RADIO RECORD

Greymouth Evening Star, 5 December 1929, Page 9

RADIO RECORD

notes for listener-in

(By

“Reception”)

AMERICAN CONGESTION TIMING PROGRAMMES Chain broadcasting in the Unitei States, which has enjoyed the greates popularity because of the generall; high grade of programmes furmshe< by the two large systems, the Nation al and Columbia, has been threatenec for more than a year by a genera order of the Federal Radio Commis sion’ prohibiting “duplicated operatioi on cleared channels.” The origina order was issued in September, 1928 and called for the discontinuance o: simultaneous broadcasting unless sta tions were separated by a distance oi more than 300 miles. The putting in to effect of the ban, however, has beer postponed several times, the latest ex tension bringing time up to Octo bei’ 1, last. Whether a further exten sion has been granted is uncertain but there is a fairly strong probability that it has. Undei’ 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 cast? of programmes of extraordinary national interest or of a nature such that public interest, convenience oi’ 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 that the man with a multi-valve set shall have a different programme from every major station within range. To show what congestion there is on the broadcast baud in America, it may be mentioned that twohhigh-porerw r er 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 WTCL, 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 / cross-talk. The remedy is found in timing the programmes with synchronised 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 dono by an ingenious remote control device operated by the announcers in tho studios, which are 20 miles distant from the transmitting plant.

AUSTRALIA’S EXAMPLE In their efforts to please the million radio listeners in Australia, the Australian Broadcasting Company is developing with considerable success the scheme for balance programmes and co-ordinated services. No longer are the programmes broadcast from 3LO and 3AR as high-class concerts, but as high-class radio productions, includ- • j ng:i _( a ) Special radio musical comedies; (b) Theme programmes with effects; (c) Radio revues, in which the items are “hooked-up,” so to speak, with specially written announcements and patter; (d) “Melange” programmes or'radio “shows” of comedy, dance music, classical items, and whatnot, carefully selected and balanced and presented with appropriate effects. The old order of tilings has passed and the Australian Broadcasting Company was quick to realise it and to adopt new methods of production. The daily mail received at 3LO is the best possible barometer for ascertaining the likes and dislikes of listeners, and for detecting “storm” centres. During the last few weeks the general tone of the letters indicates that the new programmes are giving almost universal satisfaction. The company is extending this balanced programme scheme, and it is expected that there will soon be an interstate exchange of programme themes between the various stations, especially when the company takes over 4QG and SCL, in January next.

TESTING SPEAKERS 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 ex- - pert, is an electric one. It consists of applying for a single frequency, of pure sine-wave characteristics, to the reproducei’ under test, and then picking up with a special microphone the response of the resulting sound given off from the loud-speaker in a manner that eliminates standing waves, reflections and reverberations, and then measuring the resultant electrical energy. This test is made with all other frequencies within the audible range, one at a time, starting with the lowest and running up to the highest. These measurements of the loud k speaker’s response are then “plotted” into a curve and any irregular ties will immediately show up so that the engineers can And their cause and eliminate them. Some manufacturers have gone a step further and made a complete testing machine that automatically docs this work and draws the curve itself. It records the frequency response of a loud-speaker over a i-ange 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 ever? so many speakers and actually checking the' selected speaker for performrelying on the ear alone, but obtaining an actual response curvfe -—“bad lots” are avoided in loud-speak-er production.

ATTRACTING THE PUBLIC THE INEVITABLE TREND. / 1 Naturally radio, a new industry, has t had to pass through several stages of r public acceptance just as, for example, I did the automobile. Those whose ■ memories run back to the early days I of the present century recall that at I first the jargon of pistons, carburet- - tors, clutches and spark plugs was i the regular conversational menu when I automobiles were under discussion. , This was when the automobile was a ! comparative novelty and mechanically • just in its infancy. A few years la- : ter when most automobiles would op- ■ crate in a more or less troublefree , manner the attention of buyers switched to matters of external design and, appearance, body lines, upholstery, colour, etc. And to-day, with beauty taken. foi- granted, you find again accent being put by buyers and manufacturers on mechanical matters .... the relative advantages of the eight-in-line as compared with the V-type eight, the front wheel drive with the rear drive, the four-speed-ahead transmission with the ordinary three-speed-ahead transmission. In a much shorter space of time than was required for the automobile industry to go through .these buying periods the radio industry has got down to correct fundamentals. Originally, radio sets, too, were regarded as mechanical wonders, and the more or less professional talk in every home was of this type of construction as compared with that. Then, in keeping, with the style wave of the last few years which has put colour in the home and beautified immeasurably every article of its interior, the radio was clothed in eyecatching raiment. Manufacturers vie with each other in creating the acme of the cabinet maker’s art, with which to beguile the purchaser. Now beauty and elegance of appearance is taken for granted. As in the! automotive industry, so now in the radio industry, beauty is •important, but by no means

the sole consideration of the buyer. The public is now buying “from the inside out.” Where are obtainable the newest inventions? Where are the mechanisms that produce the greatest accoustical perfections? Where is the rugged chassis and integral construction that guarantee long and satisfactory service? These are some of the points upon which buyers must be satisfied before matters of appearance become of outstanding importance.

