|Subject:||Re: [TowerTalk] loooong feedlines|
|From:||Jim Lux <firstname.lastname@example.org>|
|Date:||Mon, 03 May 2004 11:27:37 -0700|
At 10:11 AM 5/3/2004 -0700, Rick Karlquist wrote:
He used 4 wires to get a lower Zo, because he didn't want to deal with 450 ohms. Now that the 450 ohm problem has well established solutions, I can't see where 4 wires is worth the trouble.
I think that if you had a situation where you had to run the feedline very(!) close to something (that is, a distance comparable to the spacing of the wires), the 4 wire balanced line has a more "contained" field. The ultimate would be a braided cable with lots of conductors carefully balanced in position relative to all the other conductors, etc. I was looking into this when developing extremely low inductance, low loss, low electromagnetic force cables for pulsed discharges that needed to run inside a metal raceway.
Quadro-line has also been featured in one of the ARRL antenna compendiums.
As Rick says, though, I doubt that for any amateur radio kind of installation it would be worth it.
Also, it's hard enough to make a high performance balun. Trying to make a truly balanced transition for quadroline would be quite the challenge.
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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