[Elecraft] K3EXREF and Trimble Thunderbolts

[Joe Subich, W4TV]

Paul,

> 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.

What are the power requirements?  Would it not be possible to build
a basic linear supply relatively inexpensively and avoid all of the
switcher issues?

73,

    ... Joe, W4TV


On 4/5/2011 8:43 AM, Paul Christensen wrote:
> 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
>
>
>
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