Author Topic: Leo Bodnar Mini precision GPS reference clock teardown  (Read 19177 times)

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Offline mcinqueTopic starter

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Leo Bodnar Mini precision GPS reference clock teardown
« on: January 12, 2018, 05:47:47 pm »
Just a quick look inside the nice and useful reference sold by leobodnar.com.
Just tried, very useful to check cheaply my frequency counter calibration.
Installs quickly, finds the GPS fix very fast and uses an essential and robust software utility to configure it.

http://www.microchip.com/wwwproducts/en/PIC18F24K50
https://www.silabs.com/documents/public/data-sheets/Si5328.pdf
https://www.u-blox.com/en/product/max-m8-series
 
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Offline babysitter

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #1 on: January 13, 2018, 09:37:26 am »
See, a MEMS device on PCB layer :)
I'm not a feature, I'm a bug! ARC DG3HDA
 

Offline Frex

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #2 on: September 07, 2020, 04:11:46 am »
Hello,

I planned to purchase also the mini precision GPS clock from Leo Bodnard
because it allow programming output frequency in broad range and
 it have  much lower phase noise than lower cost GPS clock from BG7TBL.

Anyway, before to purchase, I asked some info to Leo Bodnard support email,
 but no answer after a week or so. I hope he's fine...

So I post my questions here, maybe some owners would have the answers :
1/ Does it support Galileo GPS lock  ?
2/ Does the provided control software is Linux compatible ?
3/ Is there a manual available with all specs (a real datasheet with measurements) ?
Thank you in advance

Frex
 

Offline Leo Bodnar

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #3 on: September 07, 2020, 07:27:46 am »
Hi Frex,
1/ Does it support Galileo GPS lock  ?
Yes, it supports GPS, Glonass, Beidou and Galileo but I tend to keep Galileo turned off.  It degrades high precision timing performance but you need a high quality stable source to see that.

2/ Does the provided control software is Linux compatible ?
You can get Linux version from https://github.com/simontheu/lb-gps-linux

3/ Is there a manual available with all specs (a real datasheet with measurements) ?
All the information is on the website http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301 There is not really much to it.

Cheers
Leo

P.S. I can't see your email, please use support@leobodnar.com for contacts
 
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Offline Frex

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #4 on: September 07, 2020, 03:14:25 pm »
Hello,

Thank you for this quick answer.
As I seen, for Linux it's not a GUI but  only by commands line instructions(?).
So now, I just need to make the order ;o)

Note that my two email (01/09  and 02/09) has been sent you
to the right email address. Maybe a spam filter ? can you check ?
(I don't have issue with my email usually)
Regards.

Frex

 

Offline chronos42

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #5 on: September 07, 2020, 06:14:10 pm »
Hi,

A short question to Leo Bodnar:

I have the two channel version of the Precision GPS Reference Clock and I am very happy with it. But why is there no satellite reciption function or acess to the GPS funcions like in the mini Precision GPS Reference Clock? What is the reason for this limitation? 
 

Offline fourfathom

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #6 on: September 07, 2020, 07:09:16 pm »
Leo, I recently got the MiniGPS, and really like it.  I had been using a very old Trimble Thunderbolt, and the Mini is giving me much less trouble.  Thanks!

A question for you:  I notice what I presume to be a thermal isolation cutout around the Mini's TCXO.  How much does that help, compared to leaving the PCB intact?
We'll search out every place a sick, twisted, solitary misfit might run to! -- I'll start with Radio Shack.
 

Offline Ringmodulator

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #7 on: September 08, 2020, 04:26:03 pm »
Hi,

can this unit communicate with the u-center software trough the USB port?

Chris
 

Offline Leo Bodnar

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #8 on: September 09, 2020, 09:37:16 am »
Quote
I have the two channel version of the Precision GPS Reference Clock and I am very happy with it. But why is there no satellite reception function or access to the GPS functions like in the mini Precision GPS Reference Clock? What is the reason for this limitation?
We will have a unified control application for both clocks at some point and you will get the access to this info/functions too.
Quote
can this unit communicate with the u-center software trough the USB port?
Not at the moment, no.
Quote
A question for you:  I notice what I presume to be a thermal isolation cutout around the Mini's TCXO.  How much does that help, compared to leaving the PCB intact?
It reduces the rate of frequency change making it easier for the DPLL BW to follow the drift.

Leo
 

Offline Solder_Junkie

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #9 on: September 10, 2020, 03:30:00 pm »
Leo, my dual output unit takes around 5 minutes to obtain lock if it was been unpowered for more than about 1 hour. It is the same even if I mount the patch antenna on my car roof with a completely clear sky view.

Should I replace the capacitor?

