Re: K3EXREF and Trimble Thunderbolts

Posted by K2QI on Apr 05, 2011; 7:49pm
URL: http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6243613.html

Brilliant - thanks to all for your replies.

I'll start looking for a used Thunderbolt to experiment with.  Sorry
if I missed this in an earlier exchange, but are there specific
Trimble model numbers known for recommended units?

Paul - I agree; can never hurt to have a disciplined reference source
for other projects.

Mni tnx es vy 73,
James K2QI

On Tue, Apr 5, 2011 at 3:40 PM, Paul Christensen <[hidden email]> wrote:

> Jim,
>
> In case you missed earlier comments, don't worry about phase noise
> performance of the external reference if you'll only use it with the K3.
> But, in addition to the K3, a high performance, low phase noise external
> reference can be distributed around the shack or work bench for other
> purposes.  I use a second output from the Trimble to phase-lock an ADAT
> transceiver.
>
> Paul, W9AC
>
> ----- Original Message -----
> From: "Paul Christensen" <[hidden email]>
> To: <[hidden email]>
> Sent: Tuesday, April 05, 2011 3:36 PM
> Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts
>
>
>>> 1.  Any reference oscillator operating at 10 MHz would work with the
>>> K3XREF?
>>
>> The 10 MHz source should have a signal level between +4 dBm and +16 dBm.
>> For
>> square wave sources, 2VDC to 3.3VDC peak is optimum.  If the source is a
>> 5V
>> logic level, use a 50-ohm resistor in series with the input.
>>
>>> 2.  All that's needed for this to work is the K3XREF, updated
>> firmware, an accurate 10 MHz clock/oscillator, and a BNC cable?
>>
>> Yes.
>>
>>> 3.  Trimble Thunderbolt seems to be a good, cheap product to try.  Any
>> others that are > $100?
>>
>> Many.  For those not affraid of getting a soldering iron hot, I think the
>> Trimble units are pretty tough to beat.  Requires making a power cable to
>> a
>> triple-output power supply of your choice.  For a while, the HP Z3801A
>> units
>> were very popular.  These use noisy DC-DC internal converters, are power
>> hungry, but offer some of the best phase noise peformance of all the
>> GPS-DO
>> units.  The Trimble units have been documented to pretty much meet the
>> phase
>> noise performance of the Z3801A.   Rubidium is another choice in the USD
>> $100 range but these too will require some creative power connections.
>>
>>> What are the additional advantages of doing this other than knowing
>> you've pretty much eliminated any frequency drift?
>>
>> Really none I can think of, but as the weak-signal V/UHF ops have said,
>> that's reason enough!
>>
>> Paul, W9AC
>>
>>
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--
73 de James K2QI
President UNARC/4U1UN
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