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[TowerTalk] Small Beam Opinions

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Subject: [TowerTalk] Small Beam Opinions
From: (Ian White, G3SEK)
Date: Sat, 14 Aug 1999 08:49:39 +0100
Guy Olinger, K2AV wrote:
>Chimneys are notoriously bad places to mount antennas, be that TV or
>ham or ...
>Unless the condition of the chimney is new, and it is built very
>robustly, chimneys have been taken down by ice and wind on the
>antenna. They are not DESIGNED to support antennas.

A brick chimney will support a lightweight VHF/UHF antenna on a short
mast, but beyond that you're living dangerously.

When you bind together a block of brickwork using chimney lashings, the
effect of the wind-load of the antenna and mast is to break that block
away from the base of the chimney, and lever it over. The only thing
holding the block in place is its own weight. You cannot rely on any
strength in the mortar to hold the block down. Obviously much depends on
the quality and durability of the original workmanship, and that's not
something you can easily judge.

The final consideration is what happens if the chimney does go over: a
large block of masonry comes through your bedroom ceiling!

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

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