Dave
 

Offline Leo Bodnar

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #10 on: September 16, 2020, 01:25:43 pm »
Dave,
Supercap should provide enough power to keep timing for 4-5 hours.
Leo
 

Offline Frex

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #11 on: September 20, 2020, 06:07:48 am »
Hello,

Just to say thank you to Leo.
I received the mini precision GPS clock and it work great.
The ability to set output to any value from 400Hz to 800M and the low phase noise
 output has decided me to choose it instead of Chinese GPSDO (BG7TBL).
A little bit more expensive, but it worth the money !
Regards.

Frex

Note : Anyway, If you serch about what could be improved,
I must say that the ability to switch output to sine instead of square would be great.
Or better, a second dedicated outputs. ;-)
 

Offline Wim13

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #12 on: December 05, 2020, 03:48:26 pm »
There are several docs on internet to calculate the output frequency 1 and 2 , but i wanted a simple formule spreadsheet.

I have the GPSDO with two outputs.

So i came to this simple sheet:
For calculation of the two output frequency's, you need just two frormules:

Output1: formule = ( GPSref  x  N2_HS  x  N2_LS )   /  ( N31  x  N1_HS   x  NC1_LS )

Output2: formule = ( GPSref  x  N2_HS  x  N2_LS )   /  ( N31  x  N1_HS   x  NC2_LS )

(SI5328,  CKIN1 = GPSref  out from the MAX 8 module)

In this sheet a sample of 10 Mhz on output 1 and 1 Mhz on output 2 that works,
and the formules.

The GPS module can deliver an input frequentie up to 10 Mhz to the Si5328, and
is then divided bij N31 for reference to the DSPLL (F3).

*Note, the Fosc frequency has to be between 5 and 6 Ghz for a PLL lock.
I think it is a kind of 5 Ghz wifi VCO ? Can not read any signs on it.

My unit has the following limits for the VCO frequency,  to lock the PLL:  4.17 Ghz and 6.68 Ghz.
So the safe limits are between  5-6 Ghz.

« Last Edit: December 17, 2020, 12:25:32 pm by Wim13 »
 
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Offline Conrad Hoffman

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #13 on: December 05, 2020, 09:17:21 pm »
Needed something for a long time and wasn't sure about the Chinese units, so just ordered one of Leo's. Time to get those counters tuned up!
 

Offline jonpaul

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #14 on: December 07, 2020, 11:31:54 am »
Hello all have both Leo's GPS and the 40 pS pulser, also the SDR radio SDRPlay.

All excellent  designs and good SW and support.

HIGHLY RECOMMENDED

Suggest to  avoid the Chinese junk knockoffs with zero support.

Bon journee,

Jon
Jean-Paul  the Internet Dinosaur
 
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Offline Conrad Hoffman

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #15 on: December 10, 2020, 02:34:04 pm »
Very impressive. The mini arrived in the US two days from shipment in the UK. The good news is I had a chance to verify it was working great. When I beat my counters against WWV I can get about 10E-7 or a bit better on a good day. This is way better. The bad news is I then had to pack it back up so my wife could put it under the tree for Christmas. I'll report back in January.
 
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Offline Conrad Hoffman

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #16 on: December 12, 2020, 01:48:59 am »
In the meantime, I don't really know how to read the Allen deviation chart; does it mean I've achieved maximum accuracy after about 2000 seconds of operation? How long should one wait to get best performance?

Also, are the antennas magnetic because you get better sensitivity on a metal ground plane?

Thanks!
 

Offline Wim13

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #17 on: December 12, 2020, 05:31:12 pm »
There is lot of information on the net about Allen deviation charts,

But on the short, on such chart can see how a oscilator performs for frequency stability on the short and on the long run.

GPS is on the short time very bad, due to radio path variations and reflections and number of satelites in view.
That can be as bad as 10E-6. But on the long term GPS is very very good, because it follows the ground stations corrections.

In an allen dev chart you can see this performance over time.

A temp controlled oscilator is very good on the short term, but less on the long run.

So if you combine these two, GPS and a TCO you get the best of these.

I have two lucent rubidium oscilators, and a HP5370B counter which i can use to compare with the Bodnar GPSDO.
My GPSDO locks in about 2 to 3 seconds, and is then  better than 10E-9

After 10 minutes i get about  < 3 E-10 measured with the HP5370, interval ~1 second. ( see graph of the next 10 minutes = 400 samples)
The rubidium clocks are about <5 E-11

And about the magnetic feet , thats is only for easy use on metal, like cars
« Last Edit: December 13, 2020, 01:57:23 pm by Wim13 »
 
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Offline Conrad Hoffman

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #18 on: December 12, 2020, 06:49:24 pm »
Thanks! That's good to know. From reading about various disciplined oscillators, I was under the impression it could take far longer to get decent accuracy. I keep reading about Allen deviation but it doesn't seem to sink in. Too much math and too little overview. Or, I'm just a dummy.
« Last Edit: December 12, 2020, 06:50:55 pm by Conrad Hoffman »
 
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Offline ocw

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #19 on: December 13, 2020, 01:02:10 am »
I made a comparison today of my three GPSDO’s: the Bodnar Precision unit, a BG7TBL version, plus a Trimble GPSDO with three both sine and square wave outputs.  I used my Anritsu MT8222A analyzer for SA measurements.  It has a built-in GPSDO.

