Show KADIO DEl DEPARTMENT lEXT I Conducted I by H. H B. B Stone r- r Tuning This week we will pill take tip P the th tuning of a a. a receiving set Since there are so many st stations on the air ar at once it is necessary ry that the set be so constructed that one station can be heard at a time Ume timeto to the exclusion o of the others The usual receiver can be tuned so as to pickup rick pick up any wave length ill d the tho broadcast broadcast broad broad- cast band There arc are waves both longer and shorter ithan than those in this band but the usual radio listener terser is not pot interested in them I f We Va know that if a n. certain note be f struck on a piano that a string b on ona a 30 violin tuned to the same pitch will vibrate in res response t to waves wives sent out by bythe the vibrating piano string tuned to a different pitch will not I be caused to vibrate ibra The string of the he violin can be tightened or loosened loosen loosen- ed within certain limits limas to bring it itin in n tune the piano The string may also be shortened or r lengthened to o bring it in tune The idea Ide of f tl using suing a a. radio is much the same It would be possible to make a aradio t radio radio adlo that would respond to only i one ne wave pe length The length of the aerial cir circuit that is It tie itlie o aerial and ground wires and all all' wiring in the theet set et directly connecting the two to would determine this wave waye length This wave ware length could be changed by t y lengthening or shortening the aerial It is obvious that this would b be e impractical We would not want wanto to o climb up and cut a 13 piece off the aerial every time we wanted to listen listen list- list en n to a different station There are re easier ways of accomplishing the same same thing and this is ds what is done dune when we turn the tuning dials of a set et Some sets have haye two connections for or the aerial one for a short aerial and one for a long aerial This 1 la Ia lao so o that the entire broadcast baud band can be covered regardless of the length of the aerial l The he actual tuning is accomplished by y means of what we call capacities and nd inductances The action of these hese is technical but the results are much the same as w we iYO e get when we i change the length o of t t he violin string I or r change its tension Capacities I are a storing up of energy and condense condense condenses con- con dense s are used to accomplish this An Inductance is the action of a coil o ti wire to delay the change in alternating alternating alter alter- current These are so worked work vork oed ed d. d out that the listener need never hink hank of them The dials are set or a certain station and the receiver er er ir is brot in tune with that station Tuning is accomplished in ent int ways wars in fu different circuits The dials on one may not correspond to hose on another For this reason a a person used to one set et may have e a little Ittle difficulty in getting results from rom another The commercial sets of today are as a rule not hard to toune toune tune une and one may become n n n a short time Of course some ere eio much nuch easier r to tune than others but buta a B little practice with m most st of them the vill bring good resins results Some sets have va e only one dial and have ha hav ha- ha au- au vantage v of very easy tuning Others have ave several and have han the advantage advantage advant advant- 1 age age ge of or perhaps closer tuning as we can can get finer adjustments with the he hand than titan we can There are some sets that are not by changes in the length of the aerial In these the current Boas goss through the primary of a transformer transform transform- er and this induces a 3 current in the secondary and this se secondary current current current cur cur- rent is tuned In this sort of a set the same station comes cornea in in- at the ame same dial reading regardless of h t aerial is used One is 15 always Safe ate In using an aerial ial about ft Tong long as this length will walla cover the broadcast I band with practically any Receiver receiver V- V o j I Dont Don't forget that any any inquiries addressed to this department will L bo gladly answered without charge |