RADIO

Southland Times, Issue 20949, 5 December 1929, Page 14

RADIO

STATICS ON WIRELESS With the advent of summer weather the atmosphere is charged with a greater amount of electrical disturbances, and reports of weak long-distance receptions and excess of static have been received. The complaints are not confined to Auckland, but have been - reported in the South, says the N.Z. Herald. Listeners-in at Wellington recently have found the Australian stations yielding poor audibility, although the volumes increased considerably after midnight. Interference from static in that centre has been reported as common. The trouble, however, is usually experienced at this time of the year. With reference to the interference by static “Listening In” writes as follows: — “I would like to ask some of your readers who have been listening in lately if they have been disappointed with the static or noises on the loud-speakers. I have a fourvalve set and I cannot get any of the Australian stations clearly, there being too much noise to hear anything. The same applies to the Southern stations in New Zealand occasionally. I would be thankful if others would advise if they are having the same experience, what is .the cause, and how to remedy it.” TESTING LOUD-SPEAKERS THE EAR SUPERSEDED. The remarkable - improvement made in loud-speakers within the past two years is due very largely to acoustic tests which dispense with the human ear altogether. Few people in the whole world have ears perfect. enough, and their sense perception trained well enough, to give an accurate account of the response of reproducers under test. The newer method, and the only reliable one for common use by the acoustical and loud speaker expert, is an electric one. It consists of applying for a single frequency, of pure sine-wave characteristics, to the reproducer under test, and then picking up with a special microphone the response of the resulting sound given off from the loudspeaker in a manner that eliminates standing waves, reflections and reverberations, and then measuring the resultant electrical energy. This test is made with all frequencies within the audible range, one at a time starting with the lowest and running up to the highest. These measurements of the loudspeaker’s response are then “plotted” into a curve and any Regularities will immediately show up so that the Engineers can find their cause and eliminate them. Some manufacturers have gone a step further and made a complete testing mach-

ine that automatically does this work and draws the curve itself. It records the frequency response of a loud-speaker over a range of 60 to 10,000 cycles. It not merely provides a series of readings to be plotted by the laboratory workers but actually draws the frequency response curve itself in about fifteen seconds. This makes possible the rapid comparison of speakers and permits of checking the performance of new models in preparation- as well as routine tests on production models. By selecting one speaker out of every so many speakers and actually checking the selected speaker for performance—not relying on the ear alone, but obtaining an actual response curve —“bad lots” are avoided in loud-speaker production. SEASONAL CHANGES Summer always brings disappointment to many people who have acquired radio receivers in the preceding winter and have neither experience nor knowledge of the vagaries of wireless, says Grid Bias in the Wellington Post. A set which has performed prodigiously in the winter and early spring in “bringing-in” far-distant transmissions, rousing the house with the wail of Japanese singers and the sound of the Samisen, shuts up like a clam when summer comes. It may make a feeble effort with the bigger Australian stations; or it may even refuse to do much with so close a neighbour as IYA. It is hard for some people to realize that this summer sickness is not a matter for grave alarm; they are not comforted by the fact that the set behaves as well as, ever in respect to the local station, or such a case as 3YA, which is within daylight receiving distance of Wellington. This failure to perform as well in summer as in winter is quite normal and a complete recovery will be made when winter returns. It is due to the same cause that cuts down daylight receiving range and which also produces fading—a breaking-up or “ionization” of the upper air by the rays of the sun. The upper air is subjected to sunlight for much longer in summer than in winter and the ionization effect is correspondingly prolonged. The summer sickness is therefore merely an aggravation of the “daylight effect.” , • Although distant reception is very disappointing during ordinary hours, it is usually better, even good, round about rnidto recover itself; darkness has settled well over eastern Australia. RADIO IN AUSTRALIA NO CHANGE OF POLICY. Discussing the question of national broadcasting in Australia at Melbourne recently the Director of Postal Services, Mr H. P. Brown, said that it was not proposed to alter the present policy. He had conferred with the chairman of directors of the Australian Broadcasting Company, Mr Stuart Doyle, but the conference, which was only one of many they had had, was not in relation to any proposed alteration of policy. “We are developing the policy already agreed upon, and there is nothing new to report,” said Mr Brown. “The policy was initiated last July, and our conferences have been simply on questions of development. We are making the necessary arrangements to take over further stations in pursuance of the present policy.” The New South Wales manager of the Australian Broadcasting Company, Limited, has tabulated and classified the letters received from listeners luring the first two months after the passing of 2FC and 2BL to the control of the company. Of the first 1093 letters 895 were appreciative of the programmes and 198 critical and offered, suggestions for improvement. A number of the complaints were regarding the modulation from 2FC, which has since been altered to meet the requirements of the Post Office Department. Most of the complaints were in regard to the paucity or the delay in the racing news. During the past month

