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GPS Disciplined 10MHZ source from China

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P.B. Christensen

GPS Disciplined 10MHZ source from China

>"If you want a good quality 10 MHz GPSDO, I recommend the one made by Leo
Bodnar M0XER. It was reviewed in QST, June 2016."

Unless the K3S architecture is different than the K3, then frequency, rather
than phase-locking is used from the external frequency source. Phase noise
performance of the GPS-DO doesn't impact performance of the K3 receiver.

However, if planning on distributing the GPS-DO to other devices, I think
it's worthwhile to note that the higher-priced version of the Bodnar is
still > 30 dB worse at a 100 Hz Fc offset than a common Trimble Thunderbolt
with the Trimble-branded OCXO (not Piezo) when powered from a low-noise,
lab-grade supply. For example, typical Trimble PN at 100 Hz is -160 dBc.
The upper-grade Bodnar unit is about -125 dBc.

Compared to what's available on the new and used markets, I agree with G4DYA
that the Bodnar's performance is probably characterized as good, but not
excellent. Again, for K3 users it isn't an issue, but if the device is
driving other test gear or other transceivers, that 30 dB difference may
mean a lot.

The Thunderbolts were once plentiful on eBay for USD $99. Scarcity has
driven that up but with persistence, a watchful eye can still spot one at a
reasonable price.

I ended up installing a Trimble unit and Lambda linear supply into a
customized enclosure. It drives a TAPR distribution amp and that supplies a
precision 10 MHz refence to multiple transceivers and test equipment.

http://tinyurl.com/j7r36w5

Paul, W9AC

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Mark Goldberg

Re: GPS Disciplined 10MHZ source from China

Thanks for bringing up phase noise. From my research on other cheap devices
(knockoff TCXOs), I have found that phase noise was obviously not
considered and in that case was truly awful. It was in the -115 dBc range
at 100hz, but, likely due to poor design, actually rose to -110 dBc at
10-100 kHz offset, which is truly awful. There were also many spurs. If
something is not specified, it is likely not even considered.

I had not realized a Trimble Thunderbolt was so good. I have been using the
output of the low aging rate option of an HP8642A for a 10 MHz reference,
no idea of the phase noise. Now you have me wanting something else!

73,

Mark
W7MLG

On Tue, May 9, 2017 at 7:19 AM, Paul Christensen <[hidden email]> wrote:

> >"If you want a good quality 10 MHz GPSDO, I recommend the one made by Leo
> Bodnar M0XER. It was reviewed in QST, June 2016."
>
> Unless the K3S architecture is different than the K3, then frequency,
> rather
> than phase-locking is used from the external frequency source. Phase noise
> performance of the GPS-DO doesn't impact performance of the K3 receiver.
>
> However, if planning on distributing the GPS-DO to other devices, I think
> it's worthwhile to note that the higher-priced version of the Bodnar is
> still > 30 dB worse at a 100 Hz Fc offset than a common Trimble Thunderbolt
> with the Trimble-branded OCXO (not Piezo) when powered from a low-noise,
> lab-grade supply. For example, typical Trimble PN at 100 Hz is -160 dBc.
> The upper-grade Bodnar unit is about -125 dBc.
>
> Compared to what's available on the new and used markets, I agree with
> G4DYA
> that the Bodnar's performance is probably characterized as good, but not
> excellent. Again, for K3 users it isn't an issue, but if the device is
> driving other test gear or other transceivers, that 30 dB difference may
> mean a lot.
>
> The Thunderbolts were once plentiful on eBay for USD $99. Scarcity has
> driven that up but with persistence, a watchful eye can still spot one at a
> reasonable price.
>
> I ended up installing a Trimble unit and Lambda linear supply into a
> customized enclosure. It drives a TAPR distribution amp and that supplies
> a
> precision 10 MHz refence to multiple transceivers and test equipment.
>
> http://tinyurl.com/j7r36w5
>
> Paul, W9AC
>
>
>
>
>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> ______________________________________________________________
> Elecraft mailing list
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Elecraft mailing list

Re: GPS Disciplined 10MHZ source from China

In reply to this post by P.B. Christensen

OK, so what was the "Item Number" on the bay? As I'm unable to find
that seller to see what exactly it was you purchased.

Or, what is the make/model number of it (if it's an ex commercial item,
such as a Thunderbolt.)

The devil is in the detail with these things.

