Radio Digest (Oct 1923-July 1924)

. ' " — J r— 22 RADIO DIGEST — Illustrated March 29, 19H THIRTY MINUTE A-B-C itiBuad t IS) in the t • vibrate the i sgular series of DOLL RED LIGHT WAVES COOLING DOWN THROUGH SLOWER FREQUENCIES REC0NI2.ED AS HEAT HOT HORSE SHOE Figure S. •waves, and are sometimes called oscilla aking of the dis e between successive waves as the wave length, this is also expressed in how many occur in a specified Tims, if the sixty waves or -rDlAPHEAM to be hoard as a hum i" apparatus such as power transformers. All such low frequencies are called audio fredea if they can be heard. broadcast station uses very high frequency energy, and for a SCO-meter wave length this amounts closely to 833.000 cycles per second. In Radio, high frequency energy or vibrations as used In broadcasting are above audibility and are called Radio frequeni Sound Important in Broadcasting Air is not required for the transmission Of light or Radio but sound must have air or a material medium. Since sound controls the intensity of broadRadio waves by means of suitable apparatus, the way this is done is important. The common range of audio frequencies is about 16 to 8,000 cycles, and varies according to the ears of individuals. Heat waves are another form of energy which can be compared with Radio. A hot horseshoe taken from a blacksmith's forge, Figure 8, in cooling down from dull red goes through a range in which the particles of iron or molecules of which it is comprised go through a great commotion, which becomes slower and slower during the cooling. Heat waves TAUT STRING Figure 9. pulsations in a second, the frequency is said to be sixty cycles. What Are Cycles? Cycles means how many waves occur in a given time; one second. In light, the waves are very short and since they travel at the rate of 186,000 miles petsecond, it is understood that there are very many billion of them vibrating each second, so the cycles are a high number. Light comprises an extremely high frequency. In Figure 7, there are illustrated three widely separated frequencies one can fix in mind. The cycle of day to night, as are extremely short compared to Radio waves. Frequency of Oscillation Having seen that Radio is concerned with vibrations, it is well to fix in mind what is .meant by oscillations. Figure 12 illustrates a clock pendulum 1, having an adjustable weight 2' which the clockworks keep in motion, swinging from 4 to 5 and back again. This pendulum like other material things has a natural rate of travel back and forth, and to change this the weight 2 is moved up if one wants the pendulum to travel faster or down for slower. One trip from posi RULER V;"'-. .. x-STfclNG,' It "-"--"• HAIR PIN 10 TO 30 FEET CHAIR. Figure 10. the earth rotates, is very slow. A similar and much faster example would be the trip back and forth of the pendulum of a clock. "The ordinary alternating current supply of a power line has sixty cycles per second. This is slow enough tion 4 to 5 and back again is one cycle, and the pendulum is said to oscillate or swing between positions 4 and 5. When the weight 2 is raised the length of the pendulum is shorter and the distance between 4 and 5 will be shorter. 0* I 5 Audio Amplification at a Popular Price The volume and clearness of amplification of this HALF PRICE transformer is always a pleasant surprise to users. Many have written us that they prefer their 3 to 1 ratio Goto Specials to others selling at double the price. $2.50 Great for reflex circuits. Type 4500 If your dealer fails you, write us, giving his name and address, and list of Colo parts you need. COTO-COIL CO. 87 Willard Ave., Providence, R. I. BRANCH OFFICES: Los Angeles, 329 Union League Bldg.; Minneapolis, Geo. F. Darling. 705 Plymouth Bldg.; Atlanta, C P. Atkinson, Atlanta Trust Co. Bldg.: CANADA. Perkins Electrie Co., Ltd., Montreal, Toronto, Winnloeg B Trust Co. Bldg.: CANADA. Perkins Elec G^^/^--,....^^^'"lfro^mT"ram'™r"'""''1"'"'r ^ ~~j ^_* trie Co., Ltd., Montreal. Toronto. Winnloeg. M^ #jutiiifititiiit«titiraire& ! r-i DIAPHRAM ^ 'AT (JEST / □ 1 \ DIAPHRAM ^y^c/ GRAPHITE 6RAINS (microphone) ^0 BATTERY ELECTRO MAGNET X 1 v PULSATING ELECTR.IC CURRENT WIRE LINE DIAPHRAM uM DIAPHRAM \?y MICROPHONE \l/ SOUND. DIAPHRAM electro-magnet\t SENDER. Now in the case of other oscillations such as Radio oscillations which occur at extremely high rate, an analogous procedure can be carried out to adjust the rate of vibration or oscillation. A further example to fix this point is furnished by a dinner gong or bell. "When RECEIVER struck, the gong is set into audible oscillation. Essentially the transmitting aerial of a broadcasting station is similarly struck electrically and set into high oscillation. Whereas the gong sets up corresponding motion in the sur(Continued on page 24 ) A *200,000.°° COMPANY stands squarely hack of the guarantee on ever u Scientific headset SEND NO MONEY! Order Today bu Postcard and Pay Postman on arrival ZO.OOO TURNS EQUIVALENT TO 3,000 OHMS We Guarantee 285 POSTPAID LOUD SPEAKER UNIT*!95 The Scientific Headset to be the greatest value on the market. Try it for five days. If not satisfactory s^nd it back, and youi° money0 will be refunded immediately. Circular0 on request. Dealers wanted. THE SCIENTIFIC ELECTRIC WORKS 98 Brookline Ave. dept. w. BOSTON, MASS. Agents for New York and Vicinity— AMBASSADOR SALES CO, ti Cortlandt St., Phone Cortlandt 6296 Use the This is not one of the old fashioned wave traps. It is inductively coupled. We guarantee satisfaction or money refunded. Tuning Unit UNIVERSAL Its efficiency improves any circuit y SILENCER Reasons Why, 1. No distributed capacity. 2. No absorption or originai signal strength. 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