THE WIRELESS WORLD

Grey River Argus, 27 October 1938, Page 10

THE WIRELESS WORLD

Completing the Camp THE PORTABLE RADIO. Spring is with us, and soon there will be summer, and the holidays. Some years ago a man who took a radio set with him when he went camping was considered to be very daring. Now, with motor car installations and the various makes of portable receivers, no holiday is complete without wireless. Writing in the October “Australian Journal,” “Spark Gap” says that the man who is going camping .in the hills, for example, will not find many difficulties to be overcome. He erects his aerial from the nearest tree, securing the other end firmly to the corner of his tent, so that wind will not cause unnecessary swaying of the wire with consequent swinging of signals. Incidentally, when selecting a tree to be used to support an aerial, pick out that which has plenty of green leaves and heavy branches. A tree aerial such as this will be a pleasant surprise to a city radio-user who is used to the efficient action of the outside aerial, as a good solid tree will give as much as, and sometimes more “pick-up,” than two or three hundred feet of wire. The ground connection should be easy to obtain. One of the best temporary earth connections is made by wrapping some bare copper wire around a glass bottle and throwing it into a convenient stream. A tincan buried in moist soil also makes an efficient earth connection. It will be found that many more opportunities for good earth connections and aerials exist in the country or at the seaside than in the city. Many owners of portable receivers, who have tried their sets out in the city and then taken them to the country, are really surprised by the increased distance and ..power of their sets. In all cases where a tree is used for an aerial support, or where the wire used for an aerial runs near or through the trees, a good lightning arrestor should be used, and whenever there is a thunderstorm in 'the vicinity the set should be turned off and not operated until after the storm has abated. Failure to use a good lightning arrestor may result in serious damage to the set if any of the trees in the neighbourhood are struck by lightning, because lightning seems to have the peculiar habit of "setting up” charges in trees around those which it strikes, and while there is very little danger from an installation where this is taken care of it is wisest to take the precaution beforehand than to worry about it afterwards.

Reactions of Nations: ' Listeners with powerful short-wave receivers and the necessary leisure were able to follow the reactions, of various nations to the events during the last week or two of the international crisis. News was broadcast in English from many European capitals. Berlin had little to say regarding the actual negotiations, but plenty concerning the Czechs. The opposite version was given by the Praha (Prague) station, and Paris, Rome, Moscow and even Tokio had something to say concerning the situation. Television Makes Headway: At Radiolympia, the British annual radio exhibition; television was the dominating feature. The 8.8. C. had a television studio in operation for at least five hours every day, and at certain periods invited visitors to stand in front of the cameras. Every detail of the programme processes was disclosed and demonstrated. Trade exhibitors also brought television equipment well before visitors. A considerable variety of receiving apparatus was shown and the prices were equally varied. The cheapest unit cost 23 guineas (sterling) and there were many at about £3O. The most expensive exceeded £2OO. The cheapest unit' was a table model 18 inches high by 23 inches long and 15 inches deep, showing a picture five inches in its greatest dimension. ■ • ••<>•* Radio and Leisure: An American magazine sent out a questionnaire with the object of discerning what people did in their leisure time. “Listening to the radio” proved to be the favourite amusement, and it appeared that women were more addicted to this than men. Use of Headphones: Listening with the aid of headphones not connected to any receiver or amplifier has been demonstrated in a London hotel. The system employed is that of the very earliest “wireless” system. A loop of wire connected to the loud-speaker terminals of a receiver is led round the room. The headphones are connected to loops of wire passed round the legs of the listeners'’ chairs. Audible energy is thus induced in the listening circuit. In 1896 practical induction telegraph systems of similar type were in use in England for distances up to four and a half miles. The virtue claimed for the present scheme for hotel is that wireless, reception is made possible in public rooms and places where the use of a loudspeaker would be inconvenient. The Aerial System: While the greatly enhanced sensitivity of the modern radio receiver permits o* reception of even quite remote stations with very inefficient aerials, down even to a few feet of wire trailing on the floor, best results are not obtained unless a good aerial system is used. ? For broadcast purposes on the medium wave band from 400 to 550 metres, a quite satisfactory aerial consists of 50 or more feet of wire, properly insulated and securely supported, as high as possible and well above roof tops and clear of trees. For short-wave broadcasts, however, optimum results are had with aerials of special characteristics, notably the “spider web” variety. Many of these : to erect where one has limited room, but. no : matter what type of aerial.is selected, if the best results are desired, the lead-in from the flat top (aerial -'should be ' by '“transmission pine.” It is regrettable that many owners fail to fit lightning arrestors

NOTES FOR RADIO AMATEURS.

