Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site crystal.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!teddy!panda!talcott!harvard!seismo!uwvax!crystal!bill From: bill@crystal.UUCP Newsgroups: net.video Subject: Re: Video connecting Cables Message-ID: <391@crystal.UUCP> Date: Thu, 10-Jan-85 16:49:14 EST Article-I.D.: crystal.391 Posted: Thu Jan 10 16:49:14 1985 Date-Received: Sun, 13-Jan-85 06:47:06 EST References: <117@lcuxc.UUCP> <1466@ritcv.UUCP> <897@amdahl.UUCP> Organization: U of Wisconsin CS Dept Lines: 47 > > I then replaced my rather nice-looking 75ohm cable (I got it with my VCR; it > > has quick-disconnect F-connectors) with another shoddy-looking one that my > > cable company had given me, and voila', the problem disappeared!! > > Definately, beware of any of the "flexible" 75 ohm cables that you > get with your vcr/disk. The shielding and the dielectric thickness are > marginal at best. Hear, Hear! The patch cables my cable company provided were all 100% shield (braid and foil shield), which I've found difficult to locate locally in short lengths -- 500 feet is a little much. The Radio Shlock ones don't have a shield spec, but they look to be lower density than the 95% ones I've seen, maybe 80% or so. Belden# type center velocity shield cap./foot 9100 59/U 20gage 78% 100% 17.3pF (1) 8241 59/U 22gage 66% 95% 21.0pF (2) RShack 59/U 22gage 75% ??? 15.5pF (3) (1) is what my cable company uses; (2) is the only belden RG59/U coax available in < 500 foot spools; (3) is Radio Shack's coax. The Belden 9100 has about the same loss as RS at 50MHz, improving to 2.2dB better than RS at 900MHz. Anyway, many of my reception problems were eliminated by throwing away the cheap premade cables and replacing with 100% shielded ones. The quality of the screw-type F connectors was probably also a factor. > I think every cable company that I have ever dealt > with has re-broadcast local channels on the same cable channel. You mean my cable system is doing something right!? The only conflicting local station is ch3, and they run a 24hour weather service on cable 3. > Shoddy cables will pick up both the cable-tv signal and the regular > broadcast signal, producing the above mentioned ghosts. > Even an inch or so of twin-lead (300 ohm) cable can act as an antenna for pickup of unwanted interference. check leads on any adapters you might have. -- William Cox Computer Sciences Department University of Wisconsin, Madison WI bill@uwisc ...{ihnp4,seismo,allegra}!uwvax!bill