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)
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