[aprssig] 6 meter APRS (message acks)

[Robert Bruninga]

> It's even worse with connected packet 
> or APRS' ... messages. 
> 
> Almost every time, each transmission goes 
> through 4-10 retries, and the ack will go 
> though 3-5 retries...

The biggest problem is client software that did not implement
the full APRS ack protocol which was designed to operate more
efficiently.  These are the original techniques for APRS ACKING
that was left out of most all follow-on user clients:

1) An automatic  back-up ack-retry after 30 seconds
2) REPLY-ACK

The first one doubled the success of acks and also had a benefit
during noise bursts

The second one almost quadrupled success when involved in a
dialog, since an embedded ack for the last line is carried
forward in only 2 bytes of each forward going text line.  First
by eliminating half the acks, and second, by now "pushing" these
acks along with the next message line.

Software that did not implement these techniques are very poor
performers on HF and unreliable channels.

See www.aprs.org/aprs11/replyacks.txt

Bob, Wb4APR