Everywhere you tune, there is some digital noise on the airwaves. Fortunately, some of it makes some sense some of the time. If you have a direct discriminator output on your radio, a computer running DOS and an RS-232 level converter, you can download DIGRAD.ZIP and learn a bit about programming the PC to demodulate this awful noise.

The following files are in the .ZIP:

File Description
DIGRAD.ASM Assembly source code to set up a PC serial port, set up timer 2 and initialize a circular buffer of zero-crossing interval data received on the serial port DSR or CTS line. The programs below are based on this template.
TRUNK.COM This program will display a host of information about a Motorola trunked system, including system ID, all trunk IDs in use and all frequencies as they are assigned.
MDT.COM This program may do nothing, as it has not been tested due to not having a good source of MDT traffic. It was ported from some really bad C code discovered on the Internet and suffers from an extreme lack of documentation.
AMPSFCC.COM The name implies the function. If you don't understand, blame the morons in the U.S. Congress.

Each .COM file has two command-line options: /xC, where "x" is a number from 1 to 4, and specifies the com port (default is COM1). "C" specifies that the incoming digital data will be supplied on CTS rather than DSR (default). Type [ESC] to exit. Slow machines receiving continuous fast data may need to have the data stopped before the keyboard will be recognized. A '386 or better is required. (This is a programming convention only. A '286 is fast enough to decode most things, but who has one?) A bottom-of-the-barrel 20 MHz 386-SX is known to work up to 10 Kbps without mangling more than about 5% of the packets. Faster computers work better. A Pentium with a good clean signal will decode almost perfectly.

These programs are not supported in any way, so please don't ask any questions, as they will not be answered. If any program works for you and does any good at all, I wouldn't mind hearing about that. But if none of them work, you find them insulting and they set your PC on fire, just remember what they cost.