The Cedarville Herald, Volume 45, Numbers 27-52

w^ . « L « r, , . - - f l.., ,,,i^ . l,in,. ,.,,l.'..-.i-J * ' J.-- |ii)<ilW * ,;.ir .iiu - - — -- THJfftg iEO ttim BUST LEARN FIRST Expiation of Torms Uted In Radioandof(ftBasic PrtnofpM. D ’V» to tk* groat interest taken In ra. <tto sine* broaijcaattiig station# have booe started, many radio terms are ■oen tod beard thgt way be unfamiliar to the novice. Some o f the moat com* Ktonly need terms are explained and defined below, Lihe light, heat and sound, radio energy is propagated in the form of a wave motion. Every one Is familiar with the ware motion set up on the •orface of a still body o f water by the dropping o f a stone into i t • Byery time a point on the surface o f the waves goes through a complete *et o f motions, and start# to repeat those motions the wave is said to have gone through a cycle. The number o f complete cycles gone through per second is the frequency," The human e ir is responsive to sound frequencies up to a few thousand cycles per second but is not capable of responding to the higher frequencies encountered in radio. Arbitrarily a frequency o f Jess than 10,000 cycles has been called an audible frequency ■•r-One which cant be heard—and fre-i gueactes above 10,000 cycles, radio dr Inaudible frequencies—-because they cannot be heard by the human ear. The particular type o f wave which propagates radio energy is an electro­ magnetic Wave. All o f us have seen hits o f iron and steel attracted by the little toy magnets made up la the form o f horseshoes, This attraction'of the magnet for the bits o f iron and steel showed the existence o f a magnetic as Wm oarrkc-w*v* and ft* ftMMfte* $• to radial* into spoonin th* $m * of tloetrwmagaotlc wav** and by its va­ riation in amplitude carry with It the variation in tb# ton* at the transmit­ ting station.„ It is th* frequency o f the csnrisf* wav* that determiner +he wave-length on which a radiophone station la trans­ mitted. By experiment it has bean found that electro-magnetic waves travel at the same velocity that light waves travel, that is, 186,000 miles per second. Wave-length Is the distance between any two similar points <a> two successive waves; for example, the dis­ tance, from crest to crest o f any two successive waves in the same direction, hnoaspred in meters, a unit o f length equal approximately to one and one- tenth yard*. Converting 180,000 miles to meters, the equivalent is 300,000,000 meters. The length of an electro-mag­ netic wave,is equal then to 800,000,000 divided by the frequency. Suppose a station was transmitting on a wave­ length o f 800 meters. The frequency o f the carrier-wave would be approxi­ mately 885,000 cycles. Just as a violinist tunes his Instru­ ment, that is, makes a certain string emit a note of higher or lower pitch, or, technically speaking, a sound wave of higher or lower frequency, by ad­ justing. the tension on the string, so may the' electrical constants o f the antenna circuit o f a radiophone trans­ mitter be changed in order to have the station emit a carrier-wave of a different frequency! . I f a tuning fork having a natural period corresponding to {piddle C be placed near a violinist who Is playing, the fork will vibrate'when the musi­ cian'plays middle C, but all other times it Will remain quiescent. This phenom­ enon o f the tuning fork vibrating whenever the, musician plays the cor-, responding note on the violin Is known as mechanical resonance. I f a radio receiver be adjusted so that electrically its natural period o f vibration will be 835,000 cycles- (360 meters wave­ length) every time a station transmits on a wave-length o f 360 meters, cur­ rent will be set up In the receiver by Amateur Radio Operator* Erecting Aerial bn the Roof, field about the tips o f the. magnet and this same kind o f a field propagates the electro-magnetic force, except that unlike the toy magnet, its power comes off in the form of wavy motions. This electro-magnetic force propagates ra- , dlo energy in all directions. The medium that transmits the elec­ tro-magnetic waves 1 b the same .me­ dium thattransmits light—-the ether. This medium.is supposed to fill all space/even that occupied by fluids and solids. Little Is known about its prop­ erties. r In radio It is more common to speak Of wave length than frequency. The wave length o f any wave motion Is the dlBtnnce between any two successive crests in the same direction. The Wave length depends upon the fre­ quency. I f the frequency Js high the wave length is short,' On the other hand If the frequency Is lew the wave length Is long. Numerically the wave length is equal to the distance trav­ eled by the wave in one second divided by the frequency. Suppose, for ex­ ample, that It were desired to know the wave length o f an electro magnetic Wave having a frequency of 835,000 cycles, Electro-magnetic waves travel