Wire a Yaesu FTM-10 to a Sena SR10 bluetooth interface

So I ride a motorcyle. And I have a HAM license. And I have a bluetooth intercom system in my motorcycle helmet. And I’d like to do both, since riding is a lonely endeavour.

I had already bought the Sena SR10 bluetooth mono interface with telephone headset and 2-way-radio feature to be able to listen to my Garmin Zumo 660 satellite navigation system and GPS based speed trap alerter (although you can do without the SR10 if the Zumo is your only other mono sound interface next to your phone). I also used the SR10 connected to a PMR so I already had set up the PTT button to my left steering handle. The PMR is a Kenwood one, so I used the Sena compatible cable for Kenwood 2-way radio’s.

Then I bought the Yaesu FTM-10E.

It is a 50W 2 way waterproof radio with remote head, covering the VHF and UHF amateur frequencies. I set up a Diamond SGM-507 antenna on one of the handlebars of the passenger seat, put the radio under the top case and mounted the remote head with a RAM mount in between my handle bars.

Yaesu FTM-10

Now, there are two options to connect this Yaesu FTM-10 to a bluetooth headset. One is as far as I know currently unproven scenario where you’d buy the FTM-10 with the optional bluetooth adapter and use bluetooth to connect to my bluetooth intercom headset. Theoretically it is possible, but I wonder how I’d manage to use PTT in this scenario because the Sena SMH10 bluetooth intercom I use does not have a PTT button included.

The other option is through the Sena SR10 bluetooth interface, which allows wired connections to bluetooth intercoms, and includes the necessary PTT button and is proven to work with other 2-way radio’s. In price, it’s also about the same as the bluetooth adapter in the FTM-10, but I already bought it for my Garmin Zumo 660 and GPS based speed trap alerter, so that part is already known territory to me.

So basically, you need:

  • Yaesu FTM-10E or FTM-10R. The connections on the FTM-10SE and FTM-10SR are different, so stop reading now if you have these 10W versions;
  • Sena SR10 bluetooth adapter
  • Sena SC-A0116 cable, which connects on one side to the SR10 and is open ended on the other side, for you to make your own cable. Which we are going to do.
  • Yaesu CT-M11, which connects to the back of the FTM-10 on one side and is also open ended on the other side, which we are going to connect to the Sena cable
  • 2 390 kΩ resistors, which are needed to make the SR10 PTT buttons work with the Yaesu FTM-10
  • Soldering iron, tape, crimp tools, a steady hand, … anything to hook up some very tiny wires together. Realistically speaking, you are going to prefer soldering the resistors to the wires and then want to make everything waterproof by mounting the connections and resistors in a little box filling it with silicone sealant.

Once you have put in your orders, got your resistors through eBay and have waited 2 months to get your CT-M11 cable, you can get to work.

Download the Connection Yaesu FTM-10 Sena SR10 file, print it out and happy soldering!

3 Replies to “Wire a Yaesu FTM-10 to a Sena SR10 bluetooth interface”

  1. I was going to let you know that a direct BT connection of the FTM-10 using the optional BU-1 chip with a BT headset is possible and does work. I’ve actually used that setup with 2 different BT headsets over the past 1-2 years. There are some caveats though on how it works depending on the headset. In the end, it does work, but probably not the best setup for most people. I recently got mine wired up to use the SR10 also, and it works much better than a direct BT connection.

