Date: Wed, 2 Feb 94 04:30:02 PST From: Advanced Amateur Radio Networking Group Errors-To: TCP-Group-Errors@UCSD.Edu Reply-To: TCP-Group@UCSD.Edu Precedence: Bulk 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??? Send Replies or notes for publication to: . Subscription requests to . Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the TCP-Group Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- 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 ------------------------------ 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 ------------------------------ 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 ------------------------------ End of TCP-Group Digest V94 #30 ******************************