RADIO TOPICS.

New Zealand Herald, Volume LXI, Issue 18713, 20 May 1924, Page 4

RADIO TOPICS.

BY THERMION.

THE MARCONI BEAM.

Following/upon.the success of the "beam" method of transmission over ; a distance of 2200 miles, -Senator Marconi is now conducting experiments with South America, a distance of 5000 -miles. The development of this beam ; transmission presents many interesting features as it is a system of directional radio telegraphy, and this is as old as the art itself, for the early laboratory experiments of Hertz were carried out by means of directive apparatus. Marconi's discovery of the great increase in range obtained by the use of longer waves, and the ■ earthed vertical aerial, practically stopped development on directional lines for the time being. The demand at the time was for increased ranges and now that the range has arrived at the maximum possible on earth attention is being turned to finding more efficient methods of transmission. Further, !the whole scale of wavelengths are becoming fully occupied andv the time will soon arrive when practically the only way of increasing the number of possible services will be by employing systems having good directional characteristics. Thus, the recent experiments of C. S. Franklin, of the Marconi Company, and his assistants on the beam method of trans mission may possibly render present methods of trans-oceanic radio communication obsolete. ; ,

In the new method reflecting system" with, wavelengths of 20 metres and leys are used. The short wave transmitting set is connected in the centre of a vertical cage aerial of small height. This transmitter is placed at the focus of a reflecting system consisting of a series of vertical, insulated wires which are distributed around a .paraboloidal arc. The radiation from the aerial strikes this reflector and is reflected back in the form of a parallel beam. The action is similar to that in a searchlight where the light from an arc is placed at the focus of a paraboloidal mirror and is all reflected hack along a narrow beam giving an v intense concentration of "the light. Light consists of waves of the same nature as wireless waves, the only difference being that light waves have an exceedingly small wavelength. Hence, for the radio waves a special wire I reflector is required. The size of the wire reflector is determined by the wavelength and would lie so large as to be ! impossible to make for long waves. Hence short waves are employed. At the receiving end a similar Reflecting system is constructed and the reception apparatus is placed at the focus of this reflector. In this way all the energy of the beam is concentrated at the receiving set. With this directional arrangement all the energy is conveyed along a comparatively narrow beam in a required direction so that there is no waste of energy, 'and therefore small power is required to cover a given range. Secrecy is obtainable to a certain extent and the interference due to atmospherics, which are usually directional, may be almost entirely eliminated. The results of the first commercial station erected on this system will be awaited with interest.

THE KING'S RADIO SET The cabinet Receiver recently /presented to H.M. the King by the British Broadcasting Company, and installed at Buckingham Palace, has some novel features. There is no aerial or earth external, .nor is there any loop aerial such as is used in the majoritv of cabinet-type sets. In order to form an aerial and earth, copper plate is let into the top part of the caDinet, and into the lower part close to the floor. The tipper plate and the lower plate form the aerial and earth respectively. The set embodies two radio-frequency valves, detecftoti*, and . three freshtp«ce-oap!acitfti coupled note magnifiers, used in conjunction with a loud-speaker. The set, in its present form, will receive only London tywadcaflfting, but the att&Dh> ment of an. outside aerial and earth to the , copper plates would enable all British stations to be heard. In a letter to the chairman of the British Broadcasting! Company, the I<ord Chamberlain says: — " Having been present on Monday at Buckingham Palace to receive on His Slajesty's behalf this set presented by your company, as representing the British wireless manufacturers generally, I was enabled personally to give , testimony to the admirable working of the apparatus, on the construction of which so much careful thought and ingenuity have been bestowed.

"I am further commanded to assure you of the gratification it affords His Majesty to feel that the installation of this wireless set in , Buckingham Palace will enable the King to form a closer acquaintance with the marvellous progress which is daily being made in'this branch of science." , . - —— t '

NOTES AND BINTS. An interesting visitor to Auckland for Fleet Week was Mr. W. Ward, of Tariki, Taranaki. Mr* Ward, who favours spider- coils, has had some outstanding successes in the reception of DX broadcasts while using two radio frcquencj stages, detector, and one or two stases audio. He has heard the following American broadcastinc stations with perfect clarity :—KFI, KHJ, KGO, WDAP and WMB (both of Chicago), WGAY (Madison), the latter beincr rated as a 100-watt station. ■, A full description of Mr. Ward's station was given in this column on November 13. Mr. Ward extends the invitation to any amateur visitine Taranaki to call and listen-in with him.

Some highly " freak " reception has been carried out with a crystal receiver at various times.. A Wanganui ama teur has received on a crystal music from Christchurch and Dunedin. It is said that his apparatus is the acme of perfection. Others have attempted to emulate his feats, but the vast amount of patient and painstaking work necessary has generally proved a deterrent. The three-coil set: setting for stations. "With the proper coils turn the secondary condenser dial round and determine the approximate position for various stations. With each setting of tho secondary condenser the primary condenser should be adjusted for greater signal strength. Loose coupling of the primary coil is desirable to prevent interference and the primary condenser setting will be found more critical as the coupling is loosened. A vernier adjustment of the primary condenser will then be found useful.

Remarkable ingenuity has been shown by Mr. J. Bingham, IAV (formerly 2AA) in the complete construction of a winder for duolateral coils. A carefully designed cam ensures correct position of each layer and winding, while a revolution counter on the main shaft gives' directly the number of turns of wire A rotating spindle to which the main shaft is geared fits into a. treadle lathe, with which it is possible to wind a 1500turn coil •in' 15 minutes. The finished coils have a perfect appearance, with wines correctly spaced and flat-edges showing no sign of bulge. "Thermion," who once wound by hand a 1000 duolateral in eight working hours, much appreciated this automatic machine.