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[aprssig] "Best" packet decoder solution

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Mon Dec 27 16:44:12 UTC 2010


Note that the one that is missing there is the KPC-3+ which, according 
to what I've read, fails miserably if the signal is flat on the air (not 
pre-emphasized) but de-emphasized on the receiving end before being fed 
to the KPC-3.  The KPC-3 apparently doesn't like the low tone being 
louder than the high tone resulting in a lack of decoding.

Some have recommended that the audio interface for the KPC-3 be set up 
so the transmit audio (KPC to radio) goes through the pre-emphasis 
circuit, but the received audio (radio to KPC) be pulled directly from 
the discriminator and before the de-emphasis (meaning, don't pull it 
from the speaker output).  This would mean that "correct" on-the-air 
packets (pre-emphasized, with highs louder than lows) would be decoded 
ok as would non-emphasized (both tones equal) packets.

I have a KPC-3+ here, but I haven't yet hooked it up to anything for 
comparison to the TNCs listed in my previous e-mail.  I haven't made 
time for this because apparently the KPC-3+ also has trouble when 
operated long term in KISS mode which is my preferred TNC interface.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

Greg Clark wrote:
> Thanks, Lynn, exactly the info I was looking for!!!
>
> - Greg




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