Show K 7 LS r ars Ls W ll 11 cl F A 0 A aj the te circuit diagram of the three tube set that was completed within one hour by CHESTER CHARLTON in radio world tile the one leour set bet la Is not one that simply lusts lasts nn an hour flour but one that it takes only ono one hour to make it will last for many years and will ul render excellent service the radio side of the circuit consists of the lie justly famous tilt three cir cult auit tuner the audio channel coin comprises arises two stages of transformer transi former coupled amplification hence tile alio three tubes all three sockets are a part of the detector timp amplifier lifler unit only the radio sille need be w wired ired the only change I 1 made was to cut the oue one inch aich lead that comes from the I 1 P posts of the two audio transformers to insert a ca C battery as aa shown in ili diagram coll coil information any of the commercial three circuit tuning colls coils may bo be used in ili tills this circuit tile the one shown tunes with a mad variable condenser rt it lias has a pan pancake calco tickler however some other sort of tickler will do ns as well for instance it if you wind your own cot coil you may use it a 3 avi inch diameter tubing for tile th 0 stator 4 inches high placing 10 turns of no 21 24 doble silk covered wire near the top LI terminate leave IL space and wind 45 turns of wire in the same direction ara for the secondary la 12 the tickler would consist of as many turns of the edme kind of wire as you can put on oil tiny any tubing that tant will rotate inside the secondary remember that a shaft tins has to pass through the secondary hence wind the ilia tickler coll coil so as to leave anchorage room thereon for the shaft where it must be joined to the tickler form A capacity tuning condenser was use used tills this has semi cincu lar far plates the fact that the condenser tins has till nn insulation end plate does not menn mean that tile condenser Is not low loss it Is to make the tuning more convenient on the lower waves and yet avoid crowding on oil tiny p part art of tile lie dial a converted dial was used the parts needed you need get only a 7 by IS 18 anch aich panel linnel a 11 ined variable varIn ble condenser a dial vernier if you use frequency cori con or a converter a 7 by 17 inch baseboard ba se board a grid leak and a knob the layout or of tile parts Is very simple As the condenser Is the only real tuning element it alone hns has a dial the tickler coll coil Is turned by means mean of a knob oven even a rheostat knob or if desirable tosi SIN si tile a 2 inch dial may be used here the rheostats jack and even the fixed condensers including the grid condenser are part of the detector her unit the wiring precautions include these connect the rotor plates of the variable varl ablo condenser to tile the grid return side of the coll coil 12 the 45 turn coll coil it you make your own this la Is tile the connection made to A plus connect the aerial coll coil so that the ground all and A plus connections connect lona adjoin tills this accounts for two terminals ono one each of primary ind and secondary and the other connections tic of these windings go to aerial and grid condenser respectively the tickler or movable coll coil may be joined to the plate of the detector tube in either manner that Is either terminal to plate actual time 67 57 minutes the shown in ili the photographs was completed in 1 minutes but we will call it nn an hour this included the drilling of the panel and the mounting of the dial two items that require a little care und and hence took a tood good fraction of the time cherev there are only about a dozen connections to make the leads tire arc brought out to binding posts tin nn jhc thc unit I 1 and a marked battery cable should bo be used for convenience in establishing contacts at the batteries |