[R-390] R-390A Tube Shields

[Roger Ruszkowski]

Fellows,

The wonder of old mail and Qth archives.

 The advantage of the IERC shield are two-fold -
one it contacts the tube glass envelope and efficiently conducts heat
away like that.

True.

A whole bunch of studies have been done on the subject.

The silver metal cans run the tubes hotter than no shield at all.

Nothing move heat away from the glass like metal
contacts inside the shield to conduct better than air.

It was practice to only run the shields on the
mixers RF and oscillator tubes in the R390 / A
You run every thing else bare in the receivers.

The army was not going to spend money on IERC shields.

But If you have some can find some use them.
They do run the tubes cooler than no shields
And much cooler than bad shields.

The operative factor looks to be the contacts that
move heat better than an air gap does.

Roger AI4NI