Radio broadcast .. (1922-30)

i yo Radio Broadcast permanent communication with the new Argentine station at Monte Grande, near Buenos Aires. Four of the existing masts at Nauen, which are more than 390 feet in height, have been removed and replaced by a series of seven towers 688 feet in height, which provides four additional antenna circuits, each of which is served by a high-frequency alternator. The new antennas will be used for American, Asiatic, African, and European services. For distant stations, such as those in South America, two or more antennas may be used together. The transmitting installation has • been improved and enlarged, and the system of grounding connections has been extended. The Grid QUESTIONS AND ANSWERS The Grid is a Question and Answer Department maintained especially for the radio amateurs. Full answers will be given wherever possible. In answering questions, those of a like nature will be grouped together and answered by one article. Every effort will be made to keep the answers simple and direct, yet fully self-explanatory. Questions should be addressed to Editor, "The Grid," Radio Broadcast, Garden City, N. Y. The letter containing the questions should have the full name and address of the writer and also his station call letter, if he has one. Names, however, will not be published. IVbat is wavelength? THOUGH wavelength has often been discussed in this and other publications, a great deal of confusion still exists in the mind of the novice as to just what wavelength is. The accuracy of the average broadcast enthusiast's conception of the subject is well reflected in a recent newspaper write-up of an installation capable of receiving waves sixty meters long. The writer goes on to explain: " — which means that the set is particularly susceptible to atmospheric disturbances sixty meters above sea level." The term "wavelength" is really self explanatory, for it is generally understood that the impulses from a transmitting station assume somewhat the form of a wave. Wavelength is, obviously, the size or length of the wave in meters (i meter =39.37 inches). Electromagnetic impulses (radio waves), under practically all conditions, and regardless of length, travel 300,000,000 meters in one second, during which time a certain number of waves are sent out. If only one wave leaves the antenna each second, the first part of it will travel three hundred million meters before it is broken off and a new wave starts — in other words, the wave is "stretched" over a distance of three hundred million meters. If the frequency is two, the first wave will travel one hundred and fifty million meters, in only half a second, before it is terminated by the commencement of the following wave. If the frequency is three, the wavelength will be 100,000,000, meters, etc., thus establishing an evident relationship between frequency and wavelength; 300,000,000 divided by either quantity giving you the other. The frequency at a two-hundred meter wave (300,000,000 4 200) is one million, while the wavelength at a frequency of one million cycles (300,000,000 -=1,000,000) is three hundred meters. It will be observed that frequency varies inversely with the wavelength, and short waves are often referred to as "high frequencies." The above relationship, stated in a mathematical for V V mula, is X = — and, transposing, N = — where X = N 1 wavelength in meters, N = frequency in cycles per second, and V = velocity of radio waves in meters per second. It is evident from the above that wavelength, in one sense, does not directly affect the number of turns of wire on a receiving coil. However, more than one tyro in his desire to receive 36o-meter stations, has multiplied 360 by three (three feet to the meter), and, zealously wound 1080 feet of wire on a tuning coil! But, in a less literal way, wavelength does determine the amount of wire on our receiving instruments. Alternating currents (radio currents are alternating currents of high frequency) in traversing a circuit, such as from antenna to ground, experience not merely the retarding effect of resistance, but also that of "reactance." Positive reactance is a result of inductance, a quality existing in almost every circuit, which causes the amperage and voltage to reach their maximum strengths at different moments. Work, such as turning a motor, or actuating a telephone receiver diaphragm, can be best accomplished only when volts and amperes work in unison (giving watts). Reactance thus results in a loss of power, which, in small radio currents, makes reception impossible. To overcome this negative reactance, condensers are introduced into the circuit, which, when properly balanced, exactly couneract the reactance caused by inductance, bringing the lagging amperes back into phase with the volts, thus permitting work to be accomplished. But reactance varies with the frequency of the current, and, therefore, at different waves, various values of condenser and coil windings (inductance) must be used. Tuning is nothing more than a balancing of the two kinds of reactance, positive and negative, so that at the wavelength to which the receiver is tuned, they nullify each other, and the weak radio currents will encounter only the comparatively negligible effect of resistance. What is regeneration? How can a non-regenerative set be made to regenerate? REGENERATION, briefly, is a method of securing amplification with a single tube, by coupling the output of the bulb back to the grid in such a manner that it intensifies the slight potential applied to it