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ZL3AI > APRDIG 11.10.03 19:35l 68 Lines 2497 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Oct 09, 6/6
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Tweak your TNC
From: Wes Johnston <wes@johnston.net>
Date: Thu, 09 Oct 2003 21:00:33 -0400
X-Message-Number: 48
Just for fun tonight, I decide to tweak TXDelay on my HT-252 radio
shack/kpc3 rig.
The default was set to 350ms by kantronics, mine _was_ 250ms because I
figured that was a safe number. Tonight I played "lets see how low we can
go" and simply kept lowering my txd until I noticed the digi wasn't hearing
me _reliably_. I noticed that my 100% sucess rate stayed until TXD was
at or below 70ms. The local digi would copy me 20% of the time with
txdelay as low as 50ms. I have since set my TXD to 80ms (TXDELAY 8 in
kantronics-speak).
Consider this:
350mS - 70mS = 280mS -> = 33.6 characters at 1200 baud.
Since the average packet is 88 characters long, we could have a reduction
of over 40% in the length of our "on air time" if we just take 5 minutes to
tweak TXD.
Procedure:
1)in terminal mode, change your UNPROTO path to just the callsign of the
local digi. U test v kd4pup
2)type TXD <cr> to see what txd is presently set to.
3)type TXD 12 <cr> to set TXD to 120ms
4)type K for converse mode and press return a few times. Note that the
digipeater is or isn't digipeating you.
5)lower TXD 10mS and repeat step 4.
As you decrease TXD you will begin to notice success rates of less than
100% (don't forget that the digi could be hearing another station instead
of you if you don't get digipeated sometimes). Just to be on the safe side
add 20mS to the length. When finished set your UNPROTO back to what it was.
I know there are those of you who want to say that you can't set TXdelay
that low because it will not allow other people's radios time to open the
squelch. My answer to that is: Most TNCs today have true DCD, so those
people should run open squelch, 2)As long as the digi hears me, it will
re-tx my packet and apply a (perhaps longer) txd to appease the yoacals
running squelch.
Thanks to Roger Barker for mentioning this in the UI-View sig.
Wes
----------------------------------------------------------------------
Subject: Re: Tweak your TNC
From: "Ev Tupis (W2EV)" <w2ev@arrl.net>
Date: Thu, 09 Oct 2003 22:48:54 -0400
X-Message-Number: 49
Nice post, Wes.
If enough people did this and posted their results, along with their
transceiver make and model, we could have a chart that everyone could use
to actually find extra channel "bandwidth".
Ev
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