    My first setup was with a Cardo Scala Q2 (non pro) so no A2DP support on that headset. The BU-1 chip actually does support A2DP (BT Stereo) for the line in and FM audio, however when you BT in a non-A2DP headset, it just forces everything over the HFP (mono) connection so audio from the music doesn’t sound that great. In order to transmit via the BT headset, there are a couple options. In the BT menu on the FTM-10, you can set it to PTT, Toggle, or VOX. With this setup, toggle is the only one that even begins to work, so when you want to talk, you push the “phone” button on your BT headset to turn on the Transmit, and then push it again to turn it off. It works fairly well except for those times you are sitting at a light with your left hand on the clutch and it’s not free to reach up and toggle your audio on/off. So sometimes you spend time rambling until you get a chance to turn off the transmit or have a longer than normal break in a conversation before you can key up again. For the PTT setting, you have to physically hold in the phone button on your BT headset which doesn’t even begin to be possible unless you are just cruising down the road since your left hand has to stay hooked to that button. With the VOX setting, I found it very unreliable and caused a lot of kerchunking on the repeater. Here is the big caveat with the BT headsets though. Since you are pairing over the “mobile phone” connection, the headset thinks you are on a phone call and keeps your audio channel between your headset and the radio active 100% of the time. It’s like being on a manual intercom mode where you just leave the channel open so that audio can be heard as soon as either party talks even though you don’t have to and can remain quiet. Don’t misinterpret this as meaning you have transmitted audio into the Ham Radio 100% of the time. You still have to toggle your PTT in order to transmit, but the audio channel is open and live meaning there is no delay in your hearing anything from the ham radio. This causes a couple issues though, the main one being that leaving the audio channel open is using a lot of your BT headset power and causes the battery to be worn down more than just if it was on standby. The other more glaring issue is that since the mobile phone connection is generally the highest priority connection on most BT headsets, this means that nothing else on the headset will work while that audio path is active. You can’t do an intercom connection, you obviously don’t have your phone connected, and you can’t listen to music in between your ham conversations. Your headset is 100% dedicated to that audio channel its keeping open between it and the Ham Radio. Well, you can hear music from the Ham radio, but in this case of the Scala Q2, its coming over the HFP connection in mono so doesn’t sound that great anyways.

    There actually is a “BT save” function that can be enabled on the FTM-10 which theoretically should allow the BT audio channel to go to standby while there is no audio present on the FTM-10 and it does do that. The problem is that once it allows that audio channel to go to standby, there seems to be no way to get it reestablished again. Audio from the FTM-10 doesn’t open it back up again and pressing the phone button on the headset doesn’t do anything either. You have to power cycle one or both of the devices to reestablish your connection. I actually believe this is a bug on Yaesu’s side. Maybe it’s not using all the correct BT protocols it would for a phone connection but when no audio is coming from the radio, and the BU-1 chip goes to standby, any audio should automatically reestablish that audio path, but that doesn’t happen. So in short, keep the BT Save feature off on the FTM-10 or you’ll constantly lose your audio connection.

    My next setup was an upgrade to the Sena SMH10 BT headset. This headset supports both HFP & A2DP connections and if you are using V4.0 or later of the Sena firmware, you have a 2nd Multi-point HFP connection which was specifically designed for the SR10, but it can work for a 2nd mobile phone etc that is HFP only. The Sena SMH10 BT headset actually can work a little better than the Q2 in this setup because it has an A2DP profile also. (I’m sure other headsets like the Scala G4/G9 or Q2 Pro would work similar to this, but I never tested them). When you pair the Sena SMH10 & the FTM-10 BU-1 chip, if you get both HPF & A2DP profiles to connect successfully, then as you move through the different mode settings of the FTM-10, it actually changes from the HFP connection while on the Ham Radio part to the A2DP connection when you select FM Radio or Line-In. This works out better since music is usually a lower priority on the headset, so when you move over to FM radio or Line in, your audio path between you and the radio has moved to a lower priority and you can actually have an Intercom conversation with your riding partner or take a phone call if it’s on the 2nd HFP connection. Again however, any time you are on the ham radio part, the main HFP connection is active 100% of the time and takes priority over any other BT headset functions. If you set the FTM-10 up to monitor one ham radio channel for active audio and then have it automatically switch to either the FM Radio or Line in when there’s no active audio, that setup can work pretty well.

