THE WIRELESS WORLD

Otago Daily Times, Issue 22397, 19 October 1934, Page 2

THE WIRELESS WORLD

NEWS AND NOTES By Magna Vox. Items of local interest are invited by " Magda Vbk ” 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. 2131., Sydney.-*--655 K.C., 858 metres. 2FC, Sydney.—66s K.C., 422 metres. 3AR. Melbourne.—62o K.C., 492 metre# SU3 Melbourne.—Bßo K.C., 371 metre#. 60L, Adelaide.—73o K.C., 395 metres. 4QG, Brisbane —760 K.C., 385 metres, IVA, Auckland.—6so K.C., 461.3 metres 2VA, Wellington.—s7o K.C., 526 metres. 3YA, Christchurch.—72o K.C.. 416.4 metres. 4VA Dunedin.—79o K.C.. 379.5 metres. 4YO, Dunedin.—ll4o K.C., 261 metres.

ANSWERS TO CORRESPONDENTS “Aerial," Anderson’s Bay.— (1) An aerial of about 60 feet, and as high as possible, should be about right. (2) If you use a crystal set off the name aerial you will certainly get interference from tho valve set to the crystal. (3) Frequently, .an earth used in the aerial terminal will give better signals on an electric set, more,especially if it is a superhet. (4) If you heard the record from that station, the proprietors would be certain to have it in stock. See them. "Selector,” Oamaru.—(l) Ability to control selectivity is of value in some circumstances, as it is possible, when interference is not present, to increase the width of the frequency band received, and so improve tone. Tone control, if the unrestricted audio-frequency band is wide, operates in njuch the same manner. (2) I have to knowledge of the eet you mention. There is no agency for it iff Dunedin. " J. D. O’M.,” Dunedin.—Generally speaking, selectivity and sensitivity are radio frequency functions, and when unsatisfactory, it is logical to look first in the radio-frequency system—tho antenna, and the radio-frequency amplifier. If the detector tube is tapped with a pencil, and a ring comes through the speaker, this can generally be taken as an indication that the audio' frequency channel is O.K. A more practical test is to lift the grid-cap of the detector valve to see if a click or a hum comes through, or, better, still, if a pick-up is handy, put a record through. A cursory inspection of the aerial is sufficient to establish its innocence or guilt. Insulation and shorts are the points to watch in connection with the aerial system.

COMBATING INTERFERENCE. The long-awaited legislation for the purpose of minimising man-made static has at last been brought down, and if the terms of the Act are strictly enforced listeners throughout the Dominion should in the future be freed from the bugbear of interference caused by electrical equipment. Portion of the regulation reads: “It shall not be lawful for any person to install, use, or sell or manufacture any interfering equipment (whether wifetess telegraphic apparatus or not).” Under this clause vacuum cleaners, violet ray machines, electric motors, washing machines, tramcars and power lines will be required to be reasonably free from those faults that mar radio reception. Under the Act, the radio inspectors are given fairly wide powers, and another clause states: "A radio inspector may, at any time, by notice in writing, require the owner or user of interfering equipment, within such period as the radio inspector may in such notice prescribe, being not less than 14 daya not more than 30 days, after service of the notice, to take such of the following steps as in the circumstances the radio inspector may require, namely:—To discontinue entirely the use of such or to discontinue the use of sueu interfering equipment otherwise than during hours to be specified in such notice; or to eliminate, and keep eliminated, the interfering effect of such interfering equipment; or to reduce and keep reduced, go as to be negligible, the interfering effect of such interfering equipment.”

