RADIO AND ITS RECEIVERS

Sun (Auckland), Volume II, Issue 617, 20 March 1929, Page 7

RADIO AND ITS RECEIVERS

by

R. F. HAYCOCK.

Conducted fcr THE SUN GOOD RECEPTION'S HOME OVER 200 STATIONS HEARD ARCTIC TO AUCTRALIA For perfect reception there are few places which can compare with the Royal Canadian Mounted Police Post at Bernard Harbour, North-west Territories, Canada. This post, which is 130 miles north

of the Arctic Circle on Coronation Gulf. Arctic Ocean, has set up a record which will probably be difficult to equal. The official report from the post gives 169 American stations, 33 Canadian stations and 16 foreign stations heard from September 1, 1927, to June 30, 1928. These are, for the most part, stations which have been heard with regularity, not just once. Of the American stations KDKA, Pittsburgh, was heard 110 times. This station is said to have been received the best of any. It is nearly 3,000 miles distant from this Arctic outpost. A number of Pacific Coast stations, among them KGO and KPO, were among the American stations frequently heard. Special calls,_ 3XN, 2XAG and 9XF, were also received. Foreign Stations Heard The foreign stations heard were mainly European. On the Continent Danzig, Berlin and Hamburg, Germany, were all heard three and four times. Madrid, Spain; Stockholm, Sweden; and Bergen, Norway, are listed as being heard several times. Reykjavik. Iceland, was heard three times. Seven stations of the British Isles came in with great regularity. Dublin was heard 42 times, and 2LO London, 67 times, and Bournemouth (6BMI and Birmingham (SITI 43 receptions. Newcastle (SNO), Aberdeen (2BD) and Glasgow (SSC) were among the other British stations heard. 9,000 Miles Away The record is not complete without mentioning that JOAK, Japan, was heard 15 times, and Brisbane, Australia, 9.000 miles distant, was received six times. Stations on the North American Continent heard most frequently were KDKA, KOA. KOMO, KFKB. KMOX, KOIL, WLS, WLW, WTAM. WLIB. WGY, WBZ. WBBM, CJCA. CKLC, CNRV and CHCY. Bernard Harbour is not the only post that receives such a variety of stations. Bache Peninsula, the northernmost police post in the world, on Ellesmere Island, within *OO miles of the North Foie, also has a, good log.

Although confined to North American stations, the best reception is said to come from KDKA, WON, WCAE. CFQC. CNRW, WGY, WCAM, WOC, WTAM, WLIB, WGN, WBZ and WSM. Pangniturng, also on Ellesmere Island, had better luck last winter. Numerous American and Canadian stations and several in England were heard, with KOA, at Denver, Col., being the best. This station used to come in nearly every evening. Pond’s Inlet, a little further down the line, but still hundreds of miles above the Arctic Circle, also heard a number of foreign stations, including Austrian, Danish, German and British. The log of this post was detailed. Each announcement and number played by the various stations reported was set down in full as long as the station was received. Going further west, reception at Herschell Island, near the Alaskan boundary in the Arctic Ocean, was fair. During the period from September 16, 1927, to January 20, 1928, nine Canadian and SO American stations were listed. At other posts, notably Chesterfield Inlet and Port Burwell, reception was also good. These reports, which have only arrived at Ottawa within the past few weeks on ships returning from annual trips to the Arctic and various trading and police posts, show that reception in those barren wastes is good on the broadcast waves.

