Bob Miller wrote:
**Thanks for your feedback! One of the reasons I am thinking about
thru the roof is for a little stealth, I would only want to put the
antenna's, ( 2 meter and 6 meters beams) about 5 ft above the roof.
They would be mostly hidden when looking at the front of the house from
the street. They are fairly small antenna's, I have them mounted on a
small telescoping mast right now with no problems for the last two
years. Rafters and joists are 2x6 and 2x8's, so I'm sure those are
heavy enough. I would think that between a cone shaped metal flashing
on the mast with rubber or some sort of UV resistant tape to seal it,
and then a rubber vent pipe seal at the roof level and maybe even some
o-rings on the mast inside the roof, plus a pan underneath the rotor
should insure no moisture inside. Of course all this would be grounded
very well! But a roof mount tower would sure be alot easier!
Tim N7XAU

I guess it depends on which one you buy, but are you sure you want a
clanging rotator in the attic? Might be loud.


It's more of a rumbling... but it comes through the bedroom ceiling,
which is not good.

For VHF yagis like the ones Tim is proposing, I had very good results
with a fixed pole and the rotor on top. A non-rotating pole is much
easier to install and make waterproof, and you can buy a ready-made
flashing adapter to take the pipe through the roof. (Back in the 1970s
I had to buy an extra concrete roof tile and drill a hole through it,
and then solder up a little 'stovepipe' flashing adapter from sheet
lead, but even that wasn't so hard.)

Inside the roof, I screwed a triangle of heavy plywood onto the roof
timbers to spread the sideways load, and then drilled the ply for
U-bolts. The pole should be supported as high up as possible, but don't
drill through any structural timbers. At the bottom of the pole, the
weight and sideways load were similarly spread over 3-4 ceiling rafters.
Very little noise comes down through the ceiling when the rotor is
outside.

It worked so well that I became more ambitious and converted the pole
into a guyed tilt-over arrangement, taking the antennas up to 10-15ft
above the roof line, and also making them easier to work on when tilted
over.

When we moved house, the pole was pulled out, and the original roof tile
was put back leaving no evidence.

YRMV (your roof, that is) but this option is well worth considering for
VHF beams.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek