Leo Bodnar LBE-1420 and LBE-1421 GPSDO - Page 1
Forum section: electronics / testgear

author: G0HZU
author_rank: Super Contributor
timestamp: March 01, 2025, 01:41:58 pm
content: I've just been given a Leo Bodnar LBE-1421 to try out on loan and wondered if anyone else has experience of these or the single output LBE-1420?https://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=399I've not played with it that much yet but there doesn't seem to be an online manual for it. Apparently it can support NMEA telemetry but there isn't much info about this. I've used the config software to get some telemetry from it but it seems quite limited.Does it have any kind of lock status flag via USB? This would be very useful for me.When powered up via USB it typically seems to lock and stabilise in about 5 minutes. It can also be programmed via USB to anywhere from 1Hz to 1.4 GHz on each of the dual outputs and it can output 1 PPS from one of the outputs when desired. This is quite neat and this makes this a very versatile device. It really is tiny, not much bigger than a matchbox.Are there any known issues with these GPSDOs?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: March 01, 2025, 07:56:40 pm
content: I have the older Mini, not the new one, but there's not much to tell. They just work. I upgraded the firmware so it outputs NMEA data and it works with the Lady Heather program quite well. What amazes me is it works fine in my basement lab with the entire house above it, though it doesn't work at work where there's a metal roof!

author: G0HZU
author_rank: Super Contributor
timestamp: March 01, 2025, 09:02:01 pm
content: Thanks. I've been doing a few informal tests on it today on a spare workbench and it is generally performing better than I was expecting. I was a bit concerned about it having a TCXO rather than a small OCXO but this hasn't degraded the short term stability as much as I first thought it would. So I still might buy one.As I mentioned on another thread I am going to have to find something to replace my ancient homebrew 198 kHz offair standard when the BBC close down the 198 kHz transmission from Droitwich. Also, the offair standard is easily upset by local EMI from test gear or other household equipment so it isn't always reliable. Usually it performs extremely well.If I could suggest improvements to the LBE-1421 it would be to have some sort of lock status indicator. I've seen this on other GPDSOs and it is a nice thing to have. The lock indicators aren't perfect though. It's possible to cause a subtle and brief frequency error by moving or rotating a GPSDO and the lock indicator doesn't always detect this type of event. It's still a nice thing to have though as it usually provides a good guide as to the status of the GPSDO.Maybe one of the LEDs could be multi-colour to reflect lock status or maybe lock status could be available over the serial interface.I've had a brief play with reprogramming it for different frequencies and this seems to work fine. It can produce some noticeable spurious sidebands either side of the main carrier, especially up at VHF and UHF but it's still impressive considering the small size of the unit.I had a look on an analyser and the phase noise obviously gets higher when programming it for higher frequencies. The phase noise at a 10 MHz carrier output looks to be very low at offsets beyond a few kHz. This is quite impressive.I've measured the time to achieve an accurate output (within +/- 2 mHz) a few times now and it seems to be able to achieve this in under 5 minutes each time. This is also quite impressive and is much faster than other GPSDOs I've tried.The risk with all this stuff is to get drawn into wanting something better and better by spending a bit more. For example, I probably don't need anything better than the LBE-1421 but I'd probably opt for a version with an OCXO if one was available even though it would at least double the lock time.

author: G0HZU
author_rank: Super Contributor
timestamp: March 01, 2025, 09:58:17 pm
content: Here's the latest warm up test of the LBE-1421. I ran this for an hour and it does seem to improve towards the end of the test time. This is stretching the limits of my test gear so I'd ideally have to borrow a more modern frequency counter than this. I think that testing this stuff 'properly' is more suited to time nuts etc.The performance in the graph below is better than I was expecting and it's better than my minimum requirement in terms of how stable it is on my frequency counter.I used a Jackson Labs Firefly 1A GPSDO as the reference for this after leaving it on all day. This little GPSDO has a tiny OCXO on it. However, I probably should be using something better than this to test the LBE-1421 properly.I might be able to borrow something better to use as a reference but I think this is already good enough for my needs.I can post up some scope waveforms of the output and maybe do some other tests like looking at phase noise (at 10 MHz and through VHF and UHF) and phase stability but it is all going to be at the limits of my current test gear.

author: G0HZU
author_rank: Super Contributor
timestamp: March 01, 2025, 10:49:54 pm
content: I had an initial look at the phase noise when set to a 10 MHz output. I can do this test at carrier frequencies all the way up to the 1.4 GHz limit of the LBE-1421 with this analyser.I am using an old Agilent E5052A signal source analyser to do the phase noise measurement. This analyser is about 20 years old now and there are much better analysers available today. However, I think it can measure the LBE-1421 quite well.I've started the capture at 10 Hz rather than 1 Hz in order to speed up the capture time. It takes a few seconds to capture it at these settings but it takes much longer if I set the start frequency to 1 Hz.A measurement like this does require a fair bit of preparation in a low noise environment and I'm just doing this in a spare room at home that has other test gear running. The yellow noise trace should reflect the noise performance of the LBE-1421 quite well.Edit:There were some very low level spurious terms on the original plot I posted up. As I'm not certain if these are due to the LBE-1421 I've changed the detection mode to 'omit' to only report noise for now. This ignores low level spurious terms. I'll have a look at the spurious levels tomorrow.

