Date: Wed, 2 Feb 94 04:30:02 PST
From: Advanced Amateur Radio Networking Group <tcp-group@ucsd.edu>
Errors-To: TCP-Group-Errors@UCSD.Edu
Reply-To: TCP-Group@UCSD.Edu
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Subject: TCP-Group Digest V94 #30
To: tcp-group-digest
TCP-Group Digest Wed, 2 Feb 94 Volume 94 : Issue 30
Today's Topics:
1200-baud Repeaters (was: 9600 b/s frequencies and repeaters)
9600 b/s frequencies and repeaters (was: 9600b settings)
Altera chip design software???
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Date: Tue, 1 Feb 94 08:25:40 -0800
From: jhays@hays.org (John D. Hays)
Subject: 1200-baud Repeaters (was: 9600 b/s frequencies and repeaters)
To: tcp-group@ucsd.edu
John Ackermann asks:
"1) In a moderately large metro area, does a 1200 baud 2M system get
saturated quickly? We were concerened that we'd get great coverage, but
that the thing would be 100% busy."
In Puget Sound (Seattle, WA area) we have 2 (soon to be 3) 9600-baud UHF
repeaters, which have relatively low utilization. [telnet seanvg.ampr.org or
44.24.108.1 from network 44] We also have a 9600 baud 2 meter repeater again
with low-to-moderate utilization. We also have a 220-Mhz. 1200-baud repeater
with moderate utilization. In vitually all cases traffic moves much more
effeciently due to the removal of the hidden transmitter problem. In a well
disciplined network (i.e. agreed upon values for WAIT timers and PERSISTANCE
variables) 100% utilization should be a goal, not a restriction to
implementation.
One of the projects within our network (WETNET) is to have all repeaters
interconnected either directly (via RF, or in the case of the UHF repeaters
over a Fiber Optic link {many, many miles}) or through as Subnet gateway. Each
of the repeaters is on its own subnet.
"2) Has anyone successfully run both 1200 and 9600 on the same repeater
system? I seem to recall something about this, but can't put my finger on
the details. I hate the idea of investing in a 1200 baud-
only system..."
This has been done. It is not optimal --- I haven't looked at the
relationships, frequency wise, between 9600-baud carriers and 1200-baud
carriers, but it might make sense to have a 9600 baud tone or sync bytes
transmitted when a 1200-baud signal is detected, and the same going the other
direction. I have also thought that such a system should have a "digi-peat"
capability between the two "LANS" ... Personally, I like the idea of one
modulation scheme per frequency (pair).
If 1200 baud-only is distasteful, why not think about 9600 baud-only?
John - KD7UW
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Date: Mon, 31 Jan 1994 23:14:12 -0700
From: bdale@gag.com (Bdale Garbee)
Subject: 9600 b/s frequencies and repeaters (was: 9600b settings)
To: tcp-group@ucsd.edu
In article <2D4D62F3@lawdept.daytonoh.ncr.com> you wrote:
: 1) In a moderately large metro area, does a 1200 baud 2M system get
: saturated quickly? We were concerened that we'd get great coverage, but
: that the thing would be 100% busy.
What's wrong with that? :-)
Seriously, regenerative repeaters at these data rates make a so-significant
improvement in your ability to approach the theoretical throughput of a given
channel due to the massive reduction in collisions, and so forth, that they
are the right thing to do. Picking a data rate and modulation scheme is at
least in my mind more a matter of doing what makes sense given what hardware
the users have, than anything else. I bet that you, like me, have more folks
nearby with 2m radios and 1200 baud modems than anything else. So, build a
repeater if doing them a favor seems worthwhile.
I've built both 1200 baud 2m and 9600 baud 70cm repeaters, and the results
were the same, only the data rate was different. The 2m repeater is down at
the moment getting a new RF deck, the 70cm machine is a Mitrek modified by
WA0ZTI for data and full duplex operation, lashed to a TAPR 9600 baud modem
with the bit-regen and clock options, further lashed to a Gracilis switch.
Couldn't ask for better reliability or performance. I wrote up the 1200 baud
repeater mods for DE-1200 modems and put them in the TAPR PSR a while back, I
have written up the interface between the Gracilis P10 and TAPR 9600 modem, but
haven't submitted it yet.
: 2) Has anyone successfully run both 1200 and 9600 on the same repeater
: system?
Don't do it. The keys to success are good DCD's everywhere, and absolute
fascism about channel access parameters (txdelay, p, slottime in particular).
I don't know how to build a DCD that does 1200 and 9600 both, and further, I
think the variability in time delays by having long slow 1200 baud frames
mixed with short fast 9600 frames is likely to confuse the TCP rtt code under
certain channel conditions. Don't do it.
: I hate the idea of investing in a 1200 baud-only system...
See above. Repeaters are about the cheapest effective throughput improvement
you can buy at low data rates. Build lots of 'em, and don't get too hung up
on the investment. If the usage on the 1200 baud machine drops to nil, rip
out the modem and bit regen and install a TAPR modem, and call it an upgrade!
73 - Bdale, N3EUA
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Date: Tue, 1 Feb 1994 18:47:27 +0000 (GMT)
From: ehall@monmth-c3tmp.army.mil (Erik M. Hall)
Subject: Altera chip design software???
To: tcp-group@ucsd.edu
I read something somewhere today that someone was giving away design
software for one of the Altera EPLDs, and this list is the only place
that I can think of where that might have been. Anyone have any information
on this? I'd love to get a hold of it...
-Erik
--
Erik M. Hall - N2NRP ehall@monmth-c3tmp.army.mil
US Army CECOM (908) 544-4968
AMSEL-RD-ST-WA-N DSN 995-4968
Ft. Monmouth, NJ 07703 "Its all about soul..." -BJ
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End of TCP-Group Digest V94 #30
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