EARTH CONNECTIONS In dry country districts, and sometimes even in the city, difficulty is experienced by amateurs in obtaining an effective earth connection for a broadcast receiver. Unless the earth connection is a good one, the most efficient aerial and receiving equipment will not be capable of giving their maximum in performance, and in cases where a small set, such as a crystal set, or one or two valve set is used, the signal strength will often be reduced by a poor earth connection to the point where the reception is extremely unsatisfactory. Where a water reticulation service is available, the most effective method of providing an earth connection is to solder or clamp a heavy wire to one of the pipes. The soldering of a wire on to a water pipe will be difficult, as the pipe with water in it tends to cool before the solder applied to it is properly melted. It is therefore necessary to use a large soldering iron heated above the usual temperature to make a successful joint. In some cases a connection to a water pipe will not be found to be the most effective that can be arranged. This applies particularly when the nearest point to which a connection to a wader pipe can be made is a long distance from the receiver. A long earth wire from the receiver to the pipe then becomes necessary, and in many cases this will be found adversely to affect the selectivity of the set. In such cases some other method of providing an earth connection should be sought. If the ground is naturally damp round the place where the receiver is j used, a large sheet of galvanised iron buried a foot below the surface, or several kerosene tins buried in a | moist spot, will provide a satisfactory (connection. A long steel spike driven into a patch of moist earth is often used, but this type of earth is not recommended, as its contact area with the soil is small. A length of copper wire not thinner than No. 18 gauge buried in a furrow betw'een six inches and 12 inches deep, and not less than 100 ft long, will provide an excellent earth if the ground in the neighbourhood tends to be damp, but it will probably be unsatisfactory in dry localities. This method of making an earth I connection can usually be applied in | suitable country districts, as the fur-

row can be made with a plough, and the labour required in burying the wire thereby considerably reduced. A copper, or heavily galvanised iron wire, dropped into a pond or an underground well will provide an excellent earth connection. For receiving purposes the counterpoise type of earth connection is still very little used, although it has much to commend it. A counterpoise earth consists of one or more insulated wires suspended below the aerial wires, and approximately parallel with them. A counterpoise is probably the ideal form of “earth” in most country districts, as ample space is always available for its erection, and as it is independent of the condition of the surrounding soil, it will invariably give good results. Moreover, a receiver worked on a good counterpoise connection will nearly always give better results than one operated from an ordinary earth, and the tuning will be found far more selective than when a direct earth connection is used. A counterpoise may consist of a single wire suspended below the aerial, but the use of two wires spaced not less than about 10 feet apart, and extending 10 or 15 feet beyond the free end of the aerial, is preferable. It is desirable, but not absolutely necessary, that a counterpoise does not constitute an earth connection for purposes of protection from lightning. Where a counterpoise is used, an earth connection of the usual type should also be provided for “earthing” the aerial when the receiver is not in use. It is desirable that an appropriate switching device should be employed to enable both aerial and counterpoise to be connected to the earth when not in use. Such a switch may consist of a double pole double throw porcelain switch. The aerial and the counterpoise should each be connected to one of the blades of the switch. The aerial and earth terminals should be connected to the two terminals at one end of the switch, and the two terminals at the other end of the switch should be connected together | and also to the earth. With this arrangement, the aerial | and counterpoise will be connected to j the appropriate receiver terminals I when the blades are thrown to one | side of the switch, and each is connected to the earth when the switch I blades are thrown across to the other side of the base.

RADIO AND “TALKIES” WIRELESS EQUIPMENT USED Another example of the manner In which equipment developed primarily for purposes of wireless communication has been applied greatly to improve some other public service is provided by the recent progress in the preparation of talking moving pictures. The “talkie" has for its basis the valve amplifiers used in wireless communication, and had it not been for the great advances made in amplifier production for wireless work, the talking picture would not be possible. The most interesting of the talking pictures is that in which the conversation is recorded photographically on the film carrying the pictures. The recording process is an adaptation of the principle on which pictures are transmitted by wire and wireless. The words of the actors are picked up on a microphone resembling an ordinary broadcasting microphone, and the voice currents are amplified in a valve amplifier identical with amplifiers used for wireless purposes. Up to the stage of amplification the process of making a talking picture is similar to that of broadcasting. Instead, however, of controlling a broadcasting station, the speech currents from the talkie amplifier are used to light a lamp. Since the speech currents are of a constantly varying strength, the intensity of light from the lamp will also be variable. The light from the lamp is applied to the moving picture film in a narrow strip beside the pictures. The speech is recorded on the film in the form of a thin strip of varying light tones. When the film is placed in the projector for screening a powerful light is placed behind the speech record on it, and a photo-electric cell is placed on the opposite side of the film. As the tone variations which constitute the speech record on the film pass betw r een the light and the photoelectric cell, they create in the photoelectric cell pulsating electric currents exactly similar in character to the speech current which were originally produced by the actors in the microphone circuit. These speech currents can then be amplified to any desired ampliture in a powerful valve amplifier, and used to operate a loudspeaker.