Disclaimer


All material in these articles are digitally scanned from the
originals.  Permission to disseminate this information was
obtained
from the authors by Peter Eaton, WB9FLW.  No copying, changing of
the digital format or reprinting may be done on this material
without the permission of the original authors and John Mc Clun,
N3REY.  You may make a copy of all articles for personal use
only. 
Any and all spelling errors may or may not be from the process of
scanning.  If an article has been spell checked, the original
misspelling  will have been corrected.  Those that are present
currently are due to NOT having been completely checked.  Any
omission of content will be corrected as time allows, the current
presentations are being made available until corrected copies are
obtained.

Please address all comments to the digital librarian, John
McClun, N3REY at  mcclun@clark.net


 COHERENT CW NEWSLETTER (Copyrighted June, 1975) CCWN 75:9       
If the input and the switching signal are exactly in phase, the
switch always connects that side of the transformer which has a
positive output, and the resulting switch output looks like the
familiar full-wave rectifier output. If this signal was ripple
filtered, the filter output would be a d.c. level representing
the average voltage of the output. Now, if the input and
switching signal are 180 degrees out of phase, the switch output
is the negative image of the first waveform, because the switch
is always connected to the transformer lead which has the
negative voltage. The filtered output would be a steady negative
voltage. If we now cause the two signals to be 90 degrees out of
phase, the switch changes position at the peaks of the input
waveform, reversing the polarity of the output. Instead of the
output being complete half-cycles either positive or negative, it
consists of alternating quarter-cycles which are mirror images
about the zero level. Thus the filtered output will be zero
volts.        If the frequency of the two signals is not quite
the same, so that there is a slow change in the relative phase
between them the average value of the output will change also. If
the signals are 1 Hz different in frequency, the filtered output
will go from zero to a maximum positive value, back to zero,
continuing to a maximum negative value, and back to zero, all in
one second. Thus the filtered output is a 1 Hz waveform. The
b.f.o. and product detector in your receiver operate on this same
principle. The audio beat you hear R has a frequency equal to the
difference between the frequency of the signal input and the
frequency of the b.f.o. The big difference with the CCW filter is
that we are mostly interested in signals which are at "zero
beat'"        Now we examine the integrator. An integrator is
very similar to a charging capacitor, except that instead of
following the familiar exponential curve for a constant input,
its output is a straight line. The slope of the line is
proportional to the instantaneous voltage at the input. Now the
integrator has an interesting feature which we must note. Just
like a capacitor, its output is not necessarily zero when its
input is zero. It can remain "charged" at a constant value when
no current is being injected into the input. So our integrator is
provided with a "dump" switch which short-circuits the capacitor
and resets the integrator to zero when needed. In Figure 3 we see
waveforms which will help show how the integrator works. In each
case, the waveform is preceded and concluded by a "dump" command.
Whenever the integrator has a constant voltage input, the output
is a voltage changing at a constant rate. If the input is zero
volts, the output is constant. If the input is a square wave, the
output alternately slews up and down. If the frequency of the
square wave goes up, the frequency of the output goes up with it,
but the peak- to peak amplitude drops off.        There is
another way to view the integrator performance also, and this
second interpretation brings us to the heart of the CCW .
filter's selectivity features. If the integrator is first set to
> zero, and then allowed to process an input signal for a certain
interval of time, the voltage at the integrator output at the end
of