Posted by
Dave-3 on
Apr 06, 2011; 12:47pm
URL: http://elecraft.85.s1.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6245901.html
Having done some long term measurements on my k3extref using an HP mHz
resolution counter i have seen no corrections during transmit. Once the k3
has "warmed up" (first thing in the morning it would take 10 minutes for the
original tcxo to stabilise enough for jt65/wspr/qrss(5Hz fsk)) I see very
few corrections being made on receive either.
All I need now is the release of the internal 144 xverter and I am good,
frequency stability wise thro 76GHz
Dave
ww2r
------------------------------
Message: 44
Date: Wed, 6 Apr 2011 00:58:58 -0700 (PDT)
From: "Julian, G4ILO" <
[hidden email]>
Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts
To:
[hidden email]
Message-ID: <
[hidden email]>
Content-Type: text/plain; charset=us-ascii
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
>
>
-----
Julian, G4ILO. K2 #392 K3 #222.
* G4ILO's Shack -
http://www.g4ilo.com* KComm -
http://www.g4ilo.com/kcomm.html* KTune -
http://www.g4ilo.com/ktune.html--
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