THE WIRELESS WORLD

Otago Daily Times, Issue 22101, 3 November 1933, 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.—Bss K.C., 353 metres. 2 PC, Sydney.—G6s K.C., 422 metres. 3AE, Melbourne.—62o K.C., 492 metres 3LO, Melbourne.—B3o K.C., 371 metres. SCL, Adelaide.—73o K.C., 395 metres. 4QG, Brisbane.—76o K.C., 385 metres. IYA, Auckland.—B2o K.C.. . 365.8 metres. 2YA. Wellington.—72o K. 0., 420 metres. 3YA, Christchurch. —9SO;K.C.. 306 metres. 4YA. Dunedin.—6so K.C.. 463 metres. ANSWERS TO CORRESPONDENTS. “ Six-valve," Roxburgh.—No alteration to the set should be necessary. In the converter a locally-generated oscillation beats with the incoming signal to produce a new frequency which is within the range of the broadcast receiver, me arrangement is simply a regenerative detector, and its output is fed to and hetilt with by the existing set just as an ordinary signal. It is, in effect, another frequency changing stage. D. M. F., Mornington. — (1) Yes, but insert a sheet of thin paper between each layer. (2)1 am afraid 1 cannot give you any definite information, as you do not mention the output current and the resistance of the chokes. A drop in the rectifier cells would depend on the spacing of the electrodes, etc. As it is a simple matter to add turns to the secondary winding, make provision for a maximum output of, say, 24 volts. “ Battery,” Waimate.—lt would be possible to use the existing A battery charging means to charge the B battery by dividing it into, say, 16 sections of three cells, the sections being connected in parallel. The current required would then be 16 times the normal charging rate of the B battery. A means for limiting the current to the proper value would lie necessary, and each group of cells would have to be, in the .same condition. This would necesssitate taking all plate currents at the maximum voltage, with suitable resistances included, to drop it to the value required for the detector, etc. In any case, this is desirable to keep all cells in an equal condition. A LEAD-IN HINT. Many owners of wireless sets are sometimes puzzled as to the best method of bringing a lead-in via steel-framed windows. The following idea will prove neat and effective, and also be linn and weatherproof:—The articles required are two pieces of triangular ebonite, 2in by 2in by 2in (with hole bored through centre of each), and a piece of “lead-in” threaded rod with two nuts and terminals. Having selected the pane through which you require lead-in, with glasscutter cut about lin off corner of pane. Holding the two pieces of ebonite opposite each other, allowing them to rest on steel frame, pass through both the piece of rod, and with a -nut on either side, screw up firmly. Attach lead-in from aerial and to set with terminals, and to make the job weatherproof, fill up the gap between ebonite with putty. Most listeners will have the few articles required in the “ junk box.” If not, any wireless stores w-ould supply for a few pence. -The same method could be used for earth wire. FIERCE REACTION. Often you will notice that the reaction 6n a set is Too fierce. In such a case, one of the simplest things you can do to get over the difficulty is to use a small variable or adjustable condenser across the detector. This can be connected between the low-tension negative and the anode of the detector valve. It does not need to be a full-blown variable condenser; a pre-set condenser meets the case admirably, and for the maximum value of this about .0003 mfd. will generally be about right. All you have to do ia to screw down the pre-set condenser (thereby increasing the capacity, of course), and then gradually loosen the screw until you find you get the requisite amount of reaction effect over the whole of the tuning range. Having got things fixed in this way you do not need to interfere with the condenser any further. K CONDENSER TROUBLES/ You are often advised to take special care about, some of the condensers in an all-electric set on the ground that these condensers have to stand the full peak voltage of the mains or the peak voltage of the secondary of a transformer, which may be considerably higher than the voltage of the mains in certain cases. But as a matter of fact, it is not only the smoothing condensers which are sub* ject to these relatively high voltages; sometimes quite a high peak voltage is applied to condensers in places that are not at first apparent.* The reaction condenser used in the detector anode circuit, more particularly w-ith power-grid detection, may have to stand up to quite a high voltage, since one side of it goes to negative h.t. and the other side to h.t. positive. The fact that one set of plates goes to h.t. positive is apt to be overlooked owing to the connection being made through an h.f. choke and sometimes an l.f. transformer primary. You will see, therefore, that if this condenser breaks downs badly it may mean a shorting, or at any rate, a direct connection — perhaps it is hardly right to call it a direct “ short ” —through the choke and transformer primary, not to mention the reaction coil. The items most likely to suffer are the choke and the transformer winding. It is important to choose a good Ci. "denser for this position—one tested well up to twice the maximum voltage delivered by the h.t. unit. THE WORLD’S TIME. With radio communication between different countries, time has taken a significance which is very confusing to a large number of people. For instance, when we hear American stations signing off of an evening the time given by the various towns is often different from what w'e expect from a perusal of a map of the countries concerned. The reason for this is that while theoretically every place on a certain line of longitude should observe the same time, this cannot be done in practice. The earth revolves on its axis in approximately 24 hours, and for convenience clocks are divided into 24 equal hours, this being the basis of mean solar time. The length of the mean solar day is constant, but the interval between one transit of the sun across the meridian to the next varies from various causes, and in order to have a unit of measurement it is necessary tb disregard the true sun and take a fictitious body known as the mean sun as the standard of meridian transit. The moment this mean sun passes any chosen meridian it is twelve noon, and the interval between successive transits is exactly 24 hours. Thus there is a difference between the time shown by a sundial and the time by a clock, or mean time, as it is called. This variation of time is called the equation of time, and varies from day to day, only agreeing in four days in the year, i.e., December 25, April 15, June 14, and August 31, the clock being as much as 16min 18sec fast and 14mm 28sec slow of solar time. The time adopted by most countries of the world is taken from the Odeg meridian of Greenwich, places east of Greenwich being faster, and west slower. To facilitate commerce the establishment of different time zones of 15 degree intervals corresponding to hourly periods was made, but in some cases, as in New Zealand, Australia, India, and the Hawaiian Islands, a meridian of 7Jdeg was chosen as being nearer true time. This marked a half-hourly period. The folowing gives the times of the principal countries with relation to Greenwich time, which is 'observed in Britain, France, Belgium, Spain, and Portugal:— —Faster Than Greenwich. — Hours. Fiji 12 New Zealand .. .. 111 Eastern States of Australia .. 10 Japan 0 South Australia 0J West Australia, China 8 Straits Settlement 7 | Burma 6J I India .. .. 5J ] Portuguese India .. 5 ' Mauritius 4 Somaliland 8 Africa, Russia, Western Europe 2 Eastern European States .. .. I

