The Advance Short-Wave Set

Radio Record, Volume V, Issue 25, 31 December 1931, Page 15

The Advance Short-Wave Set

(To the Editor.) I AM pleased with the results obtained with the Advance A.C. short-waye set. I have constructed several battery models with and without 8.G. valves in the past, but none have given the satisfaction the Advance is giving. The power supply is from a power-pack designed for about 100 mils at 250 yolts, and is much bigger than necessary. Voltage is regulated by Resistograd, the 8000 ohm resistance being eliminated. There is absolutely no hum from the "B" supply, and no tuneable hum, although the 1 m.f.d. condensers by passing the filaments were not used. The push-pull stage was eliminated, so the receiver is only 12 inches long instead of 18 inches. The output of the first audio is, however, fed into the pick-up jack on my Loftin Four for loudspeaker work. It was here a little difficulty occurred. A 1:5 transformer was used for the coupling-resuit, hopeless distortion and terrific hum from the speaker. A 34:1 transformer was then tried, but results were no better. The step-up transformer was then replaced with a 1:1 output transformer, and this proved to be entirely satisfactory. Whether the amplification is too great with the step-up coupling I do not know, but it would appear so. The gain with ‘the present arrangement is quite sufficient, all the main American stations coming in with the volume of 2YA when conditions are good.-L, McMillan (Christchurch),