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SS232K - The simple and safe RS232 interface for Kenwood rigs

Since long time, my TS850S asked to be connected to my PC for remote control (especially for contests...), but none of the classic schematics satisfied me: I did not like too much the needing of external power supply for the interface and the circuits without power supply were too much unsafe.

I designed this interface and it is SIMPLE to build (one double optocoupler, three diodes and three resistors), SAFE for the radio and the PC thanks to the optical coupling and it needs NO POWER SUPPLY!

To power the circuit I use the DTR and RTS signals of the PC: with all the software I tested, these pins are at +12V

I built mine in a very little plastic box using the ugly "spider" method and hot-glue (not suggested to beginners...) but I suggest to use a perfboard or to design a little printed circuit.

If you don't find the TLP504A, you can try the CNY74-2 (same pinout).

The cable from the interface to the 5 pins DIN radio connector is better if short (mine is about 15cm long) and the cable from the interface to the PC must be less than 10m long (mine is 2m). The DIN connector is viewed from the rear, the solder side, the same is for the DB9F

With 100W (and more...), my interface doesn’t need any filter (capacitor and/or inductor), let me know if you have RFI problems and I will suggest some filtering.

Now, my TS850 is happy and me even more happier :-))

The interface is tested and perfectly working with CT9, Writelog, Rigmaster and Easylog; I think that it will work with any software that don't needs the handshake to the radio with RTS and CTS.

My "radio" PC is a P200MMX on an ASUS TX97E motherboard but the interface worked fine also connected to the "main" PC, a PIII 933MHz (Intel 815 chipset) and a P133 Notebook  using a shielded serial cable 10m long.

Ciao and good work

Guido, ik2bcp / iu2r / ab9dg

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