes for pP06 pP07 .. seem to me not listed or am I missing something

author: cdev
author_rank: Super Contributor
timestamp: August 27, 2020, 03:46:11 pm
content: I noticed that yesterday. Its possible that I may have been wrong or that he removed them. In any case he only charges $5 for a chip burned with the code, which isveryreasonable.

author: Labrat101
author_rank: Unknown
timestamp: August 27, 2020, 05:15:17 pm
content: Quote from: cdev on August 27, 2020, 03:46:11 pmThanks .. I thought I was loosing another Marble . After reading the entire section including his field trip with the Kids up the mountain for 2 days and aa car loaded up with 3 atomic clocks and a shit load of car batteries inverters etc .and lost a few picoseconds . Wow he needs a nerd medal of the year award . really cool reading .. & the Leap Second .My Seiko watch looses less than a minute between battery changes approx 7years . I think I will stick with my the lighter wrist watch .Really interesting site well worth the reading and his work is amassingRNS

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 29, 2020, 10:38:35 am
content: Hi Folks,I have to refocus myself on the topic of our board. And beside my family and my job I‘m short of time for the hobbyThis week I got a used 10 MHz ocxo from china. It‘s a CTI OSC5A2B20, 5 Volts and CMOS output. Was 6€.It is not the typical CTI that is offered at Ebay I had to learn. It has a complete different Pin out than the other ones.Because you can not reach the chinese web page there is no access to data sheets. If someone can help me - thanks!It works as expected. But it‘s missing the Vref output. So I started with my described simple TL431 based reference. I learned very fast that the combination of a 10 turn pot and 2 resistors suffers from temperature drift.The Vcontrol input has an impedancy of about 5...10 Mohm so there is no need for a voltage follower with additional offset error. 1 mV change in Vcontrol leads to 1ppb drift. On the scope you see a change of0.1 mV as drift against the GPSDO! Terrible!!And I found that my old Fluke 45 (4.5 digit) reaches it capabilities. A new better DMM with tracking/recordingfunction is now on the wishlist for Santa Claus.I changed the R network against two NOS metal 40 turn pots in series ( one for fine adjustment) and itbecomes better. But I think that the weaknesses of a breadboard solution also have an impact.Next steps: try to bring the TL431 into thermal contact with the ocxo and cover it and built a soldered strip boardunit.To become a junior time nuts you need a good counter!With luck and after searching for several month I got yesterday a HP 53131a in near mint condition. It was not a bargain but much cheaper than all the other offerings I found @ Ebay. Inside as new, bright display only the Nextel covering is little sticky. But it came without any options. So you know what my next project will be - to build a ocxo based time base. There are several solutions out there, from china, from Gerry Sweeney and some other. There are several postings here.

author: Labrat101
author_rank: Unknown
timestamp: August 29, 2020, 11:50:32 am
content: Hi the cti has all the info in the long serial No.This number CTI OSC5A2B20 does not look right whats the number engraved on top the case?also the vc is 10k Z . on my CTI I put a 5.6K in series with the pin and the centre of the 10k ten turnpot so any adjustment would ensure the VC is kept at a 10k or above .You will have to check in the CTI archive . I noticed on a few CTI do have an enable or disable on theVC .. my one did . example .Don't put the TL431 near the ocxo I found it works perfectly about an inch away and use a large enough resistor as not to load TL431 so it gets warm I set my for about 10ma you only require the voltage and about 10ua at the VC of a cti .. you one may have different ratings .Do you know what series your CTI is ??Does it have 100618 on the top number this is the number that give the info for your version .. (example)Hi BTW I think you will find that the CETC CTI OSC is a copy of the CTS the manual can be foundI think it is the 100 series from what I could make out from your photo

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 29, 2020, 01:21:27 pm
content: The CTI ocxo

author: Labrat101
author_rank: Unknown
timestamp: August 29, 2020, 01:55:53 pm
content: Hiwhat I can tell you CTI is a rebrand . Isotemp or CTSit could be a Isotemp as the serial is very close . or a CTS I look more though all my achieveits a 160 series or 140 iso not 100% sure on that ..did it have 4 green stand off pins on the bottom . if yes its properly the Isotemp as the CTS haslaser engraving and hard to remove . the Iso has a plate label that can be removedIt has come from a communication tower .I found this from another seller and it the cheesiness version with English with the CTS cut of at the top as I have the 119 series and the look almost identicalWhich puts it almost correct to that number vc -+2v & 10k Z which is right for a CTS.not sure about the ISo JBG would know he has a load of Iso ocxo's

author: Labrat101
author_rank: Unknown
timestamp: August 29, 2020, 03:20:36 pm
content: Hi Again .. Just out of interest . I track down CTI China .. your not going to like this .They Don't make crystals they are just a test serviceCenter Testing International . So they say..I am 89% sure your OCXO is a CTS and the numbers have been mix properly for copy write .the CV for sure is +- 2volt @ 10k Z its 0.02 PPB and it should be really Goodenjoy . the data sheet I load up is correct as far as I can tell .

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 29, 2020, 07:25:06 pm
content: Hi Labrat,yes I have the same - see attached. The ocxo runs very well and I will keep it running for somme weeks tosee how it drifts. But my ocxo has a complete different pin layout than the other one.I also found a very good paper from Analog Devices regarding Voltage references and dividers but unfortunatelyI can not upload it from my iPad I have here with my Gin Tonic I‘m drinking with my wife.

author: Labrat101
author_rank: Unknown
timestamp: August 29, 2020, 07:56:55 pm
content: The Gin & tonic is the best for Time nut brain lubricationI am still waiting for my toys ..

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 30, 2020, 08:02:24 am
content: Hi Labrat,thanks for the hint with Isotemp. It seems that the company is out of business but I found thedata sheet. And yes, there are two different pin layouts!See attached.

author: Labrat101
author_rank: Unknown
timestamp: August 30, 2020, 10:58:56 am
content: Hi the Gin got to youyou loaded up an empty PDF . But I had already seen this pdf . the numbers onyour ocxo don't really tally completely which makes me think that you havea custom model from a communication system that will have better specs .and the pin lay out it is for their foot print PCB. .as you have it running it has to be good .But make sure you have a minimum resistor of 5k plus from the VC pin to the potcentre if you load the vc below 10k z min it will drift as the internal circuit willtry to return the VC voltage back to 1/2 the supply voltage .I also used the TL431 make sure the control voltage is separate from ocxo 5vI found that the heating device affected the stability if using a shared sourcewith the VC .The CTS ocxo that I bought here was also a custom model but I had the paperwork from the supplier were it came from and it was new still sealed..Nuts, what's the time !.. O I missed it again! Those ps are dammed fast little buggers

