I had a friend who refused to get any closer to the microphone than 12 ". He
was real difficult to understand due to the low audio level that resulted.
We turned up the gain in his mobile, but it was still a bit of a problem
since it then increased the road noise.
Chuck
WB2EDV
----- Original Message -----
From: Steve Bosshard (NU5D)
To: Repeater-Builder@yahoogroups.com
Sent: Thursday, April 14, 2005 5:43 PM
Subject: [Repeater-Builder] Microphone Gain and Deviation
Best answer I have found for soft spoken folks is the little mic preamp
board used in some of the old GE Phoenix and MVS radios. Little single
stage amp that operated from bias on the mic line.
I usually set the deviation limit for voice at 4.0 Khz. And allow a little
for tone/dcg.
NEVER EVER USE THE TRANSMITTER DEVIATION CONTROL TO MAKE UP FOR LACKING MIC
GAIN. A soft spoken person may need a mic preamp, or a more sensitive
microphone. Beware of excessive mic gain competing with ctcss and causing
drop or talk down. A small swamping resistor might be in order. Wish
Helper still made the modulation density meter.
SOP is to set a tone gen at around 50 mv or enough to fully modulate the
transmitter, and then set the deviation limit to around +/- 4.0 Khz @ 1000
Hz. Tone. Using the IDC to boost mic gain will lead to overmodulation and
clipping out of the pass band of the receiver, not to mention the joy you
will bring to your adjacent channel neighbors.
2 cents and 30 years,
Steve
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