[aprssig] Kenwood D700 Internal TNC Amazingly Mediocre!

[John Langner WB2OSZ]

The TM-D710 is a great radio, in many ways, but I also found the internal
TNC demodulator performance to be rather disappointing with real world
signals heard on the air.

The document below describes an experiment where a TM-D710 is used to listen
to APRS activity around my home.  We compare the number of packets received
by:
- The internal TNC.
- KPC-3+ connected to D710 speaker out.
- A "soundcard TNC" connected to D710 speaker out.

The internal TNC decoded the lowest number.  You can read about the test
conditions here:

https://github.com/wb2osz/direwolf/raw/master/doc/A-Better-APRS-Packet-Demod
ulator-Part-1-1200-baud.pdf  

Any TNC can decode a good signal.  In the real world we find a lot signals
that are not so good.   Trying to extract something from them can be a real
challenge.  Take a look at some of garbage signals people have been
transmitting:

https://github.com/wb2osz/direwolf/raw/dev/doc/A-Closer-Look-at-the-WA8LMF-T
NC-Test-CD.pdf