[TowerTalk] Fwd: 75 or 70 Ohm twinlead or ladderline cable - does it exist?
hanslg at aol.com
Sun Mar 30 17:57:53 EDT 2014
The problem boils down to what dielectric or in this case what insulation you can find for your wires. Teflon insulation is good but expensive. I don't know the characteristics of "regular house" wires. I guess that PVC might not be too good and I have no knowledge of the newer insulators. I wonder if it is possible to make a Ladder Line with small enough distance between the conductors to get 50 - 75 ohms impedance. Somehow I think it is not feasible although air as an insulator will have low losses.
Hans - N2JFS
From: Rick Stealey <rstealey at hotmail.com>
To: towertalk <towertalk at contesting.com>
Sent: Sat, Mar 29, 2014 12:10 pm
Subject: Re: [TowerTalk] 75 or 70 Ohm twinlead or ladderline cable - does it exist?
So it looks like we have an alternative to coax or open wire line to feed a
dipole for example.
If I took, say, #14 stranded, and twisted it, it would be a good match for a
center fed dipole, low loss and not a high SWR so it would present a reasonable
impedance on one band, at the output of a tuner or transmitter.
Sounds good. However, the savings over coax isn't REAL great. $50 for 500 ft
of THHN $14 at Home Depot, means 20 cents a foot for a pair. Maybe the weight
would be less than RG8X.
What about the power handling ability? Would it take maximum legal power (1500
watts in USA, before someone reminds me it's lower in G-land!).
What about using this type of line for a long run to a beam? It is obvioulsy
VERY flexible. Would the feedline radiation/reception be good enough that it
wouldn't upset the yagi pattern?
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