[ICOM] Mic jack on Icom 706

[Larry Young]

John; This is a subject that many Icom owners are confused over. Most Icom radios use a microphone with an "electret element" This type of microphone element does indeed require a dc voltage to be supplied to it. Icom supplies this voltage on the microphone input line. Because of this voltage presence on the microphone input line, when a different microphone or other device supplies audio input via the microphone input connector, a series isolating capacitor may be required. This depends on the type of input device and circuitry supplying the audio to the Icom radio. Other manufacturers may put the operating voltage for an electret microphone on a pin other than the audio input pin. Either way its no big deal. Why does Icom use an electret microphone? They have a higher audio output, thus permitting less preamplifier gain in the transmitter, and perhaps fewer RF induced audio problens.
   DC voltage does not have to be supplied from an outside source, but as previously stated, you may need to place a capacitor in series with the external audio input line. usually this capacitor is about 1 UF @ 10-15 volts DC rating..
I hope this clarifies.
Larry K4LXV

--- On Sun, 10/30/11, John Geiger <aa5jg at fidmail.com> wrote:

From: John Geiger <aa5jg at fidmail.com>
Subject: [ICOM] Mic jack on Icom 706
To: ic706 at yahoogroups.com, IC-706MKIIG at yahoogroups.com, "ICOM Reflector" <icom at mailman.qth.net>
Date: Sunday, October 30, 2011, 2:59 PM

I have an Icom 706 original and am wondering exactly what is needed for the microphone on this rig.  In terms of the mic jack, does voltage need to be applied along with the audio in?  I am wondering if I can run a cable from my computer sound card out jack to the audio in and ground connections on the mic jack and get it to work with VOX, or is some sort of voltage or other signal also required to get the audio to work correctly?  I am still not completely clear about the Icom mics and the preamp being in the mic and things like that. I should be, though.

73s John AA5JG
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