Show edited by 0 douglas editor ot of merchandising 7 2 aff ri R if y r wf i 0 ciC 00 0 i X ft cl 0 c T 1 0 0 3 0 J r 1 1 W 6 vw 1 J 11 r 1 1 V WH T L ali 4 c S w 0 0 I ali fak 6 V w 4 t z V f only the audio frequency tube Is E c 3 0 0 2 0 0 c c ta fi 1 i r d te 0 t 6 J J P 0 1 d 0 7 sew S 0 JL 2 0 77 3 s 02 W IL 7 t w 41 b it f r at s d IN H 2052 tw f 11 j P w 6 as a y 1 bof TO i four amplifications prom from two vacuum tubes By ARTHUR H EDDY if you engage yourself in converse conversa tion with the lie average amateur concerning his radio receiving set it will not be long before lie he will bring up the question of maximum range of reception cep tion which would be the paramount topic of discussion it Is thus that we ave have grown into the habit of judging tho the relative merli merit of a receiving set by tho the range that it can cover and although this method of judgment Is not til together fair find and just to nil all types of outfits yet for the average beginner or radio experimenter it does form a basis of quality the standard range of the regenerative receiver Is quite an unknown quantity for amateurs ama teura and exports experts having almost identical circuits and antenna conditions give very conflicting cori claims but bat still it if we are to base most of our claims on distance on everyday possibility of receiving a certain broadcasting station it would be very near the truth if we should limit the regenerative receiver to approximately a range of miles when using a rather sensitive detector tube most amateurs realizing this have endeavored to augment this distance by tile the use or of a combination of audio and radio frequency amplifiers in other words the reflex circuit with the former type success was assured where the sensitivity of the detector was grent great enough to detect the signal but since the sensitive tube must be a soft tube iube that 18 19 a tube that hisses at a critical point tho the number ot of audio frequency stages Is somewhat limited to adapt radio frequency amplification to a regenerative receiver after once it lias has been constructed truc ted Is by no means an easy task eket Y yet some amateurs have not only accomplished hed tills this but have bare obtained re kable results for or tile the vast majority of beginners I 1 til etrue true answer to the problem of b building a long instance distance receiver Is not the regenerative receiver audio and radio frequency e r s n nor J r th the e receiver but a receiver which Is a combination of audio find and radio frequency units in the circuit this type of circuit will not lot only have tho the desired range but will be so Coln compact pact that it will be readily portable and so simple and effle tent in its operation that the beginner can operate it as satisfactorily as tile the expert reflex Is not new I 1 but la usually described describe in peculiar ways wl ys with peculiar n names this Is at once nn an evidence eviden cL of evasion evit slon for the simple reason that at the ho end of 0 f the story the whole thing will be b a found to be the original renex reflex circuit cincu A reflex set can be made from froin a single tube and crystal detector the single tube serving for both audio and andl radio frequency amplification it if it I 1 t Is desired to operate a loud speaker wo must resort to a two or three tube reflex circuit hero here the first two tubes serve as radio amplifiers find and audio tim aro ers with tho the as detector the selie matic diagram shows a number of two tube reflex circuits I 1 if amplifier tubes are used in all stages mages tile the B buttery should be regulated no ao that the proper B battery voltage e Is applied to their respective dates Is 13 by ex perl ment usually between forty aye ave tind find seventy volts are found best beat for the alic plato plate voltage in tile the application of tho the clr chr cults culta there therb are several to be overcome the tubes for instance mu must st bo 10 coupled for both radio and audio frequency amplification but placing the audio frequency amplifier in a circuit where radio frequency currents are flowing the windings of the secondary act as aa a choko choke coll coil and prevent the radio frequency currents from passing to overcome tills this a condenser la Is shunted around the windings so tile the radio frequency currents may pass it Is suggested that tubes be used in all reflex circuits cir cults since this tube responds to radio frequency currents much better than others it if tills this tube Is used it would be ad to employ a 50 ohm rheostat in the event that a elx volt battery Is used the constructor attempting to build either of these sets should not employ direct regeneration once we the tube starts oscillating tile the set may become paralyzed duo due to the clicking c of the tubes different types of tubes have various effects with the transformers employed in the set there are a number of good radio frequency transformers transformer s now on the market at times it Is best to employ a high ratio audio transformer in tho the A ri stage with tills this type of set either loop or berl aerial a I 1 may be used it if the tube splits spills over reduce tho the values of the capacity in shunt to the lbs of tho the windings of the tha transformers in using the tubes it will avill bo be found that most of the tuning will be done by the use of the rheostats potentiometer and condenser in shunt to to loop new york herald |