Show T AW A ass ar IL V r aa T ta 3 0 52 M A t three tube tuba receiver square wound tor old coll coils two stages stage of frequency and detector can be enlarged en barged to five tube SOIL set 4 A raw by CARLTON CARL TON I 1 E BUTLER Morn umber bor angrl i taut of Engin stra mil and institute of radio ludlo anjil no sty styles es in radio receivers rec elvora have changed with the changing conditions of the ho broadcasting field A three tube regenerative o set with two stages of radio frequency fie quency amplification wits was capable of 0 giving satisfactory reception a few years ears ago but today with the worst congestion of tile the ether lanes ever eer experienced in the history of radio end and the increasing use of high power broadcasting a so ge requirements demand the use of fic quency amplifying circuits A tareo tube circuit today should use form of 0 tuned frequency amplification that successfully copes with 1020 conditions and furnishes on inexpensive set that later on may kiy IB ba enlarged enI orBed into a ove tube re celver by the addition of two stages of audio frequency amplification leave room on panl panel in the din lingrain grain shown here bere however just the three tube circuit Is illustrated lust rated as it makes a complete set bet in itself room should be left on oil tile the panel and in the hie cabinet for the other stages lit at a later date ivor this reason reabon a 24 or 20 inch panel should ile be used with a cabinet and baseboard large enough to alloy allow for tills this future expansion the three tube set will bring in just as much distance and possess all of the desirable qualities of the hilgh priced five alve tube tub e sets seta on tile market excepting volume which Is obtained when audio amplification Is added little apparatus to Is needed to construct this set and with reas reasonable seasonal onal ae care an excellent receiver can bo be liari had for very little outlay of time lime and money to construct the pet you sou w will ill need the following list of apparatus I 1 square wound horold coll coil type tl 2 square wound horold colla coils type ta indicated us as T ta and ta 8 straight line frequency variable coriden condensers sers mad capacity indicated os as cl 01 ca and ca 1 fixed blied grid condei S ir and 2 inego lim grid leak 25 ohm rheostats I 1 phone juch 3 tube sockets soth ets binding posts wire screws etc the 2 olini ohm rheostats tire are to bo be used with UV A or 0 A type of tribes if tile he type ope are ara to be used then 10 40 ohn ilni rheostats rheostat it should be substituted etli buted for I 1 or t theu lie WD I 1 H I 1 or WD IVD 12 type of tube bobin tt cilmi rheostats throughout will be correct both radio frequency tubes blips tire nn operated from one rheostat it if di sired hut but it Is usually best to linao it 11 separate sin nite control for tho the detector tube tul use double circuit jack tile alie detector d tt or tube la Is using lite hie same voltage of it batta ry us the radio frequency tubes tills this will only be its 1111 lung long us its ull all three are of the name type ti C and urn not inore thun than 45 volts ar nrc t ile be used if t n u higher voltage iengo of 11 it II fittery battery IN IH desired then the detector lach jack should bo be supplied the evolt tat if a soft tube Is to be used reduce the voltage to 2214 volts olta or less leas A biaglo circuit jaek rk Is shown la in tile the detector stage it at a later date it to Is practically certain that amplification Is IB to be added it Is best beat to use a double circuit jack in position to n void avoid tile the need for changing the preset it circuit ctr cult two iwo antenna are provided on oil the first horold coll coil these are to adapt tile the set to a long or short antenna it might inight be well to bring biln these two terminals out to binding posts on tile the rear of the cabinet so that the ant winit coil can bo be quickly over front from one to the other as conditions require more selective tuning timing or greater volume Is desired tile hip position of the lie apparatus lit in laying out the he receiver baseboard la Is nut not critical the colls may be placed side by side without Inter coupling or causing tile receiver to become unstable duo due to their confined magnetic fields |