A Headset Adapter for the FT-8800 and Similar Radios

A Headset Adapter for the FT-8800 and Similar Radios

FINALLY, A WAY TO CONNECT A HEADSET TO A LATE MODEL YAESU RADIO

By Geoff Haines, N1GY

Let me start by saying that while I did design this particular circuit, the concept is not mine. A fellow FT-8800 owner who wanted to use his helmet headset with his 8800 on a motorcycle was the one who came up with the values for the circuit. His article is available on the FT-8800 Yahoo group. I just combined his adapter circuit with a switching circuit so that I could use either a cell phone headset (not Bluetooth) or the stock hand mic. I actually use this circuit with an FT-7800, but it should work with any Yaesu Radio that uses the MH-48 hand mic.

The first circuit diagram above shows a 10uF polarized capacitor since that is the value Brian used in his. I substituted a 47uF polar cap because that is what I had in hand. Apparently the higher value works just fine, at least it does for me. If you just want an adapter and don’t want the switching capability, see the second circuit. You will note that I did change the value of the capacitor in this drawing. If you wish to use a PC headset instead of a cellular type then use 2 stereo 1/8” jacks and separate the grounds. The tip and ring connectors on both of the stereo jacks in that case would be tied together, since most PC headsets are only wired with two wires even though they use stereo plugs. See my article in the July 2007 issue of QST for details on how that type headset is wired. Personally, I find the audio quality of the cellular headset much superior to the PC version, but as they say “your mileage may vary”. Also note that pins 1 and 2 are not used in this version since there is nothing for them to connect to. A word of caution about the PTT circuit is in order. The PTT line on the radios that use the MH-48 mic demand to see some level of resistance (usually 15K or more) when the PTT switch is depressed. Otherwise the radio will lock in transmit and will only stop when shut down completely. Therefore do not omit the 27K resistor in the PTT line to pin 6. The PTT switch can easily be remoted to the steering wheel or handlebars for mobile ops or whatever. The entire circuit including the PTT could easily be built into a pill bottle or some similar enclosure to lessen the number of cables. Use your imagination when it comes to an enclosure.

Many thanks to Brian and the Yahoo FT-8800 group for the adapter design, it really works great and was very easy to build thanks to Brian’s pin out diagrams for the RJ-12 connector.

UPDATE: I have added circuit diagrams for the FT-817 and FT-8000 to this page in response to requests for them.

UPDATE 2: With help from Bill, W1WAB, we have determined that the Cellular "Earset" Adaptor for the FT-817 also works with no modifications on the FT-897 and the FT-857 as well. The list of compatible rigs just keeps growing and growing.

For the FT-7800,8800,8900 and 1802:

This diagram includes a switching function to go from the hand mic to the headset and vice-versa.

This is the simplified version of the above diagram wired as a straight adapter. To switch to the hand mic you would first have to disconnect the adapter from the radio and plug in the hand mic. I usually build the switched version but it is your choice. I appologise for the poor quality of the circuit diagram. R1 = 2k, R2 = 22K

C1 = 10 to 47uF. The ground side of that cable is not connected because in some cases it might set up a ground loop with the mic ground. The ground wire to the external speaker plug is not necessary since ground for the earphone is provided via the mic ground.

For the FT-817, FT-897, and FT-857: This version includes all the buttons normally found on the hand mic for the 817 but the UP, Down, and Fast buttons can easily be left off if you prefer a simpler device. Notice the question marks around the values of some of the components. When this circuit was first built I was not sure they would be right. Since then another ham has built one using the values I used for the prototype and tested it before I could get an 817 to test with. He says the values are fine. Anything from 10uF to 47uF for the polar cap, 2K to 2.2K for the resistor feeding the mic and 22K to 27K for the PTT resistor (The FT-817, FT-897, and FT-857 do not need this resistor but the FT-8000 and the FT-8900, 8800 and 8700 do). We have since tested the adapter on a local FT-817 and FT-897 and the original values we used in the prototype work just dandy. You, of course are free to experiment on your own to find the combo that works best for you. Mainly try different values for the Polarized Cap to see if you can find one that works well for DX and one that works better for local work. Many manufacturers include a switch on the back of the stock mic for DX or FM and that is what that switch usually changes, the value of the cap. If you find the transmitted audio too "hot", rather than turn the gain down on the radio, try a slightly larger resistor on the feed to the mic. The resistor on the PTT has to be greater than 15K, I use 22K on the FT-7800/8800 etc series. The circuit for the FT-8000 calls for a 27K, Try one of them, I suspect they will all work. Note: Text was revised 9/11/08

For the FT-817, FT-857, FT-897, FT-450 and any other Yaesu using the

P1 is a RJ-12 connector. Use one half of a CAT-3 cable (flat or round) Splice a 2 conductor cable (one half of a mono jumper with a 1/8" mono plug) into the 6 conductor cable about 8 inches behind the RJ-12. Connect the 2 wires of the audio cable to the wires for RJ-12 pin positions 1 and 2 (they are not used here). Install the components in an enclosure of your choice. Plug in a "Universal" wired cellular headset or "earset" and the job is done. Plug the RJ-12 into the mic connector on the radio and plug the mono plug into the external spkr jack or phones jack and you are ready to play.