[amsat-bb] Re: why not to buy an M2 antenna

David Metz davemetz at machlink.com
Tue Dec 10 12:46:48 PST 2013

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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