JAPAN’S PLANS. Long-distance enthusiasts will be interested to know that Japan’s five-year radio plan is proceeding apace. The management of the Japanese Broadcasting; Commission proposes to spend 10,000,000 yen' (£1,500,000) on the scheme, which includes a ISOrkilowatt station for Xokio, two high-power stations at Osaka and Kiosho, and from 10 to 15 regional stations on lower power, all to be completed within 18 months. Meanwhile, the main streets of Tokio and Osaka resound with broadcast programmes relayed by public address equipment. This is no doubt a step towards popularising private ownership of sets. AN AMBITIOUS PROGRAMME. An interesting feat of organisation lies behind the preparations for the broadcasting of the visit to Australia of the Duke of Gloucester. Minute attention to detail has been necessary in view of the great number of points at which microphones have had to be installed, and from which land lines have had to bo reserved. No fewer than 50 relays have been arranged, each of these relays having to be put on the air through 10 stations and requiring no less than 4300 miles of telephone network. There is, in addition, a large number of local relays not included in the above figures. A small army of engineers will have to tend these land lines, and a special group has to take care of terminals in 19 of the smaller towns, apart from staff at the main centres. The first broadcast was from 6WF, Perth, of the arrival of the cruiser Sussex at Fremantle, and this is to be followed by varied descriptions of the royal progress, including dance relays, official ceremonials, agricultural shows, receptions, race meetings, dinners, theatrical galas, sports displays, and an air pageant. The programme is probably the most ambitious ever attempted. DELAYED ECHOES. Among the many puzzling problems that have been presented to those whose duty it is to investigate the phenomena of wireless transmission is that of long delayed echoes. By that is meant duplicate and_ triplicate reception of a signal an appreciable time after the first reception, which would be the direct message between the transmitting and receiving points. This is distinct from the second or third reception, which may be accounted for by the fact that the signal may have taken two paths, or that duo to a signal which may have gone , twice or more times round the world. In the latter case, (the intervals between the signals are only small fractions of a second, but in the case of long-delayed echoes the intervals between first, second, and subsequent receptions are measured in fractions of a minute. The existence of this type of echo seems to have been suspected first about seven years ago when short wave signals from PCJJ, in Holland, were found by a Norwegian amateur, Hals by name, to be followed by echoes about three seconds later than the first signal. In 1928 a special series of transmissions from this station were listened to by experienced observers in Holland, Norway, and England. Echoes at various intervals up to 30 seconds were heard, but there was no uniformity about the results, more echoes being heard at one place than at the others, while the time intervals were not equal. Since then other observations have been made, but the subject is far from exhausted. Various theories have been advanced to account for these echoes, which appeared to have been brought about by some extra-terrestrial influence distinct altogether from those that cause fading and make long distance communication possible. It has been difficult to account for the observed results, but it seems that the sun has a considerable effect, a view that is strengthened by the fact that during an eclipse of the sun in 1929 there were no echoes during the period of totality. An early suggestion was that signals which reappeared a few seconds after they had been first received were reflected from the moon, but the distance there and back is such that only about three seconds would be accounted for by this journey. A theory, suggested by Professor Stormer. of Norway, is that there are masses of electrons shot out from the sun, which form reflecting clouds of electrons at distances from the earth several times that from the earth to the moon. The signals are supposed to penetrate the normal atmospheric reflecting and refracting layers, i which are responsible for long-distance 1 transmissions, and fading, and travel out

to ths electron clouds in space and back again to the earth, A directly contrasting explanation is that put forward by Dr Van der Pol, of Holland. He suggests that the waves do not leave the immediate vicinity of the earth, but that they enter that region of the atmosphere which is known as the Heaviside layer, when it is in a particular critical condition, and travel within for an appreciable time, subsequently being reflected out again to make their appearance at the surtace of the earth some seconds after they had first left. Still another explanation, due to Professor B. V. Appleton, is somewhere between the two suggestions previously referred to. It may be that the waves are trapped in between two or more of the reflecting layers which exist in the upper atmosphere, and after reflection back and forth, which takes an appreciable time, ultimately escape and reappear on earth again. Whatever may be the reason for these echoes, the fact remains that they do take place, and, with a view to providing data which may result in the elucidation of the mystery, a scheme of “ mass listening” has been recently organised in England and Europe. Listeners and experimenters from as wide a field as possible have banded together into an association known as the World Radio Research League, under the guidance of Professor Appleton, to listen to and furnish reports on a number of special transmissions arranged for from the 8.8. C. shortwave station, 6SB, the League of Nations station, HBL, at Geneva, and the German short-wave stations, DJD, DJC, and others at Zeesen. From the reports received, it is hoped that further light may be thrown on the phenomenon of long delay echoes. All this work may seem a waste of time and energy to those who are not engaged in or interested in research. Perhaps it is, but there is no knowing that it may not produce an explanationof some perplexing problems associated with short-wave transmission. The_ early experiments and efforts of Marconi no doubt seemed equally aimless at the time.