Re: Will this mic work?
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Spot on Evan,
There is a hand mic version of the Astatic D-104 that uses an internal battery. I have used them on my vintage rigs and get excellent audio reports. All this assumes the mic gain stages (as designed) of the BitX are inadequate- I have not confirmed this myself.
From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Evan Hand
As far as I can tell without the schematic of the mic, it will not work. The input of the uBitx has approximately 5 K ohms for the bias of the electret element. If the current draw of the mic is 5 ma, then the drop across that resistor would be 25 volts. At most the supplied voltage is 12 volts (13.8 with a "normal" ham supply). Not enough to run the mic. You would need to drop the resistor in the uBiTx mic circuit (R60) to 680 ohms That would give a drop of (680+220)*.005=4.5 volts That leaves 7.5 volts for the mic. NOTE: there is a 220 ohm resistor ahead of R60.