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Re: [TowerTalk] Cable TV hardline question

 Subject: Re: [TowerTalk] Cable TV hardline question Arthur Moe Fri, 29 Oct 2004 16:15:50 +0000
 ``` David Robbins K1TTT wrote: > > > calculate it so the overall length is a multiple of 1/2 wavelength you > get back whatever impedance is on the other end more or less... but I > have never found that to be really necessary in real situations. If you are calculating you must factor in the velocity factor, some where around .8 to .9 for TV hard line. The best way I have found is to instal the cable from the antenna to the shack then check the VSWR and shorten as needed. As you all know the impedance is repeated every 1/2 wave. So if you have a 50 Ohm load (antenna) the 50 ohms will be repeated every 1/2 wave back down the line. I have seen a almost 1/2 wave of 1/2 inch coiled up feeding an 80 meter vertical but the loss in the extra 100 feet of line is almost nil at 80 meters. Art > > David Robbins K1TTT > e-mail: mailto:k1ttt@arrl.net > web: http://www.k1ttt.net > AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net > > > > -----Original Message----- > > From: towertalk-bounces@contesting.com [mailto:towertalk- > > bounces@contesting.com] On Behalf Of Tim Holmes > > Sent: Friday, October 29, 2004 15:33 > > To: towertalk@contesting.com > > Subject: Re: [TowerTalk] Cable TV hardline question > > > > Yeah, thats what I was worrying about-- If anyone has any good > > suggestions, I would love to hear them, I hate to have this stuff > just > > sitting around, not doing anything. > > > > Tim > > > > >I would be concerned also, since the cable can cause an SWR > > >of over 2:1 at the radio. > > >Most VHF and UHF radios do not tolerate such a high SWR this > > >very well. > > > > > >What you can do is build a transformer using lengths of 50 > > >and 75 ohm cable mixed. It is pretty tricky to do this at > > >UHF, but it can be done if you have the test gear and are > > >careful. I don't have references, but I'd bet someone else > > >does. The devices are called non-synchronous transformers. > > > > > >I certainly look into matching the cable at VHF or UHF, not > > >because of cable loss but because of bandwidth and impedance > > >problems at the radio. A 2:1 SWR is not good for most > > >radios. > > > > > >73 Tom > > > > > > > > > > > _______________________________________________ > > > > See: http://www.mscomputer.com for "Self Supporting Towers", > "Wireless > > Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 > with > > any questions and ask for Sherman, W2FLA. > > > > _______________________________________________ > > TowerTalk mailing list > > TowerTalk@contesting.com > > http://lists.contesting.com/mailman/listinfo/towertalk > > _______________________________________________ > > See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless > Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any > questions and ask for Sherman, W2FLA. > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread [TowerTalk] Cable TV hardline question, SJ W3TX Re: [TowerTalk] Cable TV hardline question, Tower (K8RI) Re: [TowerTalk] Cable TV hardline question, Tim Holmes Re: [TowerTalk] Cable TV hardline question, Marc Wullaert RE: [TowerTalk] Cable TV hardline question, David Robbins K1TTT RE: [TowerTalk] Cable TV hardline question, Pete Smith Re: [TowerTalk] Cable TV hardline question, Tom Rauch Re: [TowerTalk] Cable TV hardline question, Tim Holmes RE: [TowerTalk] Cable TV hardline question, David Robbins K1TTT Re: [TowerTalk] Cable TV hardline question, Arthur Moe <= Re: [TowerTalk] Cable TV hardline question, Tom Rauch Re: [TowerTalk] Cable TV hardline question, jerryc Re: [TowerTalk] Cable TV hardline question, MIKE GREENWAY RE: [TowerTalk] Cable TV hardline question, David Robbins K1TTT Re: [TowerTalk] Cable TV hardline question, Al Williams RE: [TowerTalk] Cable TV hardline question, Keith Dutson Re: [TowerTalk] Cable TV hardline question, Cqtestk4xs RE: [TowerTalk] Cable TV hardline question, David Robbins K1TTT Re: [TowerTalk] Cable TV hardline question, Bob Pack, NX5M RE: [TowerTalk] Cable TV hardline question, Keith Dutson