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GI-7b Microwave Triode

I recently obtained an ancient Rusky GI-7b microwave C-band triode.  Packed in an innocent looking styrofoam container (I didn't know they had styrofoam in the bronze age - maybe that is how they floated the pyramid stones down the Nile!), it is quite a monster:

GI-7b Radar Amplifier Triode

This is a radar amplifier tube designed to operate while pulsing at up to 9 kV and 3 GHz.

To digress a bit, contrary to common perception, there are still lots of microwave electron tubes in use,  for example microwave ovens, radars, medical diagnostic equipment and satellites.  Travelling Wave Tubes are popular in satellite transmitters, because they are very efficient, very rugged and small. TWT amplifiers have been manufactured by the likes of Honeywell, Thales and others for over half a century - the frequency band just keeps going up and they now operate in the Ka band: https://aerospace.honeywell.com/en/learn/products/satellite-communications/traveling-wave-tube-amplifiers

What I would like to do one day, is build a Thermionic Valve satcom UHF preamplifier for use with a SATNOGS  Raspberry Pi earth observation ground station - just for fun.  I got some small Nuvistor tubes for that.

Really BIG electron tubes and oscillators are made in China by the Bejing Jenerator Co:  https://jenerator.en.ecplaza.net

There is also still a manufacturor of new electron tubes for audio amplifiers, the Xpo-Pul (Reflektor) factory in Saratov, Russia:   http://rutubes.com/category/reflector-tube-saratov-russia/

The big GI-7 tube is supposed to have a vacuum inside - I hope it is still in there and that it didn't crawl out through a crack in the casing - it was designed for use in a battle tank, so it should be OK!

Serious Data Sheet

The Heater and Cathode are at the bottom, the Gate in the middle and the Anode at the top.  It is wired like a simpe Triode - no confusing extra grids as in a Pentode.  I frequently wondered whether the extra grids of a Pentode really do anything useful, or are just there for marketing purposes.  Hey, five are better than three right?

Electron Tubes tend to be very forgiving things and like a little kitten, will usually try their best to please you, if you warm them up nice and cozy and feed them some lecce.  Therefore I'm wondering how it will do at a more pedestrian 335 VDC at 10 kHz baseband, in an audio amplifier output stage.  The biggest problem will likely be the 12 V, 2 A heater current - 24 Watt to do mostly nothing - maybe it will work at half that.

One should not run a tube at kilovolts in your living room anyway, since you can get X-rays and Ozone, which are both not very nice.

Some Audiophile amplifiers have a random tube or two on display and wired such that if you remove the tube, the amp stops working, while it actually doesn't do anything at all, but since I grew up with tube fired radars in the Army, I'll find a way to make it work for real!


Crazy Socket

The socket for this valve is total overkill, so I'll have to make something more aesthetically pleasing.

UHF and Microwave Ceramic Valves are usually quite easy to solder to, since the contacts are silver plated.  So I can run some copper steam tubes around the valve just for show: 

RG405/U - https://www.pasternack.com/semirigid-0.085-rg405-50-ohm-coax-cable-copper-rg405-u-p.aspx

Semi-rigid coax make nice looking steam tubes and shield the signals from 5G Audiophile interference, so you don't need a double layer tin-foil hat when you listen to my amps. https://www.aeronetworks.ca/2015/02/cool-amplifier.html

Here is the complete thermionic valve data sheet:




GI-7b Triode

Microamp per kilovolt - Hmmm...  Keep yer kotton picken fingers in yer pokkets!

What I want to do is far off the left-hand bottom end of all the curves, but it should work anyway.


For now, it will have to rest some more in my Junque Bochs.  

Maybe I'll get to it next year. 

No rush.

The tube patiently waited 50 years already, so it can wait some more!


La voila,

H


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