Over the Aerial

Auckland Star, Volume LIX, Issue 260, 2 November 1928, Page 15

Over the Aerial

(By "PHONOS.")

WIRELESS NEWS FROM FAR AND NEAR.

The Schubert centenary will be marked by a special programme from IYA on Tuesday next. Over 76,000 receiving seta were sold in Canada last year, aud of this total nearly two-thirds were of Dominion manufacture. Station IYA, from 1 p.m. to-morrow, will be broadcasting an account of the Test match between the English and New Zealand tennis teams. The broadcast of the Purdy-Fairhall fight at Wellington on Tuesday evening was well handled by 2YA, the description being both clear and'vivid.

The number of receiving licenses now held in Australia is 283,92,3, an increase of approximately 20,000 in the last six months. Listening is certainly growing in popularity in the Commonwealth.

Carnival week in Christchurch commences to-morrow, and during the following week 3YA will not observe any silent night. Special evening programmes will be broadcast, a>d racing results will be given during the afternoons.

The series of lectures oa "Old New Zealand," which have been delivered regularly for many months from IYA, concluded this week. On Tuesday next Mr. A. B. Chappell will commence on a new group of talks, his first subject being "The Maori."

According to a Southern paper the American station WHXAL, stated to be using the astounding power of 250 kilowatts, is reported as being audible on a wave approximating 2YA's when the latter is silent. Has any local listener heard this super Yank?

Tuesday evening's programme from IYA was one of the best from the local station for some time. The co-operation of vocalists and orchestra in an extract from "The Waltz Dream," provided a most acceptable item. It was noticeable, however, that an announced title of a solo and the solo itself did not coincide. This is not an infrequent occurrence.

It is a peculiar yet very general fact that from stations in cloee proximity listeners as a body expect entertainment, yet when it eomee to distant reception they are keenest upon the receipt of news. Nowhere is this better exemplified than in the transatlantic reception of the 8.8.C. stations. American listenere writing in appreciation express the greatest gratitude for the news items which they pick up from the Old Country.

In Britain and America architects are now giving full consideration to radio requirements in house building. Fixtures for aerials are incorporated in plans, which also show locations for receivers, and a wiring system which enables loud speakers to be transferred from room to room, and plugged in to wall sockets wired to the set. The writer has seen only one house in Auckland where this special radio wiring of different rooms has been adopted.

The British National Radio Olympia opens on the 22nd of this month. The latest English files indicate that this yearly display organised by the British radio trade is increasingly popular, ami that exhibits in number and variety will greatly exceed those of previous exhibitions. In connection with the Olympia the BBC will stage a demonstration of entertainment throughout the ages, in which special prominence will be given to methods by which people were entertained in their own homes during tin: past two centuries!

The American radio fair usually affords scope for the humorist. One writer perpetrates the following: — "Surely wireless is growing less and less; what with being groundless, antennalpss. battery less, and almost dialless, and now prices of sets are quoted 'less tubes. . When a radio repair man calls nowadays the butler announces: 'Milord, a radiotrician is without.' 'Without what?' queries milord. Whereupon the butler replies, "Without tubes.' " Another wasr tilts at radio cabinets. "Last year radio cabinets were wood. This year radio cabinets are metal. Next year radio cabinets will be reinforced concrete."

A London man, whose reception was upset by using a water main to which the earth lead of an ill worked receiver v.as attached, decided to use an independent earthing, but possessed no earth tube Or suitable metal to bury in the soil. Wishing to complete his experiments during a week-end, when no shops were open, he connected his set to a German soldier's helmet, a trophv of the late war, which he buried in his coal cellar. He claims that his reception is better than he can recall having enjoyed previously, and says that if the war did nothing else it made his listening pleasurable.

