Triode Valve
This is my first attempt at a web site.  So things,  
will no doubt be, dynamic for a while. Change is
the only constant.
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   I was surprised to find this tube today.  I had not seen it for several years and thought it was the one that got killed by Loma Preita back in

6C21 triode is 1 of 3 used to fire the magnetron of an AN/MPS-9 E-Band, (S-Band),  target tracking radar.  

   The actual radar that I removed this tube from can be seen at the far right of the center section of the picture of
Det 5 1CEVG Wilder ID,
(about mid page).  There are several pictures of
MPS-9 radars here.

   The MPS-9 is a, 3 degree
Conical Scan, Target Tracking Radar with a Cassegrain type antenna assembly.  The Cassegrain allowed
placing the scanner behind the antenna dish.

   Our primary use of the MPS-9 at Det 5 was to simulate a Soviet AAA radar threat for Electronic Warfare Officers, "EWO"s aboard
Strategic Air B-52s and Tactical Air FB-111s.

   Our MPS-9 was run at 2,835 kilo mega hertz, about the same frequency as a microwave oven.  (Because a British billion is a thousand
times larger than a US billion.  That makes "Giga" ambiguous when communicating about radio frequencies.).  It ran a 410 PRF with a 0.8us
pulse width.  The output power was about 250kW peak but to the low duty cycle it's average power was around 83 watts.  The MPS-9 used 3
of these tubes in parallel to fire the
magnetron.  They had a plate voltage of around 18kV at I think around 10mA.

These tubes are also called
Keyer Tubes.  They are simple triodes and perform basically the same function as the MOS switch of a SMPS.  
Basically a big capacitor is charged up to about 18kV and then discharged through the tubes and magnetron.  The energy of the HV
electrons is converted to RF by the magnetic field and cavities of the magnetron.

Below are some pictures of the 6C21.
Above is 1 of 2 magnets used with the magnetron and the 6C21.  
When this magnet was replaced it was still strong enough that I could
almost hang from it.  Because of the flanges it is hard to get the
magnet flush with a surface to get a good grip.  Now some 30 years
later,  I just tried and was able to lift 20 pounds