TT:
Al NW2M wrote a Technical Correspondence item on this subject of wind
noise. It was published in the Oct 2020 - QST (Pg. 56) -
Wind Noises Generated by Mobile Antennas. FYI.
73 de
Gene Smar AD3F
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Lux, Jim
Sent: Tuesday, March 16, 2021 10:16 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Wind Noise
On 3/15/21 9:14 PM, Michael Tope wrote:
> I don't doubt that putting the rope on the outside is more effective,
> but I have just never seen or heard of anyone doing that with a Yagi.
> What diameter rope would be sufficient. What would be the pitch of the
> turns (I am picturing a helical wrap). Any downsides?
>
> 73, Mike W4EF.....
If you look at car antennas that use the technique or tall chimneys - The pitch
on a 1" diameter thing would be "feet". Again, looking at chimneys, I think
something like 1/4" rope (or UV resistant tubing, like used for irrigation)
would probably work.
For power lines, on 1" diameter cables, they look like they're about 3-4 feet
long with a pitch of 6-8". They only put them every so often, not continuously.
All you need is something to break up the uniform air flow. You could probably
use chunks of pool noodle.
As to why they aren't seen commercially on Yagis - cost? It looks weird?
- I suspect that most people don't actually care if it vibrates, unless
the frequency happens to match the resonant frequency of the element and
it gets very large amplitude. And that would, I think, be unusual - the
mechanical resonance is low (around 1 Hz, judging by eye) - and the
aeolian excitation is going to be higher. It would have to excite a
higher mode.
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