the company made arrangements for in- - creasing its racing news service and for the relay of the more important interstate rac- I ing fixtures. Other writers complained of the omission of the evening church service from 2FC, but as that has been partially re-, stored, by direction of the Postmaster-Gen-eral, the letters on the subject have ceased. During the past two months there has been a remarkable falling off of letters from listeners to the studios of 2FC or 2BL. In six weeks only 60 letters of a critical nature have been received. It is contended by the Australian Broadcasting Company, Limited, that these 60 letters do not express the representative opinion of the great majority of the 105,000 listeners in New South Wales, and that the silence of the remainder can be taken as • an indication that if they are not entirely • 1 pleased with the programmes of 2FC and 2BL they have, at least, no reason to ex- * press dissatisfaction. It is further claimed by the company that, with the reduced revenue at its disposal for programmes, its broadcasts are at least equal in merit and variety to those previously broadcast from 2FC and 2BL. . ,

First-class wigs in Britain tost about £25 apiece, many society women spending as much as £lOO a year to be kept supplied with them.

AMERICAN CONGESTION CHAINS AND CHANNELS. Chain broadcasting in the United States, which has enjoyed the greatest popularity because of the generally high grade of programmes furnished by the two large systems the National and Columbia, has been threatened for more than a year by a general order of the Federal Radio Commission prohibiting “duplicated operation on cleared channels.”

The original order was issued in September, 1928, and called for the discontinuance of simultaneous broadcasting unless stations were separated by a distance of more than 300 miles. The putting into effect of the ban, however, has been postponed several times, the latest extension bringing the time up to October 1 last. Whether a further extension has been granted is uncertain, but there is a fairly strong probability that it has. Under the general order, “hook-ups” of several stations are permitted for one hour, between 7 p.m. and midnight. Exception is made, however, when the transmitters of

such stations are separated by a distance in excess of 300 miles, are operating on the same frequency, or special permission is received from the commission. This permission will be granted only in the case of programmes of extraordinary national interest or of a nature such that public interest, convenience or necessity would clearly be served by their duplication to a greater extent, according to the general order. The object evidently is to ensure as far as possible tjiat the man with a multi-valve set shall have a different programme from every major station within range. To show what conjection there is on the broadcast band in America, it may be mentioned that two high-power stations often have to share the same wave-length, although they are close enough together to interfere if both transmit at the same time. Thus the available hours have to be divided up between them. An example is that of WBAL, Baltimore, and WTLC, Hartford, Connecticut. These stations dare not even let their carrier-waves go on the air simultaneously, or there would be a shrill heterodyne whistle in most of the receivers tuned to them. If both had programme items running there would also be crosstalk. The remedy is found in timing the programmes with synchronized clocks, and in an arrangement whereby neither station starts until the other’s carrier-wave is off the air after the last item. In the case of the Baltimore station this is done by an ingenious remote control device operated-by the announcers in the studios, which are 20 miles distant from the transmitting plant. SHORT CIRCUITS A shock to the telephones, such as is caused by dropping them upon the floor, is liable to damage the permanent magnets and to render them insensitive. If you use a celluloid accumulator it may be an economy to renew the electrolyte every twelve months or so, especially if the accumulator is a cheap one. The local station is always capable of giving you good quality broadcasting and if the programme sounds distorted it is probably your own set or that of a neighbour which is responsible. Long-distance reception upon simple sets is not so much a question of the circuit employed as of location,' the skill of the operator, and of various other local conditions. Reaction is indispensable for long-distance listening upon simple sets, but it is not necessary for local reception unless too small a set is being used. Twisted flex should not be used for long loud speaker leads, as it is generally an advantage to keep the two leads well separated from each other. The most common cause of low-frequency howling is a run-down H.T. battery. When : a d/y battery begins to get old its resistance increases rapidly, and its voltage falls. Both of these factors, particularly the former, tend to give rise to distortion. Should it be necessary to disconnect all the battery leads from a set, disconnect their ends from the batteries before taking them off the terminals on the set. Interest has been displayed lately in television, and vague reports as to radio receivers being equipped with television apparatus in the near future have been received. The suggestion that receivers will be adapted for the use of television at an early date is contradicted by cablegrams received from American companies by an Auckland firm. The reports are as follow: — ( “The future of telvision is still in the laboratory, and static must first be overcome and controlled before a commercial value is available. Present television is highly unsatisfactory for ordinary purposes, being only of value in laboratories.” *