[Boatanchors] W2EWL VFO range? New Question
Robert Nickels
ranickel at comcast.net
Tue Mar 22 15:27:57 EDT 2011
Regarding adjustment of phasing type rigs - I found the attached tip in
an RSGB book that is similar to our "Hints and Kinks", but can't
remember seeing it published in a US publication.
Before you take a look, just think for a moment about what an SSB signal
looks like If we feed a 1 khz tone into the mic jack, with carrier
and opposite sideband properly balanced the result will be a pure CW
signal on one frequency. For instance, if the VFO is set to 3900 khz
and LSB mode is chosen, the carrier will be at 3899 khz. Now suppose
the carrier isn't completely nulled and some 3900 khz signal is getting
through. If we attach a mixer to the output we'd hear a 1 khz tone (the
difference between 3900 and 3899 khz). And that's all this little
trick does! If the opposite sideband isn't fully nulled there would be
a weaker signal on the other side of the carrier at 3901 khz, and that
would produce a 2 khz tone in the mixer. So with this trick it's
possible just by listening to the pitch of the tone to tell which knobs
to adjust - which is what you're trying to do with the ripple pattern.
I use a signal tracer instead of phones and also watch the scope as
the adjustments are being made.
You can download the scan here:
http://img24.imageshack.us/img24/526/phasingrigalignment.jpg
Credit goes to ZL2AMJ, no stranger to early SSB fans as he's the father
of the clever two-tube "Tucker Tin Two" transmitter.
73, Bob W9RAN
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