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Disk Seal Vacuum Tubes
Disk seal tubes were designed to be directly coupled with associated resonant circuits. Electrodes
are connected to disks or rings that come out radially from the body, and are separated by glass or
ceramic spacers. Spacers also grant the due clearance among electrodes, as in the picture below.
The development of disk seal tubes involved the solution of some technological aspects. The first
was derived from the different thermal coefficient of the glass and of the conductive disks to which
the glass had to be sealed. Many and many glass compounds, in combination with several metals
and alloys were tried, to find the best matched pairs. First used material was copper, with a film of
red copper oxide in the glass sealing zone. Also the effects of thickness and shape of disks was
investigated. Thin sheets of corrugated copper were elastic enough to easily follow the thermal
expansion of the glass. In the years, copper and glass were replaced with other materials, offering
improved temperature and mechanical performances.
Several disk seal tubes are presented in this section, including some TR tubes, reflex klystrons, with
or without external cavity, and one TWT. Also some hybrid structures are represented, such as
some all-glass UHF diodes and some ceramic power tetrodes: here the electrodes may not have
planar shapes, but the disk-sealed stack keeps them aligned.
All the tubes in this section were designed for operation well in UHF and SHF region: conventional
triodes can operate up to 7.5GHz, while some velocity modulated tubes were designed to operate
beyond 10GHz.
1: 1950 0004 reflex klystron used in HP 620B, 7 to 11GHz generator.
2: 2C36 rocket triode with internal feedback: intended as UHF oscillator up to 1.2GHz.
3: 2C39A, oil can power triode with glass spacers; 2.5GHz, 100W Pa.
4: 2C39B is similar to 2C39A but for ceramic spacers.
5: 2C42 was a lighthouse triode intended for pulsed operation. 1750W peak at 1050MHz.
6: 2C46 is another lighthouse triode for UHF applications.
7: 322 was an oil-can shaped UHF clipper diode. 800V PIV, 15W, 1500MHz.
8: 2-01C, UHF detector diode, used in RF probes of test instruments.
9: 1B40 was an electrodeless TR tube. 1KW at 1075 to 1095MHz. Central pin is the keep-alive electrode.
1: 3C22 power disk-seal triode. 125W Pa with forced air cooling, 1400MHz.
2: 3CX100A5, improved version of 2C39, usable up to 3GHz.
3: 4042 ceramic pencil triode; 425W pulse power output at 1-7GHz.
4: 4043, intended for CW operation, was rated for 5W out power at 500MHz.
5: 4062A ceramic pencil triode; Mu 100, 10W Pa, 4GHz.
6: 416B, made by WE, transmitting planar triode, capable of 0.5W out at 4GHz.
7: 416D used BeO spacers to increase output power up to 5W at 4GHz.
8: 446A, one of the early lighthouse UHF triodes; 10dB noise figure at 1GHz.
1: 2K28 reflex klystron, capable of delivering 125mW average from 1200 to 3750MHz.
2: 2K48, a reflex klystron with waveguide out; 20mW, 4 to 11GHz.
3: 55340 TWT amplifier; 8W output from 3.8 to 4.2GHz.
4: 5675 glass pencil triode was intended for g-g amplifiers up to 1.7GHz.
5: 5767 UHF rocket triode; CW oscillator or amplifier up to 3.3GHz.
6: 5837 reflex klystron was similar to 6BM6; 150mW, 550MHz to 3.8GHz, external cavity.
7: 5768 rocket triode was intended for operations from 1 to 3GHz.
8: 5876A glass pencil triode could be used up to 2GHz.
9: 6161 UHF power transmitting triode, usable up to 2GHz; 250W plate dissipation.
10: 6173 pencil UHF diode; 3.3GHz.
11: 6236 reflex klystron, operating from 3.8 to 7.6GHz; external cavity.
1: 6263 power pencil triode has a radiator on the plate cap; 8W Pa, 500MHz.
2: 6263A is similar to the 6263.
3: 6299 low-noise triode amplifier usable up to 3GHz.
4: 6322, also marked BL25, was an adjustable gap TR tube; 450KW at 1285MHz.
5: 6390 reflex klystron could operate from 6700 to 11050MHz.
6: 6442, a rugged ceramic triode usable up to 5GHz; 2KW peak out at 3.5GHz.
7: 6481 rocket triode intended as oscillator up to 3.3GHz.
8: 6816 coaxial beam tetrode, capable of operation up to 2GHz; 115W Pa.
9: 6864, similar to the 6816 above, with 26.5V heater.
1: 6923 low-capacitance planar diode, intended for high-frequency probes.
2: 6BL6 reflex klystron; 1.4 to 6.5GHz, external cavity.
3: 6BM6 reflex klystron oscillates from 550MHz to 3.8GHz.
4: 6BM6A is an improved version of the 6BM6 shown before.
5: 7077 cermet planar low-noise triode usable up to 7.5GHz; used as class B amp at
     960MHz in the Pioneer space probe.
6: 709A twin TR tube.
7: 721A TR tube with keep alive electrode to the top cap.
8: 724B temperature compensated TR switch, for operation in the X band.
9: 7289, similar to 3CX100A5, improved cermet version of the well-known 2C39.
1: 7391 planar cermet triode usable at frequencies as high as 6GHz.
2: 7462 planar cermet triode, similar to 7077, for T-bolt mounting.
3: 7486 another cermet planar triode, usable as amplifier or oscillator up to 7.5GHz.
4: 7554 cermet pencil triode was intended as power amplifier up to 5Ghz; 2.5W at 2.5GHz.
5: 7698 delivered 10W CW at 3GHz; 2.5KW pulse power at the same frequency.
6: 7815AL gold-plated, intended for airline operation (AL).
7: 7815R was supplied with integral plate radiator.
1: 8011 micropup UHF power triode was capable of operating at 600MHz.
2: 8596 cermet UHF power tetrode can operate at 1250MHz.
3: 8906 similar to 7815, with nickel matrix cathode.
4: 8980 cermet UHF power triode.
5: A160011 Polarad reflex klystron.
6: A160034 Polarad reflex klystron; 6.7 to 11GHz.
7: ACT27 high power forced air cooling triode.
8: CV2346 EMI reflex klystron; 8 to 10MHz operation.
9: CV273 GEC made ‘rocket’ style disk-seal triode; 3.5GHz.
1: CV67 early British reflex klystron, intended to operate as local oscillator at 3.3Ghz.
2: EA52 planar UHF diode used in UHF test probes.
3: EC157 European lighthouse triode could operate as amplifier or oscillator up to 4GHz.
4: EC55 Philips equivalent of CV273 rocket triode.
5: GL6019 UHF water cooled transmitting tetrode; 1KW out at 900MHz.
6: 707B reflex klystron, similar to 2K28; 2.3 to 3.75GHz.
7: VX5029 EMI reflex klystron; 1.8 to 4GHz.
8: WL-532A or 1B32 was a TR switch.
9: Y-1610 GE, a small planar triode capable of operation up to 7.5GHz; 2.3W at 450MHz.
10: CV58 UHF diode intended as mixer at 1GHz.
11: ZV1009 Polarad reflex klystron operates from 1.5 to 6GHz.
Latest Additions
Although not a true disk seal tube, this small UHF triode is remarkable for its design, with glass
feed-thru pins on the base and vacuum seal on the top. The triode was intended as grounded grid
amplifier in early radar receivers; 3GHz.