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: August 31, 2020, 09:15:18 am
content: Hi Labrat,yesterday I found 2 hours and I reworked the OXCO on a strip board.I put the TL431 direct on the can of the OCXO to keep at the same (stabilized) temperature andcovered the whole board with a lot of foam.I use a low noise analog PSU with an LT1083 (dedicated for behind-SPSU regulation) that is powered by an wall Switching PSU 12V 3 A.The LT1083 based PSU was on my bench for yearsMy OCXO seems to be an ISOTEMP (this 4 green glas stands on the bottom) but has a third pin layout that differs from the 2 of the data sheet.But it works. After some days running and now in the foam coating I got 10mHz deviation against my GPSDO (1 ppb).Not to bad!On the top of the photo you see the display of my GPSDO with useful information.The upper line shows the error of the 10 MHz against UTC, in this case 0.100 ppb.Left from the display the foam coated board with the OCXO and the VCO control which is used as external reference for the HP 53131A.I will use it as external reference for the HP counter and my SDG2042 untill the Trimble OXCOs 34310-T will have found their waywith the slow boat from China. I'm also awaiting a Aluminium enclosure to make it perfect.By the way, has anyone a data sheet of the Trimble 34310-T?

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: September 01, 2020, 02:37:02 pm
content: Quote from: Labrat101 on August 29, 2020, 01:55:53 pmActually, Raymond, what I've got a load of is a bunch of CQE branded OCXOs, all 12v type (the original 13MHz unit finally proved to also be 12v rather than a 5v unit I'd had to initially assume for lack of an actual data sheet) one 13MHz HCMOS square wave unit as previously mentioned plus another seven 10MHz sine wave output types I'd tracked down a cheap UK source of as a direct result of my searching for a datasheet for the original 13MHz unit I'd picked up dirt cheap (£4) at the NARSA radioham rally in Blackpool just over a year ago now.I've only ever owned CQE branded OCXOs (those seven 10MHz units represent a life time's supply). That's not to say I won't land up acquiring a few more (double ovened this time) OCXOs once I've gotten over the shock of splurging out a whole £197.67 on a used, calibrated to within 1.06uHz, Efratom LPRO-101 from (as I later discovered whilst searching the EEVBlog fora for anything "Efratom LPRO-101" related to while away the delivery waiting time) a fellow member, "testpoint1" whom it seems, did finally migrate to MA, USA after all.JBG

