[Milsurplus] SRR-11/12/13 and subminis

[J. Forster]

SubMini tubes were originally invented at Raytheon, by Norm Krim, for applications
like hearing aids well before WW II. In WW II they made possible the Proximity
Fuse, an extremely clever Doppler regen circuit which triggered the warhead when
the strength and Doppler frequency of the detected signal exceeded certain preset
limits. In the fuses, the filaments were unpowered during firing and were powered
up during flight, either by a wind turbine or the centrifugal filling of a battery
due to the shell's spin.  Very clever, those engineers.  BTW, Norm is still alive
and well in the Boston area.

It is possible to make very long life thermionic cathodes (vis, the tubes used in
submarine cables) but I'd guess the best chance would be to make tube like devices
using a field emission cathode. Such things could have almost unlimited life.

FWIW,
-John



Peter Gottlieb wrote:

> Given the most modern manufacturing processes and materials, would it be
> possible to build tubes which had a longer lifetime than solid state devices?
>
> 40,000 hours is under 5 years of continuous service, nothing special by today's
> standards.