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[OZAPRS] RE: [aprssig] TNC Trace mode

John Langtry, VE3NEC ve3nec at sympatico.ca
Sat Sep 4 02:51:54 UTC 2004


Quite right, Darryl

<G> But it's 7 bytes, not bits for the call sign.

If you want to get right down to the "bit level" of AX.25
what goes out on the air, is not just shifted "ASCII", it's
NRZI code. I'll let you all research that one ! :)

Back in our original days, our processor was an 8085 (8 bits)
running with a one meg clock. (Hey, we're talking 1979 here !)

We first tried using "assigned" addresses (one byte) like the
SDLC model in our Vancouver boards. So now our frames where
short and sweet, the "from" byte to the "to" byte; meaning that
there would be a maximum of 254 "packeteers" ... which all had
to be assigned by a local co-ordinator. Back then, we had no
concept of a real "digipeater", nor a network; So with only 6 ~ 7
of us on in S. Ontario and a couple in N.W. New York state, this
was not a huge challange to assign station ID bytes.

But it worked rather well actually, and as I re-call, it was John
VE3DVV working with Doug VE7APU, that actually worked out a way to
boost our range, with a "store and forward" machine, today called
a "digipeater". They did the software end, while Dave VE3FGK and I
did the hardware end of this project.

I have attached a picture of me, a 20 year old new Amateur, standing
beside what we think was the World's first "digipeater". (Members of
the list won't see this, as I think pictures are cut off.) Time marches
on, and I'm now 54, and we use AX.25 Rev 2 code, but time is a crewel
thing. Back then, I acutally had colour in my "fur" - today, most of
the "fur" is gone (orders of the Kitchen manager), and what remains
is more silver, than brown.  :(

vy 73 to all
John VE3NEC
905-873-8715
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