[R-390] 1.0 and 0.1 filter settings

[Dan Merz]

Barry,  the crystal may appear to always be in the circuit but it is
bypassed by C501 when the switch is in the 2,4,8,16 positions.  The crystal
filter is effective only in the 1 and .1 positions.  Apparently something is
not adjusted correctly in the crystal filter or the crystal is defective,
which is causing the filter to reduce the gain considerably.  I don't recall
messing with the crystal filter neutralizing in my 390a which is covered in
the Y2K manual; others may have words of wisdom about problems that arise in
the crystal filter circuit,  Dan. 

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Barry
Sent: Sunday, April 10, 2005 12:01 PM
To: r-390 at mailman.qth.net
Subject: [R-390] 1.0 and 0.1 filter settings

Can someone give me the "Reader's Digest" version of how these two settings
work in an R390A?  I'm working on restoring the modules for my newest
project.  After replacing C553 (just to be safe), I plugged it in place of
the IF deck in my working R390A.

It seems all four filters are working; however, when I switch to 1.0 or 0.1,
the signal disappears almost completely, no matter how closely I tune to the
frequency.  I can see that the crystal and its parallel adjustable capacitor
are always in the circuit, but going to 1.0 switches out the extra cap and
switching to the 0.1 position adds some extra circuitry into the mix.

I don't quite understand how these other two settings do their job.  If
someone could elaborate, I'd appreciate it.

Thanks,

Barry - N4BUQ

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