THE WIRELESS WORLD

Otago Daily Times, Issue 22741, 29 November 1935, Page 2

THE WIRELESS WORLD

NEWS AND NOTES

By Magna Vox.

Items of local interest are invited by " Magna Vox" for publication in this column. It is necessary that such matter should reach this office by Tuesday of each week for insertion on the following Friday. 2BL, Sydney.—74o K.C., 405 metres. 2FC, Sydney.—6lo K.C., 492 metres. 3AR, Melbourne. —630 K.C., 476 metres. 3LQ, Melbourne.—77o K.C., 390 metres. SCL, Adelaide.—73o K.C., 411 metres. 4QG, Brisbane.—Boo K.C., 311 metres. IYA, Auckland.—6so K.C.. 461.3 metres. 2YA, Wellington.—s7o K.C., 526 metres. 3YA, Christchurch.—72o K.C., 416.4 metres. 4YA, Dunedin.—79o K.C., 379.5 metres. 4YO, Dunedin.—ll4o K.C., 261 metres.

ANSWERS TO CORRESPONDENTS. "Volume," Matakanui— (1) It is quite impossible to say, as I have no idea of how the circuit is coupled. It may not indicate a fault if the control operates over only about half its range—it may be made that way. At any rate, the only reliable advice you are likely to get is from the people who built the set. (2) Yes, he makes up sets. (3) Probably as much as anyone in the Dominion. F. D. N., Tomahawk.—l should not advise you to place a positive bias on the B. class valves, but it is a good idea to reduce the bias to nil—in other words, connect the bias lead to the C plus. But, as a rule with B class valves, when the batteries are low enough to need this treatment they are just about done. As a rule the rejuvenation is most suitable for valves with thoriated filaments. I have not struck anyone who has had much success with valves having oxide-coated filaments. " Circuit," Ranfurly not. It is very much out. You have no speaker so far as I can see, and a pick-up is connected where the speaker should be. It would be in order to connect the pickup across the grid circuit of the PMIHL, and the speaker would then connect where you now have the pick-up (2) I am sorry, but I do not know the connections for this coil. I suggest you communicate with the agents. (3) 5,6, 7, and 11vulve. SHORT-WAVE INTERFERENCE. There are sufficient sources of unavoidable interference with short-wave signals, such as fading and natural atmospheric disturbances, without the annoying kind of trouble that is due to other receivers in' the neighbourhood. Unfortunately, this type of disturbance, which is caused by unskilled or thoughtless operation of radiating types of receiver, is unduly prevalent in some districts. The trouble is generally caused by the operator of such instruments trying to pick up signals which are beyond the scope of his receiver, with the result that neither he nor any of his neighbours can obtain satisfactory results from the station that is sought. Unless offenders (who can be traced if necessary) are more considerate some action will ultimately be taken. A YOUTHFUL ADMINISTRATOR. Mr C. J. Moses, the new general manager for' the Australian Broadcasting Commission, is only 35 years old, and has had a comparatively short association with broadcasting. Still, the Australian radio community have the advantage that he is not too old to learn. Mr Moses is an Englishman of Quaker stock, though no pacifist, as he held a commission in the army. He is now installed in office, and much curiosity is felt concerning the results of his appointment. A VERSATILE INSTRUMENT. Recently an Australian trawler was arrested in New Zealand on a charge of fishing without permission inside the three-mile limit. The captain was able to exonerate himself because he had been using an " echometer" depth-sounding instrument, and had recorded the soundings, which, when compared with those marked on the charts, showed that he was well outside territorial waters. In several unexpected ways the echometer, recently introduced to Australian shipping, is proving of value. Primarily, it shows the depth of water under the ship's keel. It is consequently in constant use in thick weather when a bearing cannot be obtained off the sun or a star. On the Huddart-Parker liner Wanganella, running between New Zealand and Australia, the echometer shows when the 100-fathom line is reached. The Tasman Sea is very deep, but for 30 to 90 miles off the eastern Australian coast runs a shelf showing approximately 100 fathoms. The master of the Wanganella can obtain his longitude even when the sun is obscured by means of his chronometers, and the echometer readings now assist in determining the latitude. An additional use has been found for the echometer on the British Phosphate Commission's steamer Triaster, which trades between Melbourne, Ocean Island, and Nauru. The water in the latter localities is very deep, and shipping has to attach to buoys. The echometer indicates comparatively shallow spots, where the buoys can be anchored with a minimum of mooring line. Vessels like the Adelaide Company's Manoora and the Melbourne Company's Duntroon in the interstate trade use the echometer in heavy weather to fix successive positions accurately when approaching Jand, such as Wilson's Promontory and Gabo Island. Perhaps the most constant use of the echometer is made by the trawling fleet. Five of the Cam line carry echometers, the latest to be fitted being the Goorangai. Once a fishing bank is located, the echometer not only enables it to be found readily on any subsequent trip, but assists the trawler to keep on the bank. In the North Sea and on the banks of Newfoundland the echometer indicates the presence of shoals of fish. When a mass of fish passes between the keel of the trawler and the bed of the sea the echometer shows not only the actual depth of the water, but in a blurred form of record indicates also a false bottom, which is the passing shoal. Unluckily, the fish encountered in Australian waters do not? swim at intermediate depths, being either on the surface or on the bottom. AUSTRALIAN REGULATIONS. Discussions which have taken place between representatives of the commercial broadcasting interests and the AustralianCommonwealth Government regarding the amended wireless broadcasting regulations have been referred to the Postmastergeneral (Senator M'Lachlan) and a Cabinet sub-committee, so that they may investigate the position. It is understood that among the requests made by the commercial interests is one for the appointment of a Federal radio commission, similar to that of the United States of America, comprising a judge, a technical officer, and a business man, which would replace the Australian Broadcasting Commission. It has been suggested that the commission should be controlled by the Prime Minister's department. It is understood that the Ministry does not favour such a proposal, but that it will probably order a revision of the amended regulations. Mr M'Coll, M.P., said recently that he intended to move in the House of Representatives for the appointment of a select committee to inquire into wireless broadcasting matters. His desire was to have defined the relationship between A class and B class broadcasting stations, and to have framed a basis of national broadcasting policy. THE PUBLIC AND THE STATION. There is at present no simple and direct method of measuring the response which listeners make to the varied supply of information which they receive through the broadcast programme. Such response must be measured in different ways. Sometimes it takes the form of action, sometimes of vocal or written expression of opinion. The public may respond to a broadcast appeal for a good cause by contributing sums of money, or they may respond to a message on the eve of a bank holiday by leaving less litter about — both these are responses taking the form of action. On the other hand, they may respond by letter-writing or by telephone calls —though the average man does not habitually take trouble to 1 * express himself in this way. It is estimated that the 8.8. C. receives a total of at least 150,000 letters a year, divided roughly as follow: —Appreciation, 60,000; criticisms, 15,000; inquiries, 30,000; requests and suggestions, 7000; miscellaneous, 38,000. METAL VALVES. The metal type of valve has made its commercial appearance in New Zealand, sets now being available in which valves embodying this new form of construction are included. From now onwards it

