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.

UPDATE 3: I have become aware that using a different style cellular headset (or earset, if you prefer) than the one I used for the adapters I used to sell may cause a deterioration in the audio quality of the transmitted signal. I tried several different headsets over the development of the adapter and several were fine. Several others however were not so good. If you build this adapter, be prepared to check different makes and models of the typical wired cellular headset before making a final selection. The ones pictured in the page on "a cellular headset adapter" elsewhere in this website worked just fine. There are a few available commercially that do not work so well. The adapter works well in all cases, it is the choice of a cellular headset that will affect the audio quality of your transmission.

UPDATE 4: Someone on the FT-7800 Yahoo group referred to my web site the other day in reference to the adapter for the FT-7800, 8800,8900 group of radios. Just for fun I followwed the link which was correct except it led to a different page on my site. I also discovered a typo on this page. The typo has been corrected. The diagram for the "simple" adapter without the switching function was and is correct. However the values for R1 and R2 in the accompanying text were reversed. The text is now corrected. Sorry about that, I totally missed it when I originally wrote the page.

UPDATE 5: The circuit below has been slightly modified to include two new .047 uF Capacitors near the 2.5 mm stereo jack where the cellular headset plugs in. This is to provide increased resistance to RFI which has popped up occasionally. The actual value is not critical, just the provision of a path to send the noise to ground. This same modification can be applied to the other circuits on this and other pages on this web site. These aditional capacitors are not normally needed at all. In various iterations of the design since this page was written, they have been eliminated without any degradation in audio quality. The RFI mentioned above was, in each case, traced to a malfunction in other equipment around the radio room, sometimes even outside the house.

Update 6: These circuit diagrams assume the use of a wired cellular headset. These headsets are becoming truly rare with the advent of Bluetooth. The circuits can easily be modified to use a PC style headset which has two 3.5 mm plugs. The main change is to run the recieve audio from the external speaker jack on the radio directly to the jack for the earphone side of the headset. If you are building a mic selector, you will have to run the audio+ from the external speaker jack on the radio through a switch position on the selector so that you can switch from the headset to an external speaker and hand or desk mic. If you have any problems figuring out the changes to the circuit just email me at nigy@arrl.net and I will be happy to walk you through it.

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 = 22k, R2 = 2K

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

MH-31A8J hand mic. NOTE: The RJ-45 pin numbering Yaesu uses is backwards from the way Icom counts the pins. If you are using CAT-5 cable for the project with a pre-installed RJ-45 plug on a Yaesu radio this will mean that the orange/white wire is pin 8, the orange wire is pin 7 etc. The Icom system uses the exact opposite (pin1 is orange/white, pin 2 is orange etc.). Make sure that you use the proper pin numbering system for your particular radio!

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.

This is the new circuit for the Yaesu VX-5R. It should also work for the FT-60 and maybe for other Yaesu Hand-helds as well, but I cannot guarantee that since the only Yaesu HT I own is my VX-5R. Simplicity itself, the circuit has only 2 electronic components, one 2.2K resistor and one 0.001uF capacitor. Of course there are the usual PTT switch and the various connectors and cables, but the circuit itself is very easy. I have tested this circuit on my VX-5R and it works fine. One caution to anyone building this or any of the circuits that adapt a cell phone headset to any amateur radio: I went through about five or six different headsets in developing this adaptation. Some worked just fine, others not so good. Be prepared to try a different design of headset if the audio is scratchy or less than adequate. I recently saw this effect when a fellow ham used one of my adapters (which I had given him) but then changed out the cellular earset that I include with the adapter for a different one. The audio was very scratchy. As soon as he went back to the original earset (headset) that I had supplied, the problem cleared up.