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Show I ADVANTAGES OF "LOOSE COUPLING" SHOWN I Expert Points Out Help, of This Scheme in Radio Transformer By PAUL P. CSODLEY. America's Foremost Radio Authority. At first glance the itctlon which takes place in the radio receiving transformer seems mysterious. Yet It is very simple. I easily can be explained and understuua. It should be remembered that, whenever a current flows within a' wire, there is set up around it an invisible in-visible magnetic field This del l Increases, In-creases, decreases or dies out, in strict accordance iwth any increase, I decrease or dying out of currents flowing within tho wire. If. in tho neighborhood of the cjr-. rent-carrying wire, there is .i Second Wire, the risins and falling (alternating) (alternat-ing) magnetic field will produce inj that second wire an electrical irrenl whose ariations correspond exactlj i to the variations of the m ignctfc field. The current flowlnc in this v Ire is an exact replica of that which flows, in the first But It is always a some- To ' u luuj ir VV 1 1 I j Lp' Close Coupling of Transformer, what feebler current, and it- dlrei -tion Is always opposite to tha. ot the flow In the first wire. Tho current In the second wire Is said to b "Induced." "In-duced." RECEIVING COILS. Tho receiving transformer consists of two colls of wire, one of which slides within the other. There is no actual electrical onnection between tho two. There is an inclination anions operators op-erators who understand tlir indue-tlvo indue-tlvo effect to so arrange the pr;-mary" pr;-mary" and "secondary" of the receiving receiv-ing transformer that the relationship of the two Is the closest possible at ill time Under these drcumstanoes i eg Loose Coupling of Trensforinor, the coupling is at ;i maximum and i the purpose of the device Is defeated. defeat-ed. It does not seem to be generally .known that the closest possible coupling coup-ling for maximum signal reception Is not on'y unnecessary but undesirable undesir-able .The Inductive 'coupler" ir transformer wns designed so that a maximum Of Signal current might b-transferred b-transferred to the secondary of the ! transformer, while at the same time, an increase in the selectivity of tho receiver might be obtained. ItlXiN l In order thai the intensity of sJg-, sJg-, nal currents may be retained when the coupling is reduced, both prl- mary and secondary circuits ir-tion. ir-tion. This is accomplished by a variation of inductance or capacity In the i iri uii and results In a condition of "resonance." Par better all around results with Inductively coupled receivers, be they ' tuned" to a given period of vibra- il detector or vacuum tube types, arc had when decidedly ' loose" coupling coup-ling Is adhered to. This requires i more exact tuning of both prima? and secondary circuits. The signal strength, however, remain-- t h same, and the receiver is rendered comparatively compara-tively free from interference. |