Re: GPS Disciplined 10MHZ source from China

Posted by Mark Goldberg on May 09, 2017; 3:05pm
URL: http://elecraft.85.s1.nabble.com/GPS-Disciplined-10MHZ-source-from-China-tp7630465p7630466.html

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
>
>
>
>
>
>
>
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