A Modern All-Electric Receiver

Radio Record, Volume II, Issue 49, 21 June 1929, Page 4

A Modern All-Electric Receiver

Lecture to Amateur Radio Society

At the last meeting of the Amateur Radio Society Mr. Firth, of Kirkealdie and Stains, lectured on and demonstrated a combination model of the Majestic all-electric radio receiver, — In opening his remarks the speaker stated that in 1928 the radio forecast was none too bright, and many were beginning to point out that radio was slackening up. It was then claimed that the introduction of the new Majestic had done much to stimulate interest in radio. It had answered three questions: First, it was unique, better, and distinctive in every way. Second, good reception was assured; and, third, -the all-important price factor. The march of progress had seen the im‘provement in every direction in the reproduction of music, and it became evident that power supply would be necessary and power blocks for "A," "B," and "COC" came into universal use. Distance is not now usually considered important, the stress being laid upon the better reproduction made _ possible through improved power valves and transformers. ' "The following points are worthy of e in our modern receivers," said Mr. th. "The price is as low as compatible with efficiency and appearance rchassis, all-metal, well brac- ' and completely shieldedwith large field coil and well built, power pack robust and able to geliver ample current, single dial conrol and: smooth volume control, all mives A.C., cabinet a piece of furniture, electivity sharp and clean cut, volume anol? for any home without distorSome 7500 persons are employed gvery day in the Griosly Grunow ComApennines ue a

pany, of Chicago, who manufacture the Majestic. Thirty railway truck loads of raw material go into the plant every morning, and 32 truck loads of completed radio sets go out every night. That means 4000 complete radio sets are turned out every day. Approximately 94 tons of steel are used each day, 25,000 miles of enamelled wire are used for loudspeaker coils, 16,000 pounds of tinfoil and 12,000Ib. of paper are daily required for the condensers, Technical Features, "THE circuit is the balanced R.O.L. type with the new "raw A.C, valves." Volume control is effected in the input circuit in such a manner so that there is no time to lag as in the case of a filament voltage control as when using a 227 type of valve as R.F. The antenna trimmer which permits adjusting the input circuit to bring it into exact resonance with the other tree tuned circuits is an excellent selectivity control. he valves used are the standard A.C., the R.F. and audio being the "raw" type and the detector the fiveprong indirectly heated. A useful feature in the power pack ‘is the line voltage control, which automatically adjusts the primary to the surges of the A.C. from the mains. This prevents the valves being burnt out through overloading. The power unit provides both filament supply and "B" and "C’" power. The rectifiers are UX281, and combined with chokes and condensers makes an excellent rectifier. The inductance of the magnetic field of the dynamic speaker is used as a choke in the "B" voltage supply. The speaker is of the electro-dynamic type, and will faith-

fully reproduce a wide range of frequencies. Grid bias is accomplished by applying a positive potential to the filaments and earthing the grids. This has the same effect as applying a negative bias to the grid. Having finished his lecture, Mr. Firth d nonstrated. With an aerial comprising a wire thrown across the roof and an improvised earth the receiver was able to bring in Auckland at quite good strength, though unfortunately power noises were very bad in that particular area. Christchurch and 2BL were both heard. 2YA came in at great strength and with good quality. Switching over to the gramophone pick-up by merely rotating the dial till it reached its limit, Mr. Firth entertained by several well reproduced gramophone records and demonstrated that the set was capable of delivering a greater volume than could be needed or a whisper barely audible. In conclusion, the speaker was accorded a very hearty vote of thanks for his in-. teresting and instructive lecture.