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: September 02, 2020, 04:30:45 am
content: Quote from: Bad_Driver on August 31, 2020, 09:15:18 amHi Volkmar,That LT1083 based psu with its claimed ability to reduce switching noise as a post smpsu LDO regulator intrigued me enough to track down its datasheet to see whether it included ripple rejection figures for frequencies higher than the bare typical "at 120Hz" caveat given in most LDO datasheets since I have a rather jaundiced view of this technique to 'magically cure' the switching noise issue with smpsus and dc-dc converters.I saw an actual graph going up to 100KHz with an impressive (for an LDO) rejection figure of 30dB where your standard LDO would start behaving more like a high pass filter, aggravating the problem rather than mitigating it. So, for once, this looks like it meets its claimed switching noise rejection performance and not be a waste of space as is so often the case with so many other LDOs that imply such a benefit when simply tacked directly onto the output of a DC-DC converter.The standard LDO, lacking any such HF ripple rejection can still be used with an smpsu but in this case, its job is simply to restore voltage regulation lost by the use of an RC LPF to suppress the noise before it reaches the LDO which is all fine and dandy when you can afford to take the hit on efficiency by the 2 or 3 volts lost in such a filter'. I've download the datasheet for future reference so my thanks to you for leading me to an LDO that might actually reduce the noise and HF ripple of an smpsu.Regarding that OCXO, I think you should be able to get it calibrated to better than 0.1ppb with a bit of care and perseverance. If you're using a trimpot to electrically tune it, the major problem when trying to get sub ppb accuracy lies with the quality of the trimpot and the need to really pad it out to limit the trimming range to make the adjustment less ticklish.When I was trying to trim the 10MHz CQE OCXO I'd used in my FY6600 to get below the 10ppt mark for a few hours at a time, I landed up utilising the 2G tip over effect to achieve the very fine tuning required, without having to touch that damned trimpot which so often would make the calibration worse rather than better, by altering the tilt angle of the front panel using suitably sized items as shims (a coin, an india rubber pencil eraser or two, the odd expired credit card and a DIP pin straightening tool just to name four of the items used).All of that messing around with makeshift shims to fine tune the FY6600's OCXO has become a thing of the past since I finally acquired a Rubidium Frequency Standard (RFS) and it's now used to represent the GPSDO's 10MHz reference frequency as a rather distinctive Sinc pulse via its external reference connection (the OCXO is now frequency locked to the GPSDO).I can't help you with any information on that trimble I'm afraid. If it weren't for the fact that I can't track down a suitably sized extruded aluminium project box to house my RFS, I too would be awaitng delivery on a nice aluminium project case. It seems I'm destined to fabricate a "Special" to solve my RFS's lack of proper housing wherein I can create a thermostatically controlled environment to minimise frequency variations with changes of room ambient temperature.As you may have surmised from my previous posting, I've been a little preoccupied with my latest "toy" (an Efratom LPRO-101) this past week along with other experimental activities involving my gpsdos (the MK I has been taken apart for spare parts) hence my absence from this topic thread these past few weeks.I had hoped I could keep the MK I going for a few weeks longer but I'd had to disconnect so much of the wiring from the "Five Volt" 13MHz OCXO in order to run higher voltage (possibly destructive) tests, disturbing other connections to the point where it just didn't seem worth the effort of putting it all back together again anymore.As it happened, that "Five Volt" ocxo proved to be a 12v part after all - it was rather handy that it happened to be able to pass through its activity dip transition temperature in rather short order from cold and start producing a stable 4V p-p square wave from a 5V supply with the only side effect of this low voltage operation being a protracted 7 to 8 minute warm up time.When I'd bought this very first, one and only, OCXO module, I didn't have a variable voltage bench supply to test it out on progressively higher voltages and, since it was able to still output a stable 13MHz even on a supply as low as 4.8v, there seemed a real possibility that it was a 5 volt part that might well let out its 'magic smoke' if subjected to a 12V supply so I decided to treat it as a 5 volt part until I at least had some more 'spare' OCXOs to play with (and a variable bench supply to make any such potentially 'test to destruction' experiments a whole lot more informative). Anyway, I've now relabelled it as a 12V unit and added it to my parts bin (more as a keepsake than something I'm likely to find another use for).As well as an SMA socket for monitoring both voltage and noise and ripple on the MK I's 5.17v Vcc rail (1uF ceramic cap with 1KR shunt in series with the connection to the Vcc rail), I'd added a couple of ugly banana sockets to connect a DMM to the ground and the buffered copy of the EFC voltage to monitor the output voltage from the PLL.Initially, I could only see voltage changes in increments of ten mV with my existing DMM collection so I blew a whole 13 quid on a nice Mestek DM91A "9999 counts" DMM to improve the resolution by an order of magnitude to increments of 1mV. Even this didn't suffice to let me see voltage changes before I could predict them from the phase shifts shown by the scope traces so I used a 3.16v lithium coin cell in series opposing to provide a stable dc offset that would allow the DMM to autorange to the 1000mV scale, reading the difference between the 3.298 EFC voltage and this dc offset, allowing me to see changes in increments of 100uV.Whilst a new unused CR2032 creates a remarkably stable offset voltage (better than you can get out of a TL431 imho), this was just a temporary bodge to prove the concept, hence my using a TL431 to provide a +3VDC offset to the black (formerly the ground) banana socket to allow my crappy (on account it suffers from a permanent, silent, 10 minute shut off time out battery life extender annoyance!) UNI-T 58A DMM to display the 290 odd millivolt difference in 1mV increments. The only reason for my resorting to such a low grade "Voltage Reference" was on account of the lack of a stable Vref from my under-volted 13MHz OCXO (I can now see a stable 5.1ish voltage once its supply rail tops the 11 volt mark).For my MK II GPSDO, I use the 5.127v on the 12v 10MHz OCXO's Vref pin to generate dc offset voltages in 1v increments via a string of matched 1KR resistors fed via a 120ohm padding resistor with a 50K trimpot in series with a 20KR across the 5K's worth of resistors to trim the volt drops to within half a millivolt of the 1v drop across each of the lowermost 3 resistors (if I ever need to use a 4v dc offset, I'll have to apply a small adjustment to the shunt resistance of the trimpot otherwise - the 1, 2 and 3 volt taps are matched closely enough to avoid the need for such a recalibration).The EFC, the (jumper selected) DC offset and the ground are wired to a 3.5mm stereo jack tip, ring, sleeve contacts respectively to provide access to these test points for an external voltmeter. Not only does this provide a neater connection point than the banana sockets I'd used on the MK I, it also allows me to measure between ground and the EFC to give a direct reading and also to measure the DC offset with respect to ground by way of sanity checks of the EFC minus DC offset voltage high resolution readings I normally monitor.The Vref pin on an OCXO is the most stable voltage reference you're likely to be able to access outside of a professional calibration lab so it's the obvious no-brainer choice voltage reference available to the hobbyist. Normally, you wouldn't use it to supply tens of milliamps directly to other voltage sensitive parts of a DIY GPSDO. Indeed, the manufacturers' advice in this regard is typically not to load this pin beyond a maximum of 1mA.In my case, this fixed 5.12K 1mA load reduced the open circuit voltage by 1mV from 5.128v to the 5.127v I now see across my tapped potentiometer circuit. This is of no consequence since this represents a tiny fixed additional loading on the oscillator's internal supply rail.As far as the 1.216KR worst case DC offset's impedance effect on the EFC voltage measurement accuracy is concerned, at a worst case loading of just 10nA, the voltage 'error' is simply lost in the noise. In my case, absolute accuracy plays second fiddle to my primary requirement to monitor the delta V of the EFC voltage (in such a basic James Miller based GPSDO design, minor dc offsets and temperature effects are simply lost in the wash).Harking back to the original question of how best to divide the frequency output of a 65MHz OCXO down to the required 10MHz GPSDO reference output frequency (sharing similar issues to my own 13MHz to 10MHz efforts), it seems to me, as I originally suggested, that the best way to proceed would be to divide the 65MHz down to 32.5MHz and proceed from there (you can divide by 13 down to exactly 2.5MHz which is comfortably above the 2MHz minimum clock input for a 3N502 clock multiplier programmed to multiply by a factor of 4 to generate the required 10MHz).One of the problems I discovered with all of the additional complexity (no doubt exacerbated by my using stripboard construction) was the storm of switching noise imposed by the logic gates on the supply rail polluting the 10MHz output which necessitated the addition of a series resonant 10MHz crystal between the LPF output and the BNC socket to filter the worst of the resulting jitter noise from the MK I's 10MHz sine wave output. The modest additional 1dB loss was neither here nor there (I already had a healthy +12.5dBm coming out of the LPF to start with).The MK II is essentially a 're-spin' of the MK I but using an M8T in place of the M8N GPS receiver module with a 10MHz OCXO to avoid the divide by 13 jiggery pokery (four ICs and their additional 400mW energy requirement) making use of a single sided copper clad board to eliminate the self inflicted problems of logic gate induced noise on the supply rails and improve the effectiveness of the LPF suppression of switching noise on the outputs of the DC-DC buck converter (5.31v rail) and the 5 to 12 volt boost converter feeding the OCXO's 12v pin.The end result of all these changes to the earlier design being a reduction of energy consumption once warmed up, down to just 1.4W from the MK I's already modest enough 1.8W at 12v in spite of the small (3 to 4% ) extra losses of an additional DC-DC boost converter to power the 12v OCXO.I ran an energy consumption versus DC input voltage test over the 7 to 24Vdc range (none of this restriction of a 11.5v minimum to 15v maximum supply voltage nonsense for me, thank you very much!) and, in summary, it ranged from a minimum of 1.318W at 7v to a maximum of 1.488W at the 24volt limit of the buck converter module (an increase of just 170mW for a 17 volt increase implying a fixed vampire loading of 10mA on the buck converter's input).Just out of idle curiosity, I calculated a 60 hour autonomy from a new, freshly charged 7AH SLA back up battery. Using my selected 12 and 9 volt wallwarts, the mains consumption is just a fraction over 2 watts making its energy demand on a UPS protecting a desktop computer and a file server almost invisible by comparison. Of course, in a parody of Asda's advertising slogan, "Every little helps", in this case, it's more a case of "Every little hinders.".As I mentioned, I've spent this past week checking out my newly acquired pre-owned Efratom LPRO-101 (warranty expired way back in December 2001 - normally a 2 year warranty, implying that it's now some 21 years old). The lamp voltage now reads 4.963v. It had been 4.975v when I initially tested it on a 24v supply a week ago. I've been running it from a 19 volt laptop charging brick (19.65v actual) which may account for the small drop in voltage (elevating the temperature with towelling to test its susceptibility to temperature changes had increased the lamp voltage to 4.980v and using a Poundland USB powered fan to cool it had reduced the voltage).Whilst these rubidium frequency standards (RFS) have some susceptibility to temperature variation, the real problem is in their susceptibility to barometric changes which are harder to compensate for without the use of a low retrace barometric pressure sensor and a compensation circuit calibrated to the EFC tuning slope.DIYing an effective thermostatic control of the base plate heat spreader temperature seems a somewhat easier modification than a barometric frequency compensation controller for the hobbyist to concoct. Of course, that impression may be due to the seeming absence of any on-line DIY barometric compensation projects simply because I've never sought out any such barometric sensing projects - it might be a good idea to do some research on this.Apparently, I'm not alone in my ignorance of barometric compensation measures to stabilise RFS modules. I came across a very recent research paper published only two years ago on this subject of quantifying and analysing the factors involved in the sensitivity of rubidium vapour gas cell RFSs to barometric changes for seemingly the very first time.My main problem at the moment lies with the apparent complete lack of suitably sized extruded aluminium enclosures on Ebay or elsewhere to house my new RFS module into. I spent a couple days searching till my eyes bled before giving up this Holy Grail like search for rocking horse droppings (or decent 3 rail smpsus with a 1A rated 5v rail and half amp rated +/- 12 or 15v rails - another surprising rarity also on a par with a Unicorn droppings hunt).There seems to be a huge gap between the maximum size (which still aren't quite big enough) of reasonably priced extruded aluminium enclosures and the much rarer more than large enough but overpriced enclosures being offered for sale. So much so, I think I'd rather build a customised case of my own either from my tiny stock of redundant aluminium enclosures or even from a local dealer if a tour of the local scrap merchants fails to produce what I need rather than pay through the nose for a not quite the size and shape I'd like ready made enclosure.I've tried looking for used non working kit just for their cases as an alternative way of acquiring a more suitable enclosure at a reasonable price but even here, what I've looked at has still been grossly overpriced. However, I suspect that given the right sort of search term, I might find a cheap source of suitable ready made cases in the form of "For repair or spares" sales. Suggestions anyone?JBG