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 10:35:23 am
content: Here's a couple of images of what was inside the box when I opened it. It does seem to be well made and the cables are very good quality with a nice look and feel. This isn't mine, I've only got it on loan but I am the first to use it.I can try and do some receiver sensitivity tests on it for C/N but this is again going to be stretching the limits of my signal generator. I've done this before with other GPS receivers.The LBE-1421 is normally connected to an active antenna which will have a fair bit of gain, but I test for C/N at the input SMA port when testing GPS receivers. This test probably isn't that relevant because of the gain from the active antenna but it might be interesting to try the test anyway.Hopefully it won't mess up any self learning in the GPSDO part of the receiver. One other GPSDO I have on loan here does track and record the ageing of the OCXO over time so in theory at least my sig gen could mess this up unless it is referenced to something really accurate. It didn't seem to affect it when I did the testing though as I used a decent external reference for the sig gen.

author: nctnico
author_rank: Super Contributor
timestamp: March 02, 2025, 12:03:57 pm
content: Quote from: G0HZU on March 01, 2025, 09:58:17 pmA good test is to compare the 1PPS output with a Cesium clock (or better) over a period of 48 hours. That way you can see the time drift. But you'd need an accurate time interval counter (like Tektronix FCA3100).

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 02:06:23 pm
content: Quote from: nctnico on March 02, 2025, 12:03:57 pmThanks. I don't have access to test gear like that here. There is an Rb standard and a really nice frequency counter/timer at work but I won't be able to borrow it.I've only got this LBE-1421 on loan over the weekend so I can't do much more testing on it. I might be able to borrow it for a few more days if I ask nicely though...When looking at the phase noise at higher output frequencies, the noise level generally lifts in fairly good agreement with 20*log(N).So when it is set to 100 MHz, N =100/10 = 10 and so the noise is generally 20*log(10) = 20dB higher than the noise in the 10 MHz plot I posted up earlier.See below for what I mean. If I increase the frequency to 1 GHz the noise lifts by another 20dB as shown in the other image below. I've ghosted the phase noise performance at 100 MHz onto the 1 GHz plot to show the ~20dB difference in phase noise when the frequency is increased from 100 MHz to 1 GHz.

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 05:10:06 pm
content: This afternoon, whilst listening to the footie, I've dug out one of my old HP 8405A vector voltmeters and had a play with measuring phase vs time between the Firefly-1A and the LBE-1421.My first impression is one of surprise when looking at the LBE-1421. I expected to see some obvious phase jitter but so far it all looks quite smooth.I have no idea how much of the phase shifting is due to the LBE-1421 or the Firefly-1A. However, there is some slow wandering in the phase over time with a kind of staircase shape to it. It looks better than I was expecting from a TCXO based GPSDO. I believe the modern tool of choice for this stuff is the TinyPFA but I'm using the HP 8405A and I'm logging the phase port at the back with a DVM.Obviously, I should really be using something very special (accurate/stable) for the reference on channel A of the HP 8405A so I'm once again exploring the limits of the test setup rather than measuring the performance of just one of the GPSDOs. The LBE-1421 has again performed better than I expected here though even if I allow any limitations due to the Firefly-1A.I might be able to borrow an Rb standard from someone but I feel I'm exploring stuff beyond my actual needs from a GPSDO.

author: nctnico
author_rank: Super Contributor
timestamp: March 02, 2025, 05:25:15 pm
content: A Rubidium clock may not be the best option as it has quite a bit of short term instabilities. This can be improved by adding a cleanup oscillator in series with the Rb clock (basically adding a low pass filter to improve phase noise).Another option is to compare several GPSDOs against eachother over a 48 hour period and make a comparison to see which one drifts the most and which ones agree best. I used this as a cursory test to check whether a GPSDO behaves properly.

author: jonpaul
author_rank: Super Contributor
timestamp: March 02, 2025, 06:14:27 pm
content: We have used the Leo Bodna GPSDO previous and current version with great results.The app allwos chage in F1, F2 , ratio, output and monitors thelock status, sig stregnth etc.Suggest refer to the Leo Bodnar site for specs, app notes and stability data.Leo can give you excellent support.Jon

