"Thierry" Answer direct via http://www.astrosurf.com/lombry/post.htm wrote
Hi,

A question about the installtion of a short beam on a roof/chimney.

My house is built on top of Meuse valley, 250m high, surrounded with open
field (and much wind, hi).

The roof top is at about 6m high. There is a small chimney 2m high. This
part of the house contain only the garage and in front (garden side), the
small boiler.
Here is the picture,
http://www.astrosurf.com/lombry/Radi...fil15m-eo3.jpg

I want to work mainly on bands of 20, 17 and 15m (and much less on 12 and
10, say 10% of time). So the antenna 'd be placed at 10m high and i can
reach this height : I could place a small mast 3m high on the chimney
attached with simple aluminium straps and screws, so the antenna will be
at
about 10m high. I hope it will be away from any interference with the
boiler
ignition system.

Question:
Is it important to place the beam much higher than the chimney (say at
worst
10m higher that any building) or the main problem is the height over the
ground of the house (I suspect the second) ?

At last, any experience with a TGM MQ 36SR at various heights is welcome
(I
read the eham reviews but there is not much accurate opinion in this
regard,
excepting that everybody does not share its good performances...)

PS. My alternative should be to place the antenna 5 m high over ground at
the end of the garden (60m away), simply attached to the supporting wood
wall of a small cottage ... :-(

73
Thierry
ON4SKY, LX3SKY
http://www.astrosurf.com/lombry


Thierry (http://astrosurf.com/lombry/post.htm):

in your proposed chimney-mounted antenna.

Be advised that carbon build-up from furnace, boiler, or fireplace operation
is extremely conductive and can soon form a static connection between an
antenna and the chimney-flue opening, and across various elements of the
antenna also. This is to be avoided. One poster's advice to keep the antenna
mount "upwind" was well said. Avoiding a chimney mount (on a
working/operating flue) unless other options are not available is even
better.

Best regards,

Jack Painter
Virginia Beach, VA

also posted to rec.radio.amateur.antenna