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Military Applications: Transmitting Tubes for RADAR Applications
IEEE Std 521 Microwave Letter Designation
Why not use A, B, C.......? These were established during WW2 (coded to confuse the enemy). We use A, B, C now but for history won't change here.
World War 2 and Before
MAGNETRON
The invention that help the UK and US defeat Germany and Japan during WW2
During WW2 this tube was classified as SECRET by the military because of the designed of pulsed RADAR used to defeat the Germans and Japanese. Basically a rectifier tube surrounded by a horseshoe magnet that makes the traveling electrons move in a circle and when traveling at the right speed be sent out as a large pulse that hits the target and bounces back. Became obsolete in the 1950's with the development of better RADAR designs using high power Klystron and finally the Traveling Wave Tube (TWT). Has major use in microwave ovens first invented by Raytheon (1950's) under the name Amana Radarange. It is one of the few vacuum tubes still in common use today due to its simplicity to cook food.
2J39: 12 Kw @ 5% duty cycle, 3.267-3.333 GHz S-Band Magnetron (1940s Raytheon)Serial Number 84
LEFT: Shipping Box classified as SECRET with serial number, manufacturer and date of manufacture 12/13/1944
2J55: 50 Kw at 5% duty cycle, 9.345 - 9.405 GHz X-Band Magnetron
(1944-45 Raytheon) Serial Number 59Toward the end of WW2 the development of higher frequency microwave magnetrons improved accuracy in search and surveillance of enemy aircraft and ships.
(1944-45 Raytheon) Serial Number 59Toward the end of WW2 the development of higher frequency microwave magnetrons improved accuracy in search and surveillance of enemy aircraft and ships.
2J27: 12.5 Kw @ 5% duty cycle, 2.965-2.992 GHz S Band RADAR Magnetron(1944 Raytheon) Serial Number
Packing container to hold the magnetron.
This is the signal output slot or waveguide. The dimensions are machined to close tolerance to allow only a certain microwave signal to exit.
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After World War 2 to the end of the 20th Century
5J32: 0.5 KW VHF (90-450 MHz) Twin (SPLIT) Anode Magnetron (1946 General Electric)<<<<<<<<<<<<<<<<<<These lower frequency magnetrons were used as signal jammers to prevent surveillance systems from detecting a ship or plane's position. These required external magnets (not shown). I have seen some units have security classification of CONFIDENTIAL branded on them. Has two lines to allow water to cool the anodes and all the leads and water lines are silver plated.
This tube has the US Navy ID numbers on it.Has date code show year 1953
TRAVELING WAVE TUBE (TWT)
The last and maybe the best RADAR tube
The TWT can be tuned and the signal amplified to allow more sophisticated RADAR search and acquisition in a multiple set of operating modes. The electron beam moving at a high rate of speed is conditioned by a lower frequency and slower moving wave sent on a helical patch surrounding the path of the cathode emitted electron beam. As the beam heads for the tube plate the slower wave conditions the traveling wave and by the time it reaches the plate or target it operates at a selected microwave frequency. This interaction of the two paths allows the TWT to amplify and be frequency selective, unlike the magnetron tube. Also the TWT produces a consistent output signal. TWT's are still in use in many military RADAR applications, even though they are being replaced by solid state and more modern signal acquisition techniques.
EM-778 / 8198 5-11 GHz C and X Band TWT (1962 Eitel-McCullough)
ITT WG/2D (1970s) Exposed TWT (cavity removed) used in Telephone Communication
Closeups of TWT helical loop circling electron gun and plate (tip)
KLYSTRONS
Klystrons were generally used during WW2 as oscillator tubes that generates the microwave but needed a RF pulsed amplifier to send the signal out for surveillance. Unlike Magnetrons the Klystron can reproduce the microwave signal consistently. Since it was difficult to design a high power microwave pulse amplifier most klystron radars were smaller compact systems or were for receiving instead of transmitting.
RK707A 2.5 - 3.7 GHz S- Band Reflex Klystron (made by Raytheon) developed by Western Electric as the 707A
Updated Reflex Klystrons. These are easier to operate.
1K75CS: Klystron (Varian Associates) 1960s
LIGHTHOUSE TUBES or PLANAR TRIODES
The stacked shape which gives it the nickname "lighthouse tube". The geometry is important that allows connections be made with the shortest distance allowing high frequency applications in RADAR receivers, needed to receive the reflected RADAR pulse sent with a magnetron. The pins at the base are mainly for powering the filament and biasing the cathode.
RCA 2C40 and GE 2C43 S Band Lighthouse Tubes (1945)
These tubes all the contacts except the pins are silver plated. Silver is an excellent conductor of electricity, much lower price than gold and will not flake off. Its biggest disadvantage is that it will tarnish in the presence of oxygen.
UPDATED LIGHTHOUSE TUBE
Glass was replaced with ceramic for better power dissipation and frequency response
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