RADIO NOTES

Dominion, Volume 24, Issue 147, 18 March 1931, Page 15

RADIO NOTES

By

“ETHER ”

“A GREAT BOON” Indirectly-Heated Valves CHANGED RECEPTION The indirectly-heated A.C. valve has to a great extent revolutionised radio reception. In many cases it has brought radio from the status 'of a somewhat scientific instrument to a position previously enjoyed only by the gramophone, that of an article of furniture capable of turning out music when and where required, writes Keith D. Rogers, in ‘•Modern Wireless.” In the old days before the indirectlyheated valve was brought out, the owner of a radio receiver had one main tiling to worry about. Whether he built his set himself or whether he bought it ready-made, made no difference, he had always to worry about the batteries; to see that the L.T. was up to scratch, and (before the advent of the mains H.T. unit) to keep an eye on the H.T., too. With the advent of the indirectly-heat-ed valve, those fortunate enough to have the A.C. mains automatically found their troubles solved. They could run the whole set from the mains without worrying about batteries of any type whatever. Unfortunately, so fur comparatively few listeners have A.C. mains, but the new electricity scheme will gradually make itself felt throughout the country, until most homes which have electricity installed will have A.C. By that time, if A.C. valves go on increasing in efficiency as they are doing at present, the radio set will have become a tiny little box that can be tucked away in any odd corner, simply plugged into the electric supply system, but yet capable of bringing in all Europe to one’s own fireside. The A.C. valve is undoubtedly a remarkable piece of work. It has done away with the need for providing a D.C. L.T. supply, i.e., in most eases the. use of L.T. batteries. This in. itself is a great boon, but it has in addition enabled a most amazing degree of efficiency to be obtained, a degree which with the exception of one or two super-power valves has never been approached in the battery class. , The A.C. valve in most eases can be said to be half as good again as any battery valve of the same class, but before I go any further let me assure, those of my readers who are still afraid of the bugbear of hum that an A.C. need not hum if it is properly designed. Many people have toyed with the idea of going over to A.C. They have got A.C. in their home, but they are still clinging to the battery valve (although they may use an H.T. eliminator),‘because they are.firmly convinced that the indirectly-heated A.C. valve must cause hum. In some eases they have heard commercial sets run from A.C. in which there was a faint background the whole time the set. was working. They will admit that it did not interfere with the music, and might be termed “negligible,” but it was there, and that was enough for them. , An It takes at the most only 3(1 or 40 watts to run a four or five-valve A.C. set, so that for one unit of electricity you can run the set for something like 25 or more hours. ACCUMULATOR HINTS Points to Remember 'The modern accumulator is a sturdy piece of apparatus, and it will stand quite a lot of misuse without complaining. But consistent maltreatment will have its effect in the end, in the shortening of the battery’s life, and in gradually decreasing its reliability, writes “G.W.E.” in “Modern Wireless.” One of the most general forms of assault on its life is the over-discharging of the accumulator. Running it down too far is easily done, and at first seems to do no harm. But the harm is being done nevertheless, and in time such treatment will make itself felt. How far should we discharge it, then? Till the set starts to give distortion of signals, or should we recharge it as soon as the voltage begins to drop off? The latter is the better method, for if we discharge too far, then, again, we shall shorten its life. Also, we must not forget that a voltmeter applied either to a wet or to a dry battery is not a reliable test unless that battery has been in operation for about half an hour, and is still working. I have seen an accumulator which has been sulphated "up to the eyebrows,” and not used for several weeks, give a full two volts per cell for a fraction of a minute, but, of course, when put on load that voltage dropped almost immediately to zero. Then what about the accumulator terminals? In what sort of condition are these? Are they covered with verdigris or are they nicely smeared with grease and kept thoroughly clean? I mention this point because I myself have recently been rather careless with an accumulator, and I have had a merry time cleaning up the terminals and cleaning the spade-ends of the wires from their green coating. CORRESPONDENCE QUERIES “S.G. - ’ wants to know it it’s an easy matter to fit a screen grid valve to a set which has been designed for the oldfashioned neutralised triode. . Yes, it is a long job. ■ One thing leads to another. It is, however, a perfectly feasible undertaking provided you have had experience and understand what you are about. Precautions regarding shielding will have to be taken as the screen grid valve does not automatically allow for capacity interaction. The neutralising condensers compensate for this in the old receiver. “All Wrong” says his receiver has suddenly gone silent. Tuning is all over the place. Signals are as loud without an earth as with. The trouble is almost certainly a break in the earth lead. This may have taken place above the ground or under the ground if the wire runs to a buried plate. It is also possible that the earth has been sited in too dry a place. The summer has dried up all the surrounding moisture and left the earth “in the air.”