—Slower Than Greenwich.— Hours. West Samoa •• East Samoa .. .. .. •• •• Hawaiian Islands Yukon and Alaska W Litka • • • • ; • a Pacific Coast of America, U.S.A., and Canada .. .. . • • • 8 Mountain Zones of U.S.A. and Canada .. .... • • • • ' Central States of U.S.A. and Canada • • • • ® Eastern States of U.S.A. and Canada, Panama and Brazil 5 Newfoundland | Eastern Brazil 8 Azores .. .. " Iceland 1 From this will be seen that all these times are exactly hours or half-hours, and not, as some radio time clocks show, intervals of time shorter than the above. HERE AND THERE If we are to believe the considered opinion of one radio expert who has recently paid a visit to the Australian stations where that country scores over New Zealand is in the excellence of its land lines. For broadcasting purposes special lines suitable for the purpose have been laid capable of transmitting all the desired frequencies. This enables the Australian authorities to utilise opportunities far more frequently than is possible in New Zealand. Although it is a costly business to lay special lines of this nature it makes it possible _to buy and put the best talent over the air. The cost when divided between the stations relaying the programme works out at a very reasonable figure. As regards the technical side of the actual stations, our new transmitter at Gebbie’s Pass will’be as good as, if not in advance of, any station in Australia.

Although the 8.8. C. has now been making television transmissions for over a year, it is estimated that there are_ only a few hundred “ lookers-in.” This is rather extraordinary, as in the. present stage of development results have been good. The Baird Company’s receivers are no longer experimental, and can receive the 8.8.C.’s transmissions successfully. The fear of sudden technical advances and probably, the desire to have something equal in quality to the cinematograph is apparently causing the public to hold back.

There seems to be little doubt that the French Government is at last _ taking steps to reorganise broadcasting m France. The introduction of a licence system along with taxes was the first evidence, and the effects of the Lucerne plan appear to make it essential for France to perfect her broadcasting organisation. The latest news suggests that the French Postmaster-general is preparing the way. Speaking at Lille, he said that Radio Paris would be definitely taken over by the State on November 1, and that a decree would be issued giving details of the scheme for the operation of State stations by local associations, in which listeners would be represented. A system for the reorganisation of broadcasting in France has long been in_ existence —the original to put broadcasting on a sound basis was introducel in July, 1928—but changes of Government and opposition by private interests have prevented its being passed into law. Some three or four years ago, however, a commission was appointed to inquire into French broadcasting. The commissions report was adopted, and is now being put into force. * «

During the financial year ending June 30, approximately 1,388,470 valves were imported to Australia, and of these over 1.000. (compared with 639,000 in 1931-32) came from the U.S.A. Great Britain last year supplied only 100,000, which, however, was a gain of 23,000 over the previous year; while Holland sent 260.000, a decrease of 70,000., In 1931-32 a total of 1,057,828 was imported, and m the preceding two years 734,842 and 678,530 respectively.

In Switzerland the Ministry of Posts and Cummuications has made a regulation, which came into effect on July 1, that only properly registered dealers will be allowed to sell sets and erect aerials These dealers will be licensed only after passing a technical examination. Moreover, not only the proprietors, but also the employees must pass the examination, and changes <sf staff must be notified to the authorities. Every dealer must pay the Administration five francs in respect of each set he installs.

* * North America, although not troubled to the same extent as Europe in the mattej of interference between stations of different nations, has its troubles in this respect. Certain Mexican and U.S.A. stations have caused mutual interference. A conference was recently held in an attempt to settle the trouble, but as Mexico wanted six exclusive channels and the U.S.A. would not give way to that extent, nothing came of it. In the meantime, the trouble continues.

The decrease in the number of German listeners continues. The total number registered on August 1 was 4,483,278, as compared with 4,521,106 the previous month. Of the total no fewer than 531,230 are issued free to unemployed persons, so that the total number of paying listeners in Germany is below 4,000,000.

Australian license figures are nearing the half-million mark, and a handsome prize of £75 cash will be awarded the listener who takes out the license bearing the number 500,000.

A Japanese announcer —most punctilious of men —has been getting into serious trouble fob impoliteness. Apparently he was in the middle of an interesting talk, when he paused dramatically, and then, without the slightest warning, sneezed! The cultured ladies and gentlemen of Japan could hardly believe their own loudspeakers. Let us hope there will be none of that harikari business. Politeness is all very well, but, after all, a sneeze is a sneeze, and no respecter of microphones.

In contrast to our own credit balance of over £2OOO, the Irish Free State’s Minister for Posts and Telegraphs states that the 1932 revenue from broadcasting licenses was £17,296, to which may be added Customs duties on apparatus, £64,682, and miscellaneous receipts, £220 —a total of £82,198. The expenditure on broadcasting services was £87,945 (including £46,000 for the Athlone station), resulting in a loss of £5747. During 1932 there were 33,083 licenses issued, an increase of 4438.