With the excel work file you can input the operating frequency and velocity
factor.
Not sure one of my posts went to the reflector so I will try this again.
But first, I do have 75 ohm hardline running to my 10m tower as well as my
15m tower. No transformers were used. I just cut them until I got the 50
ohm mirror for every 1/2 wavelength.
I first tried the coaxial tranny on my new 20m antenna system and it
works. Seemed to be much easier than having to keep adding or subtracting
the hardline length.
At 14.200 using RG11 and RG213 to make the tranny the length necessary for
each piece was 44.7 inches.
SHACK- RG11 (44.7") TO RG213 (44.7") TO CATV HARDLINE TO RG213 (44.7") TO
RG11 (44.7") TO 50 OHM COAX TO THE ANTENNA.
Several asked me for the file. I will try to send it in the next couple of
days. If I miss anyone please email me again directly.
Thanks.
Bob NX5M
On Fri, 29 Oct 2004 12:42:31 -0500, "Keith Dutson" <kjdutson@earthlink.net>
wrote :
> 1/12 wave at what frequency?
>
> Keith NM5G
>
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Bob Pack, NX5M
> Sent: Friday, October 29, 2004 11:08 AM
> To: Tim Holmes; towertalk@contesting.com
> Subject: Re: [TowerTalk] Cable TV hardline question
>
> Build 1/12th wave coaxial transformers on each end. Easily done if you
are
> not happy with the swr. My last install for a 20m stack was almost 300
feet
> of the 3/4" catv with trannys on each end. Tested into a dummy load I
could
> find no swr to speak of.....and the swr after all the antennas were up in
my
> worst case combination is no higher than 1.3:1. I might add that I am
also
> using 1/2" catv from the phasing/switchbox to the tail of RG213 connected
to
> the antennas.
>
> GL
> Bob NX5M
>
> On Fri, 29 Oct 2004 11:33:28 -0400, Tim Holmes <W8TAH@Zoominternet.net>
> wrote :
>
> > 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
>
>
>
>
_______________________________________________
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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