WIRELESS NEWS.

Press, Volume LXIII, Issue 18894, 8 January 1927, Page 19

WIRELESS NEWS.

BUILD YOUR OWN RADIOSET. (BFZCULLT WBITTXK JOE THE FHE33.) (By ' Electra.' : ) There is no reason why anybody with only an average income should not possess a radio set as efficient as that owned by his wealthy neighbour. Of course, 311 that the rich man has to do is to give the order, and the set is installed. But if the person of moderate means would only exert himself a little, he could come out even, with a lot of fun to boot. All he would have to do would be to buy the variself. The cost will be from a half to a third less than the price of the manufactured article.

There is at the present time a great army of these experimenters who have made and are making their own seta, and who get a deep satisfaction out of their own handiwork. They keep abreast of all the latest circuits, thereby constantly modernising their seta But there are still a large number of people who apparently are not aware oi how simple it is to get the benefit of the radio inventions that are cont.ol ed by the manufacturers with'out having to pay the high prices for the sets. One need only pay a visit to a bookshop that stocks radio test-books and magazines to find numerous describing in detail the construction of radio sets for the home builder. Besides these, there are manufacturers who make all the parts, composing receiver to match, and pack them in a carton and call them kits. "\V it li these kits there are full instructions, and -piierallv full-size blue prints showing how to build up the parts i int'> a complete receiver. By following the directions contained in thes° kits, it is possible to obtain a splendid, efficient and up-to-date set at- a great saving of money. During the last few years the number of manufactured sets has increased to such an extent that some people are getting the impression that interest in the parts business is falling on Manufactured sets are Hooding the market, but the number of amateur set builders has also jumped, and new recruits are continuing to swell the ranks. One reason for the increasing number of home builders and experimenters is the fact that radio I s still a mystery. Tt offers an inexhaustible "field "for the imagination While patents prohibit unlicensed manufacturers from using inventions and certain circuit-s, individuals making their own radio receivers are treated less strictly. The man with limited means, who perhaps could not afford to build a four or five-valve set straight away, can start off with a one or two-valve set, and gradually add to it at a later date. . The new broadcasting company has two good stations working, and there is a promise of a third in a few months' time.

Beam Wireless. The main article last week contained an explanation of what is meant by beam wireless. This week a short description on the actual station will be given. Probably the most interesting part of a beam station is its aerial system. To transmit the short waves in a given direction a special radiating system, entirely different from that ordinarily used, has been developed. A.ll transmitting and receiving aerials are built separately. They face their respective receiving and transmitting aerials with which they are to be worked Thus, the transmitter at Bodmin. England, will work with a receiving station in Bridgewater, Canada, and the transmitter, and Yomahiche, Canada, will be linked with the receiving station in Somerset, England. Very careful measurements had to be made in the case of the two communication links, so that the beams of each transmitter would exactly hit tlie aerials of their receivers. The aerials have to be absolutely parallel to each other. Outside of the ten degree beam not much can be heard,- and it is essential that the receiving station be within the beam. The signals can hardly be heard outside of the beam, and not at all at the back of the transmitter Fiv6 steel masts, each nearly 300 ft high and with 90ft cross-arms, support the network of either type ft aerial. They are placed 800 ft apart and are in a straight line On these cross-arms are hung from a peculiar caternary net the aerial proper and the reflector. The aerial consists of jM radiators each broken up in tour haltwave sections, connected together by means of special inductances and are held at an even tension against vanable wind pressure by means of a clever weight and bai&nc© system a few feet above the ground. There are twice as many reflector wires as there are radiators per bay. The reflector is placed at exactly a quarter wave back of the aerial wires. In this system the emitted wave proceeds forward, as would ordinarily be the case with a vertical conductor, and in addition the radiation goes in the opposite direction, "bounces" up against the electrical screen made up of the reflector wires, and ricochets back to intensify the _ original wave. By manipulating the circuit phases it is possible to send these waves back at an angle from the aerial, so 'ie chances of having them absorbed by earth bodies are lessened. The wavelengths used vary between 26 and 60 meters.

On the receiving end an aerial of similar construction is connected to the receiving station. There is, theoretically, 128 times more energy collected than with an ordinary aerial, but actually this varies between one and 100 times according to the receiving conditions, which change, as every one knows from one extreme to the other. Using short wares gives the beam station its long distance carrying features with a minimum of power! Not only do the installations cost less, but their upkeep is much less than the large stations used for similar communication work. Interference due to static is minimised and practically non-existent on the short waves, ensuring nearly 24 hours' working, as again--: 12 to 18 in other systems. Correspondents. "Radio Fan," Westport.—BremerTully low-loss tuners and Karas variaable condensers are to be recommended. An aerial 3o to 40-foot high and a brut "Oft long should bt. very suitable. The six-volt dry battery" would last approximately 100 hours. If you are using a one valve set you would ce auie to receive IYA. 2YK, 3YA, 4YA, and very likeiy seme of the Australian stations. The addition of'more valves would bring the stations up with more volume, and with 3 valves a loud talker could be worked The easiest way to learn the Morse code is to practice with a buzz°r and key and to get someone who knows it to transmit for you, after which you will be abie to practice by receiving ship's messages. •■With my own 3-valve tridyn set one can generally be certain of receiving any of the followinglA. 2YK. 3YA, 4YA, 2BL, 2FC. 3LO. 4QG, 2NW, and, of course, when conditions are good. American and Japanese stations,