[aprssig] Kenwood TM-271A and KPC 3+

Richard Sharp, KQ4KX kq4kx at arrl.net
Thu Jan 31 20:34:58 EST 2008

One minor note regarding using the internal packet connections.  When
connecting the receive audio wire there are two choices.  One is a dedicated
"1200 baud only" line (PR1) the other is a common "9600 or 1200 baud"
receive line (PR9).  The issue I've found when using the PR1 pin is that if
the volume knob is turned all the way counter clockwise (lowest volume) it
mutes the fixed level audio on the PR1 pin.  The PR9 pin does not exhibit
this behavior.

What's nice about using the internal connections is you can make ALL
connections needed for your TNC which makes for a "clean" setup.  Also, you
can easily monitor the receive audio by simply turning up the volume knob
without disconnecting anything -and- not worry about making your TNC "deaf"
if you inadvertently turn the knob all the way down (provided you use PR9 as
your receive audio to the TNC).

Another note - the 'PKS' pin is the PTT line.  They explain this but not in
exact terms in the manual (page 7).

If using a KPC3+ with a Kenwood TM-271A connected to the internal "packet"
connections set the KPC3+ 'XMITLVL' for a value of 75.  This will yield the
proper 3 kHz deviation.  If you have a service monitor you may find minor
differences where the XMITLVL may be slightly higher or lower but 75 should
be very "close enough" for most setups.  I've configured several of these
and use the same value and found no difference in deviation between the
different setups.  If you use the RJ45 mic jack for transmit audio the
XMITLVL should be around 35 (due to additional mic preamp) for 3 kHz


-----Original Message-----
From: Doug Ferrell, KD4MOJ

	You can actually wire this inside the radio. Check out Scott's site
at the
bottom of the page: http://www.n1vg.net/


-----Original Message-----
From: Bob Birkner

Anybody  have a diagram for building a cable to connect a Kenwood TM-271A 
and a Kantronics KPC-3+?
I have the receive connection wired, the easy part, but can't get the MIC 
and PTT grounds from the RJ-45 connected properly.
Bob  N7AIR 

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