[drats_users] TNC Port Support

[compuvet at aol.com]

Dan:

Having discussed the high speed data path idea with you in Dayton, you 
know I fully support the inclusion of a TNC channel.  I think it is 
great and would open up new possibilities for data transfer beyond the 
slow speed D-STAR data path and the D-STAR DD channel.  We too have 
lots of ARES members with TNCs. You would bring lots of our ARES 
members to D-RATS if you did include a TNC port.

As for AX25 frame support, you might start with unproto frames first 
and avoid all the callsign routing stuff.  You have all the logic built 
in to deal with the ARQ aspects of the channel and don't necessarily 
need callsign routing.

In the long run, I believe there is value in making it AX25 aware.  In 
Missouri we have a state-wide packet net built on TheNet type nodes.  
Routing is not automatic but you can manually build a connection across 
the state by sequentially connecting the nodes that you need to create 
an end to end channel.  Basic AX25 support would allow you to use this 
and other digipeater networks. It doesn't require full AX25.

I personnally want to build an AX25 stack over a high speed digitally 
modulated signal.  Packet radio needs an overhaul with newer digital 
modulation schemes.  I am studying several digital modulations schemes 
for one that is appropriate for my purpose.  D-STAR uses OFDM with GMSK 
carriers.  I read some comments that lead me to believe someone has 
written sound card libraries to encode and decode OFDM/GMSK.  If anyone 
knows who is doing this work, I would love to meet them.

I know all the pieces I need for my project exist.  I just need to 
learn where they are and put them all together.  I have even ordered a 
few GMSK chips to advance my knowledge.  Like everything in life, the 
more I learn, the more options that occur to me from a design 
perspective.  I believe I could build a prototype using the Satoshi 
board and homebrew software.  However, for the frugal hams in the 
hobby, I would like to come up with a less hardware intensive solution. 
  I have successfully tested sound card OFDM/DRM on an FM channel.  Not 
quite the fully digital solution I am looking for but it works.

DE K4LSU, Craig