RADIO IN SPAIN According to an article in the “Madrid Gazette,” the Spanish Government has taken over the organisation of broadcasting in that country. The arrangement is similar to that of the Australian Government, except that Spain goes one step further than Australia in handling the administrative as well as the technical departments. Contracts have been, let for the erection of and care of 18 transmitters, which must be placed in the principal cities, spread all over Spain. The energy of the station in Madrid must be brought on 20 k.w., and a short-wave transmitter has to be built, the energy of which may amount to 40 k.w. This last transmitter is intended mainly for broadcasting to the Spanish-speaking countries in South America. The* wavelength to be used will be 100 metres. The energy of the main station at Barcelona is to be increased and brought up to 10 k.w. The income of the managing company consists of 90 per cent, of the listening dues received, and in addition of a part of the money resulting from advertising by radio. The Government itself keeps 10 per cent, of the listening dues, as indemnification for the administration.

AERIALS FOR PORTABLES The use of a loop antenna for portable receivers is restricted to the larger type set. It is necessary when using smaller receivers, and it is advisable when using larger receivers that are stationed in one place for some time. The most popular temporary aerial for outdoor use is a length of insulated wire thrown over the branch of a tree. It is one of the simplest to erect as a tree with a suitable branch is not very difficult to find. There are occasions, however, when trees are not available, and in these cases it is usually possible to find some high structure in which to suspend the aerial. Get it up as high as possible and let both ends hang • freely. Make certain that the end distant from the set is not contacting with any conductor otherwise a leakage will occur and the benefit of the aerial be lost. For the tree supported aerial a length of insulated wire 30 to 50 feet will be required. This takes up very much less room than the 100 feet, and it is usually very difficult to get an aerial 50 feet high. Heavily insulated wire has very i great advantages from the point of view of insulation, but is difficult to carry. A roll of 24 or 26 double cottoncovered wire with a piece of rubbercovered flex in the middle forms quite an effective aerial wire. The advantage of this is that it may be carried conveniently in any small receiver. The end of this should be secured to an ordinary big reel so that this can act as a weight to carry the wire over its support.! The reel should be provided with a screw for a handle and a pencil or stick through the hole of form a winding axis. Once over the branch the wire is so arranged that only the piece of rubber-covered flex touches the tree. The aerial wire is easily wound up again if held by the axis.

In a few isolated places it Is not possible to find a tree or high structure. In cases such as these a kite aerial may be used. Unless one? is experienced in flying kites it is better to use a moderately-sized high-flying one of the aeroplane type, making the aerial wire only u, portion of the total length of the kite line. Two or three hundred feet of strong cord will be required and to the ©nd of this attach 100 feet of. strong wire such as 20 gauge enamel or electron wire. The kite should be flown so that the aerial wire is suspended' in the air as nearly vertical as possible. Once the kite is flying properly the aerial wire should be anchored by means of an insulator attached to a stake in the ground, leaving a few feet free to attach to tho receiver. An ordinary wire fence may be used as an a.erial, but a variable condenser should be interposed between it and the set. Another form of aerial reception is by using two

earths. This consists of two earth contacts spaced some thirty to foity feet apart connected by wires to the receiver. Signals are then picked up from-'the earth waves and.a caretui choice of position often results in a very good reception. Two sets of earth spikes will be required with some 40 or 50 feet of insulated wire. Ordinary 22 or 24 d.c.c. wire will do. The earth connection will be the same whatever form the aerial may take and the easiest system is to lay a length of insulated wire underneath th© aerial. This acts as a kind of counterpose earth and gives very good results, certainly better than those obtained by a poor earth contact. A contact which is less bulky for transport is an earth spike. The handiest is a piece of thin copper-or brass rod. A piece the length of a stair rod will be about right. A short lead should be soldered to one end and a terminal head should be soldered or screwed into position so as to make insertion or withdrawals easy. Other convenient earths are a piece of netting laid on the ground or thrown into a stream. A spike driven into a tree is very effective. Elaborate aerials and earths should not bo used, but there is no reason why an efficient system should not be improvised. If you cannot get good results examine first this part of the outfit, for it is likely that a change of position of either aerial or earth may make all tho difference.