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RE: [TowerTalk] Cable TV hardline question

To: "'Tim Holmes'" <W8TAH@Zoominternet.net>,<towertalk@contesting.com>
Subject: RE: [TowerTalk] Cable TV hardline question
From: "David Robbins K1TTT" <k1ttt@arrl.net>
Date: Fri, 29 Oct 2004 15:43:03 -0000
List-post: <mailto:towertalk@contesting.com>
I use it on 6m,2m and 70cm with a ts-2000 and a couple tm-261's for 2m
packet and none of them complain.  Plug it in and try it, if it isn't
good enough match for your radio add a short length of 75 ohm to the
transceiver end, this will transform the impedance some more, if you
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.


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
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_______________________________________________

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.

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