The British Broadcasting Corporation, having carried out experimental work with dramatic masterpieces over the air, ie now embarking upon a regular series, which will be broadcast fortnightly. Some of the plays proposed are Shakespeare's "Julius Caesar," Moliere's "Le Bourgeois Gentilhomme," two Ibsen plays, "Brand" and "John Gabriel Borkman," Tchekov's "Cherry Orchard" and perhaps his "Uncle Vanya," Maeterlinck's "Monna Vanna," Khalidasa's "Sakunthala" and Calderon's "Life's a Dream." It is hoped that Bernard Shaw will permit at least one of his plays to be broadcast, and if choice is given it may be "The Doctor's Dilemma" or "Candida." They will «be adapted and shortened and it is ■ expected each will last about an hour and a-half.

Gramophone records provide some of the best items which IYA puts out, but recent developments suggest that there will soon be' a general complaint as to the number which are now being used for broadcasting purposes. If the writer's memory is correct, there was a clause in the agreement granting broadcasting rights which stipulated a percentage of records in programmes which must not be exceeded. IYA, at times, must be getting perilously near this limit. A judicious use of gramophone items is generally appreciated; in fact, there are a number of listeners who would welcome a preponderance of such as the evening entertainment, but the radio public is touchy as to its fare, and it would be a pity were the increased satisfaction with local broadcasts spoiled by the over-presentation of "canned music" . _ 6 _ k

WEAK SIGNALS. Many owners of valve sets have often been puzzled by a gradual decrease of signal strength after the set has been in use for some time. Strange as it may appear, many newcomers to the ranks of radio frequently do not realise that "A" batteries, accumulator type, must be recharged at intervals. Assuming, however, that this very elementary fact is known, some other cause or causes must be looked for when weak signals occur. As mentioned last week, loss of volume is most generally due to worn-out "B" batteries, owing to the decrease in voltage. The remedy, of course, is obvious. Wβ will suppose, however, that the batteries are in good order. The valves can therefore be suspected. Valves that have been in use for a long time gradually lose the filament coating, and the filament temperature, as well as plate voltage, must be increased to obtain full volume. This effectively shortens the life of the filament and the valve burns out in a short time. When a set that has been operating satisfactorily gradually loses its volume, and the valves are found to be in working order after being tried out, it is usually due to the speaker or phones being connected improperly. The plate current is acting to demagnetise the permanent magnets in the unit, which makes them insensitive. The cure is to reverse the leads connected to the unit and the magnets will build up again. Other causes may be found in the following: —Condensers, for example, may be poorly insulated. Fibre ends on condensers are subject to leakage and cause trouble, which is hard to locate. It is best to use only condensers with bakelite insulation. Tube frongs occasionally make poor contact with socket. Clean tube frongs and socket contact springs and bend up the latter slightly to ensure good contact. The grid condenser may be short circuited. This is often caused when soldering leads to the mica grid condenser, the flux flowing between the metal lugs and over the edges. Discard condenser and use small bolts for connecting up the new one, inserting the bolt through the small holes in the condenser and fastening the leads under the nuts of the bolt. The resistance of the grid leak may be too low. Try different values of resistance and test for best results. Finally, too much "B" voltage on plate of valve may paralyse it. Try various voltages for best signals.

THE LATEST IN RADIO.

Considerable local interest centres o>l the annual radio fair which is held each September in New York. The latest American files give details of lh» fair, which was open for a week of lasmonth, and which was vieited by a quarter of a million enthusiasts. Naturally, great attention was given to television apparatus, of which several types were exhibited. Thousands formed into queues to walk past the demonstrating instruments, and to observe on the small screens the progress of a phase of radio investigation which Is still \ery much in the experimental stage, and which, to judge from reports, is still years distant as an everyday utility. The most ambitious attempt in television was the projection of radio moving pictures upon a screen a foot square. In receiving sets the outstanding feature was "electrification." "Power socket" models were featured by all manufacturers. Less than two years ago this phase was purely experimental, and those who tried the earliest "all electric" were far from satisfied with their performances. Now initial difficulties and faults have been overcome, and current direct from the mains to the set is in demand. Dynamic speakers were displayed in a great variety of artistic designs. So much attention has been devoted to the ornamental side of set and speaker that one critic of this year's radio fair su£g-**ts that in 1929 it should receive the title of the cabinet-maker's fair.

