Robert L. Nuckolls, III wrote:
>
>...............................>
> I believe what you have is a (1) battery to provide an independent source
> of microphone bias. (2) a resistor to allow d.c. energy to be coupled to
> the microphone circuit without seriously loading the audio output.
> (3) a capacitor to couple just the audio component of the microphone signal
> over to the radio without upsetting the bias to the microphone . . .
> IRRESPECTIVE of the characteristics of other microphones that share
> the input.
>
>
>
> Yes, this circuit does make sense and yes, you could have built it for
> a very little cost. I rather suspect there is nothing on the other
> side of the etched circuit board you mentioned. I'll guess that the
> resistor is on the order of 100 ohms (about 50 ma of bias to the microphone
> assuming half of the 9 volt battery is dropped across the resistor).
> Any electrolytic capacitor on the order of 10uF or more would suffice
> for audio coupling.
>
> Bob . . .
Bob,
I have built several headsets but have one with a
microphone
failure. I want to replace the microphone unit with a regular
noise-cancelling microphone but presumably I need an amplifier as the
output of the electret will not provide sufficient voltage swing to
drive the first stage of the transmitter. Can you recommend a suitable
circuit - preferably operating from the aircraft transciever microphone
input ?
Regards,
Martin
9Y4TAM
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