Re: K3EXREF and Trimble Thunderbolts

Posted by Julian, G4ILO on Apr 06, 2011; 7:58am
URL: http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6245052.html

Don.

WSPR is AFSK with a very small shift at a very low rate. My thinking is that if a stepwise frequency correction was made during a transmit or receive period, it would cause a corresponding shift of the VFO which might be enough to throw the decoder of the receiver. I don't know, that's why I was asking.

K2ULR has told me off-list that he did not believe corrections are made while the K3 is transmitting. But it might still affect receiving. I think it is important to know because WSPR is one of those modes where frequency accuracy is really helpful and habitual users of the mode will probably be interested in the K3EXREF.

Don Wilhelm-4 wrote

Julian,

Please explain why you think any vfo tuning "steps" are related to a
frequency shift induced from the audio input to the K3.  I believe this
is mixing two entirely separate parameters.

I have not actually operated WSPR, but it cannot be that difficult (nor
that precise in practice).  I believe one would use DATA A sub-mode for
WSPR work.

The VFO places the waterfall within 1 Hz of the desired fequency with
the external reference (actually that could be within 50 Hz - same
argument).  Now the software applying the audio to the K3 has to shift
1.5 Hz (or 170 Hz for that matter),  As long as the K3 can tune the
desired frequency to be in the passband, the software and audio input to
the K3 will take care of the audio shift.  The only requirement is that
the K3 remain frequency stable once the frequency is selected - the rest
is done in the computer application software.

73,
Don W3FPR