throat mike and aircraft radio

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oynif

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kurt
I have started testflying a homebuilt Baby Lakes and get complains about too much windnoise when transmitting .I have bought a throat mike but it does not work with my Icom radio. I know that the required impedance is 150 ohms but have no idea how to measure the impedance of the throat mike.
Even if could I would not know how pair it with the radio.
Can anybody help ?

Thanks Kurt
 
The impedance of a throat mic system (condenser) is about 1 billion ohms, if that helps. hehe :goofy:

To actually be helpful though, I don't think any of the throat mic systems are dynamic or carbon, they should be a condenser system (super high impedance). That 150ohm spec out is specific to old dynamic (military conversion) boom acoustic headset microphone systems. As far as I know any throat mic system (non military) should work with your iCom. If you have a very old military tactical throat system, the system is low impedance and will not work without some type of amplified impedance converter.

Also, be sure that you are depressing the PTT switch when transmitting. The vibratory triggering for those throat mics are notorious for not squelching properly. It may not be working because the pickup is not triggering. I'll also tell you that NIH and NCBI did significant testing on boom(acoustic) mics and throat(condensed) mics. They used the MRT (Modified Rhyme Test) and found that intelligibility using throat mics is significantly poorer than with the use of boom microphones in noisy and in quiet environments. Throat microphones are not recommended for use in any situation where fast accurate speech intelligibility is essential.

Another issue people have is mistaking the little twin plug connector. Make sure the connector is for an iCom radio, not a Motorola, Rap4, Vertex, or a Kenwood plug.

Having said all that, I know that iCom makes there own throat mic system as well. If memory serves it's an HS-97. Single side pickup and one ear plug though.

This is not a sales pitch at all, it's just fact. The only way that I know to remove the wind & ambient noise in open cockpit / ultralights and use your existing headset/helmet,or our headsets is the PA9-EHN mic. I'm serious. It's the best thing ever.
 
Last edited:
Archammer said:
The impedance of a throat mic system (condenser) is about 1 billion ohms, if that helps.
Click to expand...

Actually, getting an impedance of 1E9 is difficult in the extreme with the exception of folks working in silicon on sapphire where 1E12 to 1E15 is not unobtainium.

Without knowing what the person bought, it is impossible to tell what they have. They may have an old WWII throat mike, carbon, that is low impedance.

They may have a 1950-60s dynamic which is different yet. Or as you say, they may have an electret mic that is moderately high ... yet MOST electret mics overcome that with an on-board FET preamp that takes care of the problem.

OP, exactly what kind of throat mic do you have?

Thanks,

Jim
 
the throat mike in question is a LGR-32:


Technical Specifications:
Speaker
  • Output level: 102 +/-3dB
  • Impedance: 32 ohm +/- 15%
  • Frequency range: 450-20,000Hz
  • Audio Output: 30mW
Microphone
  • Type: Omnidirectional condenser
  • Sensitivity: -65dB +/-2dB
  • Frequency response: 20-16,000Hz
  • Operating Voltage: 3V
  • Current Consumption: Max 50mA
  • Impedance: 2.2K ohms
My Icom radio manual says that any microphone with an impedance of 150 ohm should Work

is it possible to pair the mike to the radio ?

Kurt
 
Archammer said:
This is not a sales pitch at all, it's just fact. The only way that I know to remove the wind & ambient noise in open cockpit / ultralights and use your existing headset/helmet,or our headsets is the PA9-EHN mic. I'm serious. It's the best thing ever.
Click to expand...

Shane is correct; this rather pricey little microphone is the best thing on the market for very noisy environments. One question I have for Shane, though, is that he says the output impedance is 50 ohms. That seemed to be a bit low even with a preamp, and I can't verify it on any other website. Not that it matters; it only needs about 15 mA to operate and this is pretty easily supplied with a 560 ohm (or thereabouts, it isn't too fussy between 470 and 1000 ohms) resistor to the +12 supply. The radio itself ought to supply this bias internally so you shouldn't have to fuss around with external resistors.

However, the throat mike in question is "omnidirectional", which means that it picks up sound equally well in all directions. That is exactly what you do NOT want in a noisy environment. It will pick up vibrations from your adam's apple, but it will also pick up exhaust and wind noise equally well. Not a good choice for a noisy environment.

If the radio in question is a handheld, be advised that handheld aircraft transceivers are notorious for not complying with aircraft standards. It SHOULD work with your transceiver but no guarantees from me.

Jim
 
Last edited:
Archammer said:
This is not a sales pitch at all, it's just fact. The only way that I know to remove the wind & ambient noise in open cockpit / ultralights and use your existing headset/helmet,or our headsets is the PA9-EHN mic. I'm serious. It's the best thing ever.
Click to expand...
I used a Flightcom A-9 mike element and foam cover in my homebuilt under-the-leather-helmet headset, and have had someone tell me that they couldn't tell that it was an open-cockpit airplane.

Depends on the amount of protection from the wind, of course.

Ron Wanttaja
 
Icom`s requirement of 150 ohm and the throat mike impedance of 2200 K ohm
should not be a problem ?

kurt
 
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