RADIO NOTES

Dominion, Volume 26, Issue 185, 3 May 1933, Page 6

RADIO NOTES

By

”ETHER”

CURRENT TOPICS AU those who helped to organise and to work the radio stations used in the recent emergency, caused by the four trampers who tvent astray in the Tararuas, deserve the thanks of tile community. Indeed, it might be said that this emergency lias afforded the first real test of the emergency corps. There is now not the slightest doubt as to its utility. Usually lack of quick communication becomes a greater emergency than tlie emergency itself. The recent quick dispatch and reception of important messages from the back of beyond undoubtedly helped iu the smooth working of the rescue organisation which was such a feature of the emergency. Incidentally, it has also proved what can be done by keen amateurs equipped with battery-driven short-wave transmitters little bigger than a pocket, torch. Those who participated in the transmission work are to be congratulated on the work they did. « * * However laudable may be the efforts to equip hospitals with radio, there arc two facts that might well be emphasised. In ■ the first place every patient docs not necessarily wish to listen to the programmes. For that reason it should be possible for a patient to be able to have peace and quiet by the turn of a switch. Kindhearted individuals who gave gramophones to be used iu base hospitals during the war doubtless never realised how their gifts were apt to be abused. Another important- point concerning the installation of radio iu hospitals is that the gear will not wear for ever. Some sort of an estimate should be made as to possible running costs, and means found to insure that the money will be forthcoming. In England at the present moment there ' are many hospitals blessed with derelict and out-of-date radio equipment that has become a white elephant. In the case of a large hospital upkeep costs are by no means the negligible sums associated with a radio set in the home. * ♦ * Some time ago the 8.8. C. Advisory Committee on Spoken English confessed itself unable to pronounce the word “Joule” —which is not English, by the way—-and asked for advice. Keplics have been received from twentyseven relatives and friends of Joule and forty-nine other people named Joule. The near relatives rhyme the word with “cool.” Six relatives rhyme it with “coal,” and nine others plus thirteen who own the name rhyme it with “cowl.” • ♦ # lit It is unfortunate for the Empire, the 8.8. C., and .Mr. Malcolm Frost, that tlie last-mentioned has fallen sick in Cape Town and must, on doctors’ advice, give up his trip round Ihe Empire to demonstrate the 8.8.C.’s recorded programmes. When illness overtook him he was going strong and doing well. Another representative will take up his work and, it is hoped, carry out the scheduled programme. No doubt many a bumble, imaginary romance lias been built up in tlie minds of some listeners by the silver tongues of radio announcers, but to Announcer T. F. .Smith, of station K.TIt, Seattle, has fallen, according to the “Christian Science Monitor,” the glory of inspiring by his voice sufficient, confidence in a British Columbia listener to cause that listener to send him .100 dollars to be invested in reliable stock. The story is prettily completed by the fact that subsequent correspondence revealed that both men come from Britain. * From April 2 the hours of Empire broadcasting to the Indian, African, nd West African zones have been extended. The Indian programmes begin in London at 1.30 p.m., and will continue till 5.30 p.m. G.M.T. The other two zones will be served with a programme from 0 p.m. to .10.30 p.m. G.M.T. The .Indian extension will, incidentally, benefit listeners in Western Australia and Malaya. 'These improvements arc due to information supplied by Empire listeners. « V The new Middle German transmitter, the most powerful of the country, has been installed at Wiederau, near Leipzig, in a location found to be particularly suitable by actual tests. This transmitter, which has been built by the C. Lorenz Company, is capable of a non-modulated output of 120 kw., which in the ease of a7O per cent, modulation, will increase to about 130 kw. Because of the narrow wavebands separating the various broadcast transmitters, it is of the utmost importance that Hie official wavelength should be accurately maintained. In fact, any fluctuation in tlie transmitter wave is bound to result in interference with neighbouring stations, thus making clear reception impossible. Controlling the transmitter by a quartz crystal is a particularly handy means of securing great constancy of wavelength, the crystal being fitted info a copper thermostat. Tlie constancy 01. temperature thus obtained is 1/1000 degree Centigrade, and the constancy of frequency is about 1/1,000,000. STUBBORN SCREWS Ways of Conquering Them Those screws I hut simply won’t go into their holes on the baseboard are a source of constant irritation to the constructor. They will fall all over Ihe place, stick under the wiring, lose themselves under components—in fact, do anything except "go home.” Several cures present themselves. Perhaps the easiest is a judicious use of soap on tlie end of the screwdriver. Screws and slotted terminal nuts can lie dealt with easily iu this way. so long as you remember to clean the soap off afterwards. When you have a component with a thin. Hat base, it is a good plan to prick holes iu the baseboard first, and then hold the component a quarter of an inch or so from tlie baseboard. This will steady tlie screws until they have a grip in the holes. A third method is to use a piece of cardboard bent at one end with a slot In it to take the screw. RADIO IN JAPAN “To-lhe-Point” Broadcasting Japanese broadcasting began in 11)25 (March). In August. 1925, there were 100.000 listeners. By September. 1925. this number had risen to 500,000. Al the end of October, 1932, there were 1,280,320 listeners. (The population of Japan is about 81 millions.) Programmes are very much to the point. They begin at 0 a.m. with physical exercises. On weekdays there, are five weather reports, eleven market reports, and live lectures; I lie odd moments are occupied with menus, music and news.

