[TowerTalk] finding rf on coax

[Jim Brown]

On Mon,11/7/2016 6:23 PM, David Voit wrote:
> I
> have an end fed wire with a 9:1 balun with about 15 feet of coax to the
> banun and 90 feet of wire with no counterpoise.

No counterpoise is your problem. RF current MUST have a return. If we 
don't provide a good return path, mother nature will find one, like the 
wiring in our home. ANY end fed wire without a counterpoise is only half 
of an antenna. A connection to earth is NOT a return -- the earth is big 
resistor! Indeed, a connection to earth does NOTHING useful for a 
transmit antenna.

However -- security products and systems are notorious for having 
TERRIBLE RF immunity. Virtually any wired security system is likely to 
have problems with RF, regardless of how it is radiated or conducted. 
And yes, problems like this CAN be the result of the antenna itself 
radiating -- that's what it's supposed to do -- but those devices SHOULD 
be built to reject RF.

For some practical ideas about counterpoises, check out the slides for a 
talk I did at Pacificon several years ago and for several ham clubs 
about how to get on 160M from small lots. It's mostly about vertical 
antennas and counterpoises. http://k9yc.com/160MPacificon.pdf

73, Jim K9YC