[aprssig] Regional Voice Alert VHF/UHF Plan B.

Robert Bruninga bruninga at usna.edu
Wed Dec 5 12:30:44 EST 2007

> > Still pondering..... And... KPC-3+ TNC is 
> > to configure them for this arrangement:
> Forget about the KPC-3.  Think instead what 
> can be done with a real (embedded) PC.  

The advantage of the KPC-3+ is that is has a built-in
speicalized MUTE circuit hardware and firmware designed just for
the purpose of splitting Audio and APRS packets.  It is much
more than a DCD.  It is a special command to the TNC that
acivates this output.  It is normal DCD, but delayed slightly (a
few ms) to give a MUTE output that is an order of magnitude more
reliable at detecting DATA and an order of magnitude less
falsing as opposed to voice and all other possible false

Kantronics added this just for use at voice repeaters to be able
to detect APRS packets on the input of the repeater, and yet
then send a MUTE signal to the voice transmitter to mute the
repeater output if there was a packet.  While not falsely muting
the voice repeater otherwise.

> USB Soundcards are $20.  TNC-X is $50.  We can 
> build a complete dual port "modern" fully functional 
> (programmable) server with packet and full audio for 
> about the same price as a new KPC3.

True.  But many people would prefer just to plug-and-play a
radio and a TNC and have something that works now, rather than
wait for some ideal solution in the future...

I agree.  Both solutions work.  And having fully programmable PC
at the site is ideal as long as someone iw writing the code...

> Bill - WA7NWP
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