Popular Mechanics/Volume 49/Issue 1/Radio Waves that Cast Shadows
Preparing to Hoist a Radio Transmitter to the Top of a Tall Tower; It Is Tuned from the Ground by an Endless Cord, and the Small Meter on the Aerial Rod Is Read with a Telescope
Radio waves so short that, like visible light, they cast shadows behind buildings, or even men, are being employed in experiments that promise to open a new era in wireless, particularly in communication with airplanes. The waves are so short that they bring home the point, which engineers have often tried in vain to emphasize, that radio is only another form of light, and not a brother of sound.
Five-meter waves are being used in the experiments conducted by the General Electric laboratory at Schenectady, and, despite the fact that they are giants compared with light waves, the two act very much the same. The average visible light wave is only about one fifty-thousandth of an inch in length, but, though it would take nearly 10,000,000 of them, placed end to end, to equal one five-meter wave, the radio signals of that length emulate light by traveling in a straight line as well as by being blocked when they meet a hill, a house or any other obstruction.
The radio waves used in ordinary broadcasting rarely cast shadows, because of their great length. There are occasional exceptions, as when a near-by mass of metal, such as a gas holder, will block reception from a broadcasting station on its other side. The long waves bend as a rule around very large objects, just as visible light waves may be bent around atoms. On the basis of their comparative size, a house or office building is no more to the long radio wave than an atom to the fifty-thousandth of an inch light wave.
Because of their straight-line propagation and the shadow effect of interfering objects, unusual arrangements were necessary in the experiments with the five-meter waves. The transmitter, instead of being housed in a building or placed on the ground, was swung in the air from the top of a 300-foot aerial mast at Schenectady. An endless rope, running over a pulley on the condenser dial, made tuning possible from the ground, operating much like a chain hoist. The small output meter, fixed to the antenna, was read from the ground through a surveyors' transit. Wires dangling from the transmitter connected to the current supply on the ground.
The receiver used was a miniature "ham" set, consisting of regenerative detector and one audio amplifier. No antenna was necessary at the receiving end for the phone cords furnished wire to pick up sufficient energy. The tiny grid-tuning coil contained but five turns of wire, a half inch in diameter, and the tickler coil was a quarter inch long and a quarter inch in diameter, inside of the grid coil. Two very small condensers were used, and to keep the leads short, they were placed as close as possible together. They were so close, in fact, that, in order to use standard-size vernier dials, extension shafts were necessary. The condensers were placed at an angle to each other and a false end was built in the receiver cabinet to accommodate the angle of the dials.
Tests were first made over a distance of thirty miles. On top of a hill, with a clear "line of vision" to the transmitter, the signals came loud and clear, but as the portable receiver was carried down the far side of the hill and passed out of the straight-wave range, the signal faded and disappeared.
Elevated to a 300-Foot Mast, the Transmitter Will Have a Clear Line of "Vision" to the Receiver atop the Woolworth Building on Distant Manhattan Island
Following a survey of topographical maps for the country from Schenectady to New York city, arrangements were made to place the receiver on top of the Woolworth building, as the survey showed that, from its great height on lower Manhattan island, the transmitter atop its 300-foot mast at Schenectady would have an un- obstructed path for the radio waves, passing over the Catskill foothills.
Condensers Are Set at Angles to Get Short Leads, While the False Front Panel Makes the Use of Big Vernier Dials Possible
The short waves used have extremely high frequencies, a five-meter signal representing approximately 60,000,000 cycles a second. A four-meter wave would have a frequency of 75,000,000 cycles. In the 15,000,000-cycle space between four and five meters, every radio station now in use—amateur, naval, broadcasting and commercial—might be operated without interference from overlapping signals. It is that enormous number of possible wave channels in the low waves that promises to revolutionize wireless. Experience has shown that a separation of at least ten kilocycles, or 10,000 cycles, is necessary between near-by stations. On that basis there are between 200 and 550 meters—the broadcast wave band—only some ninety possible wave channels, though they cover a 350-meter band, while the single one-meter band between four and five meters contains 1,500 wave channels.
The experiments are continuing, to determine the usefulness of the short waves in broadcasting over fairly limited distances. Radio engineers have been aware for some years that short waves are best for long-distance transmission. One of the interesting facts already learned is that the short-wave bands are practically free the year around from natural static, but that man-made static, such as that caused by the ignition system of a passing automobile, is particularly noticeable.