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 07:08:24 pm
content: Quote from: jonpaul on March 02, 2025, 06:14:27 pmThanks. Which app are you referring to here? Can I download it and try it? I'd like to see the lock status performance before I return the LBE-1421 to its owner tomorrow.I can't do any more tests on it after this evening as I have to pack it back in the box shortly.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 02, 2025, 09:57:10 pm
content: The Leo Bodnar units are very useful for specific purposes. I have one of the older dual BNC models and also an LBE-1420.Unlike OCXO based GPSDO units, the TCXO based LB units lock and are ready to use in a minute or so. The ability to select almost any frequency you need is very handy. I use the LBE-1420 on 49.152 MHz to lock an Icom IC-9700 radio. The LBE-1420 is quite small and can use GPS, Galileo, Russian or Chinese satellites (options set in the LB config program).The LB units are claimed to be "low jitter", relative to what I am not sure. My own comparisons between my home made Lars Walenius type unit and either of the LB units at 10 MHz, when measured against a rubidium with a TinyPFA with TimeLab software, show significant jitter. I have posted this image elsewhere on this forum, copied below.SJ

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 10:18:58 pm
content: Quote from: Solder_Junkie on March 02, 2025, 09:57:10 pmThanks. The amount of spread there looks similar to the +/- 0.0035 Hz I was seeing with this LBE-1421.Can someone please confirm if these things have a lock detect function? This is one of the questions I'm supposed to answer for the owner. They bought the LBE-1421 to replace another much older GPSDO but the older one does have a lock detect LED on it.At the moment I'm going to tell him the answer is no (in terms of what the LEDs do) and that there might be a lock detect flag via serial comms. There appears to be no manual for it so I've had to guess what the LEDs are for.It is definitely going to outperform the original GPSDO but I think it ideally needs a lock detect indicator. Otherwise how can someone know the status of it without a laptop or test gear? With the old system, one could glance at the (four) front panel LEDs and within a few seconds know how many satellites it was receiving and tracking and how many it was not tracking. Also if it was locked and also if the short term phase was relatively stable.I think the owner may be expecting something similar but it looks like the LBE-1421 can do none of this via the two LEDs.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 02, 2025, 10:23:10 pm
content: When lock is lost, the LED flashes. When all is well, the LED is on solid. Pretty simple but more than adequate. If you need to see the satellites picked up, the utility program for the LBE-1420 shows the usual bargraph with signal strength.SJ

author: G0HZU
author_rank: Super Contributor
timestamp: March 02, 2025, 10:35:33 pm
content: Quote from: Solder_Junkie on March 02, 2025, 10:23:10 pmThanks, I wasn't sure if that feature was a lost signal indicator as it goes solid within a couple of seconds of removing and re-connecting the antenna even though the output has clearly shifted in frequency and isn't settled after the re-connection is made.That LED function is definitely better than nothing and it may be adequate for the new owner in terms of a status indicator. He hasn't used it yet. I was the first to unpack and use it

author: 807
author_rank: Frequent Contributor
timestamp: March 02, 2025, 11:55:50 pm
content: Quote from: G0HZU on March 02, 2025, 10:35:33 pmI have the older Leo Bodnar Mini Precision GPS Reference Clock. When running the configuration program, the "No PLL Lock" will show red when first switched on. This corresponds to the flashing LED on the unit. When the configuration program shows "PLL Lock OK" & turns green, then the LED stays on.There's a separate indication in the configuration file to show whether it's receiving a GPS signal.I'm not sure what the grey bars are indicating?

author: jonpaul
author_rank: Super Contributor
timestamp: March 03, 2025, 11:51:13 am
content: Justgot to the webiste!!!!All Leo Bodnar info for GPSDSO here: 4 models:https://www.leobodnar.com/shop/index.php?main_page=index&cPath=107&zenid=028e0af3462e9ea6a3108f1260251f26All software/support docs PC and MAC:https://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=399&zenid=028e0af3462e9ea6a3108f1260251f26Jon

author: G0HZU
author_rank: Super Contributor
timestamp: March 03, 2025, 07:20:55 pm
content: Quote from: 807 on March 02, 2025, 11:55:50 pmThanks.It looks like the current config program is different for the LBE-1421 as it now doesn't appear to have a lock status indicator. See the image below taken from the website. Unlike your GUI, the lock detect indicator is now missing. It just indicates that the GPS signal is OK.I can't find any documentation that explains what some of the options do such as low power or the FLL (frequency locked loop?). Maybe this activates a lock detector?When pressed, the diagnostics button doesn't include a lock detect status indicator. It does show location information and some other BIT stuff though.I don't have it any longer as I've returned it to the owner and told him that it only appears to have a signal strength indicator (rather than a lock detector) and that there doesn't appear to be a manual for it.If the LED flashing thing is a lock detector rather than a signal strength indicator, then it has a fairly vague interpretation of what lock means as it turns solid very quickly when the unit is powered up and a frequency counter shows that it hasn't yet settled.The reason the lock detect is important is that this unit will be used in a large (and very solid) building that contains several GPS repeaters. So there could be locking issues in certain parts of the building. The previous GPSDO could alert the user via its LED system about the qty of satellites received and the lock status and the phase stability.I guess the next thing to do is try it inside the big building to see how it copes with the various GPS repeaters.

