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[TowerTalk] Re: Twin Runs of CATV Coax

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Subject: [TowerTalk] Re: Twin Runs of CATV Coax
From: aa6eg@hh.tmx.com (Pat Barthelow)
Date: Wed, 3 Feb 1999 17:34:31 -0800 (PST)
Interesting post, ron,

Do you know what the loss is of the balanced line made from two CATV
coax's?  We have plenty of 75 ohm hard line at N6IJ,  and I am interested
in knowing if we stand to gain anything (so to speak by using the
technique you described...

73, DX, de Pat, AA6EG/N6IJ; 

aa6eg@hh.tmx.com

599 DX Drive, Marina CA 93933
"The Contest Station from the Government"

On Wed, 3 Feb 1999, Ron Gang wrote:

> >To: Zdzislaw R Sawicki <ab2et@juno.com>
> >From: Ron Gang <gang@urim.org.il>
> >Subject: Re: [Antennas] 160 Meter Loop Feeding
> >
> >Hi Steve:
> >
> >If you have enough of that CATV hardline, let me suggest feeding the loop
> with TWO of these coaxes in parallel.  Two coaxial cables of equal length
> and characteristics may be used as a balanced feeder.  The shields of the
> cables are connected at both ends, with the inner conductors being the
> feedline, each one connected to a different side of the centre insulator of
> the antenna.  At the antenna end the shields are connected to themselves,
> and at the shack end, the shields are grounded and the inner conductors go
> to the balanced terminals of your antenna tuner.  Impedance of the line is
> twice the nominal impedance of the individual coaxes.
> >
> >Advantages over open wire feeders:
> >1.  Not affected by rain, snow or ice in terms of impedance changes.
> >2.  None of the pickup of QRN/M that open wire has, and possibly less stray
> radiation (my own experience when changing over from less than perfect open
> wire.)
> >3. Coaxes do not need to be spaced at a permanent distance, only need be
> the same length.
> >
> >If you want to use open wire from the loop in the air to the point you go
> underground, fabricate the open feeders to be the same impedance as your
> balanced coaxial feed to avoid any impedance bumps and undesirable impedance
> transformations.  The Handbook gives a formula some place for what impedance
> open wire has depending on wire diameter and distance between wires.
> >
> >Hope that this may help you.
> >
> >73,
> >
> >Ron 4X1MK
> >
> >At 21:57 02/02/99 -0500, you wrote:
> >>After many years of "proving" that Ham Antennas do not instantly mean
> >>"electronic problems" I was Abel to get the surrounding neighbors to
> >>acquiesce to the installation  of a full wave 160 Meter loop, it will be
> >>installed at about 45 feet   (its the best one can get).
> >>
> >>The first problem is that the shack is located about 110 feet from the
> >>closest spot that the loop feed can come to ground level, to complicate
> >>the issue I have to bury the feed line ( so no 450 ohm line), no problem
> >>with this issue as a solution I got about 160 feet of prime CATV hardline
> >>(free)  trenched it in over the warm periods  this winter and made simple
> >>(plumbing) N terminating adapters, nice and tight and so far waterproof.
> >>
> >>I have started to assemble the loop using "quietflex" wire (nice stuff)
> >>the second problem that comes to the surface is in order to keep the
> >>visual impact down to the smallest  profile I agreed to feed the loop
> >>with about 45 feet of (a) open wire line or (b) 450 ohm  commercial
> >>ladder.
> >>
> >>The Question is, what is the best (ideal) "balum"  and ratio to use to
> >>connect the hardline to the balanced feeder at this point it looks like I
> >>will use the 450 ohm line .
> >>
> >>Yes I will be using a "tuner" in the shack to get multiband usage from
> >>this antenna.
> >>
> >>Thanks and 73's
> >>
> >>Steve 
> >>  
> >>  oo       
> >> (__)         AB2ET
> >>"I bet two extra terrestrials"
> >>
> >>___________________________________________________________________
> >>You don't need to buy Internet access to use free Internet e-mail.
> >>Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
> >>or call Juno at (800) 654-JUNO [654-5866]
> >>
> >>------
> >>Submissions: antennas@qth.net
> >>
> 
> 
> ------
> Submissions: antennas@qth.net
> 


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