Realistic Pro-2009 Scanner (made by GRE) discriminator output info

[eccerr0r]

Just wanted to share findings.  I recently got an ancient Realistic/Radio Shack PRO-2009 scanner.  It's fairly limited in features, but apparently made by GRE.

The scanner uses a MC3357 IF final/FM Discriminator IC which is similar to the more common MC3361 towards the center/slightly rear of the PCB (to open the scanner, remove the three self tapping screws on the back, six self tapping screws along the edges on the bottom.  Loosen but don't remove the two screws that have slide holes near the headphone output, and slide the headphone jack back to clear the hole in the front of the case.  Then the cover should come off easily).

The MC3357 also has FM discriminator output on pin 9.

As it seems to also be a GRE design, it eerily also has the "TP-5" with an unmarked 0? resistor sticking out of the board near and hooked up to pin 9 of the MC3357 that can be used as the discriminator output.  It almost seems this 0? resistor should simply be removed and a ~10K? resistor put in its place...

You can also access the solder side of the test point on the bottom without removing the board which is covered by a plastic shield on the bottom.

I haven't actually tried this yet but hopefully this information is useful to someone.  Was planning to initially use this to try to decode APRS data but trying to get my 2m transceiver up and running first.

I will need to get a picture uploaded at some point, but just in case this textual description will help anyone who wants to use a Realistic PRO-2009!

[eccerr0r]

Attached, PRO-2009 board photo (old school 9x7-seg VFD!). 

Fuchsia oval in center is where the MC3357P is, and TP-5 is silkscreen marked to the left of pin 9, should be able to access this pin from the bottom too.

The potting barf on this board makes me want to puke

[eccerr0r]

More PRO-2009 mods:

For the heck of it I added a squelch break LED.  I didn't like the fact there wasn't a way to tell when scan or search hit something but the volume was down to minimum - can't hear anything.

So, I tapped off of pin 11 of the TD62501P which appears to indicate squelch break (it's +5V when a signal is received) back to the controller to stop scanning.  Lacking a good place to find power I tapped pin 14 of the 74LS26 (power) and GND.  Using a 10K resistor from pin 11 to a generic NPN (used a 2SC945) transistor with its emitter grounded, I hooked up a 1K resistor to LED to pin 14 of the 74LS26.

Now I have an LED that lights up when squelch is broken.  The response is unfortunately slow, so it's not usable as a CW detector, but it's sufficient to tell when scanning stopped at a distance even when I can't hear the scanner or see the VFD due to its angle.

Have fun!

[VidarParry]

Thanks eccerr0r:-)

Rene, Just wondering if you are intending to add this to the database on Discriminator.nl (in your copious spare time )

Cheers
...Steve

[Discriminator]

@eccerr0r Thank you for your description, much appreciated!
@VidarParry Yes, I will add it to www.discriminator.nl/ic/ shortly.

Regards,
Rene

[eccerr0r]

Wanted to add some more notes on opening the scanner:

The knobs (friction attached to the volume and squelch pots, no set screws it appears) need to be removed before you can remove the top cover.  Be careful if using a screwdriver to pry them off, you could damage the top case.

Also beware the keypad is attached to the top cover, so expect the keypad "umbilical cord" to not let you totally remove the top cover.  Simply "hinge" the top cover towards the front of the unit (after clearing the metal shield in the back.)  And don't forget to remove the built-in antenna before pulling the top cover off, simply unscrew it counter clockwise until it can be easily pulled up from the post on the PCB.

But yeah, I hope this helps someone who wants to hack their PRO-2009, maybe even make this old scanner a bit more valuable to experimenters

[Discriminator]

Rene, Just wondering if you are intending to add this to the database on Discriminator.nl

Done! It's included in the database on http://www.discriminator.nl/ic/ with a link to this thread.

-Rene