Use a 64K x 8 bit static RAM (SRAM) from an old harddrive controller card to increase the memory of a Radio Shack PRO-2042 (or PRO-2035) series scanner to 8,000 channels (normally it's 1,000).
Perfect for those SIGINT missions, the Radio Shack PRO-2042 is quite an amazing little scanner. There is plenty of room inside the case for lots of neat add-ons and modifications. To perform the memory increase modification, you'll first need to find a Samsung KM68512LG-7 64K x 8 bit low power CMOS SRAM (or any of the hundreds of equivalents). You'll also need four 100k ohm, 1/8 watt resistors and an octal encoded rotary switch. DIP switches or toggle switches will also work.
First thing you'll need to do is remove the old SRAM. Take apart the scanner and locate the stock SRAM chip. It should be labelled IC502 and will have the marking XK5864CM-10LL or XK5864CM-12LL. This is the stock 8k x 8 bit SRAM. Replacing this with a 64K x 8 bit SRAM will give you 8 address selection banks of 1,000 channels each. The new banks are not continuous, you'll need to select the address banks manually to get the full 8,000 channels.
- Controller Card Old harddrive controller card I got the SRAM from. It's the 28-pin SMT IC in the upper right (KM68512LG-7).
- Installation Installation in the PRO-2042. This is before the address select wires were added. The three 100 k ohm resistors are soldered to ground pads scrapped into the PC board. You'll need to bend the SRAM's pins straight down because it is too big for the original PC board solder pattern.
- Address Select Switch I used a hexadecimal encoded switch 'cuz that's all I had. Only selections 0-7 work.
- N Connector Replace that crappy BNC connector with a good N connector. The NSA would be proud.
Tandy Support for the Radio Shack PRO-2042 Programmable Scanner
Remove the internal AC transformer and power the scanner from an external 12 volt source. This will give you more room for modifications and the scanner will run cooler.
Solder jumper the 10 dB attenuator, it kills the high frequency response. Use a good external attenuator if you get intermod.
Remove the 1 µH shunt inductor on the RF input if you are using an antena that is at DC ground. This inductor also kills the high frequency response, but is needed if there is DC (or low frequency induced pulses) on your antenna system.
Improve the squelch performace by replacing the 100k ohm resistor between pins 12 & 14 of IC2 (TK-10420) with a 220k ohm resistor.
Narrowband FM/AM discriminator audio output is from pin 9 of IC2 the TK-10420 IF chip or use Test Point 2 (TP2).
Wideband FM discriminator audio output is from pin 10 of IC1 the KA2243N IF chip or use Test Point 1 (TP1).
Samsung KM68512 series Static RAM datasheet (147k PDF)