[Milsurplus] Fw: Who is GHS?

[Kenneth G. Gordon]

On 3 Oct 2018 at 14:19, Jim Whartenby wrote:

> As with the ARC-21, subminiature tube reliability was dismal. 

Hmmm...this is interesting to me for the simple reason that the submini tubes were originally 
designed and built to be used in proximity fuses.

One Sylvania bulletin I have here shows that at least some of those tubes were rated at 
something like 10,000Gs for survival.

I know that the SRR-11/12/13 uses those.

In that rig, many of the tubes are run very hot and this contributed to short life in that series 
of receivers.

Yet if those tubes are used at or below their maximum ratings, they are very reliable.

For instance, as I have mentioned here at least once before, back in the 1970s, I was 
working with a rather odd professor who was using them to monitor VLF and MF/HF stations 
24/7/365.

At first, we had a lot of failures, but after I modified them so that the screen voltages to the 
pentode/tetrodes was reduced to "somewhat below" the plate voltage (!), temperature 
dropped markedly, operation appeared normal, and the receivers then became much more 
reliable. 

As I remember it, the screens were essentially connected directly to the plate supply. I 
added suitably bypassed 51K resistors to the screen feed at all those tubes which required 
it and that made a big difference.

Ken W7EKB