[R-390] Tube shields

[Todd, KA1KAQ]

The reasoning behind wanting to add the IERC shields was that tests had
shown they actually reduced bulb temps over a bare/open air approach since
the inserts and overall design worked well at wicking away the heat. The
recently-depart Bill Kleronomos/KD0HG wrote an article on this for ER and,
IIRC, also posted info here a few times related to these shields.

I think some of the newer folks at the time got wrapped around the fear of
greatly diminished tube life as a result of *not* using the IERC types and,
like the never-ending 3TF7 issue, obsessed over it. Just a guess on my
part. Reminds me of the horror or radioactive meters, black cap innards,
etc etc etc. Some things just keep coming to the surface. The archives must
be bursting at the seams.

IERC shields are still out there to be had. I think the problem is, too
many folks look for the quick way out, i.e. convenience of logging onto the
internet and buying an answer. As with most other older, now-desirable
technology, it requires a bit of digging and self-application to procure
them. Though they are available, as W. Li says, not in the numbers they
were even a decade ago. Old avionics and test gear are still a great
source. I recall purchasing a piece of gear at a hamfest a few years back
that was h-e-a-v-y and annoying to handle, for $10, which yielded over 20
IERC shields, tubes, and other goodies. Well worth the effort expended.

de Todd/'Boomer'  KA1KAQ/4