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A wide range of receivers is a part of the exhibit of this firm, among which the Fidelity Short-Wave Five is of especial interest, for it covers 16-50 metres in addition to the ordinary broadcast bands. It is a superheterodyne with a triode-hexode frequency-changer and an input band-pass filter. A single IF stage operating at 445 kHz is used and is followed by a duo-diode-triode, which feeds the output pentode. Variable selectivity is included, and the set is priced at 15½ guineas.
Another all-wave set is the Universal SW4, and, as its name implies, it is designed for AC/ DC operation. It is a superheterodyne with an intermediate frequency of 125 kHz, and it costs 12½ guineas. The Battery Super 4 is also a superheterodyne using a heptode frequency-changer and covering the ordinary broadcast bands.
Two GEC television receivers are also shown.
The Osram HA1 acorn valve for ultra-short-wave work.
A considerable number of new Osram valves is shown, among which the eye of the short-wave enthusiast will be caught by the HA1 Acorn. This is a triode of minute dimensions intended for operation at very short wavelengths, of the order of 1 metre or less. It has a mutual conductance of 1.7 mA/V and a resistance of 11,800 Ω. A new low-resistance diode, the D42, is also to be found, as well as a range of valves having heaters rated at 4 Volts 0.6 Amp. These are a triode H42, an HF pentode W42, and a heptode X42; all have top-grid connections and are supplied non-metallised.
There is a new rectifier, the U18, with an output of 500 Volts at 250 mA and also a new mercury-vapour rectifier GU5, which can deliver some 1,250 Volts at 0.5 Amp. The U17 is a rectifier which finds particular application in television apparatus, for it has an output of nearly 3,000 Volts at 30 mA. A new valve which finds special application in television receivers is the MSP41, for it has a mutual conductance of 3.2 mA/V with 4 Volts grid bias, 250 Volts; anode and 240 Volts screen potentials; it is an HF pentode. The N43 is another valve designed for television sets; it is similar to the N41 output pentode, but has much lower inter-electrode capacities.
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