Kenwood: Mic Extension TM-71

[AK9R]

Just checked the cable pinout in my owners manual, slightly different from above:

1- no connection Service manual shows that the pins are connected from one end to the other of the mic cable. Service manual also shows that pin 1 on the mic connector goes to pin 80 on the MPU in the control section.
2- DC 8V, 100mA max This is the 8 volt control power rail in the radio.
3- GND
4- PTT
5- GND (MIC)
6- Mic, 600 impedance
7- No Connection No connection in the radio, but the pins at both ends of the cable are connected
8- Keypad serial data Goes to pin 79 on the MPU

Pins 3, 4, 5, and 6 are as shown in the image I posted earlier. Keep in mind that this microphone and mic cable are used on Kenwood's LMR radios where the functions inside the radio might be slightly different from their amateur radios. For example, pin 7 in the mic cable is the HK or Hook line. This tells their LMR radios that the microphone has been removed from the mic hanger. The amateur radios don't have this feature.

Funny thing, I had the radio a year before it started motorboating.

Corrosion in the mic connector. Disconnect and reconnect the RJ45 from the radio a few times and the noise might go away. Or use just a tiny drop of DeOxit on the RJ45.

 

[chief21]

For what it's worth, for years I've been using inexpensive flat phone extension cables and double-female connectors to extend the V71 microphone in several mobile installations with good results. Unlike ethernet cables, which twist the wires, the flat cable seems to keep the conflicting signals far enough from each other to prevent issues.

John AC4JK

 

[k6cpo]

This is something I've never been able to understand. A manufacturer will build a mobile radio with a removable faceplate/control head so the body of the radio can be mounted somewhere else in the vehicle. And make it so the microphone plugs into the body of the radio, not the head. They will include excessively long separation cables for the control head and an external speaker, but to extend the microphone, you have to buy a separate cable.

It wasn't an issue with my Yaesu FT-7900R because the mic plugged into the control head, but when I bought a Yaesu FTM-100DR (and later an FTM-400XDR) it became an problem. I ended up buying an extension cable from an outfit called L-Com that has worked perfectly for both radios.

 

[KD2DRM]

Machine Gun sound

After having my VM-71A in my car for 3+ years, I just started getting what was described to me as a machine gun sound drowning out my audio, which until this point had been perfect. I have been using a 6 foot UTP cat 6e cable. UTP is non-shielded cable. I wonder how I got away without the problem for so long and why it suddenly started. I am either going cat6E shielded or cat7 if I can find it without spending a fortune. I wish Kenwood would sell the mic cable separately. Don't understand or remember how I got the control head mount and radio to control head cable without the mic cable.

My cheap TYT9800 has the mic cable coming out of the control head. No extension needed. Why couldn't Kenwood have designed it that way? I have the separation cable. Radio mounted under desk, Control head double back taped to wall of desk hutch with an external speaker.

 

[AK9R]

Possibly corrosion on the mic connectors or you reoriented the cable so it now has a bit of a strain on it.

You can carefully clean the connector contacts with iso-propyl alcohol to see if that eliminates the problem.