[Elecraft] Installed K3EXREF

[Wayne Burdick]

Wes Stewart wrote:

> I really don't understand all of the fuss about 1 Hz accuracy....

Because so many customers asked for it. I'll leave it to them to list  
their reasons, but in my case, I like being dead-on over a wide range  
of temperatures without having to occasionally recheck my manual REF  
CAL setting using a beat note with WWV.


> when just changing the K3 Width and Shift controls moves the  
> frequency more than that....

SHIFT and WIDTH move the I.F. by an accurate amount, and should not  
introduce any error in the operating frequency beyond that of normal  
DDS granularity, which can be +/- 1 Hz or so depending on the band.


> On ten-meters I can listen to a crystal-controlled source and hear  
> the beat note change as Shift and Width are adjusted.

That is due to DDS granularity. There is no such error where phase  
coherency really counts--in diversity mode. In that case the two  
synthesizers are always phase-locked as long as the crystal filter  
offsets are matched.


> Elecraft considers its frequency conversion scheme to be proprietary  
> but it's obvious that not all of the oscillators are moving at the  
> same rate.

They are all subject to our DDS step size of aprox. 1/5th Hz. In  
diversity mode the DDS words are identical, but in other cases the two  
synths can be off by this amount in either direction, resulting in a  
small tuning error that is proportional to operating frequency. It  
amounts to about +/- 1 Hz.

73,
Wayne