Microlog SWL, Manual, Page: 25 / 36

designed to “hear” an 800HZ note, and the internal reference oscillator
is set to this value. If you are properly tuned, the regenerated tone
should sound “clean” and the on-screen indicator will flash in unison
with it. A key down (mark) causes the red dot indicator to turn on and
the reference tone to be heard, blank = key up • = key down.
You will be properly tuned if the audio from your receiver matches,
that is, zero beats with the frequency of the internally generated
800HZ note. A little bit of experimentation is all that is required to
display good copy on the screen. If the receiver volume is too high, the
tone will be raspy all the time and the red indicator will flicker con­
stantly even though there’s no input signal. Turn down your radio’s
audio so that with no input signal, the red indicator does not flicker
and only an occasional ‘beep’ is heard from the monitor’s audio chan­
nel. Of course, under marginal reception conditions you can expect less
than perfect copy even if the code is machine sent. In general it is best if
you use a fast AGC in your receiver.
Under noisy conditions you will find it best to use the SPEED-
LOCK feature since noise pulses may falsely set the systems’s internal
“average dot” to value representing a very high speed. Note that even
with SPEED-LOCK the system still tolerates reasonable speed varia­
tions up to about ± 50 %. Enable the SPEED-LOCK by typing ‘CTRL
T’.
You will also find that your receiver’s CW filter is helpful in reject­
ing nearby signals from interfering with the reception of the desired
signal. The SWL includes a sharp 300HZ effective bandpass which is
sufficient for rejecting undesirable signals. Your receiver’s AGC
however may act in such a way as to reduce its gain due to a strong
signal near the desired one. This is a case where a sharp CW filter in
your receiver’s IF will be very useful. If you do not have one, you may
find it desirable under such conditions to completely turn off your
receiver AGC, and backoff on the RF gain.
The de-coding algorithms used in the SWL program provide copy­
ing ability as good as a machine is capable and are considered the best
in the industry. However, you will probably observe that manually sent
code, such as by means of a hand key, will not be properly decoded if it
is sent “all bunched together” without sufficient intercharacter spac­
ing. It is a common tendency of many CW operators to suddenly speed
up and leave insufficient spacing. This is especially true when the call
sign is sent. You can improve on the reception of such senders by selec­
ting a slightly higher speed than he is using. For example, if his average
speed is 20 WPM, set the system to a speed of 27 WPM by means of the
CTRL X command. Also make sure that the SPEED-LOCK feature is
enabled. Use of this technique will enable you to copy the “FAST
DOTS” and “SLOW DASHES” typical of semi-automatic key users.
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