author: G0HZU
author_rank: Super Contributor
timestamp: March 03, 2025, 07:24:20 pm
content: QuoteI did this as soon as I got the unit. See the post above about the lack of a lock status indicator on the config GUI. Also, there appears to be no documentation but hopefully someone can provide a link to a manual or other document associated with the LBE-1421.As I mentioned, I no longer have the unit so I can't do any more tests on it.

author: 807
author_rank: Frequent Contributor
timestamp: March 06, 2025, 01:51:22 pm
content: Strange that the lock indicator has been removed. It's something that you need to have information about.Leo is a member of these forums. Perhaps pm him, or email him via his website about considering bringing back the lock indicator?

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: March 18, 2025, 07:58:33 pm
content: Dear all,In the last week, I have been testing my new Leo Bodnar LBE-1421 GPSDO, and made a video about it. It was an interesting ride because a lot was unknown at the start (the lack of a manual being one of the reasons for that), but I think I now have a better understanding of the unit, and also some talks with the staff at Leo Bodnar were helpful.The video addresses, among other things,The choice of Leo Bodnar to generate square waves rather than sine waves, and the optional LBE-1710 10MHz low pass filter.The huge differences between the Windows and the MacOS control software, and the huge differences between the software for the previous units and the current (2024) generation of GPSDO. (Bodnar told me some software updates are due…)Using the unit to evaluate the clocks of several existing devices in my lab.It's actual power consumption.Using the NMEA data.Being fascinated by metrology and measurement, I also included a section about how well we are able to measure time (compared to other SI quantities) and a visit I made myself to German's national metrology lab, PTB in Braunschweig (D), where I saw – and made pictures of – some of the most precise clocks on the globe.Altogether, I think this is a great unit, and a considerable improvement over my previous GPSDO. There is still some room left for improvement, though. Enjoy!

author: Ecogeek
author_rank: Contributor
timestamp: March 18, 2025, 09:55:16 pm
content: The LED colour is functionally confusing. If they moved to "Green" is good would be super helpful!Colouring LED with Red (some alarm state) or even white make no sense. I have two of these units the old one which uses a Red LED and new model with White. I think I'll replace both with a Green LED to stop the Red alarm screeming at me!

author: G0HZU
author_rank: Super Contributor
timestamp: March 18, 2025, 10:54:52 pm
content: Hi RBBVNL9, thanks for posting up the youtube review!I've managed to borrow the LBE-1421 again this week and I've done a few more tests on it.If left disconnected with no power overnight and then re-started the next afternoon, I found that the flashing (no signal?) LEDs stopped after about 38 seconds. I'm still not sure what this means in terms of signal or lock status but the frequency counter showed it was still slightly low in frequency by about 0.1Hz when set to 10 MHz. I used the Firefly-1A as the counter reference and the Firefly-1A had been on for about 7 hours before starting this test.To improve to be within 0.01Hz took 200 seconds and to be reliably* within 0.002Hz took about 400 seconds.* The log readout from the counter showed the odd 0.003 Hz error but this could be due to error contributions from the Firefly-1A reference and the counter itself. Once the LBE-1421 gets within about 0.002 Hz I don't have any test gear here that can reliably measure the frequency for each 10 second sample to this accuracy. My counter can do 12 digits (0.1 mHz) if I include the LSD but I don't trust the LSD on the counter.Overall, I'm still impressed with the performance of the LBE-1421 in this respect. I know I keep saying it, but it's working much better than I expected.I also measured the GPS receiver noise figure at the SMA port of the LBE-1421 and I think it is about 7dB. This is about what I was expecting, something between 5dB and 10dB. There is an active antenna supplied with the LBE-1421 and the gain of this will mean that the noise figure of the LBE-1421 would probably be fine even if it was 10-12dB. So this test doesn't really prove much, but I did it anyway.I think the square wave output of the LBE-1421 has very fast edges. Too fast for any of my scopes but I could try and post up a screenshot tomorrow. However, I think it really requires a super-fast scope, maybe 2 GHz BW and 10Gsa/s. So maybe someone else should do this test instead of me. It would be possible to use the LBE-1421 as a calibration 'comb' for servicing an old school swept spectrum analyser as it produces harmonics up into the GHz region even at low output frequencies. This would allow the frequency axis of the analyser to be calibrated across various frequency spans.I also did loads of phase stability tests with my two HP 8405A vector voltmeters. Again, I'm at the limits of my test gear, but perhaps unsurprisingly, the Firefly-1A (with its little OCXO) has a smoother phase response vs time. But there really isn't much in it between the LBE-1421 and the Firefly-1A. By contrast, the phase stability of the Quartzlock E8-X GPSDO was pretty grim. So grim I'm not going to post up the result in case this one has a fault. It does give very good frequency accuracy when averaged across a couple of minutes but the E8-X is very poor when measured across 10 seconds or even 30 seconds.

