This project was started to build a more reliable interface for programming TK941 transceivers. The radio has a logic level serial port which needs to be converted to RS232 levels to connect to a PC.

The existing devices out there used the data leads from the RS232 interface to power the interface, which caused too much loading on and unreliable data transfers. The error that was made was that the radio has the +13V supply available at the mic jack, so it was simple to regulate that and use MAX232 device for the conversion.

Programmer PCB with Cable

This project was pretty straightforward: a MAX232 converted and 78L05 regulator to power it, a modular jack and cable for the radio, and a DB-9 mounted end-on to take up the least amount of space. It fits in an off the shelf Hammond enclosure.

Below are the CAD files for this project. Contact me directly for the KiCAD and Gerber files.

The enclosure for this project is an off-the-shelf Hammond 1455D601 extruded aluminum box, which is available from several distributors. The PCB was designed to slide into it, and the DB-9 connector was mounted end-on, so any type will probably work.

It is the same enclosure that was used for the ICOM serial project.

The software to program the radio is KPG-49D. It is available from several different sources, but is older DOS software and needs a ‘physical’ COM port as was done in older machines. A newer machine with a USB serial port will not work. I have an old ‘clunker’ in the shack that runs Windows XP, and that does work.

Some successes have been reported using DosBox, but I have never tried it.

Newer firmware for the radio is available which implements the 25MHz offset, rather then the factor 39MHz as required in the commercial world. For repeater use, there is also firmware available that defeats the timer, however it is recommended to either use a larger heatsink or a fan, as the radio can get a little warm.