Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84 exptools; site ihu1h.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!ihnp4!ihu1h!parnass From: parnass@ihu1h.UUCP (Bob Parnass, AJ9S) Newsgroups: net.ham-radio Subject: Re: Scanner Info Needed (using TV antennas w/scanners) Message-ID: <633@ihu1h.UUCP> Date: Sun, 21-Jul-85 01:31:23 EDT Article-I.D.: ihu1h.633 Posted: Sun Jul 21 01:31:23 1985 Date-Received: Mon, 22-Jul-85 07:24:08 EDT References: <11586@brl-tgr.ARPA> Organization: AT&T Bell Laboratories Lines: 90 x > ............ Recient messages about ICOM and > Yaesu FRG-8800 battery backed-up RAM containing REQUIRED operating > parameters have me worried. > ............. Planned obsolescence (or required > maintenance, if the company will be willing to do it into the distant > future) is not a desirable feature in a receiver. BTW, the Kenwood > R-2000 does not have this problem. I wouldn't let the RAM/backup design deter one from buying a new ICOM R71A, as I think most people that buy one new will be swapping it for a later model before the lithium battery runs down. The FRG8800 problem, on the other hand, sounds like one that will affect owners of new and used FRG8800 receivers alike. > Is there any reason that a good quality, 25 element UHF/VHF/FM > television antenna on a rotor wouldn't be as good or better than a > "scanner" antenna? The frequency coverage is about the same, it is > directional, and the antenna feed is low loss 75 ohm coax. I am aware > that impedance matching would be necessary if the scanner input is not > 75 ohms. TV Antennas as Scanner Antennas: Textbook Answer 1. Because the lowest TV channel is around 56 MHz, a TV antenna doesn't excel in the 30 - 40 MHz range. 2. Because most stations one would monitor on a scan- ner use vertically polarized antennas, loss due to cross polarization would be experienced if using a horizontal antenna with a scanner. TV Antennas as Scanner Antennas: Experimenter's Answer 1. If you already have a TV antenna installed, try it on the scanner. Although I think you'll do better with a scanner antenna, my philosophy on receiving antennas is: if you can hear what you want to hear, USE it! I use coat hangers soldered into banana plugs on the back of 3 of my scanners. 2. The difference between using a 75 or 50 ohm antenna systems for a scanner receiving antenna is insigni- ficant. The input impedance at the antenna ter- minals of a multi-band scanner is not a constant 50 ohms over the entire frequency range, and 75 ohms is close enough. 3. Remember that there are situations in which one doesn't want a "good" antenna. I monitor a local fire department frequency shared by dozens of towns, but I'm only interested in my own. For this purpose, I use the built-in telescoping antenna, collapsed down a few sections. The majority of scanner purchasers aren't hobbyists, and are content with the telescoping antenna furnished with the radio. Most hobbyists use the "ground plane" type of antenna with a coil in the vertical element for multiband recep- tion. These antennas are made by Antenna Specialists and Radio Shack, among others. The trap is designed to allow reception on 2 or 3 of the conventional bands. Avanti's 801 scanner antenna looks weird, but it too is designed for reception within discrete frequency ranges. A new trend in monitoring is the availability of continu- ous coverage, wide band receivers. Now that reception of the 72-76, 200-400, and 800-1300 MHz bands is practical, one may consider using a set of antennas, each optimized for a particular band, or a single, broad band antenna. Hustler makes a broad band discone antenna for scanner use that sells for about $30. This brings me to another subject. My Hustler discone wouldn't fit on the porch of my apartment, so I'm buying a multi-acre farmette. I won't keep cows in my barn (aka/inlaw suite), nor grow corn, but rather will plant an antenna crop. Netnews submissions and listening activities will, of necessity, be limited during this busy time. -- =============================================================================== Bob Parnass, Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414