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 02, 2020, 08:32:56 am
content: Hi John,I'm happy to have you back here!It took a while to go through your long post! I'm in ongoing rework of my bathroom and the fiscal year end in my company is near so I haveonly little time for the hobby.I also went through the data sheet of the LT1083 because I found 2 DIY kits I bought at EBay for 5€ or so several years ago.I know that the LT1083 are not bad but this was also new for me with the ability of ripple rejection.For reference:LT1083 Adjustable Regulated Power Supply Module Parts and Components DIY Kithttps://ebay.us/oHycosCongratulations for your Rubidium Oscillator. Here a link I found but I'm pretty sure that you know this project.http://www.ka7oei.com/10_MHz_Rubidium_FE-5680A.htmlI'm not sure how risky it is to buy an old Rubidium because I learned through my investigations that they all can suffer from aging ofthe Rubidium gas in the glas enclosure. But as a perfect time nut no one can hesitate if there is a good offerNext step will be a Caesium Class 1 reference?During my tests with my new toy (HP 53131A) I had to learn that my GPSDO sufferes from some low frequency jitter around 1 Hz.You can clearly see this on the scope against the OCXOThe GPSDO is a development of german HAM. Unfortunately the link is only for a german speaking PDF but there is also a GitHub linkwith some english explanations. But he didn't have continue his work on it.http://dl0wh.de/wp-content/uploads/2015/02/DF4IAH-10MHzRefOsc_V2_UKW60-Skriptum_20150901.pdfI think I will sell it and look for a Trimble Thunderbolt instead of a Rubidium.So I can not calibrate with this tool better than 10 mHz these days. But this is in the range of the error the GPSDO reports.In my first setting I played around with different solutions for the VCO of the OCXO. It has no Vref output.But I learned from a teardown that some OCXOs only provide Vcc in serial with an resistor to the Vref output. So if youdon't have precise data sheet specs you are unsure about Vref.Since I have only a bunch of TL431 around (yes the cheapest reference source - I know) I put it direct on the can of the OCXO andas you saw on the photo covered all with foam.It was not possible to reach thermal stability with a combination of fixed resistors and a 10 turn pot.But from my old east german treasures I had some 40 turn metal pots that were dedicated for DMM trimming.I used two of them in serial with additional tantalium cap filtering - a 15k and a 2k. Because I measured the impedance of the Vco input with about 5...10 Mthere is no need for an additional OPA voltage follower with additional offset error.As mentioned before I tried to follow Vref/Vco withmy old Fluke 45 (4.5 digits) but with this I reached the limits of this device. (1 ppb frequency deviation = 0.1 mV)I have also now reached the limits of my GPSDO reference with this setting. So always room for improvement! (You know I ask Santa Claus for a Siglent SDM...)But the HP 53131A was a great buy! Nearly in mint condition! The OCXO is now used as external frequency source for the HP and the Siglent SDG.btw: I tried first time to order an aluminium enclosure from alibaba. I keep you informed how this works for me. It was much cheaper than the same offer at EBay.Regards to all!

author: Labrat101
author_rank: Unknown
timestamp: September 02, 2020, 07:37:03 pm
content: Hi I think from your diagram which I tried is not as good as putting 5 or 6 k ohmin series with the centre pin of your pot to the VC . and remove the 2k from the groundleg . then the centre of the pot will be more balanced .I tried a few ways and that gave the best results .and the vc stays closer to the 10k Z. .RNS

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 03, 2020, 07:50:37 am
content: After running the OCXO for more than one week the error against my GPSDO is 10 mHz = 1ppb.To stay realistic this is an error of 2 seconds for my whole life (till today).We are now able to measure (with the help of GNSS/GPS) such deviations.No one would try as hobby to build a Voltage meter with 9 valid digitsBut I'm with you, it's interesting to see how fare you can go with this time gambling. May be sometime someone re(invents) the flux capacitor50 years ago my Dad built his first Quartz clock with nixie tubes and decade counter based on discrete transistor flip flops. And I was so impressed to see how theclock was switching to next hour together with the "beep" in the radio.35 years ago I built my first DCF77 controlled clock (the german time standard on Long Wave), I was proud to get an atomic synced clock with anfrequency deviation (of the receiver) of about 0.1 sec. Technical you can now reach 1.5 E-6 deviation (due to all the errors of the long wave transmission and with usage ofall possible corrections)Now I'm looking on my 10 digit counter on the last 2 digits and think how to get there also 2 zerosI'm on my limits to measure the VCO with my Fluke 45. But it seems that my old 40 turn metal pots doing a good job.I tried it with additional serial resistors but they seem to have other temperature curves and the drift was much bigger.And with 40 turnspots you are sensitiv enoughI measured the impedance of the VCO input of the OCXO with 5...10 Mohms. I do not believe that a serial resistor will have an impact.best wishes for the day!

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 03, 2020, 07:54:57 am
content: One question.As mentioned I use a TL431A as voltage reference.What other, better references are available in TO92 case or in DIP??? And with an affordable price (max. 5 €/$/GBP)Any suggestion? (Vref 4...5 volts)Thanks in advance!

