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Physical Society's Exhibition 1947

Wireless World, June, 1947.
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The second post-war exhibition was held from April 9-12 in London.
M-OV Valves shown KT81 and Z77.

The new pressed-glass base type valves were shown in wide ranges by the M-O Valve Co. in both directly and indirectly heated types. The triode-hexodes are claimed to be effective at frequencies as high as 300 MHz and the types include variable-mu RF pentodes, duo-diode-triodes, output tetrodes and HT rectifiers.

Among the miniature glass-base types a television-type RF pentode is of particular interest. It is the Z77 with a mutual conductance of 7.5 mA/V.

Ferranti have a high-voltage rectifier with this same base but with a top-cap anode connector. The HR1 is designed for television EHT supplies derived from the line flyback and the filament takes only 55 mA at 0.65 V. It is rated for a peak inverse of 12.5 kV and a mean output current of 50 μA.

International Television Corporation showed the Nagard FM1 frequency multiplier. This is a deflection valve giving a frequency multiplication of 2, 4, 6, 8 or 10 times without tuned circuits. Similar in general form to a CRT, the deflection voltage sweeps an electron beam across a number of spaced bars. Each time the beam, crosses a bar a pulse is generated in the output circuit. With a triangular input wave, 10 output pulses are generated for each input cycle. By reducing the input voltage the number of bars swept is reduced and hence the degree of multiplication.

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