Mobile Radio Microphone Hack

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Mobile Radio Hack

On this page I describe how to install the option of an alternate Microphone for a Yaesu radio which uses a modular (RJ11) type hand mic while keeping said microphone's DTMF Functions.

The reason I made this modification is because I want to use the Headset from my Hand Held Transceiver, a Pryme SPM-1500 Throat Microphone, with my mobile unit for a hands free operation and to make it not pick up my car stereo or noise from things like a rolled down window, and I hate having to put a microphone in front of my face!

Now, there are some modular ADAPTERS out there but they only work with a round 6 or 8 pin type connector, and those are specific to brands as it wasn't standardized wiring. This method installs a standard 3.5mm plug to the Handset so that any microphone can be installed. Originally, I was going to put on a 2.5mm jack specifically for the size needed by headsets but as I worked and spliced the cable I found the wires to be too small to work with, and of the bizarre audio colored strand that I have no idea how to solder. Also, with a 3.5 it's a more standard size and maybe I'll use another mic at some point for who knows what.

Below is the Build Log, I made all decisions and design On the Fly.

All in all, from time first taken the thing apart to having tested the mod, found problems, and fixed it I think I spent about an hour.


Here is the back of the PCB of the hand microphone, it will be where most of the work is done. I originally planned on just taking out the connector on the bottom and making a cable that attached to that as I do not have a proper crimp tool to make a modular cable, and I always HATE splicing in-line on a cable unless I have some hard connector or box in between and this would have made it easy. But, I wanted to keep my DTMF pad on the handset and have a backup microphone, so I went another route.

This is what I decided to do: the image below shows the switch for the "Lamp" setting, which simply turns on the LED backlighting on my mic. I NEVER turn the backlighting off so I found a point where I could install a port. But then, having decided to still use the internal mic, I decided to rewire the switch to make it change between the microphones and solder the lamp contacts into a permanent 'On" state.

Unfortunately, even with with only trace solder remaining after desoldering, the switch decided to break rather than pull out so I used a different switch which unfortunately will not fit the old slider, oh well!

Also, after soldering and closing the case for the first time, the super glue on the switch was still drying and apparently the back of the case pulled enough on one wire to break it and because the switch glue was still drying, and said wire was helping hold it in place by being soldered, the switch went off alignment. No biggie, it's still usable just not the best looking thing in the world.
just a note, the black stuff you see is Liquid Electrical Tape - a jar is $6, it's one of the best investments I ever made. I used it to protect the old switch contacts from shorting as well as the new ones should a lead break.

A top view of the installed cable, I drilled a small hole at the bottom near the main cable while the case was assembled.

The finished cable, with the secondary microphone cable run through the coil for a cleaner look. I should have cut down the external cable though, but it will eventually prove useful to have left it long, it just doesn't look as nice installed to have so much slack.

This is the Pryme SPM-1500 Throat Microphone. It is one of the few that work well (the ones that are non-adjustable and really thin tend to let in a lot of background noise and are a little quiet normally, though the one I keep as a backup from before I owned the pryme is easily understood on this setup). All I need to do now is workout the PTT button in the middle, as the two connectors going into it are both Female and there is no VOX mode on it. I can open it and peep around, but for now I have to press it and use VOX on my radio (which is only a temporary solution, because if I take a slightly longer pause in speaking it cuts out) or use both the PTT on this and the radio PTT in which case I can clamp down the Pryme PTT but it would defy the point to use the hand mic PTT. What I might do is to set the PTT to Toggle rather than momentary and use VOX and bypass the main button with a switch on the side of the Pryme PTT. It remains to be seen, I may just need to tweak the VOX settings for all I know!

The two-prong connector used by many two-way hand held radios. This model is unusual in that the PTT button simply breaks the circuit to the microphone rather than use a stereo 2.5mm TRS and send a signal to the radio. This is the source of my problem for the most part because I can't work with the connectors for my Pryme PTT unit. it appears to be a small version of the standard six pin radio mic cables, Too small for me to wire easily. I may just look for a good deal on the "tactical" PTT. Of course, I plan to open the thing first: If you can't open it, you don't own it!!