[R-390] Working on R-390A IF Deck

[Bill Hawkins]

The thing that determines the value of the IF frequency is the
crystal filter at the narrowest bandwidth. You should center the
IF in the crystal passband. In some cases that might be 455.00,
but not always. Crystals move a bit with frequency, as well.

You really don't need a counter to align the set. Certainly the
military didn't have many of them in the 50s. The HP 522B would
work all the way up to 100 KC.

If the IF is peaked near 455, set the bandwidth to 100 Hz and tune
the generator for maximum output from the IF. Do this after the set
and the generator have warmed up. You would need a counter if the
generator drifts, but just to keep the frequency at the crystal
filter center.

Once the IF is aligned, go back and realign the RF and variable IF
sections - unless you didn't move the IF more than a few hundred
cycles. The bandwidth of the RF deck is about 16 KHz, right?

At least, that's what I'd do ...

Bill Hawkins