Umello Five Valve Receiver

 This battery powered receiver dates from 1930 and is quite stylish considering its early date when the norm was a rather boxy design.

 Tuning was accomplished by rotating this control which is connecting to a cheap solid dielectric tuning condenser. I suppose the limitation on space precluded an air-spaced component as much as the price. You'll note that station markings are absent. This feature only appeared a couple of years later once broadcast stations were allocated their own wavelengths.

 Below, the matching volume control which is actually a reaction control for adjusting feedback. If you haven't had experience of this, let me explain what happens. As the setting is moved away from zero the set will gradually get more and more sensitive with a tuned station getting louder and louder up to the point where excessive feedback causes oscillation of the RF stage turning the receiver into a transmitter. Station volume usually drops off and is accompanied by a hiss. The aim is to move the control to the point immediately before this happens.

 Despite the very high cost of valves and increasing patent levies on their number, manufacturers added valves to make the set sound more attractive to well off buyers. This receiver employs an internal frame aerial so it needs extra overall gain to produce loudspeaker strength signals. Unfortunately the loudspeaker is missing from this example. Early loudspeakers used a high impedance coil that could be driven directly from the output valve and, because the coil used extremely thin wire, it was common for this to go open circuit either from corrosion or from the output valve drawing excessive current. Most battery sets used three batteries. An accumulator for the valve filaments, an HT battery and also a grid bias battery. The grid bias battery was usually around 9 volts and because its drain was extremely low would last for many years. Its chief function was to negatively bias the output valve to reduce its anode current with little effect on station volume. If the battery eventually failed or became disconnected it wasn't really obvious to the user but if the output valve current became too high the loudspeaker might fail. Before the speaker failed a user might wonder why his HT battery wasn't lasting very long.

 The set has two wavebands. Back in the 1920s and early 1930s broadcasts were to be found in what are now termed "Long Waves" and the low end of the "Medium Waveband". Once it was discovered that broadcasts were reliable even at 200 meters or less the wavebands became Long and Medium. Really long distance communication was found to be possible at even shorter wavelengths and by the mid 1930s the Short Wavebands (60 to 11 meters) became popular. The switch below marked "Long" and "Short" reflects the situation in 1930 and actually refers to what would soon become Long and Medium wavebands. As you can see the wavechange doubles as an on/off switch.

 The underside of the case is fitted with a turntable enabling the case and therefore the internal frame aerial to be rotated for maximum volume or minimum interference. The latter being important because in 1930 frequency allocations hadn't been properly sorted out. Particularly at night when continental broadcasts could be extremely strong it might be necessary to null one out to reduce interference to ones local station.


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