The Radio Boys on the Mexican Border.
by Gerald Breckenridge.
FOREWORD
The development of radio telephony is still in its infancy at this time of writing in 1922. And yet it has made strides that were undreamed of in 1918. Experiments made in that year in Germany, and by the Italian Government in the Adriatic, enabled the human voice to be projected by radio some hundreds of miles. Today the broadcasting stations, from which nightly concerts are sent far and wide across the land, have tremendous range.
Estimates compiled by the various American companies making and selling radiophone equipment showed that in March of 1922 there were more than 700,000 receiving sets installed throughout the country and that installations were increasing so rapidly it was impossible to compute the percentage with any degree of accuracy, as the gains even from week to week were great.
When you boys read this the problems of control of the air will have been simplified to some extent. Yet at the beginning of 1922 they were simply chaotic. Then the United States Government of necessity took a hand. The result will be, eventually, that certain wave lengths will be set aside for the exclusive use of amateurs, others for commercial purposes, still others for governmental use, and so on.
In this connection, you will note that in the story Jack Hampton"s father builds sending stations on Long Island and in New Mexico. This is unusual and requires explanation.
The tremendous growth of amateur receiving stations is due in part to the fact that such stations require no governmental license. A sending station, on the other hand, does require a license, and such license is not granted except upon good reasons being shown. It would be natural for the government, however, to give Mr. Hampton license to use a special wave length--such as 1,800 metres--for transoceanic radio experiments. Extension of the license to the New Mexico plant would follow.
THE AUTHOR.
DIRECTIONS FOR INSTALLING AN AMATEUR RADIO RECEIVING TELEPHONE
In order that the boy interested in radio telephony may construct his own receiving set, the Author herein will describe the construction of a small, cheap set which almost any lad handy at mechanics can build.
Such a set should be sufficiently powerful to permit of successfully picking up the concerts and other programme entertainments being broadcasted frequently by stations throughout the country.
Two drawings are given herewith which will enable boys to visualize the appearance of the set, and will be of aid in following instructions.
Referring to Figure 1 let us examine first the construction of the receiving inductance marked L. The latter is shown in detail in Figure 2, and consists of a heavy piece of cardboard. The back of an ordinary writing pad will do.
[Ill.u.s.tration: Figure 1]
First, draw the circle out with a compa.s.s to the diameter shown and then divide off the outside into an unequal number of divisions as shown. Draw a light pencil line through each of these marks to the centre of the circle. Now with your scissors cut out the disc, after which you cut the slots as shown.
The slots should be about one-quarter of an inch in width and of the depth shown in the drawing. Two such discs should be made and, when all cut out, should be given several coats of sh.e.l.lac to add stiffness and to improve the insulating qualities.
Now at your hardware dealer"s buy one-quarter pound of No. 24 double, cotton-covered wire and proceed to wind the coils in the manner shown.
Keep the windings even and avoid all joints throughout the length of winding.
When you have finished, mount the coils as shown in the drawing. Make sure that the windings on both coils run in the same direction. If you fail to do this, the set will not work.
For the detector, it is better to purchase a good make of galena detector at any radio supply store. If you are handy with tools, however, you can buy the galena and make your own detector. It will work with more or less satisfaction.
Your next need will be the condenser. The condenser consists of a series of aluminum plates, some of which are movable and the rest stationary.
Buy a small variable condenser. Its function is to tune the secondary circuit, which is accomplished simply by turning the k.n.o.b. Such a condenser could not be made without the use of a good set of tools, and the author strongly advises it be bought instead of made at home in order to avoid trouble. The aluminum plates are s.p.a.ced very closely and great care should be taken to avoid bending them, as they must not touch each other.
The aerial for this set should be about 60 to 100 feet in length and as high and clear of surrounding objects as possible. A simple porcelain cleat at either end, as shown in the drawing, will serve to insulate it sufficiently.
Your ground connection can be made best by wiring to the cold water pipe, although wiring to a steam or gas pipe will do almost as well.
You are now prepared to mount the various instruments in their proper locations. For your table instruments, get a good pine board about seven-eighths of an inch thick. Buy four binding posts and use one for the aerial wire, one for the ground wire, and two for the phones or head set.
To operate the set, first bring the hinged coil of wire close up to the fixed coil and adjust the detector until you can hear in your receivers the loudest click caused by the turning on and off of the key to a nearby electric light. If no light is available, a buzzer and dry battery should be used. When the detector is properly adjusted you will be able to hear the buzz quite distinctly in the head phones if the buzzer is not too far away.
[Ill.u.s.tration: Figure 2]
The actual adjustment of the detector is rather a delicate job, and once it is in the proper position it is a good plan to avoid jarring it, as it is liable to get out of adjustment very easily.
Once the sensitive spot on your detector is found, slowly turn the k.n.o.b on your condenser and at some spot on it you should be able to pick up signals of some sort, either of radiophone or spark. If the set does not work, then go over all your wiring and be sure that the windings of the two coils are both running the same way.
The above set will work well for short distances, say up to twelve or fifteen miles. Beyond that, however, it will not receive music unless you have unusual facilities for putting up an aerial to a considerable height and well clear of surrounding objects.
Such a set should be constructed at a minimum of cost and may later, after you have become familiar with the operation of radio appliances, easily be converted into a set of much greater range by the use of a vacuum tube as detector and may even, by slight changes, be given the much desired regenerative effects.
CHAPTER I
A CRY IN THE AIR
"Well, Bob, here we are again. And no word from Jack yet."
"That"s right, Frank. But the weather has been bad for sending so great a distance for days. When these spring storms come to an end the static will lift and well stand a better chance to hear from him."
"Righto, Bob. Then, too, the Hamptons may not have finished their station on time."
The other shook his head. "No, Jack wrote us they would have everything installed by the 15th and that we should be on the lookout for his voice. And when he says he"ll do a thing, he generally does it. It must be the weather. Let"s step out again and have a look."
Taking off their headpieces, the two boys opened the door of the private radiophone station where the above conversation took place and stepped out to a little platform. It was a mild day late in June, and the sandy Long Island plain, broken only by a few trees, with the ocean in the distance, lay smiling before them. A succession of electrical storms which for days had swept the countryside in rapid succession apparently had come to an end. The clouds were lifting, and there was more than a promise of early sunlight to brighten the Sat.u.r.day holiday.
The boys looked hopefully at each other.
"Looks better than it has for days, Frank."
"That"s right."
A few moments more they chatted hopefully about the prospects, then re-entered the station.
Frank Merrick and Bob Temple were chums, a little under 18 years of age each. It was their bitterest regret that they had been too young to take any part in the World War some years before. Frank was dark, curly-haired, of medium height and slim, but strong and wiry. Bob was fair and sleepy-eyed, a fraction under six feet tall and weighed 180 pounds. A third chum and the leader of the trio was Jack Hampton, 19 years of age. He had gone to New Mexico several months before with his father, a mining engineer.
All three boys were sons of wealthy parents, with country estates near the far end of Long Island. Frank"s parents, in fact, were dead, and he lived with the Temples. Mr. Temple was his guardian and administrator of the large fortune left by his father, who had been Mr. Temple"s partner in an exporting firm with headquarters in New York City. Jack Hampton also was motherless.
The boys were keenly interested in scientific inventions, and were given every facility by Mr. Temple and Mr. Hampton for indulging their hobbies. Such indulgence required considerable sums of money, but the men believed the boys were worth it. In fact, both gentlemen were scientifically inclined themselves, and were able to give the boys much valuable advice.