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: September 03, 2020, 10:28:04 pm
content: Quote from: Bad_Driver on September 03, 2020, 07:54:57 amIf your OCXO provides a Vref pin, use that instead of the humble TL431 for your temperature stable precision reference.I've attached a photograph of a couple of circuit sketches. The topmost shows the +3000mV DC reference offset circuit I'd had to resort to with the MK I GPSDO for lack of a properly functioning Vref on the grossly undervolted 13MHz OCXO (a total lack of a datasheet to indicate its working voltage had forced me to play safe and assume it was a 5V part with a very slow warm up characteristic) to reveal Vfc voltage variations to tenths of a millivolt using a cheap 4 digit DMM.When it came to re-spinning the MK I design into a MK II using a proper 12v 10MHz OCXO with a fully functioning Vref, I gladly gave up the use of a separate TL431 voltage reference for the much more temperature stable 5.127 volts on the OCXO's Vref pin. I'd been well annoyed by the TL431's +/-1mV drift with modest changes of temperature by then.The second sketch shows a rough circuit layout for adding a calibration trimpot to the OCXO board installed into my FY6600. Looking at it now, I'd be inclined to replace the 33KR with a 27KR and use a 1 or 2K trimpot in place of the 22 turn 20K one that's currently giving me grief when trying to achieve the more precise calibration that's now possible with the sheer stability (absent from any GPSDO, let alone my own MK I) of an LPRO-101 RFS.Of course, when I do finally get around to revamping this circuit, I'll be recording the actual voltages that now currently apply before recalculating better optimised resistor values which I'll probably scale down to a tenth of the existing values giving me a loading of ~0.5mA and a lower impedance tuning voltage source. Whether the Vfc input impedance is 68K or 5M doesn't really matter (it just means the position of the trimpot wiper will be displaced a fraction of a turn which matters not one jot in this case).BTW, whilst I'd ventured into my basement (one time radio shack and workshop, much neglected these past two decades) yesterday afternoon to empty the dehumidifier's two litre tank for the umpteenth time these past three weeks or so, I thought to check out materials to build an enclosure for my RFS and found a ready made unused instrument case lurking on top of a cabinet with 20 years' worth of grime that, in spite of it being in plain sight, only caught my eye as a result of my actively seeking out a means to fabricate a suitable enclosure for the RFS.It cleaned up quite nicely after giving it a good scrub with washing up liquid in the kitchen sink. It's a little larger than I was aiming to fabricate but that proved useful in that it saves me having to cut down the 6mm thick duralloy heatsink plate salvaged from an ancient Pye Cambridge 25W solid state PMR base station that I was using as a heatsink for the RFS during my initial tests.Rather than mount this baseplate directly to the base of the case, I'm planning on mounting it on stand offs so I can use a small fan to recirculate the air underneath it and neatly avoid having to cut out vent slots in the case - there's ample surface area for the internal airflow to transfer the 10 or 11 watt's worth of heat dissipation with only a modest rise in temperature. I can easily mount a temperature sensor to the topside of this alloy plate to control the fan or fans and cutting vent holes if needed is still an option (the big plus point of DIY projects).I've attached additional photos showing the RFS sat on the alloy plate, resting on top of the case to give you a sense of the scale of the job, along with a couple of pictures of the MK II GPSDO. The front panel is identical to that of the MK I whilst the rear panel is a tidied up revamping of the MK I's layout. The red LED is a simple power on indicator. The green LED flashes at 4Hz 50/50 ratio to indicate unlocked GPS state (confirming that the user settings are still valid bynotwinking at the default 1Hz rate), eventually (36 seconds from a cold - it's been powered down for over four hours - start) turning a solid green to show GPS lock. I haven't bothered showing an OCXO lock state which takes about another 10 or 15 minutes to achieve with another 15 minutes to properly stabilise to within a +/- 10ns phase deviation.The rear panel shot shows the following connectors: Left to right, top row first - 10MHz sine BNC, Vcc voltage and noise and ripple test point SMA socket, stereo jack for gnd, 2v ref and EFC voltage meter connections, finishing with the SMA GPS antenna socket. On the bottom row, we have a USB mini B socket (FTDI232 module) and the standard DC jack extreme right for connecting a power source in the voltage range 7 to 24 volts (peak power demand ~5W, warmed up ~1.4W).Considering my choice of a 1000s PLL TC, this is remarkably quicker than similar PLL designs using TC values of just a 100s or less. The reason being my use of a ridiculously simple startup acceleration circuit. I see little benefit in speeding the locking process any further since the OCXO itself needs at least half an hour to properly stabilise anyway.Originally, after trialling a TC of 500s, I upped the TC to 5000s (I had planned to raise it to just 2000s but didn't have any more 5.6M resistors, only a few 10M ones, so 5000s it was). With a 5000s TC it took 3 1/2 hours to finally stabilise (I was curious enough to wait it out and see whether it would finally lock - I'd had to dial the initial 500s TC with the MK I right back to a mere 38 seconds before it would stop endlessly bouncing around and even at this short TC value, I'd still had to resort to a biasing resistor to assist the locking up process).Obviously, for a piece of lab kit that's only intended to be powered one time only and run 24/7 for years at a time, a 3 1/2 hour startup is neither here nor there. However, with having to restart it several times during the testing phase, I had a long hard look at how I could speed up this process and came up with my rather cunning accelerator circuit which shortened the startup time to a more reasonable 30 to 40 minutes. Cutting the 5000s TC back to 1000s has trimmed another ten minutes or so off this time. I have a feeling that now I'm using an M8T in place of the M8N gps module, an even shorter TC may be a more optimum choice but I'll let that idea stew a while longer for now.The black insulation tape on the RFS is to overcome the very low IR emissivity coefficient of its Mu-metal cover leading me to apply it to the aluminium plate and the top cover of the GPSDO to improve the accuracy of my IR temperature readings. The 'scope traces are the 10MHz output from the RFS (CH2) with a 1MHz Sinc pulse (CH1) from the AWG locked to the GPS 10MHz so I can, if required, reliably detect how many nanoseconds of phase drift has taken place during an overnight run if the RFS has drifted by more than one cycle. With the RFS, I can now be confident that it will take more than two hours to drift by a single 10MHz cycle. I've set the scope to trigger on every tenth cycle put out by the RFS which saves me guessing as to whether or not the RFS has slipped by more than one cycle during an overnight run.Of late, I've been seeing one cycle slip periods of 5 to 10 hours (and longer, barometric conditions allowing). The Mestek is showing the difference between the 2000mV DC offset and the EFC voltage (279.5mV). If you examine that picture carefully you should be able to spot my resistive GPS antenna splitter amongst the detritus.JBG

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 04, 2020, 11:11:48 am
content: Hi Johngreat job! I think I have ordered the same enclosure you used for the GPSDO from China for my project!And what a beautiful scope!Are you happy with your upgrade?As mentioned before I found a tear down of an CTS OCXOhttp://syncchannel.blogspot.com/2016/03/schematic-of-cts-1960017-10mhz-ocxo.htmlThe schematics is interesting. As expected there is a varactor diode for f-trimming. But Vref comes "only" froman resistor and a Zener diode.Unfortunately I found out that my awaited Trimbles seem to have no Vref out. I have to check it when they wil have found there way to me.Question regarding the Rubidium standard:As I learned the rubidium frequency is 6.834.682.610,904324 Hz (sorry folks, outside the imperial world we use "," instead of "." and vice versa)So there must be a FLL involved to get 10 MHz. Have you looked on phase noise? I this a problem?