All three had clean 10 MHz outputs.  The Bodnar unit was nice in being able to provide 450 Hz to 808 MHz outputs.  However, some frequencies are not as good of quality.  I provide views of 43.2 and 330 MHz as two examples.  The BG7TBL FA-2 is the best thing that I have for precise frequency  measurement.  Using the BG7TBL GPSDO as its reference, the Bodnar unit was measured 164.2 uHz high.  The accuracy of that measurement obviously is dependent on both of those devices.  The MT8222A measured the fifth harmonic of 190 MHz from the Bodnar unit at 950 MHz as being 0.15 Hz low.

I also tested my BG7TBL 10 MHz DA dated 2019-09-13 on its front panel.  It has eight outputs and did not change the quality of GPSDO's feeding it.

The Trimble GPSDO had poor frequency accuracy: 0.425575 Hz high.  I include pictures of its circuit board in case anybody knows how to improve that.
« Last Edit: December 13, 2020, 05:01:19 am by ocw »
 
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Online bingo600

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #20 on: December 13, 2020, 08:59:30 am »
How do you know it's the Trimble that is off , and not the BG7 ?

I would prob. initially have trusted the Trimble , due to it being a Trimble , and not a non "Home made board"

Edit: The board w the 8-chan is the BG7 (Based on a Trimble Top board) ?

Edit2: For how long has the boards been powered up , an OCXO can take several weeks to settle.

/Bingo
« Last Edit: December 13, 2020, 09:06:42 am by bingo600 »
 

Offline Leo Bodnar

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #21 on: December 13, 2020, 11:50:36 am »
The Bodnar unit was nice in being able to provide 450 Hz to 808 MHz outputs.  However, some frequencies are not as good of quality.  I provide views of 43.2 and 330 MHz as two examples.
These look very ugly.  How exactly are you measuring this?  I.e. what instruments, refernces, settings and measurement procedure?

I have quickly thrown a mini GPS clock set by config software to default 330MHz on a E4406A, set to 40Hz RBW - using its mediocre internal oscillator (all my Rubidium and OCXO references are at work.)  I have used standard magnetic puck antenna right on top of E4406A, inside my house.

Here is what I have after 100 averages (took about 10 minutes)

Phase-noise wise, what you see here is the noise of E4406A, mini GPS clock is cleaner - you should see about -70dBc/Hz at 10Hz offset off 330MHz carrier. Carrier offset is not precisely 330.0000000MHz since E4406A is not locked to anything and has not been calibrated for ages.

Cheers
Leo

Edit: I have also added 43.2MHz take.  The shape of the carrier on your screenshots look like Blackman-Harris window, so I have used one too.
« Last Edit: December 13, 2020, 12:12:09 pm by Leo Bodnar »
 

Offline ocw

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #22 on: December 13, 2020, 05:41:49 pm »
Quote
How do you know it's the Trimble that is off , and not the BG7 ?

It is the Trimble vs. BG7TBL, Bodnar, MT8222A, and many other local RF sources which I know are GPS locked.  Attached are pictures of the the Trimble's front and rear panels.  Planning to get back into it, I left its mounting screws off.

The Trimble was only on for several hours before the measurement, as were the other GPSDO's.  They had much better accuracy, agreeing the other known accurate frequency sources.  With my common use being at random locations, I need reasonable accuracy after hours of warm-up, not days.  The others can achieve that.
 

Offline Wim13

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #23 on: December 13, 2020, 06:29:36 pm »
 I made a screenshot of the 10 Mhz and 330 Mhz signal of the Bodnar GPSDO, plotted on a SDR,
not to overload the SDR there is a 40 dB att inserted. Still have a 100 dB range.

it looks normal for me not bad at all.
 

Online bingo600

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Re: Leo Bodnar Mini precision GPS reference clock teardown
« Reply #24 on: December 13, 2020, 06:33:26 pm »
Quote
How do you know it's the Trimble that is off , and not the BG7 ?

With my common use being at random locations, I need reasonable accuracy after hours of warm-up, not days.  The others can achieve that.

While that says something about your usecase, and preferred unit.
How does it prove that the Trimble is the one that is "Off" ?

Seems to me that a Rubidium is what you might want , since you can't wait for the OCXO to stabilize.

/Bingo


 


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