might, therefore, be expeced that • the merits of this type of valve will be emphasised by the sales and advertising sections of the radio receiving manufacturing industry until those who, either from choice or necessity, adhere to glassenclosed valves will be made to feel that their receivers are hopelessly inadequate and out of date. That is the way in which various new technical developments have been introduced. Often the development has been really worth while, but sometimes the advance has been more superficial than real. In the case of .the metal valve, if everything turns out as is expected there must be undoubtedly an improvement in certain types of receivers, such as automobile sets and in some circuits, particularly of the shortwave variety. But there does not seem to be justification for a serious disturbance in the radio trade or the feeling that a set which has not metal valves is for that reason an inferior piece of apparatus. There is considerably more in the design of a successful receiver than the inclusion of-a particular type of valve. One might as well say that the inclusion of electrolytic condensers was essential in a set of good quality. This, everyone knows, is not so, for there are plenty of first-class receivers which do not use components of this type. The primary difference between the new metal type of valve and the type now in use is that the glass envelope has been replaced by a metal container. The adoption of 'this form of construction has introduced problems in manufacture, particularly the successful leading in of the wires to the various valve elements through the metal jacket. The solution of this problem has been largely one of research into materials. It has been overcome by the inclusion in the steel envelope of eyelets of a special alloy in which glass beads are embedded. The leads are taken in through these beads. The internal construction and arrangements of the electrodes do not differ very greatly from those of glass valves, but because of the construction more rigidity can be obtained. The capacities are also different, while the leads to the elements, because of their shorter length, have less inductance. These are matters of considerable importance in certain types of circuit. Beyond this the new type of valve has the advantage of being generally much smaller in size, .while there is the self-screening property of the metal envelope, a fact which will enable independent screening cans and similar devices to be dispensed with. Another difference is the contact pin and socket arrangements. The series of metal valves so far produced comprises about 10 different types, the majority of which are equivalent to certain types of glass-enclosed valves. The same range of glass valve has varying numbers and dispositions of pins requiring sockets of different constructions. The pin arrangement in the metal valves, however, is such that they will all fit into the same socket. This has simplified matters somewhat, because a universal type of -socket can be produced. Into this socket, which has eight pins, every valve of a series will fit, but each valve is only provided with the number of pins that are necessary for its proper operation. The correct location of the pins within the socket is obtained simply and without the necessity for inspecting either the socket or the location of pins. There is a projecting stem from the base of the valve, and this stem is provided with a key. Within the socket is a corresponding hole and keyway. Therefore the valve may be placed in position by inserting the projecting stem within the hole in the socket, rotating it until the key registers with the keyway and then pushing it into position, a simple and accurate operation. There has been considerable discussion in the United States, where this type of valve originated, as to both the need for it and its advantages. The question is still undetermined. One valve maker has gone so far as to compromise, so to speak, by including within tire glass envelope approximately the same construction as is available in the metal container and fitting this glass-enclosed type with bases and pins of the kind fitted to the metal valve. There is little doubt that the metal valve will be used considerably, provided, of course, that it proves its worth. As yet it seems premature to become over-enthusiastic about the type, especially as it is not certain that adequate supplies are available. At this stage there is perhaps quite a lot in the suggestion of one valve manufacturer, who, tabulating the advantages of metal valves, includes sales appeal due to its novel construction.