author: 807
author_rank: Frequent Contributor
timestamp: March 19, 2025, 12:43:00 am
content: Quote from: RBBVNL9 on March 18, 2025, 07:58:33 pmJust a mention about the old Mini Precision GPS Reference Clock. You include it in your table (by putting "mini" in brackets in the heading) when comparing functions to the new models, but the software for the old 2 port unit is different to the 1 port (mini) version, so the table is wrong for the mini version.I attached a screenshot in one of my posts above showing the latest (v1.20) software. Unlike the old 2 port model, it now supports NMEA too. The GPS coordinates (which I blanked out) also includes altitude.

author: G0HZU
author_rank: Super Contributor
timestamp: March 19, 2025, 01:12:23 am
content: Here's a screenshot of the control GUI for this LBE-1421 when I did the receiver noise figure test. It's running 1.07 firmware rather than 1.09 but it's not mine so I'll leave it at 1.07.The date and co-ordinates are 'strange' because this is what I set the sig gen to, 53N 1W and a date last year that corresponds to when I last created any GPS data for the sig gen using 8 satellite signals.It's possible to set the number of satellites and the signal strength and then work out the receiver noise figure from the C/N data reported by the receiver. I used the Heather program to get numerical C/N data as I think that the LBE-1421 only provides a bar graph. Ideally, all 8 satellites should have the same C/N because they are synthesised inside the signal generator but I often see some fluctuations here.

author: EvgenyG
author_rank: Regular Contributor
timestamp: March 19, 2025, 01:13:50 am
content: Quote from: G0HZU on March 18, 2025, 10:54:52 pmLeo has specifications on the website. Added after I askedRise/fall time of output signal at 10MHz is300ps/260psmeasured between 10% and 90% levels.

author: G0HZU
author_rank: Super Contributor
timestamp: March 19, 2025, 01:25:44 am
content: Another test I did was to lock the sig gen to a good master reference and then watched how stable the 10 MHz output from the LBE-1421 was compared to the 10 MHz master reference set to the GPS generating sig gen.Ideally, everything should agree once the LBE-1421 locks to the satellite signals generated by the sig gen. However, because of the short term drift in the master reference and also in the LBE-1421 there was still some phase drift when I locked a HP 8405A VVM to the master reference and then measured the 10 MHz from the LBE-1421.I should probably use a very stable master reference. It doesn't need absolute accuracy, but it should be stable. I might try this again using the 10 MHz OCXO in my old HP 8566B analyser as the master. This big old OCXO has very good short term stability. I really have no idea if this test setup has any merit but it seemed an interesting thing to try. I could also turn down the C/N from the sig gen to see how the LBE-1421 copes with weak GPS reception. However, it's probably better to do this with real GPS signals and a step attenuator and DC block and a bias tee for the patch antenna.

author: CTintheUK
author_rank: Newbie
timestamp: March 19, 2025, 08:08:39 am
content: Thank you RBBVNL9 for the information-packed video.I too am a recent buyer of an LBE-1421. I too think it's a great unit.From a posting by Jim Lux on Time-Nuts, I note that "the 1pps is NOT derived from the disciplined oscillator, it's the raw GPS receiver output". I guess that suits some users, but I would have preferred it the other way. Also, I would have loved to see "ePPS" (embedded pulse-per-second) in the capabilities list. Is anyone else looking out for a GPSDO with an ePPS output, I wonder?

author: G0HZU
author_rank: Super Contributor
timestamp: March 19, 2025, 02:34:35 pm
content: I've run the LBE-1421 for about an hour today and I've taken a thermal image of it. It runs very slightly warm so I thought it would be interesting to capture this. My workroom is currently at 21 degC but the bench surfaces are down at about 16-18 degC. The LBE-1421 shows 29 degC in the image below. I've not measured the current consumption via USB yet. Has anyone else measured the current consumption?

