Show circuit diagram of radio broadcasts Four Tuba universal receiver which gives tone and volume there Is but one real type ot circuit which may be called i nl versal and that la alie combination 0 one stage of tuned neutralized radio uni a regenerative detector and somo kind of audio frequency amplifier which will produce good quality writes arthur U lynch editor of radio broadcast A circuit which would perform sat in city and country on dry cells or with a storage battery without wasting B batteries which would give more than ordinarily good quality of reproduction on a loud speaker over comparatively long distances which was easy to build and easy to operate after it was built and last but not least a circuit tor which could be procured in any town ot any size in any part ot the world that was our notion ot what the universal should be we believe we have found it what the diagram shows from a study ot the schematic dla cram it will be seen that there ore two coll assemblies one a primary and secondary in the antenna clr cult LI and 12 the latter tuned by the variable condenser cl the other a tuned radio frequency transformer of the auto tr u former type and n tickler coll the latter being fixed in position but adjusted electrically by means pt the toto to TO ohm resist ance shunted acroca it these colls are indicated in the diagram by 13 and 14 by properly using the wiring already provided on rhe general radio companas comp anys colla io both these coll units are instantly provided no changes whatever joeed be made us the colls are of solenoid type with two windings on a single form two such forms are nece sury on each form there la a email and a large winding the small ones are used for LI and 14 while the large ones are used for LL and 13 the tap indicated on 13 Is easily provided by picking up a turn of the large coll and scraping clean it Is merely necessary to solder the prop er wires to it to carry out the correct circuit arrangement in 13 this tap Is made 89 turns from the grid end and the tap on 12 Is made in the exact center of the coll these colls may be used with mad variable con censera to cover the broadcast re quency range list of parta required the following list of parts Is required for the receiver but suitable will be in order ono panel inches one royalty COO to 50 ohm vari able resister res lster ore each electraj elec trad and mad fixed condensers tl e following general radio parts two colls type two variable conden sere with vernier attachment capacity either S L W or S L C type two dials type cue neutralizing condenser type two audio frequency transformers 2 1 I ratio type 2851 four sockets type or use with lubes having UV base and type UX for tubes with UX bases one binding post strip with 8 posts type two rheostats 10 ohms type one boxley filament switch and jack and one electraj elec trad grid leak resistor of 2 one each and ampere branch filament ballasts and mountings tb urge to 1 mad condenser across the B batteries la optional but advisable low drain on batteries one of the outstanding features ot the universal Is ita low drain on the B batteries a maximum of 7 amperes only being required As regards the tubes it has been found that the A type are about best for gen eral all round work except in the last audio stage where the use of an UX Is advocated A plate potential 0 alto mill be necessary for the UX tube and also a negative grid bias of 9 volts mr lynch says that one of the transformers may be of a higher ratio thail 2 1 if the receiver la to be located a long way from the nearest broadcasting station but it should not be of a higher ratio than 6 1 contrary to general practice we are ad to place the higher ratio transformers in the last and not in the first stage of audio amplifier resistance coupled stage switch scheme when three stages of resistance cou pled amplification are used the 01 ol ume Is often too great from nearby high powered stations and as no way Is provided for cutting in between stages as in transformer coupled am the arrangement shown in the diagram was devised for cutting I 1 down to the second amplifying tube greater volume Is desired the little wooden plug Is left loosely in the jack by merely pushing the plug in the loud speaker Is automatically con to tte plate of the second am tube the third resistor cou pier and tube being disconnected in the same operation A filament control jack was used for this purpose and the plug may be plan for cutting down to second amplifying tube either a homemade home made wooden plug or an old phone plug this gives the set a sort of soft pedal control the i p aerator tunes in a powerful station finds the volume far greater than he needs pushes in the little plug and behold the music Is greatly softened radio digest condenser plates before placing a condenser in the act hold the plates up to the light and look through the spaces between the condenser plates while rotating the rotary plates to make sure that the rotary and stationary plates do not short at any point A tip when wiring in wiring the set always bring the A battery wire that carries the B negative through the battery switch this Is a positive insurance to the set when the switch Is off both A and B are off the get |