CCWN 76:67
MORE THOUGHTS ON RECEIVER DESIGN F0R CCW BY RAY PETTT

       I feel that CCW is a technique that should be used as the
finishing touch to an already-existing high-performance receiving
and transmitting system. By this I mean that we should utilize
the best-available non-coherent receiver design concepts to start
with, and then adapt these to CCW by using appropriately designed
frequency synthesizers. It makes little sense to me to attempt
CCW with its 5-Hz bandwidth and such but with a receiver that
will flatten out under conditions of moderate interference 10 kHz
away--a receiver weakness which could be eliminated with good
design without CCW'

        In the October 1975 issue of Ham Radio, page 26, Rhode
described a receiver front-end which appears to me to be the best
design yet published in amateur literature. It uses a few
carefully-chosen components in a surprisingly simple circuit and
yields dynamic range greatly exceeding anything being sold in the
amateur market. Wes Hayward, W7ZOI, published an article,
"Competition Grade CW Receiver" in QST, March and April, 1974.
I went to Wes' home in Beaverton, Oregon, some time back, and he
showed me his prototype. I have never heard a better-sounding
receiver. Internal noise in the i.f. and audio was nil, and the
agc had instantaneous, perfect response--no pumping, popping,
overshoot or hang-up on noise. His approach--placing the entire
i.f. and agc system between two 9-MHz KVG cw filters--is the
secret behind the panel.

        In the meantime, I did some work with front-end filters.
I discovered that certain toroids made by Indiana General have
superb characteristics for use as the inductors in beautiful
ham-band filters. I made a set of such filters using the tables
in Zerev's "Handbook of Filter Synthesis". Once aligned, each
filter covers an entire ham band without need of adjustment
(no preselector control required'). Each filter has 50 ohm
input and output impedance, required no taps on the inductors,
and has less than 1 dB of insertion loss. Image rejection
using a 9-MHz i.f. and a 5 MHz local oscillator for 20 meters
is in the order of 100 dB.

        At this point we make our receiver (or transceiver) CCW
compatible by designing a synthesized local oscillator and bfo.
Design work I've been doing indicates that the way to go involves
a super-clean VFO synthesizer covering 1.100,000 to 1.599,990 MHz
in 10 Hz steps and individual VFO signal up-converters using
phase locked crystal oscillators and mixers-- one for each ham
band covered

        I think it would be worthwhile for readers of CCWN to
work together on building equipment of this type.