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Author Topic: 450 Ohm Twin Lead and Aluminum Siding  (Read 908 times)
KO1D
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Posts: 384




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« on: July 01, 2009, 10:45:25 AM »

I am looking at houses with the YL and moving soon. Many of the houses we are looking at have aluminum siding, something I have not had to really deal with while a ham.

If I run a wire antenna up and the 450 ohm twinlead requires me to have the feedline run along the aluminum siding, what, if any, interaction might there be.

There are 3 antenna types I am considering for HF: loop, G5RV (small lot) or some kind of doublet depending on how lucky I get with trees.

Thanks!
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W3LK
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Posts: 5644




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« Reply #1 on: July 01, 2009, 11:40:17 AM »

Keep the ladder line about 12-15" away from the siding and put a twist every 8-10 feet in the feedline.

How do you plan to bring the feed line into the house?

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
KO1D
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Posts: 384




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« Reply #2 on: July 01, 2009, 11:47:24 AM »

TBD. One house we are looking at I might drop it into the vent on the side of the house nearest the peak. Then bring it down the walls to the basement as I think that is where I will wind up. Short term solution may be bringing it a window and stuffing the window to prevent drafts.

Thing is that a G5RV twinlead is a 10m section I believe. Also not sure if the twinlead radiates for the doublet.
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WX7G
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« Reply #3 on: July 10, 2009, 08:16:38 AM »

The ladder line can be spaced a distance from the aluminum equal to the ladder line wire-to-wire spacing. Even this close spacing to the aluminum just begins to reduce the ladder line characteristic impedance.

If you are feeding the G5RV via a tuner the length of the ladder line and/or coax does not matter.
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AA4PB
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« Reply #4 on: July 10, 2009, 10:25:41 AM »

The main issue with ladder line in the vicinity of aluminum siding is keeping it from moving in the wind and changing the spacing. As the spacing changes, you'll likely find the SWR on the transmitter side of the tuner going up and down. As long as the spacing is not real close you probably won't have any problem with unbalance causing the line to radiate.
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K9FON
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Posts: 1012




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« Reply #5 on: July 17, 2009, 08:22:07 PM »

Make sure the vent is not aluminum. If it is, id get a plastic vent to replace the aluminum vent.
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