[Milsurplus] ARR 15, how to narrow selectivity???

[James Young]

My ARR-15A has the same "barn door bandwidth" you mention. The write-up in
Electric Radio a number of years ago mentioned the same wide bandwidth due
to over-coupling in the first two IF's. The author mentioned opening the IF
cans and replacing the capacitor which couples the primary to the secondary
with a smaller value in the first two IF circuits. I recall he mentioned
having some success with this approach, but the fellow gave no specifics as
to the value he used, or how to get into the IF transformers. He reported
reducing the IF bandwidth from about 20kcs to 8.5kcs, a useful improvement
without compromising the variable IF scheme.

73 Jim Young W8MAQ

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net]On Behalf Of
boeing377 at aol.com
Sent: Wednesday, June 03, 2009 6:55 PM
To: Milsurplus at mailman.qth.net
Subject: [Milsurplus] ARR 15, how to narrow selectivity???



My Collins R 105A ARR 15 is now working perfectly including the wonderous
electromechanical autotune. It is as broad as a barn door however?and I'd
like to narrow it wothout butchering the radio. This rcvr has a variable IF
as part of the tuning so a fixed freq xtal or mech filter does not seem
useful.? I guess I could make a tunable outboard additional IF stage, but
that seems extreme. Any practical ideas?

73
Mark
AF6IM
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