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: September 04, 2020, 09:27:34 pm
content: Quote from: Bad_Driver on September 04, 2020, 11:11:48 amIf it is the same enclosure, it will measure 100 by 100 by 50 mm where the split halves interlock (need to be slid apart meaning the "Lid" can't just be lifted up after undoing the four topmost screws). That's not a problem for the MK II version since, unlike the MK I where I'd soldered the front panel LEDs' flyleads directly to the PCB, I've used a plug ended flylead to connect them to the main board. I only need to undo (just) four screws to release the rear panel, allowing me to slide the PCB out and unplug the front panel LEDs.I chose those particular enclosures out of a range of similarly sized ones mainly on account the end plates were a nice clean rectangular shape rather than be cursed with a half a millimeter or so trimmed off each of the short (or even all four) sides to within a few millimetres of each corner. It seems to me very likely that was also an influencing factor in your own case.The 'scope is nice enough but it is really an 'overkill' solution for the testing and monitoring I'm currently doing. If I had enough room on my bench to keep the 1202 alongside, I'd be using that instead since it consumes some 30 watts less power (22W versus the 52 or 54 watts of the 2104X+ (now hacked to the 2504X+ specification).It's a little disappointing that instead of just a 50% increase, I'm seeing a 150% increase over the 1202's energy consumption with the added insult to this 'injury' of energy consumption in the form of a threefold increased boot up time (46 seconds versus the 16 seconds for the 1202).The extended boot up time might be an inescapable consequence of a larger and more precisely initialised calibrated feature set that no amount of cpu 'grunt' could speed up but the energy consumption increase came as a bit of a shock.I could see the energy requirements of 2GSa/s DACs being double that of the 1GSa/s DACs used in the 1202, assuming the same generation of silicon technology being used but I'd have thought the energy budget for the supporting processes would have remained pretty much the same, hence my expectation of a 50% increase in overall energy consumption as opposed to the surprisingly high 150% increase I actually observe.At the end of the day, the increased energy cost for the improved performance and features is a relatively small price to pay in the larger scheme of things so there's little to be gained by worrying unduly about it. I only mention it to warn others of these hidden costs (protracted boot times and a 2.5 increased energy consumption) and to make it clear that Siglent should do better unless they want to advertise their next but one generation 'scope as being higher output space heaters than those old dual beam Tektronix 'scopes of the fifties and sixties if this increase of energy consumption keeps following this trend.Other than that 'minor' criticism, it's a very nice DSO indeed.I had a look at that blog article on the CTS OCXO. I wasn't at all impressed with the design of the thing. A resistor fed zenner for a 4.1v reference??? Really!?!?and, to make things worse, a 150 ohm resistor in series with its output -150mV drop for a 1mA load (and here was I thinking the 1mV drop with a 1mA load on the CQE OCXO's 5.127v Vref pin was a bit much but, "what the Hey, it's a fixed load in addition to the other internal fixed loads that will only introduce a tiny fixed offset that can readily be perfectly compensated for in my source of fixed dc offsets for my EFC monitoring circuit.").I'm very surprised that those trimbles lack a Vref pin. I'd have thought that any self respecting OCXO manufacturer would not be so stupid as to give up the opportunity to make their internal temperature stabilised oscillator and thermal controller Vcc rail available for external use via the Vref pin as a "value add" product feature to help boost their sales figures, especially when the cost of the Vref pin itself outweighs the cost of the internal wire link to an existing temperature stabilised Vcc rail. When I see such monumental stupidity as an unused Vref pin (or even none at all), my immediate thought is, "Yeah, they must have shit for brains!".When a Vref pin voltage is available, that usually (the CTI OCXO being an obvious exception) gives you immediate access to a reference voltage that's only second to a very expensive lab standard voltage reference. The absence of such a pin where the datasheet specifies for example, a maximum 1mA current loading, would be best interpreted as a manufacturing statement which says, "Our internal voltage reference is just too shite for use elsewhere so we're not going to let you see just how shite it really is!". IOW, steer clear of any OCXOs that don't provide a Vref pin voltage with a specified safe maximum current loading.The caesium atomic clock redefined the second as being precisely 9,192,631,770 periods of the hyperfine transition frequency of a caesium atom in the ground state at absolute zeroto the nearest whole periodbut all atomic standards based on other alkali metals such as the rubidium atom don't neatly fit an exact number of oscillation periods into an atomic second. The actual frequency being 6.834 682 610 904 29 GHz or 6,834,682,610.90429 Hz to five decimal places of accuracy. I've just realised (dang the European habit of using the comma and fullstop arse about face as numeric separators!) that you've used a six decimal accuracy. You must have tracked down a more recent figure than mine.If the rubidium atomic clock had come first, the definition of the second would no doubt have been defined as "6,834,682,611 periods of the hyperfine transition frequency of a Rubidium atom in the ground state at absolute zeroto the nearest whole period" instead, leaving the caesium definition with five trailing decimal places as a secondary standard.Since the second is now defined, arbitrarily as being precisely 9,192,631,770 periods of the hyperfine transition frequency of a caesium atom in the ground state, all other atomic based oscillator references are, by definition, secondary standards. In the case of the compact rubidium oscillators or frequency standards (RFS), this allowed the freedom to use a FLL and a rubidium gas that didn't require a cryostat to hold it at absolute zero.It's not just the fact that an RFS can be fine tuned and therefore needs to be calibrated against a primary standard or frequency reference, such as a GPS timing source, that's directly traceable to the primary standard, that makes it a secondary standard so much as the fact that being a secondary standard it is freed from the need of a cryostat, allowing the atomic physics package and its supporting electronics all to be housed in a physical package smaller than a half height optical disc drive which can be used to provide a frequency reference with at least an order of magnitude better accuracy than the best double ovened XOs can achieve with the added bonus of not suffering the random frequency shifts that can afflict even the best double ovened XOs which makes it a very attractive alternative frequency standard where weight and bulk are major considerations (they work even better in the vacuum of space which completely eliminates the issue of barometric sensitivity that plagues ground based RFSs)The Datom and Efratom LPRO-101 bends the 6.834GHz excitation frequency ever so slightly to allow a 20.0000000MHz VCXO to generate a 60MHz lamp excitation RF field and a precise 6.834GHz. The 20MHz VCXO is also divided down to 10MHz and filtered to remove the odd harmonics to produce the 10MHz sine wave output.The FE-5680 uses DDS technology to generate its 10MHz from a less inconvenient choice of exciter reference frequency which unfortunately introduces a high level of spurs and jitter noise, requiring the use of a separate 10MHz VCXO to clean the output up for use at frequencies of 1GHz and beyond. The 10MHz sine output from an LPRO-101 can be used directly to drive transverters going all the way up to 24GHz. Therefore, since I don't have any means to measure jitter and phase noise, I take it on faith that jitter and phase noise won't be an issue for any of my envisioned future projects.https://febo.com/pages/oscillators/rubes/JBG

