[TowerTalk] expected life outdoors

[jimlux]

There's a bunch of interesting stuff about degradation of coax outdoors, 
etc.

This brings up an interesting question.  What is a *reasonable* life for 
something outdoors?

If you really want a rotary joint to last 50 years without touching it, 
maybe flexible coax isn't the answer, but rather, a RF rotary joint.

Hams, as a general class, have a reputation for unreasonable 
expectations of life - people get some sort of surplus that's already 20 
years old, install it outdoors, and gripe when they have to replace it 
20 years later. (I exaggerate, but we've all read the posts on eham that 
seem like this).  I know I have plenty of stuff in my garage that I got 
30 years ago: "some day this might be useful" - am I really doing myself 
any favors by using that surplus roll of coax that was probably 
manufactured in the 1960s or 1970s?  Is my report of its success or 
failure meaningful, considering nobody else has that same coax, stored 
in that same way. If I fling imprecations on that particular model of 
coax, is that meaningful to someone buying coax today?


There are plenty of examples of installations of equipment (e.g. 
electrical distribution and transmission) with notional 40-50 year life 
that are now 70+ years old and having not entirely unexpected problems.

Is it really reasonable to expect a "design to cost" amateur radio 
mechanism (like a rotator) to last 40 years with no service or problems?

And, as well, manufacturers do change their materials and processes - 
the end product still meets the "data sheet specs", but might have very 
different other properties. And if you're depending on those 
"undocumented, untested" properties, you might be in trouble.  This is 
no reflection on the manufacturer, but rather, on the user who relies on 
happenstance.

(In the space business, we obsess about this kind of thing, which is why 
space parts cost >10x the regular stuff.  We too, just like hams, save 
ancient spare parts, and then have to deal with reconditioning them, all 
to save some marginal apparent cost)