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tony sayer tony sayer is offline
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Default Radio Antenna On Chimney ?

In article ,
the_constructor scribeth thus

"dave" wrote in message
...
On 17/07/2010 22:45, the_constructor wrote:
Being a white stick radio operator, I have to find someone to put the
antenna up on the chimney stack for me, but before I do, I need some
advice
please.

Obviously, a small pole needs to be attached to the chimney stack so that
the antenna which is a glass fibre aerial weighing 0.9Kg can be fitted
just
above the stack itself. Neither I nor my neighbour have chimney pots.

I would estimate that the pole would be overall about 3 feet long and
then
the antenna fitted at the top of the pole to clear the stack.


At this point, I have to ask is the antenna for V/UHF, or HF use? If the
latter, I would advise a double lashing kit.

Should I use 1 or 2 lashing kits to hold the pole. The pole will be 2"
alli
scaffold, already obtained, curtousy of the housing refurbishment
contractors.


Have you gone for the thick walled stuff, or the zip up type?

Dave


Yes, I am a licensed radio ham. Jim G1SSO located in County Durham.

The bracketry I was thinking of is something like this:

http://www.aerialshack.com/inch-chim...ket-p-346.html

This is the spec of the antenna:

Compact white fibreglass dual-band base antenna for 2m and 70cm.

Frequency Bands 2m/70cm
Max Power 200W
Length 1.7m
Radials 3
Gain (2m) 4.5dB
Gain (70cm) 7.2dB
Weight 0.9kg
Type (2m) 3 x 1/4 wave
Type (70cm) 3 x 5/8 wave

The alli tube that I have is 2" dia and roughly 3/8" wall. As I say, I would
imagine all I need is about 3 feet.

I was thinking of running a 10mm green earth cable from the mounting
brackets down to a ground spike, but someone commented that it may upset the
antenna. Also I want a termination box with an N socket attached, on the
wall in my shack and to run a similar cable to ground.



All comments gratefully received.



Jim




Thats not that much of a load but its more of a load that I'd feel happy
with the bract chosen for what your trying to do!.. Put it on a decent
lashing, a competent aerial rigger if you have one round your away can
advise. Or if you have one a decent couple of wall brackets on a gable
end might be better.

It should be able to clamp to a standard 50 mm dia pole we use similar
aerials for PMR applications and don't have problems usually they come
with their own brackets sometimes we have to supply them but it
shouldn't be rocket science.

The bit about earthing sounds duff info!, you won't upset the aerial at
all at those frequencies. Very very few aerials on domestic premises are
earthed with a view to lightning protection, this does require more than
a bit of Green earth wire a solid lump of Ally or copper and earthing
plates or driven electrodes are required.

An "N" type outlet shouldn't be a problem either and earthing that and
disconnecting the aerial lead in thundery weather might be better then
nothing. If your belted by a direct strike expect that to be vaporised
and an insurance claim!. What it will help with is small induced
current side swipes..

73's
--
Tony Sayer