[Elecraft] KX3 frequency stability

[Wayne Burdick]

Tony,

The KX3's temperature stability is specified at +/- 1 ppm typical over  
0-50 C. That's +/- 14 Hz on 20 meters. Normally the short-term  
stability would be far greater than this. However, during long key- 
down periods there is some heating of the RF board, which includes  
both the PA and oscillator circuitry.

We included closed-loop temperature compensation for this effect in  
hardware and firmware. Normally this compensation is entirely  
sufficient, but apparently it doesn't meet WSPR/JT65 requirements.

I should be able to provide a user-settable fine compensation value in  
the menu, although it would be a bit of trial and error for the user  
to determine the optimal value.

Wayne
N6KR


Tony Estep wrote:

> ....KX3 frequency stability on receive seems fine, as evidenced by  
> nice level
> lines on the graph...

> The frequency stability requirements both of WSPR and JT65 are
> considerable. WSPR transmits 4-frequency FSK, with the tones  
> separated by
> only 1.5 hz. The whole bandwidth is 6 hz.