TRACTOR FITTED AS FIRE ENGINE HELPS GUARD FORESTS
Forest-Fire Engine, Made from Tractor, with Trailer Carrying the Emergency Water-Supply Tank
By making various alterations in a familiar brand of tractor, an efficient engine has been afforded the guardians of a California forest to help combat fires. It has a six-speed transmission, pneumatic tires, a three-speed pump, reels of hose and, on the trailer, a tank holding 520 gallons of water. This may be used while the hose is being led to a creek or other natural supply. A particular advantage of the outfit is that it can climb steep grades. In a recent test, one of the tractor engines was driven 215 miles over mountain roads in ten hours. When the destination was reached, the trailer was disconnected from the tractor and a plow attached, making a firebreak up a thirty-percent grade in low gear.
GAS FOR CURING SEASICKNESS LATEST TRAVEL AID
Taking the Seasickness Cure on Deck: Gas Administered from the Cylinder is Said to Relieve the Malady
Comfort for the travel who suffers from seasickness is seen in a gas remedy a German physician has prepared. It is carried in cylinders like those used in a dentist's office and the patient inhales it through a flexible tubing and cone. Treatments can be given on deck and are said to be effective immediately.
"FIDDLE" THAT SOWS GRASS SEED AIDS GOLF-COURSE KEEPER
By Working the Handle Back and Forth, Disk Is Revolved and Seed Is Distributed from the Bag.
Maintaining grass on golf courses is simplified with a hand-operated sower introduced in England. It works by pulling a "bow" back and forth as though playing a cello. This action causes a disk to rotate and scatter the seed which falls upon it from a holder above.
THREE HUNDRED MILE AN HOUR PLANES CARRY BALLAST
English speed planes, which took the Schneider trophy away from Italy this year, were so fast that they had to be specially weighted on the right-hand side to overcome the tendency of the plane to turn with the propeller. The winning plane, which averaged 281.49 miles an hour on the closed triangular course, attained a speed of more than 300 miles an hour at times on the straightaway. The winner, a Supermarine equipped with Napier engine, had a right-hand pontoon considerably longer and heavier than its opposite mate, as shown in the center sketch on the opposite page. It was unusual in several particulars. For one, the fuselage was built of sheet duralumin without any internal bracing or reinforcement, deriving strength from its tubular shape along. The engine was water-cooled and the radiators occupied practically all the leading edge of the very short wings. Special ventilation was provided to blow the burned oil fumes and other gases out of the fuselage, to keep them from overcoming the pilot. Another of the English entries, which, however, crashed on its trial flight in Italy, carried all its gasoline in a large tank in the right-hand pontoon to offset the engine twist while in flight. The third type of British ship, of which two were built, was the Gloster Napier, the only biplane entered, the others being of the low-wing monoplane type, in which the wing is placed below the fuselage instead of above it. The Glosters were unusual in that the powerful engines were geared down to fairly slow turning. Wing stuts were of duralumin because strength equal to wood can be attained with considerably thinner sections. The wing radiators, used to cool the engine water, were supplemented by radiators in the pontoons, which utilize the sea water for cooling while the ships are on the surface.
SECRETS OF THE WORLD'S FASTEST SEAPLANES
ELECTRICAL "MAN" OBEYS HUMAN VOICE ON PHONE
Left, Mechanical "Man," Which Opened and Closed Doors, Rang Bells, Turned Lights Off and On and Responded to Other Spoken Orders, and, Below, the Master Voice That Calls Up Three Washington Reservoirs and Reports Back the Amount of Water Each Contains, the First Practical Job the Electrical "Robot" Has Undertaken
An electrical machine that answers the telephone, starts and stops machinery, reads the water gauges at reservoirs and can be made to perform an infinite number of other tasks, has been constructed by Dewey M. Radcliffe, a government engineer, and R. J. Wensley, of the Westinghouse laboratory staff. Three of the automatons have been installed in the war department at Washington, taking the place of nine watchmen who patrolled three water reservoirs. When the official in charge wishes to know the depth of water in any of the reservoirs, he calls central on the telephone, gives the proper number, and the mechanical man answers, reads the gauge and reports back the depth. A similar machine, demonstrated at the Westinghouse offices recently, turned lights off and on, started and stopped an electric fan, operated a searchlight and an automatic sweeper, and even opened and closed a door. A laboratory model was worked by the human voice speaking into a telephone transmitter, delicate selectors and relays responding to certain tones and syllables. For practical installation, the human voice has been replaced by electrically operated tuning forks, which transmit the desired note. The mechanical man grew out of the need for a device to control distant machinery without the prohibitive expense of maintaining special private wires over long distances. At the control office in the war department, the telephone stands on a small box, which has on it three push buttons. When the waterworks official wants to check the water level in the reservoirs, he calls the number of the reservoir, the operator completes the connection, and the hell at the other end rings. The signal operates a relay that lifts the hook and starts a buzzer that sends back through the transmitter a signal to advise the caller that contact is established and also the desired information.
