Re: suitable material for horn cover

Neil Smith G4DBN
 

I use thin polystyrene sheet. It is just about transparent to RF and you can use polystyrene cement to fix a rim, then use a thin smear of clear sanitary silicone to glue it to the horn.  Note that it is almost always sold as "Styrene sheet" to distinguish it from expanded foam polystyrene. Styrene is actually a liquid, go figure....  Modelling suppliers usually stock it.  Loss tangent is a few parts in 10e-4, on a par with PTFE.

HDPE is also very transparent, but you'd have to find a way to fix and seal it.  Polypropylene also, but again, very tough to fix.

To prevent condensation, you could fill the horn with polyurethane foam if you are feeling brave, or carved up expanded polystyrene if not. It is very hard to prevent condensation inside a metal horn with a radome.

Neil G4DBN

On 17/03/2020 10:50, Christopher Rayns wrote:
Hi,

im after a suitable material to cover the face of the horn during wet wx so is there a preferred material less likely to block rf or affect operation. Im looking at a my 5 band feed that I have from rfhamdesigns thats looks like a type of perspex of sorts.

any suggestions please

Chris

G0WUS



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