Radio Broadcast (May-Oct 1922)

82 RADIO BROADCAST full strength. It is the facts just stated that make a coil antenna a radio compass. The method of using a coil antenna to determine direction is best described by an example. A coil antenna is set up free to rotate. It carries a pointer which passes over a circle graduated in degrees; the zero point of the circle being to the north. A signal is picked up after proper tuning. The coil is rotated until the signal is just about to become too faint to hear. The position of the pointer is then read. Say this is 164 degrees. The coil is again rotated in the same direction until the signal reappears with the same intensity at which the first reading is taken. Another reading is taken. Say this is 196 degrees. The average of these two readings 164 + 196 2 gives you the position at which the coil is broadside to the station. In this case it is 180 degrees. This is the north and south line as o is at the north. The transmitting station then is at right angles to this direction. The transmitting station of the example lies in an east and west line. Whether it is east or west of the coil can not be told by any simple radio method, but this general direction is usually known. For greater accuracy, four readings should be made and their average taken. The third and fourth readings are approximately 180 degrees from the first and second reading and are obtained by continuing to turn the coil around. However, unless the coil has been specially designed for a radio compass, it is not worth while taking these extra readings as the first two will give as great an accuracy as the coil will allow. The cause of inaccuracy of an ordinary designed coil will not be discussed in this article. A coil may be mounted inside a room and will receive signals as well as if mounted outside unless the room has a great deal of metal in it. However, if a coil is used as a compass inside a room, there is likely to be an error due to that fact. Thus a radiator in the room will pick up the radio waves and re-radiate them, thus becoming a secondary source of waves. This will affect the loop, causing it to show a direction wrong by as much as 10 degrees in some cases. It has been found that coil antenna diminish the interference due to static. This is a great advantage in their use. In general, the smaller the loop, the more the static is diminished. Another advantage lies in the fact that, because of their directional characteristics they eliminate many interfering' stations. Other advantages lie in their compactness and ease of construction. In conclusion, it is desired to point out that for any given condition, such as wave length and kind of apparatus to be used with it, there is a certain sized, spaced, etc., loop that will give better results than any other loop. With this article for a guide a few trials ought to produce this one best loop for you. MERCHANDISING RADIO A Discussion of Some Interesting Points for the Retail Store to Stimulate Sales By a. henry TO-DAY we find radio apparatus upon the counters of the hardware store and even the corner drug store, but we wonder whether or not this condition will continue after the present rush for radio apparatus has subsided and the steady, normaF demand for equipment again prevails. Many authorities on radio merchandising agree that the present demand will, in all likelihood, be supplied within the next few months, and that preparations for supplying an even greater volume of business next year are to be arranged during this summer. There are two distinct classes of radio dealers, but only one is to be a permanent feature in this merchandising field. First is the dealer who knows nothing whatever about radio other than that it is a very popular pastime and it offers him an opportunity to make a rapid turnover. The other and more stable radio dealer is the man who understands the radio business thoroughly and is not satisfied to limit his