Radio Beacon

Radio Record, Volume I, Issue 48, 15 June 1928, Page 2

Radio Beacon

y% ‘WONDERFUL AID TO AVIATORS od SIMPLE AND EFFECTIVE HE aviator of the future will reseive his radio compass bearings visually, and will not be required to fly with a headset clamped over his ears, as a result of the development of visible radio, a demonstration of which was recently made to prominent govern- | ment Bureau of Standards at College United States Congress by the Government Bureau of Standards at College | Park, Md, While the new method gives. a visible signal, it is not to be confused with television, the principle being different. ue new direction finder resembles in appearance an ordinary compass. | A needle-like reed, moved by electrical impulses received from a radio beacon, is on the dashboard of the plane, and warns the pilot if he leaves his designated course for an instant. This visual indicator, as it is called, is the latest aid to airmen developed by the Bureau of Standards of the Department of Commerce. It does away with headphones, and also eliminates wire antenna. Cnly Small Set Needed. (PHE radio beacon system for guiding aircraft permits the marking out) of an invisible but infallible course along which aviators can fly regardless of fog or other weather conditions. To make use of this system, an airplane need only be provided with a small receiving set carrying an indicator, An oceasional glance at the indicator tells the pilot whether he is following the course, or how far off if he has dev‘fuated from it. The directive radio-beacon is 4 special kind of radio station, usually located at an airport, just off the landing field. Instead of having a single antenna like an ordinary radio station, it has two loop antennas at an angle with each other. Each of these emits a set of waves which is directive, ie., stronger in one direction than others. When an airplane flies along the line exactly equidistant from the two beams of radio waves, it receives signals of equal intensity from the two. lf the airplane gets off this line it re-_ ceives a stronger signal from one than. the other. Reeds Vibrate om Signal. HE indicator connected to the receiving set on the airplane shows when the signals from the two beams are received with equal intensity, by means of two vibrating reeds which are tuned to different modulating frequencies used on the two antennas at ‘the directive radio-beacon — station. ‘When the beacon signal is received the two reeds vibrate. The tips of these reeds are white with a dark background behind them so that when vibrating they appear as a_ vertical | White line. The reed on the pilot’s right is tuned to a frequency of 65 cycles, and the one on the left to 85 icycles. It is only necessary for the ipilot to watch the two white lines iproduced by the vibrating reeds. If ‘they are equal in length, he is on his ‘correct course. If the one on his right ibecomes longer than the other, the airplane has drifted off the course to the right ‘into the region where there is more of the 65 cycles). If he drifs off the course to the left, the white line on the left becomes longer. Yelis Pilot Location. HIS beacon system has an additional feature whereby the pilot is informed of the distance traversed along the course, This is done through the installation of supplementary radio beacons of another type, which have been named "marker beacons" to be placed along the airway at short intervals. These markers are of very low power, and emit a characteristic signal which the airplane pilot will receive for one of two minutes. They tell the pilot when he is passing over a_ specified place, so that he cau locate himself and know his position. In fact, through keeping track of these marker beacons, the pilot will be uble to gauge wind conditions and note any change in direction or velocity as he proceeds during the flight. These "marker beacons" operate a 60-cycle reed vibrator mounted on the airplane’s instrument board, Each marker beacon will send the characteristic signal assigned for its location, which will coincide where possible with the characteristic flash signal of the light beacon at the same location. Thus the marker beacon signals will come to the pilet in a logical and automatie manner. Require Special Sets. GPECIAL receiving sets and antennas for use on airplanes in connection with the beacon system have been developed. They are even simpler than those in use hitherto. The familiar trailing wire, with its possible dangers and its directive effect introducing apparent variation in the course, is eliminated. It is replaced by a short special receiving set which is highly sensitive, light in weight, and exceptionally proof against engine ignition interference, (NE of the problems still to be worked out is caused by the discoyery jbat radio fading sometimes causes alight shifts of the indicated couxse at

-- night at distances over fifty miles, This effect is at its worst in mountainous regions where the beacon is most needed. One solution under consideration is placing the beacons closer together, less than 100 miles apart, This may haye some other advantages, allowing greater simplicity and reliability. This night yariation may be greatly reduced by the new short antenna ; this remains to be inyestigated, . )