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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 13th Jul 2020, 12:25 pm   #1
GSBX1220
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Default Racal Acoustics Microphone ID req

Hi folks

I have a couple of Racal microphone inserts. I think they are electret, but I wonder if anyone can ID them. Part No is 554285.

I get a resistance of around 2k in one direction, but around 14 meg in the other. That's why I think it's electret. But I would rather a more positive ID.

They are the same fitting as the dynamic one in my jetgard headset, but may not be direct swap.

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Old 18th Jul 2020, 10:45 am   #2
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Default Re: Racal Acoustics Microphone ID req

Decided to take the chance and fed it with 1.5v bias. Seems to produce audio ok. How it sounds on-air is yet to be seen!
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Old 30th Jul 2020, 6:52 pm   #3
Sparks
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Default Re: Racal Acoustics Microphone ID req

Only just seen this. The microphone is a noise-cancelling electret type, 2000 ohms. The mic capsule itself is tiny, about 5mm diameter.

This microphone was an option on the later Racal Astrolite headsets. NATS was a major user.
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Old 2nd Aug 2020, 11:03 am   #4
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Default Re: Racal Acoustics Microphone ID req

Hi

I'm using it with my Jetgard headset via my Datong ASP speech processor. The bias voltage I'm feeding it with (to be on the safe side) is 3v. I could not find any specs on the mic.

The headset came with the dynamic insert, but the output from the dynamic insert was too low to drive the processor. The electret drives the processor fine and I have not had any complaints on air!

Cheers.
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