Re: TNC Quirks

David Ranch

Hello Joshua,

1. I establish a connection from the Kenwood (KJ7LVZ-9) to the handheld (KJ7LVZ-2) which is connected to a Raspberry Pi running linBPQ and Simple KISS.  But when I try and connect to KJ7LVZ-9 from KJ7LVZ-2, I get no response.  The Kenwood never transmits; never responds to the connect request.  CONOK is set to ON on both TNCs.  Can't figure that one out.

Your first sentence isn't complete so I cannot tell if you ARE able to create a connection or not but I'm assuming KJ7LVZ-9 (D710 TNC) to KJ7LVZ-2 (BPQ32) works.  It's the reverse path that isn't responding.  Do you have CONOK enabled on the receiving D710 TNC?

   Here is a cheat-sheet that might help

2. When I am trying to write a message on the Kenwood using the W command, it's all fine and dandy until I want to exit the body using (return), (CTRL+C), (return).  All I get is new lines, the message never finishes.  The only way for me to exit the message is to restart the TNC. 

When you start the message, the TNC prompts you with:

   You terminate with either a <cr>/EX<cr> or <cr><ctrl-Z><cr>

I recommend to use "/ex" as that seems to be the common standard

3. What's the importance of PACLEN?  The TNC on the handheld defaults to 236 even though I have the config file set to 128 and the Kenwood defaults to 128.  They connect fine with different PACLENs.  I can set them the same and everything is still kosher.

PACLEN is the AX.25 payload MTU and the bigger it is, the faster your throughput *could* be assuming you have perfect RF conditions.  If you have poorer RF conditions, you might consider using something smaller like 128 bytes as well as use a smaller packet window (aka "MAXFRAME").   Generally speaking, these are some of the common settings:

   - Excellent RF conditions for UHF/VHF AX.25 - PACLEN: 255
   - Excellent RF conditions for UHF/VHF AX.25 over NETROM - PACLEN: 236

   - Decent RF conditions for UHF/VHF AX.25 - PACLEN: 128
   - Decent RF conditions for HF AX.25 - PACLEN: 64

   - Poor RF conditions for any packet: forget about it - the retries will kill any effective communications

Btw, I have another cheat sheet that takes new Packet users through the using connected and unconnected packet operations here:

PPs.  You can find ALL TNC commands in the "TNC COMMANDS LIST" section (PDF page 36) of Kenwood D710 instruction manual -


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