PC/IF Data cable project.

For PRO-92 / PRO-93 / PRO-95 / PRO-2067 / PRO-2053 Scanners

In general, there are two types of cables that can be built for these scanners: one-way and two-way. The one-way cables will allow you to upload data to the scanner only - you cannot download data from the scanner. The two-way cables let you upload and download. This is useful if you already have data in the scanner, and want to retrieve it, modify it, and send it back to the scanner. If you only care about creating data on the PC and sending to the scanner, then a one-way cable is sufficient.

The RadioShack or GRE PRO-92/-93/-95/-2053/-2067 scanners all can be programmed by computer if a suitable interface cable is available. Both cables below allow two way data transmission. The popular Two Transistor Cable works on all five models although it is really intended for the PRO-92/-2067. These radios use 5 volt logic which matches the cable's output voltage. When used with the PRO-93/PRO-95/PRO-2053, correct operation relies on the clamping diodes in the radio to reduce the output voltage to 3.5 volts as required by the logic chips in the newer models. Photo 1 and Photo 2 show how the circuit can be built into a 9 pin headshell without using a circuit board.

The second cable uses an op amp to automatically match the logic voltage in the radio and it provides a larger voltage swing to the computer for better noise margin. Powered by the computer's serial port, the Simplified Op Amp Programming Cable can be built into a 9 pin headshell. The photos of the top view and bottom view show the component placement.

Early reports indicate that the PRO-95 scanner sometimes does not work well with some cables when reading data from the radio. In this regard the PRO-95 is more finicky than the PRO-93. The reason for the difference is not clear. Both radios use the same CPU but each is programmed with different firmware. The clamping diodes connected to the PC/IF jack are ordinary silicon switching diodes in the PRO-93. They were changed to Schottky diodes in the PRO-95. The Schottky's have higher reverse leakage current and higher junction capacitance but neither of these factors is large enough to account for the apparent difference between the radios. The op amp cable has been tested with the PRO-95 and it worked well for data transfer in both directions. The number of PRO-95's in use has grown and most users report that the two transistor cable and Purple Computing cable both work fine.

Cable for Trunker

This cable diagram shows how the control channel scanner and tracking scanner can be connected to a single PC serial port for running Trunker. If you are using a laptop computer with no serial port, I recommend getting a PCMCIA serial card from Socket I/O. It comes with a DOS enabler, works flawlessly, and has none of the operational problems that plague USB to serial adapters.