Ian White wrote:
>The tower will always have resonances - several of them - and so too
>will the guys. One effect of guy tension is to move these resonances
>around in frequency, and also to alter their degrees of damping and
>mutual coupling. It's very much like several interconnected tuned
>circuits.
>
>The wind will try to excite all available resonances, and a strong wind
>will pump in as much energy as the resonances allow. If a major tower
>resonance coincides with a guy resonance, you're in real trouble.
>The effect of normal good guying practise is to keep these resonances
>well separated and as well damped as possible; but they always exist.
>
>That's the limit of my 'hand-waving' knowledge, but it does give a feel
>for the subject. Yes, it would be interesting to hear from a real
>structural engineer!
>
>
>73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
> 'In Practice' columnist for RadCom (RSGB)
>Professionally:
>IFW Technical Services Clear technical English - world-wide.
A very interesting topic, Ian, that we have discussed very little here. Yes
indeed, towers do have dynamic characteristics and they seem to be almost
totally ignored by us amateurs. I ignore them simply because I don't have a
clue about how to deal with them. I wouldn't have the slightest idea how to
determine the resonate frequency of a tower, for example, so I would not
know how to keep the guys on a seperate frequency.
How critical is all this? Is it only critical in really tall towers like
over 300 feet or should we be worrying about it at 50 feet?
Who knows about this stuff? Speak up, please.
Stan w7ni@teleport.com
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