[Elecraft] K3: REF IN

[Jan Holmer SM6TUW]

Since some time I am working on a solution just for fun (
http://n2.nabble.com/KREF-EXT-Option-tc2461086.html#a2461086 ). 
My GPS-derived clock was built from VE2ZAZ design and it works fine ( it is
also used for other purpose in lab).  PLL is a ADF4001 programmed from a AVR
ATtiny2313. 
So far the system is running stand alone with a VCXO external to the K3
since my KTCXO3 does not have a voltage control connection. It is certainly
possible to modify the KTCXO3 to a VCTCXO but I didn´t dare to do that yet.
Maybe Elecrafts supplier can provide such a beast?

If you are planning to use the K144XV as IF for higher order transverters it
would be important to get this reference accuracy.

73  Jan


Ian White GM3SEK wrote:
> 
> David Pratt wrote:
>>Page 17 of the K3 Owner's Manual (Rev D2) shows an SMA connector for 
>>"Input for external standard frequency reference" for which a KREF3-EXT 
>>option purports to be available eventually.  I understand from what has 
>>been said earlier is that this will be for a 10MHz standard so you will 
>>need to use the 60kHz MSF signal to lock a 10MHz TCXO or use a GPS, 
>>Rubidium or Caesium standard.
>>
> 
> The schematic of the KSYN3 board shows a header (J4) with connections to 
> the 10MHz input, the 49.380MHz output from the existing oscillator 
> module and a V_ctrl line going back to the oscillator module. This 
> suggests that the KREF3-EXT module will have a phase-locked loop to lock 
> the oscillator to 10MHz.
> 
> (Also on J4 is a mysterious "100Hz" bus which wanders around many other 
> areas of the K3... anyone know what that is?)
> 
> However, phase locking to an external reference still doesn't mean that 
> the K3 will be precisely on frequency.  Due to the internal arithmetic 
> of the K3's synthesis and mixing scheme, the frequency you see on the 
> display is not quite the frequency you actually get. As Wayne pointed 
> out on 17 November, "this translates to a VCO step size of about 0.5 Hz 
> on 160 m, 1 Hz on 20 m, and 2 Hz on 6 m. Other bands are between these 
> values."
> 
> What the KREF3-EXT module should be able to deliver is complete freedom 
> from frequency drift, for almost all practical purposes. There could 
> also be great communication value in being able to lock a pair of K3s to 
> the same global GPS standard, even when they are half a world apart
> 
> In the meantime, the K3 already has the most important kind of frequency 
> and phase locking - between its own two receivers for true diversity 
> reception.
> 
> 
> -- 
> 
> 73 from Ian GM3SEK
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