Show 7 ANT ar A 1 P ca A COOL U 0 1 Q B F ca aj r B A BOG PHONES single tubo tube reflex circuit one stags stage radio and ono one stage audio with crystal detector by CARLTON E BUTLER associate member institute of radio Engl engineers and american institute of E electrical engineers loudspeaker loud speaker operation usually accomplished complis hed bed only through the use of multi tube receivers Is obtained by the use of a single tube lu the circuit described in this article sufficient volume Is secured to work a loud speaker on stations a fafty mile radius and the headphones 1200 miles or better under favorable weather conditions requiring but a i single tulie tue the receiver can be assembled tuto luto a very small box complete with batteries for or portable use the controls of tile the set get consist of but a single dial and a rheostat so that hat tile the panel can be practically as small as the dial itself A cabinet 0 by 6 by 0 6 inches will contain the complete receiver and both A and B batteries can be included by making the cabinet and baseboard slightly larger the tube itself dwa double duty in the receiver amplifying ohp current first in the form of radio frequency then it Is detected by the crystal and returned to the buhe to be amplified at audio frequency this efficient means of getting tile the roost most out of one tube Is called re flexing increases tho the volume in addition to the advantages adan gained by the use of the reflex principle of construction the use of the newly invented low loss dougli nut coll coil for a tuning inductance increases the volume at least 35 per cent more than annen tile the ordinary varlo coupler or varlo form of tuning Is employed tile the advantage gained by the use of the low loss doughnut coll coil designed by frank Is due clue to the fact that the magnetic field of the coil to la self contained so BO that there hero Is no spraying effect of lines of for fori ns as found with the open end type of colls coll coil pickup pick up of interference Is practically eliminated making the receiver tune much sharper than when ordinary colls colla are used few parts are required for the circuit and construction Is within the limits of the novice wiring la Is without complications and the receiver can be constructed on a panel 6 by 10 inches tuning Is accomplished by a single dial eliminating the difficulty in operating a radio set often experienced by persons unfamiliar with receiving sets seta the parts needed in addition to the panel the following apparatus Is needed 1 low loss doughnut coll coil coupler type 1 low loss logs variable condenser mad capacity preferably the straight line frequency type so that the stations on the lower wave lengths may be easily separated 1 iron core radio transformer 1 low ratio audio frequency transformer form er I 1 I 1 either fixed or variable crystal detector I 1 fixed mica condenser of each of the following capacities mad med and mad I 1 vacuum tube socket 1 telephone lione jack binding posts find and wire the receiver Is compact enough to be used as a portable set and will give satisfactory service providing a good aerial and ground sire anre obtained whenever the outfit Is to be used |