[Hammarlund] Unknown tubes and WW2 military secrets

[Kenneth G. Gordon]

On 1 Oct 2014 at 12:20, Peter R. Zidek wrote:

> Second to the secrecy of the Manhattan project during WW2 was the development
> of very small subminiature tubes that helped the war effort in both the
> European and Pacific conflicts. 

Exactly correct: at one time, there were something like 110 companies 
making those and as far as we have been able to tell, there was not one 
single security leak during the entire period.
 
> These tubes were designed by Raytheon to withstand up to 50 G's without
> damage and were used in artillery shells as "proximity fuses. 

Yes.

> Prior to their use and especially in the Pacific Theater was the tremendous
> failure rate of Naval and US forces artillery shells not exploding properly
> in the Proximity of enemy aircraft.  

The failure rate for shooting down enemy aircraft from ground or sea-based 
sites was extremely high. The proximity fuse corrected much of that.

> Notable tubes of that series included CK-526, 6007's, and others. They
> typically required 1.4 volts on directly heated filaments and 22.5 to 90 volt
> DC on the plates. 

Yes. Later, there were a series made by Raytheon which had more "normal" 
filament voltages: 6.3, 12.6 and 25.2 for use in military gear.
 
> Both heaters and plates had comparatively small current
> requirements. 

Yes.

>  After WW2 and before the advent of the transistor they were frequently used
> in small portable radios, walkie-talkies, hearing aids, Geiger counters,
> scintillators and such. 

Yes. My step-father bought a portable radio which was loaded with those. It 
was very easy on batteries.

> They are still somewhat plentiful from old tube suppliers. 

SOME are: some are not. The 7963 is one of those I wish I had at least 50 
of. As it is, I have about 10. These are a dual-triode with a transconductance 
of 13000 umho.

> I use them to restore vintage Geiger counters and Scintillators and they are
> virtually mechanically indestructible. 

According to Raytheon's info on them, they are guaranteed to have a life 
expectancy of 100,000 hours of continuous operation. 

> They are also less susceptible to EMP destruction than solid state
> equivalents. 

Indeed!

You have provided some interesting links. Here is a site dedicated to those 
tubes, and the ham who operates this site has an extensive listing of the 
various types.

http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

Ken W7EKB