hey ole man:

been there done that.

Scanners that used crystals are pretty straight forward in todays
standards, no secrets there.
I made a living selling the crystals for those scanners.
Or you could do a PIC stamp based cpu that programmed from a regular
PC could do what you need to be done.
a.k.a. frequency synthesis, and scan the scanner with just the PIC
using the scanner as an IF

To beef it up would need sum front end work or, software to program
out the images.

Transverters do that all the time and is very common place in ham
radio.
















hhey


On Feb 11, 12:35*am, FyberOptic wrote:
Hey folks, I was wondering if anyone better versed in analog
electronics could help me out with an idea. *I've seen various
projects on the internet where people have repurposed old radio
equipment for other uses, like using a CB to receive amateur radio
frequencies. *So stuff like that got me wondering. *I have an old
crystal-based scanner that belonged to my dad. *It has a range of
30-50 and 148-174mhz. *While police/fire/rescue have all moved to
digital systems, I know that the city's public works still uses
frequencies in the latter range. *I'd like to be able to receive
those, without buying several crystals. *So I'm wondering if it's
possible to create some kind of oscillator (LC-based or whatever) to
simulate a crystal for this type of device. *It wouldn't be nearly as
accurate/stable of course, but I'm curious if it's possible.

I mean, I'm sure if one went in and started trying to physically
modify it they could find where to directly inject an external
oscillator frequency. *But I'd prefer to keep it in its original state
if possible. *That would mean I would have to work with whatever
circuitry normally generates the oscillation with the crystal. *That's
why for starters I'm mostly asking in a broad sense if it's possible.
I know anything more detailed than that might be hard to offer without
knowing what's actually in the scanner (even I don't have a
schematic), but any insight would be much appreciated!