[Kenwood] Kenwood TS-930S Microphone Impedance Setting?

[Dr. Gerald N. Johnson, electrical engineer]

Not surprising that the high impedance microphone output has more ALC
action, getting to high impedance involves a transformer that steps up
the voltage. So there's more voltage, but not more power from the
microphone. And since the input of the radio has the same gain, probably
the difference between MCL and MCH is a microphone load resistor
(connected for MCL and not for MCH) the low impedance connection will
always provide more audio for more ALC action at any give microphone
gain control setting. Driving a 500 ohm radio with a 50K microphone will
tend to give a poor frequency response, probably rolling of highs
excessively though that depends on the microphone. That's the most
likely result with a dynamic microphone and transformer. With a crystal
microphone like the original D-104, the lows disappear when loaded with
such a low impedance and its high frequency response peak gets
drastically exaggerated. The microphone response will be flattest when
the microphone impedance is lower or equal to that of the radio input.
Going lower in microphone impedance won't affect the relative frequency
response, but will demand more gain in the transmitter audio circuits to
get full output.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson. Reproduction by
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