Show 0 o p G 6 00 ei the wiring diagram of the amplifier herein described by SIDNEY E funkelstein in new york herald tribune the honors in audio frequency am seem to be divided more or less evenly between the transformer and the resistance coupling methods bach system has its stanch adherents icho are eer ready to fling masses of facts figure and fancies into each others faces whenever a discussion of relative merits arlace the trans former supporters are just as firm in their belief of the superiority of their instruments as the resistance men are in their views on the advantages of their devices the writer has used both transform era and in the construction of a large number of sets and after studying the general tilled from them has come to the neutral conclusion that both systems are good but that they are even better if they are combined in the jour nall fashion to the of the best features of each the advantage of the greater am per stage afforded by the transformer combined with the flawless reproduction but lower alon of the makes the ideal combination in the majority of abets A complete amplifier of this ad vant ageous type can be made at home at surprisingly little trouble and ex pense and once on hand it finds ap to receiving circuits of all kinds it may be built permanently into a set or it can be left available as a separate unit for connection to experimental tuners for the last purpose it Is especially convenient as it saves the constructor of a new set the worry of providing suitable amplification to follow the detector tube part an amplifier such as the one shown in the illustration will require the following parts which can be purchased at any radio store biard rub or composition baseboard 12 inches long 4 inches wide and inch thick one heavy audio transformer not above 3 to 1 ratio three stand ard tube sockets two resistance cou pling units with two one and one ohm resistors one mad fixed condenser eight bind ing posts and the usual bulbar and mounting screws A definite assembly procedure should be followed first the general of the instruments should be determined and all the necessary screw holes made in the panel before thing Is fastened down perma aa 1 ri he devices should be pushed closely together there Is no danger from howling there Is only one transformer so as to allow room on the right and left hand short edges for input and output binding posts f the wiring will give no trouble As a eta t the P and B post of the amplifying transformer should be connected directly to the two hind ing posts on the extreme left which are desna ted as the input tr finals the fixed can denser Is also placed across the wires and can be hidden comfortably out of way beneath he ottom baseboards of cour sp sm ill holec have to be drilled in the corn position to pass the wires wherever lessary nes sary the filament posts next the filament posts of the three pockets which are all marked P are wired as shown in the diagram and lead finally to the A battery binding posts these should be the left hand two of the row of four alie long edge of the baseboard with this much done the second irv of the transformer can now be wired k to the grid and filament posts of the first tube locket progressing across the condenser and resistor wired in the manner indicated in athe accompanying hook up with the resistor units that were employed in thie particular amplifier the ting soldered tabs of the spring mountings make the placement of the wires a abort and simple task the two posts on the extreme right are the output to one L run a nire from the P terminal of the last socket and to the other a wire from the plus post which Is immediately adjacent the A plus and minus I 1 posts it will be noted are joined together all the wiring should be done with standard round or square tinned bus bar the wire need be insulated with cambric tubing only in places where two wires unavoidably pase each pother very closely very little coer ing will be found necessary the tab rows which are all equipped with strong screw binding posts need not be soldered but those to the fixed con and the mountings must be ahe battery should be of volts ie the requirement for resistance amplifiers with this voltage the ohm resistors should be employed in the plate cir cults of the first two tubes while the ohm leak goes between the first and second bulbs and the ohm resistance rest stance between the second and third in the grid leak positions this Is clearly shown in the wiring diagram owr make circuit very selective alle a regenerative circuit may be readily obtained by inserting eter I 1 the plate circuit it Is not so simple a task to obtain a tickler feed back with ordinary apparatus on the unless honeycomb coils are used there are of course couplers with fixed tickler windings binary apparatus however the double coupler teed back circuit objections to single circuit action are overcome and there Is corn tuning in every circuit and any desired degree of coupling between them As commonly employed the primary switches of one coupler are connected to the antenna and ground as usual scheme that gives fine controls Control 1 ol 01 amount of inductance 3 the secondary of this coupler how ever Is connected to the ends atthe primary winding of the second cou pier the switch points of the second coupler go to grid and filament like the usual secondary connections the secondary terminals of the second coupler are connected to the plate clr cult 3 the wave length of the primary cir cult it adjusted by the switch points on the first coupler aided by the con denser in the ground circuit this variable condenser should have a ca coupling secondary Is adjusted by rotating the rotor of the fart varlo coupler the secondary circuit Is tuned by the switch points on the second coupler and he coupling between the secondary circuit and the plate circuit Is adjusted jbv the rotor of this coupler the secondary of the leond coupler acts as the plate tickler coll tills circuit should be very selective and ghe a little better lhnn the average sets results radio news g I 1 t PS ji i CHECK SQUEALING stop squealing squeal ng in the radio frequency set by 1 moving the coll closer 0 o esthe end variable condenser 2 cutting down the number of turns on the coll primary 8 alie grid bs with n potentiometer 4 inserting a critical resist ance such as a rheostat rheo lit series with the grid of be radio frequency tute allow space between units when building hen building a set a site rule to follow Is to keep each piece of op at least two inches or more away from other units the biggest mistakes often made in the construction of home built receivers are try ing to cramp the instruments in small quarters and alie uie of metal for the mounting coils and other in in the radio frequency cir cult should be placed as far to rear and away from other piece of apparatus as possible winding of cola to space alree on colls the orrell distance start the coll with thread and wire at the sime time applying con elder ably more tension to alin when no thread ie tided after the fattened the thread thre fd may be |