KJ4NTS wrote:
On 6-Aug-2009, Michael Coslo wrote:

I'd say with this setup, you could do DXCC. DXCC and other awards have
been achieved on more modest setups than what you are looking at
building. You won't be the loudest signal on the band, but there can
only be one of those anyhow.

How much attenuation is a wood roof with asphalt shingles going to introduce? All of the duct work
in my house is in the crawl space, and the phone and cable TV lines are also in the crawl space. So
there is no metal other than the roofing nails, and there's nothing between the antenna and the sky
other than the roof decking and shingles. I don't expect them to add a lot of attenuation, but I
could be wrong.


Attenuation isn't a real concern, except when it's raining or the roof
is wet.

What should be a concern is the following:


1) weird interactions between antenna and conductive stuff in the attic.
Don't expect the same feedpoint impedance vs frequency you get with
the antenna out in the open.

2) Fi The voltage gets pretty high at the ends of a dipole when
you're radiating even 100W. Or, more to the point, the voltage gets
high in nearby wires that happen to be the "wrong" length. A small
ember smoldering in your attic is a huge problem. This is something you
need to figure out how to check.. keeping the active ends of the dipole
clear of flammable stuff is straightforward, but the accidental
excitation of something else, isn't. (wiring isn't a problem.. it's
usually connected to something else that shunts the current.. it's
isolated conductors, like plumbing, HVAC ducts, etc. In your situation,
yours is in the crawl space, so you're in good shape.)

3) RF exposure. Do your calculations and make sure you're not cooking
things you shouldn't be.