The Kenwood TK-8180 is my go-to preferred radio for GMRS stuff. It is a rugged radio with an excellent remote-head kit, and a nice display. It’s generally pretty easy to find them in good condition on eBay, and accessories are plentiful and compatible with a long line of Kenwood radios.
The TK-8180 (and TK-7180 VHF radio) have an excellent expansion port in the back that uses a standard DB-25 female connector, which makes it super easy to interface with. In my Jeep, I mount the remote head high above the roll bars near the roof to keep it out of the way and the body of the radio under my seat. However, I don’t want to have the mic up there, with the cable drooping in my face. Luckily the expansion jack can take mic audio and PTT signals instead of the mic jack on the head.
Even though this is rather trivial, I’m documenting the connection here for my future self, and others, as I have seen people ask about this before. I’m using a KMC-35 mic, but this should work with most any Kenwood commercial mic (keypad mics that use the serial connection will not have DTMF functionality).
I used a simple surface-mount box meant for ethernet to provide a mic jack low on the center console. If you’re familiar with (and/or your surface-mount box is marked for) T568B ethernet wiring, I kept the wire colors consistent here to make it easier. I used the software to set AUXI/O7 (pin 12) to “External PTT (Voice)” and “Active Low”. If you choose a different pin for PTT, make sure to adjust accordingly in the table below.
| RJ-45 Pin | DB-25 Pin | Signal | T568B Standard Color |
|---|---|---|---|
| 1 | W/Orange | ||
| 2 | Orange | ||
| 3 | 6 | Mic Audio | W/Green |
| 4 | 25 | Mic Gnd | Blue |
| 5 | 12 | PTT | W/Blue |
| 6 | 7 | Gnd | Green |
| 7 | 14 | SB (+12v) | W/Brown |
| 8 | Brown |
The TK-8180 can also tolerate both mics being connected at the same time, and the radio will route audio from the proper one depending on which PTT is pressed. This is not important for my application, but may be for others.