Re: cling film?


John Fell
 

Hi Ben,
Polystyrene boxes and cling film are OK for temp /P .
Problem at 1.3GHz and above are large rain drops gathering close to the feed entry which will do their dielectric thing and reduce signals .Hard to wipe off up a mast ....
Longer term radomes can use thin PTFE sheet secured across Horn/feed mouths .Ideal mounted so water slides of and cannot puddle .Use RTV silicone adhesive to retain in place .Check the installation daily from ground to ensure birds have not  pecked through the sheet .A small drainage hole at the lowest point will help to eliminate and condensate .
I am a big fan of spray on or dipped Silicone conformal coating - works VERY WELL.

It is a good idea to have an idea of "average" conditions , so a daily check can be made using the system.Sun noise is a good near calibrated source or Cold Sky /ground on the higher uwave bands .

Keep up the good work .

73
John
G0API

On Sun, 24 Jan 2021 at 11:14, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
As my uw antennas are all temporary, ie I put then up and down only when needed, akin to portable op's but from the home qth, I noticed after the last 23cm use which was in the rain here, got soaked inside but that's another problem, that there was water shorting or very nearly shorting the folded dipole to the boom. 

I guess those with permanent setups way up high have other techniques for wx or such.

Has anyone with portable experience, non so far here, tried say cling film over the radiator or a plastic bag etc? 

My 23 and 13 are standard Yagi folded dipole type, I'm ok on 9, its a flat panel in an outside protective cover and my 10Ghz ex mil dipole on wg feed did have a plastic cover over it, presumably to stop the ingress of water to the wg but it was cracked so I removed it. A small piece of cling film over the end would stop any ingress I'm guessing. 

Anyway, thoughts?

Ben.G4BXD

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