TYPES OF VALVES Light on a Subject Now Becoming Obscure THREE PRINCIPAL KINDS Doubtless newcomers to radio aie becoming more and more muddled by the never-ending succession of valves that, are appearing. The following facts concerning the main types of English valves may help to throw light on the subject:— Although the various valves listed by the valve manufacturers differ in certain details, there are virtually only three main types which we need consider under this heading. Battery and mains valves are fundamentally the same, differing only in the means employed to produce the necessary electron emission. This is achieved in the battery valve simply by coating the filament with thorium, which becomes active and emits electrons upon the passage of a low-ten-sion current through the filament. Thus the filament is also the cathode. In the mains valve the filament and cathode are separate, the name heater being given to the former because its work is merely to heat up the cathode (which is a coated tube surrounding the heater) to the temperature at which it gives off electrons. Constructional Variations. The constructional variations are solely to meet the different conditions under which the valves are operated, and have no bearing upon their ability to amplify or detect. These two classes of valves can therefore be grouped together for all practical purposes, but it must be remembered that the mains class are more efficient than their battery equivalents, and in consequence are not interchangeable stage for stage in a receiver designed primarily for battery operation. Dealing with the three types '.f valves in common use, we have: (1) The screen-grid or four-electrode valve. (2) the three-electrode valve, and (3) the pentode, which has live electrodes. The screened-grid (S.G.) valve is used principally as a high-frequency amplifier and occasionally as a detector. Advent of S.G. Valve. Prior to the advent of the S.G. valve high-frequency amplification had to be carried out with the aid of the threeelectrode valve, which was generally neutralised to prevent self-oscillation. The S.G. valve has four electrodes, the extra one being the screening grid, and when this is joined to the appropriate tapping of the H.T. supply perfectly stable amplification can readily be achieved. The variable-mu valve is a particular form of S.G. which permits the magnification given by the valve to be varied at will without introducing distortion. 'l’uriling now Io the three-electrode valve, among its many uses are those of detection and low-frequency amplification. The "II” and "11D” types make very good detectors, while the “I" type performs excellently as first; stage low-frequency amplifiers. Power and Super-Power. Bor the output stage there arc the power and super-power types. The lastnamed is capable of handling more power than the former, but does not magnify weak transmissions to quite the same extent. There is no advantage in using a super-power valve unless the sensitivity of the receiver is such that it overloads a valve of the ordinary power type. The pentode is a power valve with five electrodes, its primary advantage being the ability to give a relatively large output, for a small input. In other words, the pentode magnifies a weak transmission to a greater degree than a three-electrode power valve, and for this reason is it good valve to use in cases where it is desired to get. the utmost from a set. But. this high magnification is often a limitation, because it is easy to overload a pentode.

HUNT FOR TRAMPERS Emergency Radio System HOW CORPS OPERATED lu view of the prominent part taken by radio amateurs in the recent search for the missing (Tampers in the Tararuas, the following description of the gear used is of especial interest.: — The Radio Emergency Corps comprises some .12 or 1-1 sections throughout New Zealand. Each section lias about 12 members and the whole corps is under the command of .Mr. IV. G. Asbbridge, of Wellington. The Wellington section has .15 members, three porta ide stations, and six stations which can act as a base in an emergency. The portable transmitter and receiver as used at I he Mountain House, Mount Holdsworth, consists of a twovalve receiver (detector and one audio), with variable resistance regeneration control and Hartley transmitter. Four-volt valves are used throughout and are interchangeable in case of breakdown. Receiver and transmitters are housed in one case, and batteries in another, the total weight being from 13 to 141 b. complete wifli aerial, headphones, key. message pads, etc. Various types of aerials are used, depending on where Hie station is erected —generally an aerial anil counterpoise system is used. The power supply consists of three batteries. 4J volts, in parallel, for lilamenls, and a tilt-volt block for high tension. Extra H.T. batteries may be added if the occasion warrants their use. At .Mount Holdsworth the above station was erected at the Mountain House and another intermediate station was erected at the tearooms on the summit of Hie Rimulakas. The base station was in Wellington. The equipment at the Summit was similar to that at Holdsworth, but of higher power. The base station was a multi-valve, crystal-control station with 100 walls input Io the final amplifier. All the transmitters and receivers cover the 75-85 metres amateur band as well as the 100-105 metre emergency band. USEFUL DIAL INDICATOR A very useful and effective dial indicator can he made from an old bone or wliitewood knitting-needle. A hole is drilled in the panel above the tuning dial or in the most, suitable position, find this should be slightly smaller in diameter than the needle. A small section of the needle about the thickness of the panel is cut. off and tapped into the panel hole. If preferred an ink mark can be put on the indicator. White bone looks particularly attractive against a black or mahogany panel.