    This above setup seemed to work pretty well when I had v4.0 of the Sena SMH10 software installed, but as they upgraded the SMH10 to V4.1 and then V4.2, I seemed to have much more difficulty getting both the HFP & A2DP profiles to pair reliably every time I connected. What I found was that if I was on the Ham Radio channel while I powered up, usually only the HFP connection would connect, again leaving your mobile phone channel 100% open. However, if you cycled through the modes on the FTM-10 and got to the FM-Radio or Line in, instead of forcing the audio over the HFP connection like it did on the Q2, it would drop your HFP audio channel all together and your connection would be lost. It was almost like it’s expecting the A2DP channel to be there to switch over to, but it’s not. The only way to get it back would be to power cycle one of the devices. My work around for this was to make sure the FTM-10 was either in FM mode or Line In mode when I powered on and usually that would force both profiles to connect, but again it wasn’t 100% reliable every time it drops your audio, you have to power cycle to get it back.

    The battery life on the Sena SMH10 was way better than the Scala Q2, so even though my audio channel stayed connected 100% of the time and is very taxing on the battery, I was still able to spend 8-10 hrs on my Ham Radio when I participated in bicycle events providing communication. That’s pretty impressive from the Sena’s. I’m sure other BT headsets would work similarly, but they each probably have their own caveats on how they handle that transition from HFP to A2DP on the various modes of the FTM Radio. I believe the Yaesu BU-1 chip has now been replaced with the BU-2 chip. I’ve never tested it and not sure if it works the same or not?

    So in short, the direct BT connection between a BT headset and the FTM-10 with the BU-1 chip can work, but be aware that basically you are most likely stuck with your audio channel open 100% of the time between the headset and the radio. I have since moved on to using the SR10 connected to my FTM-10SR radio and a BT connection between my SR10 & SMH10 using the Multi-point connection. This setup works much more like you expect it with a standard PTT button and when there is no audio from the Ham radio, the connection between the SMH10 & the SR10 goes silent. Since the SR10 is not stereo and doesn’t support A2DP, that means you can’t enjoy stereo FM music from your FTM-10, but for me that’s a not issue. I can still use my primary HFP & A2DP BT connection for my smart phone and I listen to stereo music from my Android phone.

    Regarding your comment about the FTM-10SR having different connections compared to the FTM-10R or E models, I’m not sure it is? I have the 10SR and my buddy has the 10R and we both wired up our Yaesu CT-M11 and the Sena SC-A0116 cables the same way and they both worked fine.

    1. Thank you for your insights! I ran into a fellow HAM operator over the weekend who has the combination FTM-10E + BU-1 chip + Scala headset, and he mentioned he got it working with voice activation, which is not what he desired. In the end, I think the SR-10 route is a bit more expensive but allows greater flexibility.

      I am currently looking into getting a second FTM-10E on my motorcycle. Over the weekend, I ran into issues which would be solved with having two FTM-10’s mounted, with a toggle switch for mic input. I needed to monitor over two frequencies at the same time, and be able to transmit on both frequencies quickly, but as far as I can see there is no dual channel VHF/UHF transceiver with waterproof remote head.

      I don’t remember why I mentioned that the FTM-10SR and FTM-10SE have different connections. Maybe because the CT-M11 cable does not mention these devices specifically, but looking in the manual for these devices I cannot find any difference in their function.

  2. Wooter and Daniel, I don’t know if you’re still monitoring this 3 years later, anyway I have an FTM-10SE and BU-2 on order, and use Sena 20S headset. I have also recently obtained an SR10. I’ll be trying the 20S ‘2nd mobile phone’ connection to the FTM, and also the 20S ‘selective pairing’, to see if it’s possible to pair the SR10 to the FTM via HFP and the 20S to the FTM via A2DP (not sure it will be possible to ‘unbind’ the HFP and A2DP on the FTM). If I’m lucky, I’ll find that the BU-2 works better than how you describe the BU-1’s operation, and I’ll be able to just pair using the combined HFP/A2DP ‘2nd mobile phone’ profile of the 20S.

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