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Helmet Micro Avionics PM100 - connecting Baofengs


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I have a Micro Avionics PM100 helmet w bluetooth and would like to connect to Baofeng radio.

I wrongly assumed their pigtail cables would make that possible - but they don't sell one (that I am aware of) that works w Baofeng 2-prong plugs. So I am making one by hand by cutting the Baofeng socket from a baofeng headset and the barrel connector from a Micro Avionics pigtail. 

The four contacts that need to be connected are GROUND, SPEAKER, MIC, PTT. Speaker works, PTT works (activates Baofeng TX) but the microphone seems to emit just noise instead of my voice. Does anyone have experience with electronics/microphones that could explain that behavior ? 

Also open to other suggestions to connect up a Baofeng to my helmet. Thanks guys !

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I have noticed that the more modern radios now use separate wires/connections for Mic and PTT.

Earlier configurations combined the Mic/PTT function and there was an extended period where there was a 'standard' of sorts for the connections. Unfortunately the radio manufacturers now 'mix things up' with different connections on the dual or single multi contact plugs. It's a bit of a nightmare.

You confuse me by saying 'by cutting the Baofeng SOCKET from a baofeng headset', I would have though the headset would have a type of PLUG on it?

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Thank you both for replying so quickly !

While I haven't solved the puzzle yet, I thought I would share what information I have at this point, also as reference for future DIY'ers. 

I love the MA PM100 helmet otherwise (with Bluetooth, audio out for gopro etc.) but trying to connect to the Baofeng has grayed out my hair somewhat. My original (and at that time naive & wrong) assumption was that given the widespread use of Baofengs, there would be a compatible pigtail for the PM100 interchangeable lead system. But no. So DIY it is !   :)

As I mentioned I took one of the cheap headset cables included with the Baofeng radio and cut the cable to use its plug 
and then I took a Micro Avionics Kenwood/Midland interchangeable lead and cut it to get the bayonet 4-pin inline connector.

I ferreted out the cable colors to the various functions (GND, SPKR, MIC, PTT) and connected up corresponding leads on each cannibalized cable. Result:

  • Audio in helmet works (ie remote radio can transmit and Baofeng RX audio will come into helmet. 
  • PTT seems to work, the connected Baofeng lights up its TX LED....BUT: there is no actual mic audio from the helmet, just static.

I attach a diagram for reference.

The PM100 also has a set of DIP switches for additional configuration. I think the only ones relevant to this project are:

  • switch 8: PTT type  ON=hard ground OFF=resistive ground (most radios)
  • switch 9 & 10: changes mic transmit from ring to tip (ring: 9 ON, 10 OFF,  tip: 9 OFF 10 ON)

I tried 8 on and off and both ring and tip for 9/10 but the results are the same. If that is useful, there is also an image from the Baofeng radio manual showing how PTT / Mic are (expected to be ?) wired.



PM100 Baofeng cable.png

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Looks like all functions are referenced to the Ground connection so should be doable.

I'm guessing you need the 9&10 switches set for ring. Have you included the 10uF capacitor in series with the mic connection?

Try it with whatever value cap you have to see if it is necessary.

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