BY "CAT’S WHISKER”

to their aerials/,^ fact, which is contrary, to the requirements ■of the insurance companies, and might result in the failure of a company to meet a claim should a fire, occur. ■. ' ■

Direction Finding: , Direction? fipdlpg ,an old wireless art, but in its most modern applications, nam6ly»oto aeroplane navigation, it is still short of complete development, The need for accurate rapid results over long ranges at all times and seasons has made it obligatory to remove, as far as possible, the inherent faults of the older systems, and has forced the development of many new schemes. The general principles of direction finding have been known from the beginning. Fifty years ago Hertz observed that the direction of- propagation of waves could be determined, and he and many others used transmitting, arrangements having directional .pro? perties. In 1914,-direction finding was useful, and in the succeeding years it developed rapidly. The battle of Jutland in 1916 is said to be due' in no small measure to the efficiency of direction finding observers. _ Careful measurements made at stations in England showed that some of , the German fleet had changed its position by about four miles. This was rightly interpreted to mean that the German fleet had left the Wilhelmshaven basins for the Jade River preparatory to putting to sea. The British Fleet left Scapa, and the battle was the re-, suit. The progress that was made in those years showed up faults that were previously unsuspected, and since many workers- have been trying to evolve accurate, but practical, systems. The trouble is that the same influences that cause fading and other faults in communication, systems alter the nature of the incoming waves, .and the apparent direction of arrival which give wrong Indications, the discrepancies depending upon the wave-length and the distance from which signals come and the time of day. The simplest form of direction finding equipment is a loop aerial. When it is at right angles to the direction of arrival of a wave, no, or very little, signal is heard. ’ There are many variations of the rotating loop system. Another system uses fixed loops. This is generally known, as the Bellini-Tosi, after the men who originated it in 1907. Two loops at right angles are connected to two coils, which are also at right angles, and inside the coils a third loop is rotably mounted. This small loop is used to obtain the bearings. All these systems depend upon the same principles, and they are all open to the same fundamental defects. They are all adversely affected by changes in the condition of the path of the wave which affects the nature of the wave itself, or the di? rection of its arrival. Such changes may occur at any time with short waves coming, from long distances, and always with all waves round about sunriset or sunset, find at night. Adcock, in 1919, suggested a way of avoiding errors by arranging aerials so that only the unaltered component of the wave was used for observations. There have been many modifications of this system, but all require spaced aerials and an area •which is too big for, .use on ships and aeroplanes.. Therefore, its use is confined to fixed stations. Medium wave installations have been made in many parts of the world, and tests have shown that at night it is infinitely superior to loop systems. Shortwave systems operating on this prin-, ciple have also been developed. . They are more compact, but are only use?, ful for close approach, or for relatively long distances because short; waves have a “skip” distance within which nothing is heard. • •••••• Canberra Short-Waver: Installation of transmitters for the naval short-wave radio station at Canberra will cost £116,037; The station will 'maintain- direct contact with the British Admiralty, the ships of the Australia Navy, and with the Darwin station. ’ ’> • » • ■ • * • • Fire Escape as Aerial: • The 8.8. C. has provided its mobile television unit with an aerial mounted on a modified fire escape. The escape extends to 80 ft. and a mast 20 ft. high, has been added. The Corporation expects, that, it wifi save a day every time the unit is set up as the major problem in an “outside” television transmission has always been the finding of a good site fo’’ the aerial. A direct line from the site to headquarters is always required. - A Novel Valve: .. A popular type of valve in America now is known as metaglass. The , base and pins are similar to those of metal. tubes, but the envelope is of glass and all other characteristics are similar to those, of the glass type. Manufacturers of most receivers now are prepared to fit either metal or glass valves, but- the former ' cost more and no improvement in performance is promised.

