Linux-Hams archive - July 1997: Re: KISSPARMS - ??? Help with a simple Txdelay question

Re: KISSPARMS - ??? Help with a simple Txdelay question

Woolner, John (nxnsh.uibgcpbni@fastlane.pl)
Wed, 9 Jul 1997 15:18:00 +1000

->Alan K. Adamson wrote:
->>
->> I was reading the man file for kissparms and tried to do as
->it said. I believe is said that the txdelay was to be set in
->ms. I have a TNC that I know can do 20ms, so I did a -t 20...
->This didn't work. So, I tried up through the ranges. I went
->to -t 150 and the delay was longer, but still no connects. So
->I thought, well, maybe the factor was off by 10X Well, you
->guessed it, I did a -t 200 and everything started working.
->What did I do wrong or read wrong....It looks like the txdelay
->param i
->
->You tnc might be able to do 20mS but I'd consider that pretty quick
for a
->half duplex radio link.
->
Alan,

This is a common misunderstanding on how to set txdelay. Txdelay needs
to be the SUM of the following times.

1. Time for your radio to key-up and emit a stable signal on frequency
2. Time for the receiving radio to receive, unsquelch/freq lock and emit
stable audio.
3. Time for the receiving MODEM/TNC to detect, generate a stable
demodulation
clock and demod the data.

That is the total time from when you commence to key-up and send flag
characters (or whatever) until the TNC at the far end is receiving valid
flag characters.

Further, this needs to be set for the slowest receiver in your area.
With a pair of crystal locked radios running open squelch you may be
able to do better than 60ms txdelay (I usually add 50% or 50ms whichever
is smaller than the best (of the slowest user) txdelay I have been able
to establish reliable contact with. Relates to about 100ms for a simplex
multiuser net where all are crystal radios (some stations will work with
40-50ms) upto 200-300ms for the 1200bd net where there are a lot of
synthesised rigs.

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John Woolner Email: fpeshndd.kwih@innovationplace.com
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Phone +61-6-254-3140 (h) Snail: PO Box 118
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AUSTRALIA
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