BLACK BLOTTERS FOR BANKS TO DEFEAT FORGERS
By using the blotter that has been applied to a signature, forgers have sometimes fashioned an accurate reproduction of the writing, but with a type of blotter now being employed in banks, they will no longer be able to do this. The blotters are black, so that the ink is almost completely lost in the color. Besides this advantage, they are not so easily disfigured.
TURN OF WRIST WORKS JACK WITH COMPRESSED AIR
Raising a car with a twist of the wrist in a few seconds is accomplished with a compressed-air jack now on the market. It is operated from a service-station air line, or with a small container of air compressed to 120 pounds and released from the tube into the jack.
Jack in Place and About to Raise the Car When Compressed Air Is Released by Twisting Tube Handle
GAS MASK AS DIVER'S HELMET WOULD AID IN RESCUES
Submerging to Test Fireman's Gas Mask as a Diver's Helmet, Wearer Stayed Under Twenty Minutes
That a fireman's gas mask can be successfully used as a diver's helmet was demonstrated recently by Capt. C. H. Virdin, of the Los Angeles department. Wearing one of the masks, he remained submerged for twenty minutes. It is thought that the equipment would prove of special service to companies detailed along water fronts or where emergency calls for rescues of drowning persons are likely.
CENTER OF INDUSTRY MOVES TOWARD THE WEST
Centers of industry and population of the United States are gradually moving westward toward the center of agriculture and the latter, in turn, is a bit nearer the geographical center of the country than it was a few years ago. The industrial center has moved seventy-five miles south and west in the last eighteen years, and is now in northern Indiana. The center of population is also in Indiana, in Owen county, 170 miles south and slightly west of the industrial center and almost at the Illinois state line. The agricultural center is about thirty-five miles southwest of Hannibal, Mo.. and the geographical center near the middle of the northern boundary of Kansas, close to Nebraska.
SPEED BOAT TO CROSS ATLANTIC IN FIFTY HOURS
Eight-Motored Speed Boat for Rapid Trips across the Atlantic Is to Be Built after This Model
Trips between New York and Paris in fifty hours are anticipated by a French inventor in a boat he has designed to rival aircraft. It is in the model stage so far and shows similarities to a submarine, being fitted to travel under water for a considerable time. It is to have eight motors, six for forward and two for reverse travel, with a total horsepower of 2,400. A maximum rate of over eighty-six miles an hour can be attained, the designer believes.
THOUSANDS OF QUAKES YEARLY BUT FEW PERIL MAN
As many as 30,000 earthquakes may occur yearly, but not more than thirty are what can be considered catastrophes so far as man is concerned, according to R. M. Wilson, of the geological survey. Sensitive seismographs show that the earth is almost constantly quaking and trembling somewhere, but hundreds of the disturbances are so slight that they cannot be considered "earthquakes" in the accepted sense of the term, and fewer still possess sufficient intensity to cause great damage in centers of population. Just a few weeks ago, a severe quake was registered on instruments in various parts of the world. It was believed to have occurred somewhere under the ocean off Alaska. No damage was reported, hence the quake is not recorded as a catastrophe, although it was a severe shake. Between Sept. 1, 1924, and Aug. 31, 1926, 551 notable disasters in various places were tabulated in "The World's Health," recently published in Paris. The list included sixty-six earthquakes, four volcanic eruptions, nine avalanches and landslides, 197 floods, 148 cyclones, eight tidal waves, twenty-three droughts, forty-eight big fires, seventeen famines and thirty-one plagues of locusts.
