A ramble about my experiences with 2-way radios, Bluetooth, cables, and Roger. Maybe this will be useful to somebody some day. I mostly work with Motorola radios and their horrid proprietary headset connectors but some of the principles should be the same for other vendors with nicer connectors and less weird cable.
The tl;dr was that I found Bluetooth was less than ideal, DAI cables into headset adapters are cool but do take caution for audio levels, and Roger hooked into those same adapters seems to work well in initial tests.
I attempted to use Bluetooth between my Motorola SL4000 radio and my ComPilot last night.
Not really expecting much, I paired them, and immediately once connected I got an “incoming call” ring, so I pressed the ComPilot to “answer” it, at which point the audio from the radio is connected. Until then, all audio, even alert tones such as low battery won’t be passed through, plus it’ll ring indefinitely which I’m sure will become annoying!
One thing to note - unless you turn the mic gain down on the ComPilot you’ll be constantly getting audio through that as well, so my preference there is to just turn the “own voice” option off, as well as make sure the aids aren’t attenuating mic input when in the streaming program otherwise what’s the point of having the hearing aids in! Oh, and the automatic programs won’t be running, this may mean less audibility for you unless you’ve fine-tuned the streaming profile. Another thing to note is you can’t key-up the radio (transmit) unless you press the talk button - and depending on how the radio was programmed it might be the either the ComPilot’s mic or the radio’s mic that’ll be used when you transmit, so you’ll have to work out which one. I suspect the ComPilot will run out of battery pretty quickly too - it’s “talk time” figures rather than standby when the audio is connected as it’ll be putting out a signal the whole time, even for radio silence.
So sure, it “worked”, but it’s a little impractical.
So back to the drawing board… drawing on an old idea from a while ago…
Here’s a cable that goes between the radio and whatever 3.5mm audio device you like. They were sold as “covert” headsets, coming with a 3.5mm socket (wired in mono) and a nasty pair of cheap earbuds, presumably for undercover personnel to try to blend in with the cool kids and their iPods or something. It wasn’t completely our use case, but seemed ideal still - I originally enquired about “cheap headsets that we can cut open” and the company in question suggested this as an alternative (although they were far from cheap!)
I ordered a bunch of these for some events I worked at where several staff had a very strong preference to use their own headsets when on long desk-based shifts because they’re wayy more comfortable than anything we could get as standard from the hire company, and I rewired them to replace the mono left-channel only output with a left and right channel, but I soon realised that you could also plug in a 3.5mm to DAI cable (attenuated!) with great success. Due to the weird output levels the radios often give along with strong RF emissions induced on the cable as well as nasty impulse noise from the time division multiplexing in the case of digital radios, you may need to use an isolation transformer circuit and additional attenuation with much older aids where the DAI input is wired in-line with the mic to avoid blowing up ant amplifier circuits - but nothing I had was that old, so it wasn’t an issue for me. I’d still exercise some caution here and check the output levels with a true-RMS multimeter or better an oscilloscope before plugging anything in however. If in doubt or test equipment isn’t accessible, always isolate and attenuate, and you can always lower the attenuation later. Better to be safe than sorry!
My experience with these is that the audio does come out very hot, but this is totally a fault of the radio itself. On Motorola DP3600s it’s not such an issue, but we had DP4800s the year after and didn’t realise the output would be stronger, so we found ourselves having to tape the volume dial in place with some electrical tape so not to accidental knock it past the first position - the controls on the hire radios were often a bit too loose compared to my far less used and less worn radios that I owned. I don’t remember whether the output gain was adjustable in the radio programming software but I suspect it may have been. Regardless, some kind of in-line attenuator would have been really nice to have if we’d have known, as you never know what the radio hire companies will send you in terms of programming, especially if you’re working with a supplier who you’ve not used before.
Given I knew I could get this to work with a DAI cable, the next logical steps to me were “can this work with Roger?”
I’m pleased to report that yes, it works! I’m using the 3.5mm input cable for my Roger Pen, in this case, which is a little impractical in terms of device positioning - the mic for the “headset” is where the 3.5mm audio out jack lives, which means there’s no safe place for me to tuck the Roger pen away. I’m planning to make up a short extension cable later so I can safely tuck it away in my pockets, although I figure if I were to use a multimedia hub instead, I’d be free to select whatever length of 3.5mm cable I wanted, plus the battery life might be better. I am somewhat concerned for battery life with the pen.
There are a couple of caveats that come to mind with this still. Firstly from an audibility point of view, bear in mind the auto programs won’t be running. My goals here are to try not to compromise the performance of the hearing aids as much as possible but still to get audio in from the radio.
If you’re a self-programmer like I am you could copy the fine-tunings from the soundflow programs, and you will probably want to ensure the mic gain isn’t attenuated in the Roger program. I found that EasyRoger was not great in this case as it kept flicking back and forth between soundflow and easyroger due to lack of input, and it sometimes takes a while to wake up again and reconnect meaning you’ll miss a transmission, so a roger program in the program list that you can access with a button and stay there with is ideal in this case.
There is, I believe, some battery life implications here as the Roger receivers will be permanently powered up rather than asleep when the radio isn’t sending audio, but I don’t think it’ll be that much different scenario from a full day of meetings with the receivers turned on and a table mic transmitting away. I’m not convinced there will be that much of an impact but I could always be wrong.
I found with my Sky Qs, the mics are fixed in omni-directional mode when you use a Roger/DAI+mic program, and I’m not sure if this is just a peculiarity of Target as I could have sworn my old Nathos aids let me fix into directional in iPFG when using a DAI+mic profile. Ah well, maybe I’ll figure that out at some point, but for now, this does seem relatively workable for me.
I’ll try and report back after next weekend’s event with my final verdict of how well the Roger and radios setup worked out, as for now I’ve only tried it for half an hour or so in my workshop.
If you’ve read this far, I suspect you’re probably interested in doing something similar as I couldn’t find much out there in the way of how to hook these up electrically speaking, and so I hope it helps.
If anyone else is doing anything similar, I’d be curious to know what works (or doesn’t work!) for you. I know there was this thread where there was some discussion about physically modifying some headset types to let you stick a RIC in at the same time as an earpiece.
Maybe I could get some moulds made with holes for an extra tube (assuming there’s space!) to use a traditional acoustic tube headset but I’ve yet to try and persuade any labs to have a go at making one, but that’s always another option to be considered.
Please do excuse my awfully messy workbench!