[ICOM] Pro III ALC in SSB-D mode

[Mike McCarthy, W1NR]

 The ALC is "Automatic Level Control" and will only kick in when there is
too much audio and it needs to be limited.  I would suspect that there is a
mismatch between the soundcard and the radio.  The audio input in the back
of the rig (ACC 1 pin 4) is 10k ohm impedance at 100mV.  Most line outputs
from soundcards are about the same.  You should be using an audio isolation
transformer between them.  I am using 10k:10k miniature coupling
transformers from Mouser.  I found that the 600:600 Rat Shack variety don't
work properly.  If you are trying to drive it from an 8 ohm speaker output,
you are going to have a mismatch.  You might also check the specs of the
soundcard to see if it is a standard line out or something different like
600 ohm or such.

Mike, W1NR

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of NZ8J
Sent: Sunday, October 09, 2005 1:26 PM
To: icom at mailman.qth.net
Subject: [ICOM] Pro III ALC in SSB-D mode

I have a digital interface connected to ACC (1) and it seems to be working
fine, however on page 54 of the ProIII manual it says:

 "When operating in the SSB data mode adjust the PC output so that the ALC
meter doesn't go outside the ALC zone"

The ALC meter does not seem to function in the SSB-D mode, am I doing
something wrong, or is there a problem with the radio?  I can adjust the
output of the sound card to vary the power output of the radio, but the ALC
meter does not move...

Thanks in advance for any info
73
Tim
NZ8J


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