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 08, 2020, 11:34:05 am
content: Hi folks,on Friday the awaited parcel from China arrived (my TRIMBLE 34310-T). I never before got such a good protected delivery for electronic parts!I awaited that grey thin mail bag that they usual use but it came a hard box with a lot of foam plates inside, and additionalprotective covering, inside another bag with the both OCXOs. Well done! Bought at KEEPINGTOUCH.COM - never heard about before.And good news! The OCXOs do very well, I kept them running for 4 days now. And surprise, both with Vref out!I learned that this are Trimble OEM products for the telecom industries, thatswhy you find no data sheets. But a HAM fromNetherlands had done a lot of investigations.http://amateurtele.com/index.php?artikel=208First measurements:Vcc=12 V, output sine 5 Vpp, impedance 280 ohms.Vref on both 5.943 VCold startup current 700 mAwarm current 200 mAVco for 10 MHz: OXCO 1 = 3.51 V; OCXO 2 = 8.45 V (hmm big difference)delta V/delta f : 1V = 1.4 Hz (#1) 1.1 Hz (#2)The frequency is rock solid against my other OXCO. Now I can start the improvement of the HP 53131A.After looking around I found out that the solution of Hexley fits best to my needs.https://www.eevblog.com/forum/testgear/ocxo-for-hp-53131a-a-new-design/Thanks to him for his support with this and some other things!Volkmar

author: Labrat101
author_rank: Unknown
timestamp: September 15, 2020, 08:42:19 pm
content: Hi Bad_Driver,I finely got my Leo Bodnar the first one The British post office (Royal Fail) lost thebloody thing at the airport.So they resent it DHL . I got done for import taxbut after a 6 weeks run a aroundit got here .So it came pre set both channels are at 10Mhz so I am using 1 channel for my frequencycounter 10Mhz Reference in . and the other for calibrating .This is a really good toy . It locks in about 15 seconds . I set my other ocxo up it was just10.000,000,147 Mhz Now its 10.000,000,002 Mhz I just can't get it the last digit as the slightest touch takes down to much but its locked solid at that for about 3 hrs.So I wont get that job at NASA.really happy with it . well worth the extra bucks and the pulse out has a really nice rise &fall time of 2.5ns . I cant fault it . . Just love stuff that works out the Box first time .The UNI-T 962 never turned up so I contacted them and they said it had been returnedThey put the wrong post code onCopy & Paste. so I am not a happy camper . they said they would resend it . I gave them the details in large print .maybe I will get to see it before the end of the world

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 23, 2020, 03:13:43 pm
content: Hi Labrat, hi John,sorry but as mentioned some times before I'm busy with the real lifeAs I told you I own a Bodnar pulser I bought to have a source for very sharp square waves (40ps rise time). I ordered it direct in UK and it show up after 2 weeks!A great piece of engineering art!And I also took the GPSDO into account. But if you have opened it you will find a cheap UBLOX m6 GPS receiver. As I mentioned above I bought a well looking GPSDOfrom a german HAM but unfortunately it suffers from a very LF jitter around 1 Hz which you can be only seen on the scope when compared to an OCXO.After some investigations I think this comes from a modulation of the V_control that is generated by the PWM signal from an Atmega as far as I can see.Have you seen any of this low f-jitter?These days you can get a original TRIMBLE Thunderbolt for around 160 € from China. I think I will spend this money and sell the other one on Ebay again.Unfortunately this month a HP 34401A 6.5 digit DMM in mint condition and with calibration from the last year (and not from the last Millennium) crossed my way, I couldn't resist ...So my budget for the hobby is exhausted.I spend some efforts nowadays to get my equipment running with PC-software control to make some long term measurements.But this is more demanding than expected. The old boxes need a RS232 connection (not so good, but working anyway) or better an GPIP-bus connection (more money for cables and interfaces needed). The old HP Benchvue software is not available for free anymore. Any suggestions?The new boxes from Siglent use USB or Ethernet. Best would be Labview but this is a very complex piece of software!As explained in the other board I will rebuild the FY69 box into its state of origin. I never uesed it after improving it (and having the SDG2042/2122). I have better use for the PSU I used for it (for the Trimble GPSDO may be).I keep you informedStay in good health!B.D.

author: Labrat101
author_rank: Unknown
timestamp: September 23, 2020, 10:41:43 pm
content: Hi Bad_driverGlade to hear you are still OK.As you know I got the 2 channel GPSDO and its outputs are rock solid . Have no complaints .And No I did not open it . One half of me said go on have peek . and then I remembered the oldsaying if it aint Brock leave alone . So it will stay a surprise not to know.I have been playing with my new toy the UTG962 other than the Rise & Fall time is slow @ 15nsI am really happy with it and the 10Mhz square is not bad I can live with it .The Jitter wobble on the FY made my Brain vibrate .basically it a very nicely built and all the waves are steadier .I was wondering if it has a secret service mode for calibration, would be great just to nudge it a little on the small frequency error .If it got one I will seek it out .Yes:: Labview is a very complex piece of software! mind blowing complexall the best to all you guyskeep well . keep calm . we are all nerds we will work it outPS The 20KG Hammer did stop the jitter

