[TowerTalk] Re: Twin Runs of CATV Coax

[Pat Barthelow]

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
> 


--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm