From: utzoo!decvax!harpo!npois!ucbvax!telecom Newsgroups: fa.telecom Title: TELECOM Digest V2 #61 Article-I.D.: ucbvax.7199 Posted: Fri May 14 16:48:18 1982 Received: Sat May 15 04:19:24 1982 >From JSOL@USC-ECLB Fri May 14 16:33:21 1982 TELECOM AM Digest Saturday, 15 May 1982 Volume 2 : Issue 61 Today's Topics: Product Report - VADIC 3451 INWATS Prefix Assignments Query - When Did N1X And N0X Start In LA? Mobile Radio Through ATS-3 Area Code & Prefix Assignment Listing - V&H Coordinate Tape ---------------------------------------------------------------------- Date: 13 May 1982 18:23:57-PDT From: decvax!minow at Berkeley Re: Vadic 3451 I have one and it seems fine. If you're going to use it at home, make sure it has the three-position "manual/voice/data" switch, so it doesn't answer your phone for you. One annoyance: it seems to generate some interference with one of the local FM stationns (at 90.9 mhz). Sounds something like a subcarrier whistling in the background. Any suggestions for fixes would be welcome. Martin Minow decvax!minow ------------------------------ Date: 13 May 82 21:34:06-EDT (Thu) From: J C PistrittoRe: Vadic 345x series modems: I have had personal experience with around 10 of the new 3451 models (the ones with the voice/data switch up front with the other two switches) Every one worked right out of the gate, and 8 of them are used daily for cross country (Baltimore Md to San Francisco, and Houston TX), with absolutely no failures. These things are carried around in peoples brief cases, luggage, etc regularly also. All were obtained within the last 6 months, thru a distributer near Washington DC. -JCP- ------------------------------ Date: 14 May 82 12:54:25-EDT (Fri) From: Carl Moore (VLD/VMB) cc: cmoore at BRL Subject: "800" prefixes Interstate "800" prefixes (those not ending in 2) are assigned by area code (as far as I can tell), as are the intrastate ones (those ending in 2). For example, 221 would be NYC from outside NY state. (This is as it is now, before the changes I have seen mentioned earlier.) I do not know how restrictions (other than state-line mentioned above) are imposed on availability of "800" prefixes via numbering system. ------------------------------ Date: 14 May 82 12:56:51-EDT (Fri) From: Carl Moore (VLD/VMB) cc: cmoore at BRL Subject: N0X and N1X in L.A. area (213) I have list of 213-area prefixes clipped out of a 1976 directory and such list does include a few "area-code" prefixes. Someone said such prefixes were put in starting in 1978(?). ------------------------------ Date: 14 May 1982 12:40:40-PDT From: eagle!karn at Berkeley Subject: Mobile radio through ATS-3 ATS-3 is indeed a geostationary satellite. There was an article on ATS-1 and -3 about a year ago in 73 magazine, which suggested that hams might apply to NASA for permission to use channels during off hours. There is a demo at the Goddard Space Flight Center Visitors Center using one of these satellites to demonstrate round-trip propagation delay. They use two 10-element yagi arrays, although I don't know how much transmitter power is used. In response to 20 watts being sufficient from a mobile whip, here's the equation for isotropic antennas: Path Loss (db) ~= 23 + 20*log(d/l) where log is base-10 d = distance l = RF wavelength, same units as distance At two meters, the path loss to geostationary orbit (distance ~=40,000KM) at 2 meters is 169db. I assumed that the satellite and ground whip antenna have unity gain. 20 watts from the ground would arrive at -156dbW in the satellite receiver's front end. If it has a 50-ohm impedance, this corresponds to .11 microvolts. Lots of narrow-band FM receivers quiet reasonably well on .11 microvolts, but the link probably would be marginal. Older satellites were not noted for particularly good receiver front ends. Orienting the whip probably helped things. Speaking of power requirements for satellites, it is quite feasable to 'hit' Amsat-Oscar-8 (a low polar orbiting 2m -> 70cm amateur repeater satellite) with an audible signal using a standard 1 watt walkie talkie and its built-in rubber antenna. It is also very easy to hear the 300 milliwatt 2 meter FM beacon on Uosat-Oscar-9 with the same walkie talkie. Its amazing what you can do with low power when you don't have the earth in your way! Phil Karn, KA9Q Bell Labs, Murray Hill, NJ ------------------------------ Date: 14 May 1982 1431-PDT (Friday) From: lauren at UCLA-Security (Lauren Weinstein) Subject: V&H coordinate tape I have gotten several requests for information about obtaining the area/code prefix information tape I mentioned recently. The person to contact is: Pat Jennings AT&T Long Lines (816) 391-5708 Ask about the "V&H Coordinate Tape". The current price is about $50. --Lauren-- ------------------------------ End of TELECOM Digest ********************** -------