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: March 19, 2025, 05:11:43 pm
content: Thanks for the thermal image. I wanted to make one but my camera stopped to work.QuoteYes, see my video (posted above). The LBE-1421 draws between approx. 300 and 350mA, at 5V, so more than the published specs (that mention 250mA max.)Best, Rudi

author: RAPo
author_rank: Super Contributor
timestamp: March 19, 2025, 05:43:36 pm
content: Do you have atinyPFA? Would love to see an added analysis with this (relatively) cheap hard -/software.

author: G0HZU
author_rank: Super Contributor
timestamp: March 19, 2025, 07:14:17 pm
content: Quote from: RAPo on March 19, 2025, 05:43:36 pmSadly, no but I have a couple of old HP 8405A vector voltmeters. I don't know how these compare to the TinyPFA, but the phase stability vs time is excellent. The accuracy of the phase over the full +/- 180 deg probably wont be as accurate as the TinyPFA but I'm not sure if this matters much in this case.See below for the noise floor and stability vs time of the DMM recorder port of the HP8405A phase meter when set to the +/- 180deg range. This is across several minutes.

author: G0HZU
author_rank: Super Contributor
timestamp: March 19, 2025, 07:21:16 pm
content: The main limitation I have at the moment is that I don't have a stable reference like a Rubidium standard and I'm unlikely to ever buy one. I might be able to borrow one in a few weeks' time though.In the meantime the best I can do is reference two HP 8405A VVMs to the 10 MHz output OCXO from my offair standard and then see how the LBE-1421 and the Firefly-1A track the phase of the offair standard using the two HP 8405A VVMs.This isn't an ideal way to compare them but I think it is OK to note that the LBE-1421 has slightly more fine wiggle in its trace (compared to the Firefly-1A) and this suggests that it isn't quite as phase stable as the Firefly-1A. But there is very little in it.If I had a decent reference to replace the offair standard then this test would be more trustworthy.The slow rollercoaster ripple is probably due to the offair standard although some of it may also be due to GPS propagation issues. But I think most of it is due to the way the 198 kHz signal propagates from Droitwich to my house.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: March 23, 2025, 05:02:23 pm
content: I just finished using the Leo Bodnar LBE-1421 as a reference to evaluate the internal frequency standards of 19 lab instruments.This was also my first time using a tinyPFA phase and frequency analyser, it was a very interesting and pleasant experience! I also did some testing by feeding it with the same signal to find out the maximum accuracy.Some of my units had great performance (one was only 6.10-10 off the Bodnar (so less than one perbillion). That was a device with one of the best clocks around in the days it was sold, but still going well ;-) Other devices varied - a lot.You can find more information in the video below.Best, Rudi

author: RAPo
author_rank: Super Contributor
timestamp: March 23, 2025, 06:17:04 pm
content: That was a lovely video Rudi, thanks.I was wondering: do you have a dedicated frequency counter (e.g. a Racal 9901) that can measure ratio of frequencies (n*chA/chB)?It would be great to see the result.

author: G0HZU
author_rank: Super Contributor
timestamp: March 23, 2025, 08:18:47 pm
content: Yes, that was a very interesting video Rudi, thanks!It's the first time I seen some tests using the TinyPFA. Here at home I have a couple of HP 8405A VVMs which can so similar things but they take a long time to warm up and stabilise if the aim is to look at the phase stability on the finest phase range. Even then, I think they will struggle to compete with the TinyPFA, but they are both quite close I think, once fully warmed up. They are huge and very heavy and very old. These VVMs date back to the late 1960s and I think the oldest one I have here was made in 1967/8. It requires regular maintenance to keep it working to full spec as the components are so old. I've had to replace numerous leaky transistors and tired caps in the older one across many years. So I can't recommend anyone to buy one unless they can find one made in the 1980s rather than the 1960s.I also finally found time to measure the current draw from the LBE-1421. I had noticed that it gets slightly warmer when the outputs are programmed up towards the 1.4 GHz limit. This obviously makes sense so I wanted to investigate this a bit further. I also wanted to see if the units ever draw higher current in a brief surge etc.The first test I did was with one output set to 1 PPS and the other to 10 MHz and then I started the LBE-1421. To measure current, I have an active sensor that uses a 0.1 ohm sense resistor. This can be used on power cables up to about 100V as it isolates the sensor resistor from the output that feeds to a scope. It has a bandwidth of up to about 150 kHz.The scope plots below are scaled as 1 division = 100 mA so you can see that the LBE-1421 initially only takes 100mA for a couple of seconds as it initialises. The current then jumps up to about 300 mA. It then stays like this with no surges or dips in the current.The next plot shows the scope zoomed to the startup phase of the LBE-1421. I've limited the sample rate to just 50 kSa/s on the scope and this seems to be adequate.

