kick start CW filter

[Emil Dular]

OK, I'll admit that chasing intermittent faults is aggravating, but here is
a wierd one.

The CW filter in an SB-102 has taken to acting strangely.  As you tune below
the peak, towards zero beat you get the sharp cutoff you expect. But after
you tune below the zero beat frequency you pick up a tone again. It is not
as loud as it would be in a direct conversion receiver, but it is loud
enough that you can copy nicely a strong station 5 to 7 kc away. Switching
to the SSB filter the signal below zero beat is virtually gone.

Checking the switches, cleaning the contacts, reheating solder joints,
tightening mounting nuts, new lockwashers have all "fixed" the problem, at
one time or another, for an "indeterminate" amount of time. Last night while
listening to a signal on the "wrong side" of the zero beat, I tapped the
case of the filter and "presto" everything clears up.

Now I seem to recall from back in the dim and distant past having crystals
in transmitters where a thump on the case was needed to get them
oscillating.  (Poor people have poor ways.)

Does anyone else remember having to "kick start" crystals?  How common a
defect is this? Aside from the obvious, that is replacing the filter
assembly, how would you go about dealing with a stubborn crystal?

Emil de WD4SCZ

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