Conventional Transmitting Tubes
In this section are listed some of the transmitting tubes introduced from the early 930s to the 950s.
Anode power ranges from few watts to few thousands watts. Only at very low power transmitting
tubes are similar to receiving ones. For medium and high power tubes special materials were
required in their manufacturing, since many of them operated with plates at very high temperatures,
sometimes from dull red to cherry or white red. Up to few hundred watts many tubes were
convection cooled, even if most of them required some air flow toward the glass envelope near their
maximum ratings. Higher power levels required direct cooling of the anode. In these tubes anode
was usually made of OHFC copper. The external surface was someway connected to the heat
Glass had to withstand very high temperatures without melting and, more, without cracking near the
glass-to-metal sealing. Special hard glasses were developed, with the addition of small quantities of
boron. Glass compositions with thermal coefficients matched to that of the alloys used for
electrodes or for input pins were introduced.
In this section with few exception for some low power tubes, cathodes were filamentary, made of
thoriated tungsten. This resulted in a reasonable compromise between efficiency and life, at the
typical anode operating voltages.
Several materials were used for anodes. Graphite or molybdenum were capable of withstand the
high temperature of medium to low power tubes. Often industry took advantage from the getter
action of some metals. Tantalum and zirconium were used in tubes operated with plate temperature
in the order of 500 to 1000ºC, or at visible red. OFHC copper, directly sealed to glass, was
commonly used for external anodes.
Operating frequencies range from 30MHz to several hundreds megacycles full ratings. It is very
interesting to see how the shapes of the envelope and of the electrodes changed in the years, to
enhance the frequency behavior
1 - 100TH capable of dissipating 100W at 40MHz full ratings.
2, 3 - 15E 20W power triode, intended to operate as UHF oscillator at 500MHz.
15R HV rectifier, gridless 15E, 20KV PIV, 30mA.
4 - 3-500Z VHF zero bias triode, used in many linear amplifiers.
5 - 304TL is the assembly of four 75TL in the same tube. It was also used as radar modulator.
6 - 35T is capable of operation at 100MHz; plate was cherry red.
7 - 3C24 is capable of dissipating 25W. Grid to the side pin.
3E29, pulse rated version of 829
4-125A, VHF beam tetrode; 120MHz, 125W anode dissipation
4-65A, 65W, operation up to 150MHz
4D32, VHF beam tetrode; 50W anode dissipation
4E27, VHF pentode; 75MHz, 125W
4PR60B was a rugged beam tetrode intended for pulse modulators; 20KV, 60W
5933 is the hig-rel version of the well known 807
5D21 power tetrode was used as radar pulse modulator. 20KV, 15A pulse capability. It has quad
cathode structure, grid radiating fins and top corona guard ring.
6146 VHF power beam tetrode; 20W, 60MHz
6907, an improved version of 832A twin beam tetrode, usable up to 1000MHz.
715A was designed to operate as radar pulse modulator.
808 has tantalum plate and can be operated up to 30MHz full ratings
826 VHF triode can be operated up to 250Mhz; 60W anode dissipation
829B was a classic design VHF dual beam tetrode, capable of 40W anode dissipation
832A, dual VHF beam tetrode, 15W
833A has zirconium coated plate; 400W anode power dissipation, 30MHz
845 has graphite anode, 75W dissipation; well suited for audio modulator applications.
860 early VHF tetrode, about 1929, capable of 100W anode dissipation and operations up to
120MHz. The plate is supported by two rods to the sleeve on the right side. Other electrodes are
fastened to top and bottom glass pillars.
97-136A02 is a ruggedized version of the QQE 06/40
E1148 was one of the many tubes developed for low-power VHF communication equipment
LD5 German UHF triode; 25W anode dissipation, operation up to 1GHz.
PE1/100 European transmitting pentode; 100W anode dissipation
QQE 04/20 is the European version of the 832
QQE 06/40 is the European version of the 829
RD12Ta was another UHF German triode from 1942: 5W dissipation, 1GHz operation
RK20, mid 930s, was capable of 40W anode dissipation; up to 60MHz operation possible
RL12P35 was a rugged German transmitting pentode, capable of dissipating 35W
RS682 German transmitting tetrode, capable of 300W anode dissipation
T50-1 transmitting triode from Brown Boveri
VT-127A VHF triode derived from the electrode assembly of the 100TH. The swelling on the
body keeps glass far enough from the hot plate, while the protruding glass tubules help to
lengthen the distance from the heat source to the glass seals.
VT-191 is one of the door knob tubes, intended for operation in the UHF region
VT62 VHF triode capable of operation up to 100MHz
YL1150 VHF European beam tetrode
3-200A3, a sturdy VHF triode capable of 200W anode power dissipation. Its mechanical design can
be appreciated in the pictures above.
Transmitting, External Anode
External anode power tubes are by far more efficient and smaller than tubes with glass envelope.
Anode, usually made of OFHC copper, is in direct contact with the radiator. These tubes required
special processes to seal the glass parts to the metal blocks.
- 8011 micropup triode, capable of operation well in the UHF region
- 2C39A, oil-can UHF triode, was capable of 100W anode dissipation; 2.5GHz.
- CV2, here without radiator, could dissipate 1.1KW with forced air cooling.
- 7698, derived from 2C39, is cooled by direct heat transfer to the external cavity
- 6161 is rated for 250W plate power; 900MHz full ratings, up to 2GHz at reduced ratings.
- 4X150A, a classic design, capable of 150W power dissipation; 150MHz.
- 4X150G is similar to the one above, with frequency raised to 500MHz, or 1.5GHz, pulse.
- 6076 air cooled 3.5KW triode, capable of operate up to 220MHz.