kick start CW filter

[EP Swynar]

Hi Emil,

My experience here is *sorta* similar to your situation there, yet entirely
different again...! FYIW, here's what happened to MY SB-102...

The received audio quality on LSB, ONLY, suddenly began to sound very tinny,
and "pinched" --- similarly, the RF output on LSB was nowhere nearly as high
as what it was on USB.

I suspected that maybe something inside the crystal IF filter had somehow
shifted, electrically --- but then why would the problem only be on LSB?

It turned out that LSB carrier-generating crystal had shifted frequency with
age, enough so that the end result was that a good chunk of the audio was
OUTSIDE the passband of the IF filter...I confimed this by placing the probe
of my digital frequency meter close to the crystal itself.

The fix was simply a swap of the crystal, & all was well again.

Good luck there with your situation...!

~73~ Eddy VE3CUI - VE3XZ


*****************************************



----- Original Message ----- 
From: "Emil Dular" <wd4scz at AOL.COM>
To: <HEATH at LISTS.TEMPE.GOV>
Sent: Friday, November 21, 2008 2:28 PM
Subject: kick start CW filter


> 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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