PIONEER RADIO Early Days in England REMINISCENCES OF AN ENGINEER The first regular programme broadcasts from Writtie, England, are related amusingly by Captain P. P. Eckersley, formerly chief engineer to the British Broadcasting Company, in “Popular Wireless.” Writtie —a long, low hut full of long, low people—suddenly finding fame for half a crowded hour of glorious life every Tuesday at 8 p.m. precisely. A. chop and a beer at the pub, some six of us, and back through the mud, and the “dark” lantern showing us the way, overeoated and rather happy. Through wet grass to the army hut, and then to crank up the engine. This is reluctantly coaxed from immobility to a shattering roar, the lights go up 10 T.U.’s and generators begin to squeak over. Two Emma lock! Switch after switch chases power into the proper circuits, valves crinkle into a glow, high tension, and a sluggish meter shows us four magnificent aerial amps. (But never worship the amp., it’s power that counts!) Gingerly I pick up the microphone, gazing out across the field to the lighted orange window of the receiving hut 50 yards away. “Hullo, Ash! Hullo, Ash. is my speech 0.K.? Hullo, Ash, 0.K.? 0.K.? 0.K.? Hullo, hullo, 1,2, 3,4, 5,” ad lib. And a bald head intersected by the bright bands of the telephones nods a welcoming "Yes!” The test is O.K. Shut down. Anxious eyes on the station clock (alarum, 5/-). Tick, lock, tick. Ready. On. 0.K.? (Whisper.) Kirke nods, his eyes on every needle. “Hullo c.q. Hullo c.q. This is WRRittle calling; 2 emma tock WRRittle. I hope you are hearing me, 1,2, 3, 4, 5,6, 7,8, 9, 10. Hullo!” And so on for a minute. A One-man Opera. “Our programme to-night begins with two gramophone pieces played on H.M.V. record No. 37058192. Oh! Toll! Wolli, Sop, Edith Swinger with Orch. Patent No. 92315, disc stamp 77860666606.” You’ve no idea how much reading matter there is on a gramophone record. As time went on we became more ambitious. Lampoons, rhymes, plays, singers, gongs, noises off; the 8.8. C. has never had a programme idea that had not its embryo conceived at Writtlc! Once the artistes failed. Fog! Dense fog! I was in London at 5.30, arrived Chelmsford by train 7.40, drove a motorbike through the thick fog (and Ashbridgo frozen with fear and cold in the side-car) right up to the door, flinging myself on the microphone (at 8 precisely) and gave the whole programme myself! It was, I remember, an opera! My reputation for leg-pulling got me one of the most amusing postcards of my life. A certain singer came to sing, and sang. The programme was reminiscent of some of the dirgier Sunday type we are so familiar with to-day. Even I became a bit depressed. My joy wns in inverse proportion to my sadness of the night before, when next day someone wrote to say it was the best burlesque I had ever given! The Louder the Clearer. And another singer who had the somewhat unscientific idea that the louder he sang the more clearly would he be heard in far-away Europe! The wish was perhaps father to the thought,. because he had left a bride to come to our barbarous land. If the wish were father to the thought, it was at any rate factual enough to count upon the equipment—more power, outside a sergeant-major, I have never heard. It was such a surprise ioo, because his intentions were not revealed to us, due to the lack of a common language. Nor did his accompanist (who was, incidentally, very charming, and caused havoc among the staff) reveal anything of the plot. Going All Out. It was the duty of one of us to hold a microgjione in front of the singer. That night our trustworthy and wellbeloved Kirke was chief microphone-bear-er. The opening bars were played. A whistling sound and the banging of windows heralded the singer’s cataclysmic intake of breath, but Kirke and microphone went hurling backwards as the exhalations were caught in the powerful vocal chords of this tremendous erEvery needle of every instrument flicked hard over, the engine groaned, sparks flew from here and there, the staff was seen running for blankets to damp the microphone. I wonder did the waves ever so faintly titivate the charming ears of the far-away bride? At least, there was some fiilfilment under the vaulted roof of the Heaviside Layer. Good days, dear days, and everything so new and untried and spontaneous. Wynn with a new doggerel, MacLarty with a new inductance, Ashbridge getting his circuits purer every day. Vast, long, windy arguments putting volts and amps in their proper place, patient improvisations to measure things and a steady and growing knowledge. It was surely a fitting cradle for the two chief engineers of the 8.8. C. But we spend too long in the Elysian fields; the stiffer climb awaits us, and we must leave the childish and vivid realities of the beginning, for the more breath-taking lower slopes where we started to carry that “banner with a quaint device to regions full of snow and ice?” (Is that right?)