This section is paraphrased from a posting that Pete N2MCI made on the EFJ yahoogroup:
You will need to build a programing cable. The schematic can be found here. Pay careful attention to the drawing as Johnson numbers the microphone jack pins very different from Ethernet. You can cheat and buy a DB-9 (NOT A USB VERSION!) Kenwood KPG-4 programming cable (under $10 on ebay) and then make a pinout changer - a 6-pin screw terminal RJ-12 jack wired to a stub of a common 8-pin RJ45 ethernet cable (and I'd use a stranded ethernet cable rather than a solid one).

Programming cable pinouts
Kenwood mic jack			EFJ pin	86xx Function		EFJ pin	96xx Function		EFJ pin	71xx Function
Pin	Function
1	12v		6	12v		8	12v		5	8v
2	GND		2	GND		3	GND		2, 4, 7, 9	GND
3	PTT / TXD		8	TXD		10	TXD		3	TXD
6	Hook / RXD		1	RXD		13	RXD		8	RXD

Besides the pin numbering, there is one little quirk about the EFJ 86xx programming cable... The plug that goes into the microphone jack of the radio is a special 8 pin RJ-12 made by Virginia Plastics and not the normal 8 pin RJ-45... You can use a 8-pin RJ-45 but you have to take off a few thousands of an inch off each side.. I use a a grinding wheel to take most of the excess off, and use a hand file to fine tune the fix... It's not critical as the spring tab latch centers the plug... If you don't have a grinding wheel you just to get to do more filing.

Here's a description of the mike jack pins and the wire colors used with their 9800 RPI programming cables:

Radio Mic   RPI Programming Cable
A--- Orange >---RxD
1--- Black  >---GND
2--- Red    >---MIC AUDIO OUT
3--- Green  >---HANGER
4--- Yellow >---20V PROG
5--- Blue   >---BATTERY
6--- Grey   >---RX Audio IN
B--- Brown  >---TxD

By the way, the Kenwood KPG-4 and the KPG-46 programming cables are the exact same unit except for the RJ connector on the radio end of the cable. The KPG-4 has a 6-pin (RJ-11 / RJ-12-style) connector. The KPG-46 has an 8-pin connector (RJ-45 style) and the center 6 pins are wired the same and the outer 2 pins are not used. So if you have a KPG46 on hand you can make the same type of adapter as described above by using a KPG46 and an RJ45 jack rather than a KPG-4 and an RJ12 jack.

Here are two programming adapters/cables for the Challenger series:

• EFJ Challenger Programming adapter, provided by Craig Clark N5XNQ
• EFJ 7180 - 7187 Challenger Programming adapter, provided by Craig Clark N5XNQ

This page split from the main page 16-Nov-2011.