http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6242401.html
> and International Power. They offer excellent performance and low
> noise. I am using an International Power IHBAA-40W. Also look for
... Joe, W4TV
> Those of you considering a GPS-disciplined oscillator for use with the
> K3EXREF may be interested in this: I recently purchased two Trimble
> Thunderbolts on the surplus market to compare against my HP 58540A and
> Brandywine GPS4 units. After several days of testing, I'm retiring the HP
> and Brandywine units. All devices have exceptionally good stability, but
> the Trimble units consume far less power, run substantially cooler, and the
> monitoring interface provides much more status information than the prior
> units.
>
> In recent discussions with John, KE5FX, he has performed phase noise
> measurements across several GPS-DO units and even various oscillator brands
> within the Trimble Thunderbolt model.
>
>
http://www.thegleam.com/ke5fx/tbolt.htm>
> Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS
> correction, its phase noise performance is good but not exceptional. By
> contrast, the Trimble-branded OCXO offers phase noise performance several
> degrees better than most other GPS-DO units near Fc. The area between 1 Hz
> and 100 Hz is usually a good indicator of the overall phase noise
> performance. It's not easy getting good numbers that distance from Fc.
> Although the phase noise performance will not carry over to the K3, it's an
> important parameter if the GPS-DO will be used in other applications or
> other transceivers that phase lock onto the 10 MHz external reference.
>
> Some suggestions:
>
> 1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the
> better quality OCXO units with the Trimble-branded label. KE5FX has sampled
> several from this batch. As noted, early units with the Piezo-branded OCXO
> are worse in terms of phase noise performance. I do not know the OCXO
> quality of recent units;
>
> 2) You will see Thunderbolts in a high quality case where an internal DC-DC
> converter is used. My recommendation is to avoid being tempted by the nice
> looks and what may be perceived as a "better" unit. I can almost guarantee
> that the switch-mode converters will present noise problems with your K3
> receiver -- and seen on your panadapters. I've been down that road with
> other GPS-DO units and ultimately, I scrapped the converters and fed them
> with linear supplies. Stick to the basic ugly OEM Thunderbolt module and
> feed it from a triple-output linear supply;
>
> 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and
> International Power. They offer excellent performance and low noise. I am
> using an International Power IHBAA-40W. Also look for HBAA-40W. The user
> must add a fuse, power cord and wiring harness. It's a little more work,
> but you get a lot of performance for the money;
>
> 4) Look for sellers who will accept offers. Both my Thunderbolts were
> purchased for USD $70 ea and a small shipping change.
>
> Even if you have no plans to use K3EXREF, get one anyway as a precision
> frequency reference for your station.
>
> Paul, W9AC
>
>
>
> ______________________________________________________________
> 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>