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[aprssig] Mic muting

Ray McKnight shortsheep at worldnet.att.net
Mon Dec 18 01:46:43 UTC 2006

The Kenwood TM-V7A, once a top end radio(about 7 yrs ago)
*does* have the data connector, but also does NOT mute
the mic audio line when the TNC keys the radio.  Very
frustrating and a stupid design flaw.  The radio also has
a hot "audio in", as one side of the receiver will listen
to the PLL tones on the 2nd side and cause the radio to
do all sorts of unpredictable things, like change freq,
etc.  For such an expensive radio, it seems little thought
was put into these things.  I won't be buying another
Kenwood in this lifetime.

-----Original Message-----
From: aprssig-bounces at lists.tapr.org [mailto:aprssig-bounces at lists.tapr.org]
On Behalf Of Scott Miller
Sent: Sunday, December 17, 2006 13:20
To: 'TAPR APRS Mailing List'
Subject: [aprssig] Mic muting

I very rarely work with mic encoder mode, and I just wired up a TM-271A for
some testing yesterday.  It worked fine, but I noticed that the mic audio
isn't muted when the PTT is released.  If there's too much background noise
it mangles the packet data.

I haven't seen any tracker circuits with a provision to handle mic muting,
but I don't have a TAPR Mic-E schematic available either.  Was it able to
mute the mic?  Or is it not a problem with most radios?  Most of my testing
in the past has been with radios like the Kenwood TK-90, where there's a
separate accessory connector and the mic is muted when the auxiliary PTT is


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