First of all, thanks for the responses so far, guys. The info is
certainly helpful. I'm not completely opposed to modifying the
scanner, but it's good to hear that I might not have to. I'm much
more optimistic now on attempting the project either way.



Scanners commonly use 3rd overtone crystals in the 25 to 50 MHz range. *
Higher frequency crystals are possible, but maybe not practical. *
Therefore, the radio will usually multiply the oscillator frequency to
receive the higher bands such as 160 MHz or 470 MHz. *What this means to
you, is that a Variable Frequency Oscillator (VFO) that covers 25 to 50
MHz (or whatever it takes, you work out the math) will work for both low
and high bands.


That may very well be the case. If I recall correctly there are high/
low ranges. The "low" range is 30-50mhz, with the "high" at
148-174mhz. Back when my dad used it we'd always assumed that you
bought a crystal for the particular frequency you wanted to hear, but
that may not have been the case!

It's a Radio Shack PRO-77a, by the way, which I saw someone comment
elsewhere that Radio Shack tends to use 10.7 for the IF on that
brand. A shame I can't find any kind of service manual or something
for it.