Show lied by douglas editor of U A 0 50 IL 0 jaca 0 1 to D A 15 A ak AMA aw ZY mir L T t flit fit L v so F low U 5 MCI UK jaa mitat it 0 0 D A B A around I 1 set shown Is an old circuit to which has been adapted an Apar lodic mary that Is Semi Adjustable the most revolutionary principle developed in radio tuning devices in the last year Is tile aper lodic coupler this Is one in which a few turns of wire Is substituted for the customary variable condenser and tapped coll coil primary its benefits benell ts are manifold the new three circuit set that tins has enjoyed the lie limelight tills this season along with the owes its exceptional properties entirely to the primary aside from this it was nothing but an old single circuit blooper the set shown la Is tin an old circuit to which has been adapted an aper lodle primary that Is semi adjustable so as to control the degree of selectivity with but little effort tills this principle can be adopted adapted to any of the old style circuits ordinary parts the parts used are tile the ordinary variable condenser of capacity or 23 plates and a varlo coupler either of the DO 90 or ISO degree variety tilts this last lias has to be rewound according to specifications ficat ions that will be given the basic circuit Is that of the original DP de purest furest ultra guillon and has an excellent range volume and tonal quality in its original form it was susceptible to radiation and therefore was undesirable as an up to date re celver in its new form practically alt all radiation Is eliminated if the tube Is kept below the oscillating or live point the set when lini slid la Is capable of satisfying the most critical fan fail on the points of selectivity as it can be adjusted to any degree so that it can tune out powerful nearby near by interference or broadened for distance when there Is little interference parts required the tuning units and construction al utilized in building the set are one varlo coupler special winding one or 23 plate variable condenser one 7 by 9 panel one rheostat one socket one plunger type var variable lable grid leak ono one grid condenser baseboard dials wire screws binding in posts etc good parts of course tend toward making the set more effi efficient clent the most important being the var variable lable condenser which should bo be ot of the low loss type grounded metal and plates connected to the rotor the aper lodle coupler Is made up of throe three separate windings one of CO 50 turns turna and one of 12 turns on the stator of the coupler and other of 12 turns on the rotor tile the 50 turn tum winding and 12 turn aro arc spliced spaced about s of an inch apart the rotor winding la Is exactly in the center of the rotor ball or tube the two 1 i turn colls coils are connected to one another ns shown in the illustration tion find and form the aper lodle primary the 50 turn colt coll Is the secondary and Is tuned by the variable condenser which Is shunted across it wind the colls coils tightly and fasten the ends of the wire firmly about no 24 gauge gaug a double silk or double cotton covered wire should be used throughout the connection between the 12 turn stator and rotor colls coils should be made with a piece of flexible lAtzen draught of mul ti strand flexible wire do not use the frame or bearing ns na a friction contact Is noisy at the lie best mounting mount the coupler and variable condenser on the two opposite sides of the panel about three or four inches apart care should be taken when wiring to make all lends leads as shown and direct as possible disregarding square corners note the load lend from tile the secondary to the plate connection tills athla Is in no way connected to the filament or ground any type of vacuum tube works effectively use a rheostat of tile the proper and 45 volts of B battery on and A types 22 volts on WD 11 and 12 and UV types the grid leak being flexible can be adjusted for any tube the tuning control la 1 the variable condenser this logs and the settings are permanent for all stations the rotor of the coupler Is solely for the purpose of controlling selectivity boston traveler |