DEFECTS IN SPEECH RECORDED TO AID PUBLIC SPEAKERS
Embryo orators and actors at the University of Southern California, have a means of studying the defects and good points of their own voices in an instrument that registers the tones as they are spoken and repeats them as a phonograph does. It is essentially a combination recorder and repeater, and the voice is sufficiently amplified as it is rendered by the machine, so that a number of persons can hear it at one time in a classroom or other place. The volume may also be diminished to suit a smaller area.
Speech Repeater in Use: Tones of the Voice Are Recorded and Amplified for Study of Defects
LIMITLESS-SPEED HIGHWAY IS BUILT FOR SAFETY
What is claimed to be the fastest public highway in the world for motor vehicles has been developed in the vicinity of Milan, Italy, with such success during recent months that plans have been projected that call for the ultimate addition of many hundreds of miles of such highway. These are known as "autostrade." Believing that speed in itself is no serious hazard in modern motor-car travel, because of the high degree of mechanical reliability of these vehicles, the Italian highway builders have created roads leading to four divergent points, near Milan, on which there are no speed restrictions. On these broad, smooth thoroughfares, motor cars travel from fifty to eighty miles an hour and the records show an almost negligible accident factor. The engineers have reduced the number of curves to a minimum and eliminated all grade crossings. Furthermore, the road is well protected by fences which shut out possible intruders. There are no abrupt grades in the autostrade. All cars are checked on entering and leaving these highways. The control gates are in charge of watchmen who exact a moderate toll from users, note the number and name of the car and, of course, are in a position to exclude any drivers who may be, for some reason, incompetent. Because fast traffic is an impossibility through towns and villages, these new roads have been laid out to avoid all intermediate centers of population. In the year just passed, the average daily traffic on the thoroughfares amounted to about 2,000 cars, and the next extensions of the system that are now contemplated will be similar roads to Brescia and Venice.
One of the Concrete Bridges on the Bergamo Branch of the "Autostrada," and a Futuristic "Billboard" Figure: It Attracts Attention Even When Motorists Drive at High Speed
CIGARET LIGHTS ITSELF
CLOCKWORK IN SAFETY RAZOR MOVES BLADE SIDEWAYS
Operating the Clockwork Razor in Which the Blade Moves Rapidly from Side to Side
Shaving with a safety razor recently introduced in England is somewhat like running a mower, for the blade oscillates from side to side instead of remaining stationary with respect to the holder. This is accomplished by a clockwork mechanism in the handle. The razor is said to be especially adapted to stubborn beards.
AIRPLANE TO FLY STRAIGHT UP THIRD OF A MILE A MINUTE
Realization of one of the fondest dreams of aviation is anticipated in a plane that, it is hoped, will be able to rise vertically at the rate of 1,900 feet a minute, make perpendicular descents in safety with the motors dead and thus permit landings in restricted areas. The ship is not a helicopter, engineers report, but is classed as a vertically rising airplane. So far, its possibilities have been judged wholly on the basis of wind-tunnel tests with a model of the plane. So convincing have these demonstrations proved, however, that a large aircraft company is reported to have voted $75,000 for the construction of a full-sized ship from the model plans. The small unit employed in the tests had four wings, but it is expected that the big ship will have only three. They are to be in a horizontal plane and will rotate at a speed of 120 to 135 revolutions per minute. Each of the wings will have a thirty or thirty-five horsepower motor to turn it and will be mounted on a vertical shaft above the fuselage. There will be no propeller in front, the forward motion of the plane being attained simply by tipping it forward. This gives the wings a new angle, and since they are set for climbing, their revolutions will tend to send the plane ahead. Comparatively slow speeds will be made, from fifty to seventy miles an hour being all that is promised. As the ship comes down, the wings revolve, even if the motors are dead, creating a breaking drag against the force of gravity. This feature is expected to prove of great aid in forced landings, through fogs, for instance, or in alighting in confined spaces such as the tops of buildings or ship decks.
LIGHT SHINES AROUND CURVES FOR SAFER AUTO DRIVING
Hazards of driving the automobile at night are reduced by a special headlight so adjusted that a wide beam is projected to both sides of the road, without glare to approaching cars and with better illumination of the highway on curves. The lamp plainly shows the road before the driver turns. It is not intended to take the place of the regular spot or headlights, but for special service on winding roads.
Front and Rear Views of the Car Equipped with the Broad-Beam Light; Above, Illumination on Curves