There was a good article on using non-synchoronous transformers versus stub
matching on 75 ohm cable TV hardline, and how to build them in the Sept 1978
Ham Radio magazine. I have used a non-synchronous transformer on both ends
of a 200 ft run of scrap cable TV hardline for my 40 M beam for over 20
years and it works well. I used the W2FMI 50/75 torroid transformers that
Amidon and other sells on my multi band antennas since the non-synchronous
is for one band only. 73 Mike K4PI
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "Tim Holmes" <W8TAH@Zoominternet.net>; <TowerTalk@contesting.com>
Sent: Friday, October 29, 2004 1:59 PM
Subject: Re: [TowerTalk] Cable TV hardline question
> > I also came up with some Cable TV hardline. Its 1/2 inch
> (I think) -
> > Jacketed in PVC with an Air Dialectric. I have been
> looking for ways to
> > connect it for my VHF / UHF antennas. Also I am concerned
> about the
> > impedence mismatch.
>
> 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.
>
> _______________________________________________
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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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