This lead is externally powered so is, technically, a KPG-8.
This lead was designed for Kenwood radios but works on quite a few other brands I am lead to believe, see the bottom of the page for a list of (allegedly) compatible radios.
I've drawn a schematic that I found with colour for ease of circuit tracing along with a slight modification.
The original I had was for the KPG-22 and showed power being supplied by the PC via the CTS and RTS lines on the serial port but some PCs and USB to Serial adaptors can't power the circuit in this way so I have adapted it for external power, a 9V PP3 type battery would be fine or connect it to a 13.8V DC supply. This has "turned" it into a KPG-8!
For the construction you can use strip board, dead bug method or even produce your own PCB if you like. Just follow the schematic. Component layout is not really critical for this circuit, although beginners (and the more experienced) may have to double check polarity / orientation of components.
Once made up check your soldering for bridged connections and wires for stray whiskers. If your construction is small enough it may fit in the shroud of the 9 pin D socket, if not a small box with short leads connecting to the 9 pin socket will work just as well.
UPDATE November 2010 John, ZS6JON contacted me with this note (I don't know which programming lead he made but all 3 Kenwood ones on this site at the time were basically the same with different radio plugs fitted):
Greetings from South Africa.
My Kenwood programmer packed up and I was searching the net and was pleasantly surprised to find your article. Very easy to read and clear. Well done.
If I may ask you a question on the article.
I see that you have R 1 and R2 listed in the components list but not on the diagram.
(Yes they was left over from the PC powered design, I forgot to remove them from the parts list, done now)
I built it as per the diagram and testing had no success. I shortened the cable to the serial port with still no success. When My previous programmer was working the radio used to go to "PC" on the display. Now I get nothing yet.
Have I maybe missed something do you have any tips on where to look.
Well after comparing the notes I had with a previously made device and the diagram I suggested that perhaps the CTS and RTS pins on the serial plug required jumpering together. John tried this and no joy, then he noticed that some other pins were also jumpered on his dead device, in his own words:
This is what I did.
RTS (Pin 7) and CTS (Pin 8) are connected together.
DTR (Pin 4) and DSR (Pin 6) are connected together.
After I did this, everything worked great..
I have updated the diagram to reflect this modification. Thanks John.
To use the interface with your radio you will need the software relevant to your radio. This is usually purchased from the manufacturer or a third party. There may be programs available from other sources, offering various features. Follow the instructios in your manual / software instructions or help file for connecting and data transfer.
If you need software for your radio try searching with Google or your preferred search engine.
This lead is listed to work with Kenwood handheld radios:
TH-F6, TH-F7, TH-G71, TH-K2, TH-K4,
TK-240, TK-249, TK-250, TK-253, TK-255, TK-260, TK-260G, TK-270, TK-270G, TK-272, TK-272G, TK-273, TK-278, TK-278G,
TK-340, TK-349, TK-350, TK-353, TK-355, TK-360, TK-360G, TK-370, TK-370G, TK-372, TK-373, TK-373G, TK-378, TK-378G,
TK-2100, TK-2101, TK-2102, TK-2107, TK-2118, TK-2160,
TK-2201, TK-2202, TK-2206, TK-2207,
TK-3100, TK-3101, TK-3102, TK-3107, TK-3118, TK-3160,
TK-3201, TK-3202, TK-3206, TK-3207, TK-3301,
Also listed for:
FDC handheld radios:
FD-268, FD-278, FD-288, FD-289, FD-6288,
Linton handheld radios:
LT-2188, LT-2268, LT-2288, LT-3188, LT-3260, LT-3268, LT-3288, LT-5288, LT-6188, LT-6288,
PUXING handheld radios:
PX-333, PX-666, PX-777, PX-888, PX-999, PX-3288,
WEIERWEI handheld radios:
WOUXUN handheld radios:
KG-659, KG-669, KG-679, KG-689, KG-699,
I cannot guarantee the accuracy or completeness of the above list, I found those radios listed on various sites as using this lead.