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: September 24, 2020, 05:28:40 am
content: Quote from: Bad_Driver on September 23, 2020, 03:13:43 pmHi Volkmar,It's funny you should happen to mention that 40ns pulser - I ordered one just yesterday.Assuming the Royal Mail don't do what they did with an order for a small pack of ten bi-colour LEDS I'd placed with a UK based Ebay seller over a fortnight ago, I might just see it delivered by the end of this week.[EDIT 2020-09-23] It arrived in this morning's post! (along with a small ziplock bag of ten bi-colour LEDS stuffed inside of a small unpadded envelope with a 1st class stamp from the seller mentioned below)That Ebay seller is shipping out another pack of LEDs which hopefully, the Royal Mail won't lose this time. I'd placed orders with three other UK based sellers on the same day and they all arrived within just one to three days (no later than their estimated delivery dates) but this one was even overtaken by an order for a pack of four 1 metre SMA patch cables I'd placed with a Chinese supplier on the same day!A year or so back, I'd considered ordering the cheaper single channel Leo Bodnar GPSDO (just £99.99) but held off on account it was using a VCTCXO rather than a VCOCXO - I wasn't aware (or realised the significance) of the use of a navigation gps receiver back then otherwise I would have spent even less time agonising over whether or not to blow a hundred quid for a "Quick Fix" Frequency Reference standard for my home lab.In retrospect, as nicely made as it was, I'm rather glad didn't give in to my desire for this "Quick Fix" otherwise I wouldn't have learnt as much as I have done over the past couple of years by pursuing my own DIY GPSDO activities.If by Chinese manufactured Trimble based GPSDOs you mean those BG7TBL units being discussed in a thread that's been going since August 2015 right up until yesterday here:https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg3143006/#msg3143006I'd just like to point out that this does suffer from a very slight negative frequency offset of 0.2mHz, presumed to be the result of a still uncorrected rounding error in its control algorithm. For most users, this probably won't matter (it's an error of just 2Hz when the 10MHz is multiplied up to 100GHz).However, for those using it to re-calibrate a RFS, I'd expect that otherwise insignificant offset to become seriously annoying in very short order (I know it would annoy me!). I just thought it was worth pointing this out in case you weren't already aware of this frequency offset and it was important to you that your GPSDO standard remained resolutely phase locked to the GPS master clock.JOOI, I checked out pricing of those pre-owned HP 34401A bench multimeters and found a UK seller asking a mere £399 plus £19.50 postage (about the price of a SIGLENT SDM3045X Dual-Display Digital Multimeter). It looked in good condition but no mention of recent calibration. A brand new SDM3065X 6 1/2 digit Bench Multimeter from Telonic Instruments would knock me back a cool £740.40 inc VAT. I'm not surprised your wallet is still recovering from the shock. Even at "bargain prices" these bench meters aren't cheapIt's just as well that I can manage quite nicely for the time being with a cheap 9999 counts Mestek to monitor the 2.2833v EFC voltage in tenths of a mV by reading the 283.3mV difference against a temperature stable 2v dc reference offset I'd built into the MK II GPSDO for just this purpose. I know I'll eventually be spending a few hundred quid on a 6 1/2 digit bench meter but why rush into spending some 396 quid on a 4 1/2 digit meter when a 13 quid Mestek and a handful of matched 1K resistors can get the job done for just a fraction of the cost?I emailed Telonic Instruments just yesterday afternoon for a discounted price quote on the SDG1032X. I'd finally reached a decision after two months of agonising over whether to go for the higher spec (but no special square wave function) SDG2042X or the cheaper SDG1032X with a decent square wave function that stretches all the way to 60MHz and decided that the square wave option of the cheaper model would best serve my needs.I figured that if it did turn out that I'd underestimated my need for a 1.2GSa/s 16 bit arbitrary wave function generator after all, I could easily rectify that 'mistake' by simply chucking an extra 490 quid at the problem (and keep the '1032X anyway for generating high frequency square waves).I think the reason Siglent decided against incorporating the '1032X's square wave feature into the '2042X may have been to persuade their customers to own both rather than just choose one over the other, thereby generating an additional sale of the 1000X model alongside of the 2000X models. IOW, Siglent appear to have spotted an opportunity to "Have their cakeandeat it!". Never mind, it's only money.I might have an answer out of Telonic by tomorrow but, whatever the outcome, I will be purchasing an SDG1032X to supplant my much modified FY6600 which may yet prove a useful spare thanks to the external 10MHz reference feature that I'd added to it.[Edit 2020-09-24] I got my reply. No luck on the discount but I wasn't too surprised with such a "cheap" item of testgear (Oh how almost two year's ownership of an FY6600-60M changes your perception of what is "cheap"!). I've ordered one anyway. It was only £277.20p VAT paid and next business day delivery (probably Monday 'cos I'd missed the 3pm deadline).If it just ends up gathering dust on a cupboard shelf and I find myself cannibalising it for the 10MHz OCXO, I can always add a divide by 5 circuit to the 50MHz TCXO board I'd used as my first XO upgrade which I suspect will be quite susceptible to a dose of frequency injection locking (better than just scrapping the whole generator for the sake of recovering a valuable OCXO). Anyway, that's all for the future and since I still have a "Lifetime's Supply" of these 10MHz CQE OCXOs going spare, that could prove to be in a very distant future I may never ever have to deal withAnyway, that's the latest news and information I have to offer at the moment. I think I've mentioned the Efratom LPRO-101 I'd bought the tail end of August which I've had running 24/7 since then, providing some interesting insights into the effects of the GPS system's shortcomings on the behaviour of my my James Miller styled DIY GPSDO.I had intended to keep the MK I going a bit longer to compare it against the RFS alongside of the MK II but it fell apart when I was trying to test the 13MHz OCXO on increasingly higher voltage rails that I didn't want accidentally destroying any of the 5 volt parts during this testing process so it looks like I'll have to breadboard another GPSDO using a NEO-M8N gps module (but without the 13MHz OCXO and all the paraphernalia of a divide by 1.3 rat's nest of TTL jiggery pokery used by the original MK I).I'll just use one of my spare 10MHz OCXOs since what I really want to compare is the performance of a NEO-M8N against that of a NEO-M8T in regard of phase modulation effects imposed, for the most part, by changes in electron density in the ionosphere.That little side project should keep me occupied whilst I await delivery of a nicely sized extruded aluminium enclosure I'd ordered from China to house my LPRO-101 in so I can stabilise its temperature and, ultimately compensate for barometric pressure changes to create the most stable RFS it's possible to achieve in a home laboratory environment. I'd spent the best part of 200 quid on that rubidium oscillator and I intend to maximise the return on this investment.John

author: Bad_Driver
author_rank: Frequent Contributor
timestamp: September 24, 2020, 06:59:28 am
content: Hi John,fast answer because I'm on the jump to a business trip.I found my HP 34401A not at EBay (there the HP stuff is overpriced) but at Ebay "Kleinanzeigen" (do not know the english brand name, the Ebay local marketplace where people sell there things as on a flee market).I paid 340 € incl. delivery for a device in mint condition.I know this chinese HAM brand you named but I take into consideration this: (my PSU I used for the FY69 should be uesed)https://ebay.us/NSvlkUThis is a real Trimble and the firmware isn't so old. But not this month!So I have to hit the road. cu best regards to all B.D.