These Triode-pentode valves are really two tubes in one envelope. They were highly popular for home audio
applications in the late 1950s and throughout the 1960s. You could get reasonably nice audio for driving a loudspeaker
with a few watts and get the whole amplifier in one simple valve.
Note: These tubes are all Triode-Pentodes, but the ECL80 alone has an
internal connection between the two cathodes,
which are connected to pin 3. Both the ECL82 (6BM8) and the ECL86 (6GW8) have separate connections to each cathode.
The ECL80 pentode section has a SEPARATE connection for the Suppressor Grid (7) and the Cathode (3)
The ECL80/6AB8 will give you about 2-3 Watts RF out, and an ECL82/6BM8 will give about 8 watts. An ECL83 will give about 6 Watts. 6DX8/ECL84 and ECL85/6GV8 will give maybe 8 watts and the ECL86/6GW8 will give about 12 Watts out.
Other tubes with some interesting possibilities: 16GV8, 18GV8, 30PL15, 6GV8, CV10707, PCL805, PCL85
I have now built a two valve transmitter with a 2E26 final at about 20 Watts - next will be the 6BM8 project!
Another tube that would be very interesting to try in a simple transmitter
is the 6HU8, which is equivalent
to the European ELL80 is a dual PENTODE output tube intended to give 6 Watts + 6 Watts stereo output, or as a push-pull
15 watt amplifier. You could probably use it to make a fairly compact CW transmitter.
1 = Gt, 2 = Kp, G3p, 3 = G1p, 4 = Htr, 5 = Htr, 6 = Pp, 7 = G2p, 8 = Kt, 9 = Pt
1 = Gt, 2 = Pt, 3 = Kt, 4 = Htr, 5 = Htr, 6 = Pp, 7 = Kp, G3p 8 = G1p, 9 = G2p
1 = Pt, 2 = Gt, 3 = Kt, 4 = Htr, 5 = Htr, 6 = Pp, 7 = G2p, 8 = Kp, G3p, 9 = G1p
1 = Gt, 2 = Kt, 3 = G2p, 4 = Htr, 5 = Htr, 6 = Pp, 7 = Kp, G3p, 8 = G1p, 9 = Pt
CQ Magazine, March 1989: 6BM8 Transmitter
QST, March 1971: McCoy, Lewis G. and Wilson, Gus. It uses a single 6T9 triode-Pentode. The triode section is a Pierce oscillator, and the pentode power amp section is the final. It puts out about 5 watts trouble-free.
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