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Author Topic: Balanced feed-line running along concrete roof tiles  (Read 1301 times)
KG6SII
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« on: October 03, 2012, 04:08:06 PM »

I have about a 10ft section of 300Ohm twin-lead laying on my concrete roof tiles, from a vent to the center of my dipole.  Do I need to insulate the twin-lead from the concrete roof?

Thanks,
Glenn KG6SII
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W5DXP
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« Reply #1 on: October 04, 2012, 06:08:21 AM »

Do I need to insulate the twin-lead from the concrete roof?

A possible clue would be to measure the impedance (or SWR) under dry and wet conditions. Ordinary concrete absorbs water which could have a large effect on twinlead.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W8JI
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« Reply #2 on: October 04, 2012, 06:49:42 AM »

I have about a 10ft section of 300Ohm twin-lead laying on my concrete roof tiles, from a vent to the center of my dipole.  Do I need to insulate the twin-lead from the concrete roof?

Thanks,
Glenn KG6SII

It is never a good idea to lay an unshielded  balanced line on anything. It should always be ***spaced *** several line widths away from other things, including roofs or dirt.

Insulation does not help, air spacing does.
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WB4SPT
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« Reply #3 on: October 14, 2012, 05:56:30 PM »

I don't think "dry" cement tile will affect your signal much.  But, I will say the tile will be abrasive and tear up your PE insulation.
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KA7NIQ
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« Reply #4 on: October 21, 2012, 08:03:01 AM »

I have about a 10ft section of 300Ohm twin-lead laying on my concrete roof tiles, from a vent to the center of my dipole.  Do I need to insulate the twin-lead from the concrete roof?

Thanks,
Glenn KG6SII
Well, I own a tile roof cleaning company here in the Tampa area www.saferoofcleaning.com and see moisture up there quite a lot.
The tiles on a roof can and do get wet, and retain water, from both the rain and humidity here in Florida.
I think the water might effect the twin lead, but you will have to measure to be sure.

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