[TowerTalk] Cable TV hardline question

[Bob Pack, NX5M]

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 at earthlink.net> 
wrote :

> 1/12 wave at what frequency?
> 
> Keith NM5G
> 
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Bob Pack, NX5M
> Sent: Friday, October 29, 2004 11:08 AM
> To: Tim Holmes; towertalk at 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 at 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.
> > 
> > _______________________________________________
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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.
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at 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 at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> 
> 
> 
>