The damage shown in the photos is simply the plastic (my guess is it is
Delrin) breaking down from UV exposure. Back in the 80's I built my own
circular polarized antennas for 70cm and 2M for AO-13. Having a lathe I
made some parts from white Delrin (a nylon like material). After about
ten years it showed the same UV damage. Note that the black plastic
element insulators in the photos are not cracked. The black pigment
used in the element insulators apparently protects them from UV. After
learning this lesson I started using the black Delrin for my home brew
antennas and have had no problems with UV damage. All that said, some
plastics are more resistant to UV than others. I have two M2 antennas
in use for terrestrial use and after ten years of being up in the
elements they are both working well. Note that the UV damage may not
have gone all the way to the core of the component yet. If it is still
mechanically intact (and just looks awful), it can be salvaged by
coating it with a thick black sealant and covering that with black
electrical tape.
--73-- Dave WA0AUQ
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