Heath tuners for NBFM?

[MNHopkins]

I now own two Heath FM tuners: a classic FM-3A with book and a later, Happy
Days looking AJ-31 which sounds better.  Since Dallas has but one classical
music station, I want to adapt one of the tuners to demodulate Narrow Band FM.

The FM-3A, given the book and all seems the candidate.  It operates only at
10.7 (no 455 kc section) and the front end looks like a '50s VHF tuner with
the 6BQ7 so often seen in Tecraft and other ham stuff.  But how to narrow the
response?

There is, for instance, a 47 Ohm resistor used to couple between the IF cans.
Why?  Should I replace it with a cap?  A large or a small (my bet).  Moreover,
does one simply tune for maximum smoke on these ratio detecting devices to get
the narrowest response?

Finally, is this an opportunity to use the bookless model '62 sweeper I have
on hand to sell for a friend before it escapes me forever?

73 de ab5L, michael in dallas, student of Tecraft and International (ICM) ham
products and mementoes of Six Meters' Golden Age: 1957-58
Michael Hopkins
Box 226841
Dallas, TX  75222    MNHopkins at AOL.com

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