Show AN 7 A aa 4 S t s is 60 J be C ar a r DAIT AMP A abat wit ing diagram of the five tube three control radio frequency re no celver described in this article by HARRY J MARX manx in new tork herald tribune simplicity efficiency and high quality all combined are the arguments for the receiver described in this article the circuit was first worked out front from a simplicity ond end efficiency angle trick features have been eliminated i but every possible little development for improvement in operation has been incorporated the circuit la Is shown in the illustration two stages of 0 highly efficient tuned radio frequency amplification a detector and two real stages of audio frequency tion certify to long distance range and the best of tobe quality in reception three low loss pickle bottle colls coils combined with high quality straight line frequency condensers are the major factors in selectivity the os ellin tion control permits operation just below the oscillation point of the tube and insures maximum performance with the best beat tone quality and a min minimum 1 drain on the B batteries battersea batt erlea one of the particular features of this circuit Is the efficiency of the cadlo stages not only in the selection of good transformers but also in the proper use of bypass by pass condensers n order to liter filter out all stray radio fre quency currents and extraneous noises there remains much that Is still to he be ditc itc learned lerr ned about the intelligent use of bypass condensers C battery in the grid returns of the audio transformers Is another ft actor in good audio amplification the loud lond speaker cau can be plugged in on elther the first or second stage jack of the audio frequency amplifier the lust last jack 1 it filament control for tho the lust tube so there Is no unnecessary current consumption Asumption co when only the first stage Is used size of set the use of a 24 inch panel makes the set a compact one without unnecessary crowding and coupling which would be detrimental to satisfactory operation there Is no overcrowding in the panel layout and each of the controls la is so placed for convenience veni ven lence ence in tuning the use of real vernier dials makes tuning timing a pleasure the controls are by no means complicated or difficult to operate A rheostat Is used for the detector tube another for the two radio frequency amplifier tubes and a third for the audio stages the sockets are universal and therefore permit tile the use of either storage battery or dry cell types of tubes A resilient spring action la in the socket design assures a perfect contact and the elimination of noises incises by its non rigidity nine binding posts on a raised strip are easily accessible and meke me mc ke battery connections a simple matter everything la Is easily assembled and wiring Is a simple rapid operation with none of those tricky inaccessible connect connections ionti which are the bane of set eel constructors apparatus required them the first question every fan an asks aski before lec bedding iding on the building of a set la in what parts will I 1 need the th following Is the list of apparatus lie lecter by the writer for use in ID his set 1 panel 8 10 by 7 by 24 inches clies I 1 baseboard by 8 by 23 indies inches 3 eastern classic colls coils type EB 3 national Equi cycle codden condensers den sers sera mad 3 NeI national lonal variable velvet vernier dials i 2 multistage RD R D melo formers 5 eby UX cushion sockets 9 eby ensign binding posts 1 binding post strip 8 3 10 16 by by 17 2 carter imp rheostat IRA IR 0 6 0 ohms 2 carter imp rheostat IR 25 25 ohms I 1 carter imp pilot switch 1 carter hold tite jack no 1 carter hold tite jack no 1 Centra lab rad radi lohm olim no 11 ohms 1 turn it grid leak I 1 turn it panel control 4 condenser conden sera 3 type 05 ined I 1 Du dubilier biller condenser type nad I 1 Du dubilier biller grid condenser type 0 1 mad 15 lengths wire no 14 black red green yellow brown I 1 erminet to suit miscellaneous screws lugs solder etc in the selection of tipp aratus as listed above it would be well to just consider the reasons for their use the pickle bottle type of low loss winding has bus become very popular because of its high selectivity features the colls coils when used with the condensers mentioned iwer the complete wavelength band as required fur for our popular broadcast reception the vernier dents dints have the unusual feature of a variable vernier ratio in other words the vernier adjustment can be made coarse or fine us its desired color wiring the use of color scheme in wiring Is based on some definite plan that Is to be followed in wiring the set this schedule should be followed all negative A leads use black all positive A leads use red all grid leads use green all positive B amplifier felds use brown all positive B detector leads use yellow in building the function and potential of each lead can then be told at a glince dont permit the wiring to run too close to the colls coils keep all the plate and grid leads as short as possible |