How to Become a Radio "Reception" Prophet

Radio Record, Volume I, Issue 43, 11 May 1928, Page 3

How to Become a Radio "Reception" Prophet

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air contains, compared with what it could contain if saturated at the given moment. With the help of thermometer and hygrometer, we can forecast static still more effectively, with the aid of these pointers: 1. If the barometer reads above 80 inches and has been rising during the preceding twelve hours, and if the temperature and relative humidity are falling, static is not likely withia the next twelve hours, 2. If the barometer reads below 39 inches and has been falling during the preceding twelve hours, and the temperature and relative humidity are rising, static will prevail during the next twelve hours. 38. If the barometer is constant while the relative humidity falls, static is likely to reduce in tensity if it has been current. . 4. If the barometer is constant while the relative humidity rises; static may increase if it has been current. 6. If the relative humidity and temperature remain constant while the barometer rises or falls, a change

from the prevailing intensity of static will be effected less quickly than if the relative humidity and temperature changed as indicated in statements (1) and (2). -- The reader is cautioned here not to take these statements too literaliy. They represent merely guides to probable occurrences, and will occasionally be found to be inaccurate, because quite exceptional atmospheric conditions happen from time to time. For example, there are times when the barometer is high, that is, above 30 inches, but begins to fall while the relative humidity rises It may not yet have reached 30 inches when rain or snow begins, yet static will not make itself known. At all times pressure is the dominant ‘influence, while temperature and relative humidity, if operating according to rules 1 to 2, merely help to strengthen the forecast which the -pressure-change indicates. A POPULAR FALLACY. 'HWHESE last statements call atten- ! tion to the popular misconception

that whenever it rains or snows static will be prevalent: This is not at. all true. ‘The writer has experienced some of the beSt reception during such storms, but in these instances atmospheric pressure was higher than is customary when rain or snow occurs. On the other hand, much static has been experienced on some clear nights under high pressure conditions, when on these occasions abnormally high relative humidity was) accompanied by a sudden drop in temperature. Since these cases are exceptional, although not always rare, perhaps we should not allow them ta impress us too strongly. OPPORTUNITY FOR INVESTIGATION HILE we have attempted here to sugyest a simple instrumental method enabling the average person to forecast for himself the proba-. bility of static, we refer again to the utilisation of the daily weather map by those desirous of making a detailed study of the whcle problem.

The writer has found many relationships between the location of the -receiving and sending stations with respect to the extent and intensity of a high or tow pressure area, and the probakility of static. The details cannot be presented here, but a few major conclusions may be noted. (By way of explanation of the term isobar, the reader is referred to the map on which he will see concentric lines outlining high and low pressure areas. If these are close together the pressure is intense or strong, but if far apart it is weak. If close together, the pressure area as a unit ‘moves more rapidly than when the isobars are far apart. Amy line drawn at right angles across a series of isobars indicates the isobaric gradient.) Here are some conclusions drawn from a study of these maps: 1. If a line connecting the receiving station with the broadcasting station crosses the intervening isobars at right angles, reception is at its best.

2. The steeper the isobaric grad ient {that is, the closer the isonars to each other), the stronger the reception. 3. The more nearly the transmit~ted waves approach parallelism with the isobars, the weaker the reception, Under these conditions fading occurs, 4, Reception is weaker when the transmitted waves cross from one pressure area into another than when they travel only within one area, 5. Reception is better in winter than in summer because the cyclones (Lows) and anti-cyclones (Highs). are more intense in the winter period. 6. Shallow or flat pressure areas favour much static. We need more investigation in the field of the relationship of static to atmospheric conditions. Here is an opportunity eminently worth while for both the experimenter and fan.