High-frequency valves

You won't find these in your old radio! Due to the special physical requirements of high-frequency operation, these devices look very different from conventional valve types.

High-power RF triode, forced-air cooled (5" high)

> General Electric 2C46

From Dennis Davis :  The GE 2C46 appears to be what we called a lighthouse tube. Such were used in the US Bell System TD-2 microwave links installed just after WWII. The output was 0.25 watt, in a 0.5º beam, and carried 6 channels - each channel was 1200 voice circuits or one color TV circuit.

< Triode(?) with central metal anode, connected to metal slab for bolting to heatsink.

>General Electric GL-860

2K25 Reflex Klystron.

A low-power device (1.3W) used as a local oscillator for microwave communications equipment and radar receivers. Output is via a co-axial pin, and the device can be mechanically tuned with the screw on the left, which applies vertical compression to the metal envelope.

< CV67 Small Klystron

Tuning adjustment on right, output waveguide on left.

>Marconi K301 Klystron (2.5" high)

> High-power RF triode. Marked 'KMOV7850 K 00-0436 ACT 25'

I found data on a similar looking ACT28 device, (below), described as a 'Pulse modulator' valve, rated at 11Kv,50A.
Thanks to Dave Walker at London Gatwick Airport for the following info :  They were used for the power amplifier in a bank of 4 valves in our 600Mhz radar transmitter. You can see the venting for the forced air cooling on the valve. Their lifespan was very short, sometimes no longer than 200 hours, and supply was limited. The radar was decomissioned around 1990.

>CV2346 Klystron (3" high)

< CV1256 power device of some sort! 3¼" high excluding pins

Danial writes :  The cv1256 tube is a pulse triode similar looking to nt99 - these were used in ww2 uhf radar sets in pairs or quads. I am a collector of old microwave tubes and would like to know if you know of any people/ web sites/ shops etc which sell or
swap in these things.Please email if you know of any.

> CV52 odd-looking internal construction, with unusual in-line pin configuration, one  thick pin & 4 thin ones. 2" high.

< CV397 Disc sealed high-frequency triode. David Eaton writes :   The number is the british military equivalent of the Mullard TD04-20. Heater 6.3 v 1 amp. Plate power 20 W plate volts 400 max max freq at full ratings 600 mhz. with power output 23 watts reducing the ratings to 3.5 watts max freq 2000 mhz.

> Raytheon ML-8533 Ceramic triode, with screw-on aluminium heatsink at base. Karl Kolbus writes : We used them back in the 1960's the the Air Force UHF transmitter model T-217. They were used as frequency doublers/ triplers to feed the 4x150's (2) in the P/P output stage. They were tuned by the old style meshing air-gap, segmented plate variable capacitors which were servo-rotated, depending on the transmitting frequency selected. That's fine except to tune it, you would select the lowest frequency, then 'home' the servo unit to bring the plates into position, bend the appropriate plate for that freq., rotate the servo to it's operating position, and check the output. Then repeat the process, again and again until you got your peak output. Now repeat that whole process for all the segments on the variable; I think it was 12. Needless to say, it took some time. Now consider this: Housed in an anodized steel box and forced-air cooled, the circuit was so touchy that, when you screwed the cover back on and torqued down it's 16 ! counter-sunk flathead screws, more often than not, the output would drop from it's nominal 15 watts to almost zero. You then had to back off some of the cover screws a little until the output came back up. But, you never knew which ones! Lots of fun. By the way, the tube is shown upside-down. If operated in that position, it would self-destruct. Even in the upright position you couldn't key the transmitter for longer than 15 or 20 seconds at a time without risking damage! 

< CV79 Small magnetron

> RCA VT-228 Transmitting Triode, with side anode and grid connections

< Eimac JAN-CIM-15E

Pat Jankowiak writes : The 15E put out a 5KW pulse at 600 MHz for use in dive WWII bomber radar.

>Bomac JAN-CBNQ-721B TR Cell. Used in radar equipment to stop the high transmit power damaging the receiver.

Telefunken YH1110 travelling-wave tube. This device is a used as a microwave power amplifier in communications applications including satellites.

EEV BS502 TR tube. Used in radar applications to protect the receiver from the high power transmit signal.

CV16 - possibly a klystron ? Upper electrode is hollow - maybe an entry port for a microwave signal ?

VT98A Power triode (1938) Used in 1.5 metre mobile ground radar transmitters. This one is in the London Science Museum, but I have subsequently got my own one (marked CV1098), which looks identical apart from not having the red colour around the base.