author: G0HZU
author_rank: Super Contributor
timestamp: March 23, 2025, 08:22:53 pm
content: Here's the current draw when both outputs of the LBE-1421 are set to 1.4 GHz. I'm not sure many people will ever use it like this but the current draw went up to about 400 mA as in the screenshot below.This is still within the 500 mA capability of many USB ports so I don't see an issue here. I found that the unit ran maybe 5 degrees warmer when both outputs were set to 1.4 GHz but this wasn't a very well controlled thermal test.

author: EvgenyG
author_rank: Regular Contributor
timestamp: March 24, 2025, 12:39:30 am
content: Watching frequency difference works really great on an analog oscilloscope. Your fps will be limited by 1/sweep time and not LCD refresh rate.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 24, 2025, 07:41:07 am
content: Quote from: G0HZU on March 23, 2025, 08:18:47 pmI have posted my TinyPFA plots of a Leo Bodnar against my rubidium a few times on one of these forums. See image below where I produced plots comparing the Leo Bodnar to my home made GPSDO. The GPSDO designer (Lars Walenius) posted details on one of the EEVblog forums and created quite a lot of interest. Sadly Lars died from cancer some time ago:https://www.qsl.net/g4aon/gpsdo/SJ

author: G0HZU
author_rank: Super Contributor
timestamp: March 24, 2025, 11:52:33 am
content: Thanks, there's some interesting info there on your site.Last night I ran both of the HP 8405A VVMs for a few hours to get them stable and measured the phase stability on the finest range. The plot below shows the phase stability and drift across one minute. I've offset one of them slightly to make it easier to see the data for each.The older HP 8405A (made in 1967) is slightly worse than the newer one (made in 1986) but it has taken a lot of maintenance to keep the older one working about as well as the newer one. I'm not sure how this compares to the TinyPFA across one minute.This is taken from the phase recorder output at the rear of the instrument. The other way to do it would be to measure the phase externally by monitoring the relative phase of the two 20 kHz IF outputs (A and B) from the VVM. This should be better and one day I might try this using something like the Analog Discovery 2.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: March 24, 2025, 01:49:20 pm
content: Jeremy, you “need” to build a GPSDOIf you look in the Projects, Designs and Technical Stuff part of the EEVblog forum, you will find 2 or 3 designs. There is also a simple one by G3RUH that is entirely logic based.http://jrmiller.online/projects/ministd/frqstd0.htmKnowing where to stop is hard, I have 4 x GPDSOs and one rubidium.SJ

author: KedasProbe
author_rank: Frequent Contributor
timestamp: April 06, 2025, 02:42:00 pm
content: Hi,I updated the firmware (1.07) and it's nice to have the selection of satellites now.I also tried the new low power setting but it still has a DC component 1.44V and it increased output power so you would have to add a high-pass filter at the output to remove that.Some scope screenshots the settings/setup is in the filename: (note: ignore the rise time, this scope isn't fast enough)I made them with 50 Ohm and without 50 Ohm connected.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: April 12, 2025, 12:27:16 pm
content: FYIEven with a DC blocker in 'Low power output' mode the USB power usage hence heat remains the same.I don't see much use in that, if you want a lower dBm then add the correct attenuation.I did a quick check of the 'FLL' setting and it does reduce the 'faster' changes but the Mini is still better (like 50% smaller jumps, at least with mine).For the test my Mini is 24/7 on while the LBM-1420 was only a few hours on.

author: crysti
author_rank: Regular Contributor
timestamp: May 20, 2025, 08:01:10 am
content: I tested the LBE-1420 module and a $70 GPSDO from AliExpress using a TinyPFA at 10 MHz and –5 dBm. When synchronized to GPS, I’ve attached the Allan deviation plot. What bothers me is the variation when the GPS signal is absent.With the AliExpress GPSDO, which uses a reclaimed OCXO, I see no significant difference without GPS signal, whereas with the LBE‑1420, if I disconnect the GPS antenna, the deviation between the two reaches 2 Hz (0.2 ppm) over a 600‑second interval. To me, a short‑term variation of 0.2 ppm seems quite large for a TCXO.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: May 20, 2025, 09:35:37 am
content: Recently the white LED on my 1420 became intermittent. Talking with the technicians at Leo Bodnar, it appears that is not an uncommon failure due to running too much current through the LED. I only had a red LED in my spares stock and it wasn't a 90 degree one either, however it is rated at 20 mA and is much less bright than the dazzling white one originally fitted. The 1420 is still under warranty, but the tech didn't mind me repairing it and it would still be covered under warranty.Incidentally, I haven't checked mine for initial stability as it runs 24/7 here. Regarding the loss of GPS signal frequency stability/accuracy, I wouldn't expect a TCXO to be particularly good, some of the "better" ones are only 0.5ppm.SJ