at the same speed as do light waves, that is, 186,000 miles per second, Di­ viding the 186,000 *»y 885,000 the wave length would be .228 miles or 896 yards.' In radio work It is measured fn meters. A meter Is equal to ap­ proximately L I yards. Converting 896 -yard* into meterr the wave length would be 896 divided by 1.1 or 800 m etersj This is the wave length on which KDKA operates. It also means that the. electro-magnetic waves sent eat from this station have a frequency of 886,000 cycle*. FUNDAMENTAL TpftlNCIPLES In a radiophone transmitter there are two requirements that must be fulfilled, First, there miiat be a source of high-frequency current, say, between 15,000 and 1,600,000 cycles so con­ nected to an antenna and ground sys­ tem that energy in the form of electro­ magnetic wavS will be radiated. Sec- ond, there must be some method o f controlling this high-frequency current or modulating it so that’ the variations in the amplitude o f th* high-frequency current will be directly proportional to the voice or music to be transmitted. electrical resonances, Stations trans­ mitting on any wave-length other than 860 meters will not cause a current to be set up in the receiver. The portion o f a radio receiver that changes,the wave-length at which it is electrically resonant Is called a tnner, Suppose that “A " station, trans­ mits on a wave-length o f 200 meters -and "B” on a wave-length o f 860 me­ ters. By adjusting the tuner until the constants o f the receiver make it elec­ trically resonant to a 200-meter wave or a 860-meter wave, either o f the two stations .can be picked up,. but both stations cannot be picked up simulta­ neously. - Tbls is the reason thyt more than one transmitter can be operating at one time and yet only one can be heard on a receiver without interfer­ ence from the others The other necessary part of a radio receiver Is the detector. The function of this,portion o f the receiver is to utilize the small currents In the tuner that are set up by a transmitting sta­ tion and make them audible through the medium o f a telephone receiver. I f the telephone receiver were connected directly to the tuner the high-frequency current would not operate the’ dia­ phragm o f the receiver and even If the diaphragm Were set in motion it would be too faBt a motion to be picked up by the human ear. In a simple receiver the detector us­ ually consists of two pieces of mineral in contact or a piece o f mineral in con­ tact with a metallic spring. Either combination is known as a crystal de­ tector, A detector of this type is Bath­ ing more than a rectifier; that Is, when an alternating current is applied at the terminals the current is allowed to flow only in one direction, How One Editor Uses Radio. The editor of a paper in an iso­ lated town lit the northwest is using the radio in a.most ingenious .and ef­ fective way. An aamatenf radio friend in a big city 50 miles away buys the latest editions of the city papers as soon as they are off the press, reads the 1 it news into his transmitter, and a typist in the country office copies the hew* as It comes in over the office re­ ceiver. The editor, through this in­ genious plan, is always “First with the Latest" In his home town, EAGLE“M1KAD0” Jo*1i*1 KH encilNo.174 Made 1« five gradwi •* * * m 'l m w * : m '***** taunt MM Y<m ...... t* A.. . - „. jS L .a .... 1 ; f- ') ■*: f ' ,V .-‘Jf s 4 § 4. I '/ } \ i " Si t & t ^ "I 1 I | I' 1 " A '• 1 ■ ! i •S Neckwear P RESENTING an as­ sortment of varied patterns in durable silks seldom offered at this unusual price of $ 1 lO to*40 it’s as hot as a furnace and as close as an unventilated room man needs the right kind o f Clothes to put him at his ease. # And here are Clothes-—light, airy and com­ fort-producing—that will make you feel like a babe after a bath. ' Palm Beaches, mohairs, 1crashes, home­ spuns, linens, silks, etc.—yes, all the popu­ lar fabric* Underwear n HECK up on your V " Summer Underwear needs, then come here for the, best values of­ fered this season at » S t r * a w s On the S treet *2 t o ®8 f ) R MORE properly speaking ^ —the Men one sees on the streets are all beginning to wear Straw Hats. P VERY day dozens come here * -» for theirs, and probably most of the smart Sailors you’ve admired came from us. 1 ET us supply your Straw *-* Hat—we know what’s right and will held you make your selection. * 3 W . D . o A l e x a n d e n C o Hart Schaffner & Marx Clothes • "1 1 (• rx , *\1 - f-5. - I * ! * !v -i ;':_ ;1 ? ■\ [; /■ V IPfh iff ,« lit if V: | £ jl «>- u V "• "t t* R x tra ^Trousers * ,> At An Extra Low Price s PARTICULARLY in the good old Summer time is ‘ 1 a pair of Extra Trousers a necessity. And in "this special selling—due to a most advantageous purchase—we’re able t<f offer you greater values than it ’s been your good fortune to find in several years. «aT •‘W- I ,•■*5*'* **{3* ->**0 —•yr-;