The manufacturer has not neglecled the interests of the battery-set owner, for whom there was an extensive exhibit of eliminators that will put older models on a par with most recent types as far as current convenience is considered.

LOOSE COUPLING. What is meant by loose coupling? This question is very frequently asked. Coupling, of course, means linking, but in radio, however, the connecting link is purely magnetic, and therefore invisible. To understand how different circuits in a wireless set can be coupled together it is necessary to remember that wherever the current is flowing a magnetic field extends around the conductor carrying the current. It follows, therefore, that where two coils are in close proximity to each other, each coil carrying its own magnetic field will interact one on the "other, and thus the two different fields are "coupled," yet without any visible link. Strong interaction between the coils is termed "tight coupling," whilst when kept well apart this interaction is comparatively slight, and the circuits are said to be "loosely coupled."

OAK FINISH ON CABINETS. Amateurs who build their own cabinets will find that an excellent stain for oak can be made by mixing Japan black and turpentine in equal quantities. The liquid should be applied with a rag to well sand-papered surface, and with two or three coats a rich brown shade will be obtained.

MELBOURNE CUP BROADCAST. 3LO will relay an account of the Melbourne Cup on Tuesday afternoon next. Country listeners may in some cases be able to pick up the description. There is the possibility, however, that all who care to listen in may hear a full description of the running of the Cup. The short-wave stations in both Melbourne and Sydney will be broadcasting accounts of the great race, and, if these 'are coming through well, IYA may pick them up and re-broadcast them so that the Cup may be visualised by every crystal listener.

A CRYSTAL DETECTOR TIP. In a conventional crystal circuit the crystal detector is always connected between the telephone receiver and the aerial terminal. Thus the 'phones are at low potential, and do not carry H.l , '. current. But this condition obtains only when the detector is rectifying in the direction from the aerial. Thus it is always well worth while changing a crystal detector's connections round experimentally. It is frequently found that in one position results are superior to that obtainable when the current is passing in the reverse direction through the crystal.

CRYSTAL RECEPTION. Crystal users should always remember that too much care in the construction aud maintenance of a good aerial and earth cannot be given. The energy available for working the phones of a crystal set are always less than the energy picked up by "the aerial, owing to unavoidable losses in resistance, etc. On the other hand, if taking advantage of the amplifying powers of valves,, the energy available for the output may be hundreds of times greater than the initial energy in the aerial. For this reason the crystal set owner should always try for maximum aerial efficiency. FALSE ECONOMY.

It is a commonplace to state that in wireless it is bad policy to buy cheap and inferior articles. Anyone who has had experience, for example, of cheap values of unknown characteristics, knows that he will only get a fraction of the value out of a thing of that kind that he would get out of a standard article.

It is surprising, to take one instance, how often an experimenter will make shift with frayed flex, or with badly fitting valve pins instead of wander plugs, although new articles would cost only a few pence. A str«y strand from a frayed wire may easily cause a short in the H.T., or may find its way to a stray strand from some other wire and result in burnt-out wires.

Old fixed condensers, particularly those with paper dielectric, and old grid leaks, should always be used with caution. A faulty condenser across the H.T. battery will speedily account for several times the cost of a new one, and a grid leak in which the resistance has increased by a few megohms will ruin the working of any set. Old variable condensers, too, should be examined very critically. It is hopeless to catch elusive stations if there is any backlash about the movement of the spindle or if the design of the condenser is eueli that hand-capacity effects are bad. A variable condenser in which there is risk of the vanes touching may cause a lot of damage if used to control reaction in some circuits. Wornout rheostats or switches will usuallv annnunce their faults for themselves.