author: crysti
author_rank: Regular Contributor
timestamp: May 20, 2025, 03:14:29 pm
content: I have now tested at constant temperature, without GPS signal, but after 2 hours of operation with GPS synchronization. Just under 0.1 ppm.For example, I found a VCTCXO, model LFTVXO075807, same size 3.2mm x 2.5mm at 20 MHz, priced at €10, which has an ageing specification of ±0.02 ppm max per day, which is significantly better than the current one, which ages at over 0.1 ppm per hour.I believe that part of the reason for the VCTCXO’s low precision is the use of PWM instead of a 16-bit DAC

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: July 28, 2025, 08:34:41 am
content: There is some news on the Leo Bodnar LBE-142* front...Firstly, last week, the macOS app received an update. It is now more on par with the Windows version, which I appreciate. The macOS app now has:Dynamic model (stationary, portable, airborne)NMEA on Out1Selection of GNSS (GPS, SBAS, Galileo, BeiDou, GLONASS) (the last two are mutually exclusive)(But still there are some things only the Windows app can do, and some only the MacOS app can do...)In the picture below, you see the new app version, compared to the previous one, and to the Windows app.Second, there is a new family member:model LBE-1423, which has a differential output. For when you need a differential clock, like with FPGA's.Best, RudiYT: Rudi's Electronics Lab

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 28, 2025, 04:16:32 pm
content: Is there anything better in practice with one of these compared to the BH3SAP GPSDO?I wonder if there's a benefit besides Leo Bodnar's name being on the device.Thanks,Josh

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: July 28, 2025, 05:00:47 pm
content: The advantage of the Leo Bodnar units is that (a) you can output any frequency from 1Hz to more than 1GHz(b) the power requirement is very low, I power mine from a USB “wall wart”(c) they are very small(d) they are stable in a couple of minutesFor critical applications, the jitter is not as low as can be obtained with a decent home made GPSDO with a high grade oven. Expect around 3 parts in 10^10 from a Leo Bodnar, my home made GPSDO (Lars Walenius design from these forums) gives around 2 parts in 10^11The above measurements were made with a TinyPFA, rubidium standard and TimeLab software.My home made unit only outputs 10 and 1 MHz, takes 20 to 30 minutes to stabilise, is mains powered, compared to the “one to two” minute to stabilise for the LB units and low power consumption.

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 28, 2025, 06:26:41 pm
content: Quote from: Solder_Junkie on July 28, 2025, 05:00:47 pmThis one?:https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/It sounds like the DIY route will be both better and more fun.Is that project still what you would build today, or is there another project to consider?Thanks,Josh

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: July 28, 2025, 06:31:51 pm
content: This describes the build:https://www.qsl.net/g4aon/gpsdo/SJ

author: KungFuJosh
author_rank: Super Contributor
timestamp: July 28, 2025, 06:44:20 pm
content: Any thoughts on this one?https://www.eevblog.com/forum/projects/budget-gpsdo-a-work-in-progress/https://sourceforge.net/projects/minimal-gpsdo/I like that he shared the full project, so I can adjust it if needed.Thanks,Josh

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: July 29, 2025, 09:13:33 am
content: Quote from: KungFuJosh on July 28, 2025, 06:44:20 pmThere are at least 3 GPSDO projects on this forum:https://www.eevblog.com/forum/projects/James Miller has a circuit for a really simple GPSDO, a cheap "eBay" Ublox GPS module can be configured to output 10 KHz for this project, the original Navman Jupiter GPS modules are long since obsolete and mine failed, I now use a $10 eBay fake Ublox Neo 6M board:http://www.jrmiller.online/projects/ministd/manual.pdfI built one of the above a long time ago and still have it. I haven't any experience of the "work in progress" GPSDO in your link.SJ

author: ch_scr
author_rank: Frequent Contributor
timestamp: July 29, 2025, 11:29:34 am
content: It's also relatively easy to DIY GPSDO with LEA-M8F now (no Arduino needed, the Ublox does it all by itself).They are quite expensive modules new, but there are used ones on Aliexpress for a good price.The M8F not only outputs it's internal precision 30.72MHz, but has two inputs and can control a (specific model of) I2C DAC to discipline an external OCXO.It will then "lock itself" onto the OCXO, and you can use the other input as a frequency "counter" still(think it provided quite a high-res measurement of the second OCXO connected - you might have to tell it the expected frequency before hand though, hence the quotes around "counter").The documentation is nice, fun to play with...