Radio age (Jan-Dec 1925)

r RADIO AGE for June, 1925 The Magazine of the Hour 3BI IB! L M. B. Smif/i Business Manager Jfie Marine ftho Hour /l Monthly Publication Devoted to Practical Radio E]E]E==3EIE==:ir:ir=^=1r1r=^=":11 IBI IBI IBE 1BI 'BE 3131=' Frederick A. Smith Editor irni imi ini int= SEES Make This a Radio Summer by Reducing STATIC Disturbances LS the Summer season advances, the l\ "static belt" creeps farther and •* •* farther north from the equatorial zone, and by the time that this issue of RADIO AGE is off the press it is certain that the great majority of our readers will have been given a taste of imported tropical conditions, and will be in the market for any ideas or devices which will enable them to tune out that roaring, crackling and crashing that mars their reception and subdues their DX ambitions. We can be grateful that the northerner is treated to only a few months of this sort of trouble instead of having static at his door all the year around as they do in the tropics. Manj' anti-static devices have, been suggested from time to time which are either wholly or partly successful in reducing the intensity of the static crashes so that the signals can be distinguished above the general uproar. Some are simple and others are rather complicated in theory, but all of them are well worth a tryout until one particular arrangement is found that most perfectly meets your local conditions. Any static eliminator which so reduces the interference to a point where the crackling is not audible during the program, and can only be heard faintly during the intermissions, can be considered highly successful from the broadcast listener's point of view, and with careful attention to the following matter, the amateur can generally rig up some sort of contraption which will greatly improve the clarity of the signals and somewhat extend the range of his receiver. As noise from static and radio signals are both the result cf electrical disturbances, and since both strike the aerial at the same time, it is rather a difficult matter to "unscramble" them so that the charges induced by the electromagnetic radio waves are retained, and the impulses due to atmospheric electric charges are grounded and rejected. In fact, this separation is partly made possible by the fact that some radio signals are of much higher frequency (or shorter wavelength), than the static impulses, and hence the two can sometimes be By ROSCOE BUNDY How to Make a Good "Anti-Static' Device separated by some form of tuning or filter system. By suitable arrangement of choke coils, which will stop the radio waves but which will allow low frequency and D. C. static to escape to earth, it is possible to greatly reduce the rattlings and other disagreeable noises. Atmospheric Electricity STATIC may be due to two causes: (1) To strong electrical charges deposited on the aerial by the highly charged air particles of the atmosphere, and (2) True electromagnetic waves sent out by lightning discharges or by emanations from the Aurora Borealis. That the atmosphere is a highly charged envelope may prove a novel explanation to many of our readers, but it has been proved repeatedly by meteorologists that the A «• 3» 2» U^g7W£j mwMwwwm^w F/e./ upper strata of the earth's atmosphere may be charged to hundreds of millions of volts above the potential of the earth itself. These charges may not be directly evident to our senses, but they can be measured by the proper instruments carried in sounding balloons or airplanes. Variations in these charges are painfully evident to the listener-in during the Summer season. By some means, not universally agreed upon by scientists, each molecule or minute particle of air carries an electrical charge. This charge may have been produced originally by the friction of the air molecule in rubbing over solid objects or over other molecules surrounding it. Again it may have been the result of the action of sunlight or of evaporation. Whatever the cause, it can be easily demonstrated that the air is a strongly charged mass of varying intensity and polarity, sometimes positive and sometimes negative, but always with the charge in evidence. At high altitudes the potential or intensity of the charge is greater than at points near the earth's surface, and at cloud levels the concentration during thunderstorms may reach hundreds of millions of volts. In fair weather, the charge may have a much lower potential, but in general we can estimate at least 50,000 volts near the normal cloud levels. One investigator estimates the increase to amount to approximately 100 volts per foot of height under average conditions in northern latitudes, but this is only the roughest sort of a guess. Actually, the potentials change day by day at any locality and also through a still greater range with the seasons. The relative polarities of the earth and atmosphere may change completely within a few hours, and again, the polarity may not be the same at all altitudes, alternating strata of positive and negative charges being found at different heights. As with all natural phenomena it is an irregular and complex proposition. Fig. 1 illustrates what is known as a "uniform potential gradient;" that is, it shows the even and gradual increase in voltage or potential as we increase our