73
Dave G0WBX

On 09/05/17 21:53, [hidden email] wrote:

> Date: Mon, 8 May 2017 16:26:10 -0600
> From: "Jay Miller" <[hidden email]>
> To: <[hidden email]>
> Subject: [Elecraft] GPS Disciplined 10MHZ source from China
> Message-ID: <001001d2c84a$1881a390$4984eab0$@mindspring.com>
> Content-Type: text/plain; charset="us-ascii"
>
> I was curious so I bought a GPS disciplined 10MHz source from China using
> the eBay seller "cybereveryday." I have a calibrated scope and a Rubidium
> 10MHz source. I noticed a frequency offset on three of the WWV frequencies
> when I plugged it into the K3 XREF module after getting "GPS Lock" rather
> than using my Rubidium lamp standard I measured the 10MHz output from the
> GPSDO and it is 10,000,025 Hz. (2.5 PPM) The eBay ad states "Accuracy: than
> above OXCO 2 order of magnitude." The point is, even using the K3 zero-beat
> method with 15 MHz WWV I can get closer to being dead on frequency than
> using this Chinese mfg. GPSDO. Again, Elecraft quality and engineering WINS.
>
>
>
> Jay Miller, N4NUI

Elecraft mailing list

Re: GPS Disciplined 10MHZ source from China

In reply to this post by P.B. Christensen

The advantage of the Leo Bodnar unit is that it can do a lot more than just act as a fixed 10 MHz reference. It covers the range 450 Hz to 800 MHz, so has many other uses around the shack.
I use mine for frequency locking the 116 MHz Local oscillator of an a G4DDK Anglian 144 MHz transverter.

If it is just a 10 MHz reference that is required then other units with better phase noise are available surplus, though be careful as some may require a bit of work if they are very old, however the Chinese do make some very nice 10 MHz GPSDO's which are reasonably priced. I have one and a matching 8 output distribution amplifier which also contains a fallback OCXO within it. I also have a surplus HP Z3801A, it is large, requires a 48V DC power supply, I use it as my main 10 MHz shack and lab reference for microwave counters.

The Leo Bodnar can be switched on and is locked and stable in about a minute from cold, unlike high accuracy GPSDOs with OCXOs which can take 15 to 30 minutes to reach lock and really are designed to be left switched on and consuming power all the time, so that may be a consideration in a ham station that is not always attended and you want to power everything down for safety or to save electricity.

Lastly if you want a very nice shack GPS time clock. I recently found this USA kit on Tindie.

https://www.tindie.com/products/nsayer/gps-clock/

It is a digital LED clock which is GPS locked. Note it isn't a frequency reference, only a timepiece.
It can display hours minute and seconds plus optionally tenths of a second.

All on one PCB and runs from 5V DC at about 200mA max. I built one and am most impressed. You can have it show local time with auto DST correction, 12 or 24 hour format, or leave it on UTC for the shack. I have not noticed any RFI from it, even in its wooden enclosure.

It does require a GPS Lock to work, so if you live in a basement, unless you mount an antenna outside it won't work. From a cold start it takes about a couple of minutes to lock, sometimes less. I leave mine on as the power consumption is relatively low.

I have no connection with the designer, other than as a customer.

73 from David GM4JJJ

On 9 May 2017, at 15:19, Paul Christensen <[hidden email]> wrote:

>> "If you want a good quality 10 MHz GPSDO, I recommend the one made by Leo
> Bodnar M0XER. It was reviewed in QST, June 2016."
>
> Unless the K3S architecture is different than the K3, then frequency, rather
> than phase-locking is used from the external frequency source. Phase noise
> performance of the GPS-DO doesn't impact performance of the K3 receiver.
>
> However, if planning on distributing the GPS-DO to other devices, I think
> it's worthwhile to note that the higher-priced version of the Bodnar is
> still > 30 dB worse at a 100 Hz Fc offset than a common Trimble Thunderbolt
> with the Trimble-branded OCXO (not Piezo) when powered from a low-noise,
> lab-grade supply. For example, typical Trimble PN at 100 Hz is -160 dBc.
> The upper-grade Bodnar unit is about -125 dBc.
>
> Compared to what's available on the new and used markets, I agree with G4DYA
> that the Bodnar's performance is probably characterized as good, but not
> excellent. Again, for K3 users it isn't an issue, but if the device is
> driving other test gear or other transceivers, that 30 dB difference may
> mean a lot.
>
> The Thunderbolts were once plentiful on eBay for USD $99. Scarcity has
> driven that up but with persistence, a watchful eye can still spot one at a
> reasonable price.
>
> I ended up installing a Trimble unit and Lambda linear supply into a
> customized enclosure. It drives a TAPR distribution amp and that supplies a
> precision 10 MHz refence to multiple transceivers and test equipment.
>
> http://tinyurl.com/j7r36w5
>
> Paul, W9AC
>
>
>
>
>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]