High Frequency Tubes

When operating in the realm of microwave and broadcast frequencies, electron tubes must take on unusual forms. The most common types of high frequency tubes are klystrons and magnetrons, which are used to generate microwave-level frequencies. Magnetrons are still widely used today, as the heat source in consumer microwave ovens. Klystrons still see use in broadcast transmitters for television and radio stations, as well as airborne and ground based radar installations.

 


Sperry 2K41
 

The Sperry 2K41 is a two-cavity mechanically tuned klystron used in various military radar and communications systems. This tube generates frequencies from 2660 to 3310MHz, with a filament voltage of 6V, beam voltage of 1200V, and a reflector voltage of 750V.

Sperry 2K41
Raytheon 2J51
 

The 2J51 is a tunable air-cooled magnetron with a range of 8.5Ghz to 9.6Ghz. Unfortunately this sample is missing several components, including the large semicircular magnets that would be clamped to each side of the tube. The 2J51 can generate microwave pulses in excess of 40 kilowatts.

Raytheon 2J51
Raytheon 2K33
 

The 2K33, made by Raytheon, is a mechanically tunable reflex klystron that operates in the 22 to 25 GHz band with a 40mW output. The tube is tuned by varying the length of the envelope through a flexible metal disk seal, a large mechanical lever arrangement on the top of the tube provides for this function. This unit lacks the bracket and tuning knob seen on some similar klystrons that is used for mechanical tuning, though the mounting flange is present and a knob could easily be installed.

Raytheon 2K33
Sperry 2K46
 

The 2K46 is a tunable air cooled klystron frequency tripler, with an output of 8.1 to 10 Ghz. The heater voltage is 6.3 volts and the output is rated at 1.5kV. The inputs and outputs are coaxial.

Sperry 2K46
Sylvania 5789W
 

This device was somewhat difficult to identify, but research revealed that it is a magnetron. The copper portions of this device that are mounted on either side of the waveguide are slightly magnetic, suggesting that the device originally had much larger magnets attached. The output of this tube is a fixed 34 GHz and the power requirement is around 14 kV. According to the book Tube Lore, this is the first commercially available US magnetron for the Ka band, and was released in 1949.

Sylvania 5789W
Klystronics 7238
 

The Klystronics 7238 appears to be a fairly typical metal-enclosed reflex klystron, almost surely electronically tunable. This tube uses a modified octal base commonly seen in small klystrons, in which one pin is replaced with a long waveguide. Specifications are unknown.

Klystronics 7238

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