Oscar N. Dame
Id many instances amateurs are not able to erect poles suitable for the elevation of aerial wires, and while light wire strung from insulators placed on trees has served the purpose temporarily, a very efficient way to erect the antenna is by means of the kite. In some of my experiments I utilized the square kite because of its large surface. One objection to the square kite is its occasional unsteadiness, whereas the box kite stays put " when properly handled. But I found that the flat kite could be specially designed so as to be very applicable to my experiments, and the cost of construction was less than half that of a box kite; also the entire time consumed in building was much less.
My reason for wishing to elevate my atenna to a height of 500 to 600 feet, was to experiment with the radiation of horizontal waves, rather than for experiments in receiving, and I required as many square feet of radiating surface as could be controlled handily with ordinary manila twine. It must not be assumed, however, that the flat kite is superior to the box kite for general purposes of elevation, as elaborate experiments by both the War Department and the Smithsonian Institution have repeatedly proved the superiority of the box kite.
There had long been a diversity of opinions as to the sending distance of small spark coils, and also as to the superiority of a plate atennse over the harp form consisting of many flue wires, or a single wire. Researches abroad tend to show that a metallic plate properly elevated will send waves a greater distance than any other kind of aerial. To disprove this theory prompted me to construct the kite described in this article, and I hope every wireless enthusiast will try the experiment in the field as soon as convenient.
The flat or square kite is made of two light but strong sticks fastened together like a cross or X. Nearly every boy has made one or more of these kites with varying results, but I will go into the details quit© specifically so every amateur will meet with perfect success.
First procure two strips of spruce free from knots and splints, 1 1/2 in. wide by 3/4 thick, and 5 ft. long. Measure to the center of each piece, and at this point which is 2 1/2 feet from the end, fasten the two by winding with tine, strong wire. With four staples, a piece of No. 18 copper or iron wire is run from end to end of the strips and there fastened. About this wire the cloth covering of the kite is to be glued. In fastening this wire the frame should not be made a perfect square, but one-third longer than its width.
Sufficient unbleached cotton cloth of extra width is procured, or what is better, some Holland such as is used in the manufacture of window curtains. This latter is more expensive than cotton, but has a finer texture for kite purposes. An old curtain is obtainable in nearly every home. A piece of the goods is cut 3 in. larger all the way round than the kite frame, and then fastened to the wire frame with good fish glue, the cloth being lapped about the wire on all sides. The cloth is not stuck to the wooden pieces, but on the back side of the kite strips of stout cloth may be pasted over the strips near the ends.
The slings of this kite are of heavy twine. It will be noticed that the upper V piece of twine is of just the length to reach to the center of the kite, and the twine from the center which is fastened to the V piece is as long as from the center to the top edge of the kite. If these proportions are not followed, the kite will not fly accurately, but tend to bob and dive beyond control with every little variation of the wind. A short loop is fastened at the lower end of the kite, to which is affixed the tail. This tail is of the rag pattern, and for this size of kite should be made of four inch strips of old cotton cloth fastened together. The tail length should be in the vicinity of 35 feet. A bob or tassel of short pieces of cloth, weighing two pounds, will be required on the end of the tail. Additional weight maybe affixed to the bob when a heavy wind demands.
I might say right here that there is no reason except that of durability, why this kite cannot be made of brown manila paper or newspaper, for that matter. Most kites fall once or twice before being flown successfully, and for this reason cloth is used.
About sixteen square feet of tin foil of thinnest texture, such as is used in making spare coil condensers, is next procured, and the outer or front surface of the kite covered. This foil comes in long strips 5 in. wide and weighs little more than paper of the same size. The foil is stuck on with glue. Some very fine bare copper wire is then threaded on a needle and very coarse stitches placed all across the surface of the kite. This answers to connect all the foil strips together metalically, and also helps hold the foil to the kite. Some more bare copper wire is fastened through the covering of the kite and foil at the center cord, and wound about the cord to the point where the flying string is affixed.
The kite string is stout hemp twine, purchasable at any hardware dealer's for 15 cents per ball. The distance above the earth the kite is to be flown must be roughly estimated, and considerably more than that length of No. 36 copper wire, insulated or bare, wound on a reel or spool. The outer end of this wire is affixed to the fine copper wire coming from the kite, and the spool itself fastened to the bottom of the kite by means of some thin cotton thread or rotten strung. After the kite has been elevated a few minutes, the spool may be released by jerking the kite string. This wire, after falling to earth, is then run along in parallel with the fiying string until it reaches the operator, where connection may be made with the sending apparatus of the wireless outfit.
As a result of experiments with my kite, numerous conclusions were reached. First of importance was the fact that with an electrolytic receiver at a distant point, very little spark coil discharge gave excellent results, whereas the same coil attached to a single aerial wire was very erratic. It would seem, therefore, that experiments with kites of this type will establish what foreign experimentalists have long believed to be true, that large capacities at considerable height require but very small transmitting energy.