To-dav’s Programme* THURSDAY—OCTOBER 27, 1938. IYA Auckland—6so k.c.: ■ 7.0: Breakfast; 9.0: Close down; 10.0; Devotional; 10.15: Recordings; 11.0: Talk to women; 11.10: Recordings ; 12.0;; Lunch. music; 12.30: Midweek service from St? Matthew’s Anglican Church; 12.50: Lunch music; 2.0: Recordings; 2.30: Classical hour; 3.15: Sports results; 3.30; Talk, prepared by the A.C.E., “Let’s Have a Picnic!’; 3.45: Light music;' 4.0: Weather; 4.30: Sports results'; 5.0: Children’s session; 6.0: Dinner music; 7.0: Government and overseas news; 7.30: “The Whirligig of Time”; Talk, “Science (34)—The Modern Science of the Inanimate,” Dr. Douglas Robb; 8.0: (R) ’ “Westward Ho!” (Charles Kingsley’s novel), presented, George Edwards.,and company; 8.15: “Fourth Form at St. Percy’s.”.; 8.30:. A Studio Recital by the Auckland Commercial Travellers and Warehousemen's Association Choir, 1 conducted by. .Mr? W. Henderson; The Choir, “John Peel”', (arr.'• West), “Farewell Thou Lovely Forest Glade”, (Fraiiz Abt); 8.37: (R) Renee Clicm-

'U (violin); 8.40: The Choir; 8.47: > (feV Egon Petri (piano); 8.53: The Chbif;.9;o: Weather 'report and station notices; 9.5: ’ (R) Talk: "British industrial’ Conditions To-day,” Professor. J., R. Richardson, Professor oi Industrial Relations, Leeds University; 9;2Qu (R)*The< Upper Norwood Salvation Army Band; (R) Harold Walker (cornet); 9.30: (R) “Dad and Dave*from Snake Gully”; 9.43: CR) BBC Military Band; 9.51: (R) Dino Borgioli "(tenor) ; 9.54: (R) Massed 'Bands of the Aidershot and Eastern 'Commands';'lOfi: "Swingtime.” _ An hour of dance music; 11.0: Close down. 2YA Wellington—s7o k.c.: 6.50: Weather; 7.0: Breakfast session; 9.0: Close down; 10.0: Weather: 10.10: Devotional; 10.25: Recordings; 10.45: 7 A talk to women; 12.0: Lunch music; 1.0: Weather; 1.30: Educational Session; 2.30: Classical music; 3.0: -Sports results; 3.30: Weather; 4.0: Sports- results; 5.0: Children’s session; 6.0: Dinner music; 7.0: Government and overseas news; 7.30: “Who’s 'Who and What’s What —a •ramble in ■ the news by “Coranto , ’8.0: The Royal Wellington Choral Union present the concert version of “The Flying Dutchman” by Richard, Wagner (relayed from the Town Hall);‘10.0 (approx. : ): Music, mirth afiif melody; 11.0: Close down. 3YA Chrntchurch —720 k.c.,: . 7.0: Breakfast session; 9.0: Close ‘down; 10.0: Recordings; 10;30: Devotional; 10.45: Recordings; 11.0: ,Talk under the auspices of the Christ? church Branch of the National Council of Women; 11-15: Recordings; 12.0: Lunch music; 2.0: Recordings; 2.30: Talk prepared by -the A.C.E., “Let’s Have a Picnic”; 3.0: Classical music; 4.0: Weather. Light music; 4.30: Sports results; 5.0: Children’s hour; 6.0: Dinner music; 7.0: Government and overseas news; 7.10: News and reports; 7.35: Talk under the auspices of the New Zealand Federation of Young Farmers’ Clubs: Mr. H. G- Stevens (Ellesmere .Young Farmers’ Club)—“lmpressions of an Australian Tour”; 8.0: “The Case of the Dangerous Blackmailers,’’ by George Edwards and Company; 8.40: (R) Tuschinski Organ solo, Pierre Palla; 8.48: “Personal Column"; 9.0: Weather forecast and station notices; 9.5: “Talk: Mr. Leicester Webb, “World Affairs”; 9.20: Dance music; 11.0: Close down. 4YA Dunedin —790 k.c!.: 7.0: Breakfast session; 9.0: Close down; 10.0: Recordings; 10.15: Devotional; 10.50: A talk to women; 12.0: Lunch music; 1.0: Weather forecast; 1.30: Educational session; 2.30: Recordings; 3.30: Sports results; Classical music; 4.0: Weather; 4.30: Light music; .4.45: Spores results; 5.0: Children’s Hour; 6.0: Dinner music: 7.0: Government and overseas news; 7.30: Gardening talk; 8.0: Leopold Stokowski; 8.43: (R) Talk by Mr. Leon Gotz, "Leaves from a Planter’s Notebook” (No. 3), (second series); 9.0: Weather report and station notices; 9.5: “Fairies and Furies in Music”—a selection .of orchestral programme music or music with a story; 10.0: Music, mirth - and melody; 11,0: Close down.