ALL-ELECTRIC SETS

Sun (Auckland), Volume III, Issue 711, 10 July 1929, Page 16

ALL-ELECTRIC SETS

DAYTON TRIED OUT I have tried out all sorts and makes of radio sets during the past ten years, and during the past week have had the opportunity of trying out an all-electric for the first time. The set was a Dayton, which was kindly lent to me by Superadio, Ltd. I had read a lot about all-electric sets but I was' surprised to find how efficient they are. The Dayton is a six-valve set with a rectifying valve and special transformer. It is contained in a compact walnut case and is a handsome adjunct to any room. Tuning is effected by one dial, with a vernier for fine tuning. The tone is excellent and the set is very selective. All the Australian and New Zealand stations were heard at good volume at night and Wellington was heard well in daylight, while , in the late afternoon Christchurch was at good strength. Using the set at Devonport, no difficulty was experienced in separating Auckland and Christchurch. I was surprised to find how well some of the minor Australian station came in and also how , easy it was to hear 3AR Melbourne ■ and 7ZD Hobart, and 4YA Dunedin. A.C.. hum is audible when close to ; the set but quite inaudible through the speaker. The set is supplied with Utah speaker, which reproduces music ; with great fidelity, and as the whole \ outfit is sold at a very low price, it is certain to be favourably received by * those who object to battery operated ; sets. < LIGHTS INDICATE ALTITUDE | 1 AUTOMATIC MEMORY METER j Red, yellow and green lights are ’ usually associated with railroads or highways, but Dr. E. F. W. Alexanderson, engineer of the General Electric : Company, has found a new use for these beacons. In the new radio echo altimeter which he has developed, and which was demonstrated for the first . time at the All American Aircraft Exposition, the lights do not indicate "stop,” “go,” or “caution,” but give a visual warning of altitude to an avl- ' ator. In the Alexanderson altimeter, which has been successfully employed in actual flights, when the green light flashes on the cockpit panel the pilot knows that he is 250 feet above ground; when the yellow shows he is 100 feet above ground, while the red light warns the flyer that the ground is only fifty feet below. “Nearly two years ago army flyers from Wright Field consulted with engineers and scientists of the General Electric Company, outlining to them some of the most serious problems of aviation. Among these problems they mentioned the Importance of a method for measuring the absolute height above ground,” said W. T. Meenam, representative’ of the company. “In rain and in fog, as well as in nightflying, the , Hot has no means of knowing infallibly his distance above ground and consequently the perils of operation under these conditions have been very great. “Dr. Alexanderson set to work on the theory that the time interval required for a radio impulse to travel from a plane to the ground and back again to a receiving set on the plane might be practically adapted as a reliable altitude indicator. The apparatus, while still In an experimental form, is the result of many months of patient investigation by Dr. Alexanderson and his assistants. Visual Unit is Small “The visual recording instrument is small and may be mounted on the cockpit panel in full view of the pilot. It consists of a motor on which ground distance up to 3,000 feet may be recorded, but it is in the lower regions that danger lies and it is to the recording of levels down to fifty feet that he has been most interested ” said Mr. Meenam. “Because the time interval between the outgoing and the reflected radio impulse is so short, radio waves travelling with the speed of light, an indirect method of making such measurment was adopted by Dr. Alexanderson. In his experiments he used an oscillating reeciver, one of the type which sends out a wave which may be picked up on other receivers as a squealing note or beat. The echo or reflected signal was picked up on the same receiver which sent out the wave. Dr. Alexanderson discovered that every time the airplane changed altitude by half a wave length a whistling note went through a complete tone cycle, from low pitch to a high pitch and back again to a low pitch. By counting the cycles of the tone it was possible to measure the altitude, the measuring stick being one-half the wave-length of the antenna oscillator.” By means of the meter, graduated from 3,000 to 200 feet, the pilot may read his altitude within those limits at any time. The echoes indicating height are periodic, becoming stronger as the plane approaches ground. The periodic character of the echo and the chance that the pilot would not see the instrument at the instant an echo was recorded presented a problem which Dr. Alexanderson met by developing a memory meter. In this instrument the echo is recorded as altitude when it occurs and the meter continues to hold that reading until a stronger echo, indicating a lower altitude, occurs. In approaching the earth the meijiory meter gives a continuous indication of altitude. If depth sounding is desired when climbing, in which process the echo is becoming weaker, a push button may be used to eliminate the memory features of the meter and each succeeding reading is indication of the next echo. Thus a depth sounding may be taken at any time during the cruise, whether the plane is ascending or descending.