Re: K3EXREF and Trimble Thunderbolts

Posted by P.B. Christensen on Apr 05, 2011; 7:40pm
URL: http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6243587.html

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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