Someone already try to remove properly the fibo feedhorn platic cap ? Is there a way to change it ?
I think it is not easy to remove the cap, and even more difficult to place it back. Most likely, after you remove the metal ring, it will be broken. It, probably, can be replaced by another one, but some kind of special tool will be needed. BTW, one of the Fibo feedhorns I have come with a removable plastic cap. I also have another one, exactly the same but different color, which I do not remember where it comes from. But, I feel those caps are special for satellite LNBs, so should not steal a lot of signal. If you decide to remove the cap and have difficulties installing it back, I could give you one of mine.
