[Collins] AOR DDS-2A Revisited

[Dr. Gerald N. Johnson, electrical engineer]

A huge fallacy of frequency setting of SSB is presuming one can set the
receiver frequency to exactly the transmitter's suppressed carrier
frequency.  Tuning halfway between the limits of understandability is
only a first approximation. The proper scheme requires a high fidelity
ear that can match received harmonic components to the true harmonics of
the fundamental voice components. This gets the most natural sound (like
AM or FM) but takes a lot of skill and stable equipment. MARS frequency
tolerances tend to be unenforceable because of the uncertainty of tuning
to an incoming signal.

I notice every year at FD that many new hams accustomed only to VHF FM
activity rarely achieve tuning accuracy as close as 200 Hz and their
contact rate suffers as their replies get lost in the adjacent QRM.

Another problem with 10 Hz digital readouts is that too many assume that
if the signal is not copiable having tuned 340 (or 1000) Hz away that
its a NEW frequency suitable for initiating communication on top of that
already using that spectrum.

I did achieve a 1 ppm result in one ARRL FMT using nothing but my 75S3B
and its built-in calibrator. I know from later tests that I won't hold
frequency that close because 10 Hz is needed for successful unattended
HF packet and it won't do that.

73, Jerry, K0CQ, Technical Advisor to the CRA.
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.