is that Kapton film ?
Yes, it's just there to keep the bugs 'n weather out.
Some time ago, we joked around about using plastic lids off liquid washing detergent, or caps off aerosol deodorant.
Whatever plastic you choose, it's easy enough to test if it affects your signal.
Get a signal without the plastic, then hold the plastic in place by hand.
I may be wrong, but what I see over the face of my Invacom LNB, looks to be
Kapton plastic film.
Looking down inside Dish Network bandstacked FSS LNBs, I thought the same thing.
You can read about it on the DuPont site, or Wikipedia may have an
[ame="http://en.wikipedia.org/wiki/Kapton"]Kapton - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File
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See Google for Kapton tape, with adhesives for all applications.
If in fact they do use Kapton, it may be because it will hold up in all sorts of conditions, and handle the UV bombardment of outdoor use.
Whatever you choose to use, put a second piece out in the elements where you can easily inspect it.
From time to time (every few months), check the sample for deterioration.
Hey, you know who might know what they used?
Maybe Brian of SatelliteAV.
I wonder if replacement discs are available?