What is this tube?

[VK7ZL]

This tube was given to me yesterday.
The bottom of the small cylinder is marked Telefunken. The small cylinder slides inside the larger one and the brass studs on the bottom make contact with brass strips inside the larger cylinder with the terminations on the outside. There are six contacts around the bottom. The stud on the top of the small cylinder slides into a ceramic disc at the top of the large cylinder which also has a contact attached to it.
The numbers on the small cylinder are BAL 716 & RV2  P800  45 40. At the top is 30/40 & 400548. There are no numbers on the large cylinder.

I am sure someone will recognise it.

Bob  VK7ZL

[N4zed]

http://www.nonstopsystems.com/radio/hellschreiber-tubes.htm

??

[kb3ouk]

Telefunken made a tube known as the LS-50 that also had that handle on top. After WWII, the Soviets made a clone of it called the GU-50. The Soviets loved to copy tubes from everyone else, maybe change them slightly, then give them a new name. GU-48 is a 833A clone. GU-13 is a 813 clone, while the GK-71 is a true pentode version of the GU-13 (internally it's a 803, but physically looks like a 813).

[W7TFO]

It is interesting to see the parallel development of tube technology in the attached article.

Also the invention of the pentode and Bakelite by Germans...

73DG

[G3UUR]

Hello Bob,

The important part of the lettering on the tube is RV2 P800. This is a 2-volt filament general purpose tube made for the Wermacht and used in many of their bits of radio kit. You should find more info on some of the German websites or possibly some of the British ones dedicated to military radio.

Hope that helps!

73,

Dave.

[VK7ZL]

Thanks to all for the information. The Germans were certainly innovative.

Bob  VK7ZL