[AMRadio] Boat Anchor Crystal alternative?


SBJohnston at aol.com SBJohnston at aol.com
Fri Jul 16 10:30:22 EDT 2004


jcandela at prodigy.net writes:

> Your CW rig looks pretty neat. I hope to finish mine as a Central
> Electronics 20A exciter. With the 20A the VFO is beat against a 9 Mhz rock,
> so it can run all the time. I hope that Don's issue requiring maximum
> shielding bypasses my configuration. It would be neat if someone could adopt
> a DDS VFO to replace the stock VFO in something like a Ranger, and place it
> within the Ranger as a VFO replacement. Getting VFO output on 160, and 40
> was stock, and then 80, 20, 15, and 10 meters came about from frequency
> multiplication. Any ideas on the easiest way do pull this off?

That would be quite neat, although the VFO in my Ranger is already pretty 
stable - surprisingly so.  But the concept is good - there are *many* boatanchor 
rigs that have poor VFOs.  Using the DDS VFO in a transmitter or receiver 
alone is quite straightforward, but in mulitband transceive it gets more 
complicated.  And for CW mode you have the 700 Hz transmit offset to consider.

In my rig the VFO runs all the time, in RX it is the direct-conversion L.O. 
and in transmit it is the first stage.  For CW I key the driver and the 
sidetone oscillator.  T/R switching is semi-break-in.

Getting the 700 Hz shift was a puzzle. Right now for CW ops I just shift the 
tuning manually from rx to tx, but WA1FFL is going to send me new software 
that keeps the VFO on all the time and shifts it up 700 when the "key" line is 
closed.  I figure that signal will come from the T/R relay

Steve  WD8DAS

sbjohnston at aol.com





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