| Show avs nis alv P aej A 6 V A a aliv iov s TO tito schematic wiring ram of the four tube Ro celver showing how condensers are connected to coils by HERBERT E HAYDEN in now new york herald tribune A circuit of it general usefulness ts Is the ono one shown in tho the diagram for it will operate fairly well even under most unfavorable conditions and Is difo kafe in n tie ho hancq of tho the novice bilco the it has chive con controls cantron troN and tho the set tuny bu be logged alint 1 la 4 once the settings for it 11 given station are determined they will always lie bi taw slime samo unless tile aerial 1 li 4 changed one olio of tile the chier chief advantages of it tho Is it inny lo lie 10 readily adalat ed for fil tully use anyone who know chii combination could hear tile stations normally illy this la in not true of regenerative sets seta there la Is nil all elo mont of great uncertainty of setting lit in the regeneration control dial to overcome this yet retain tile lio advantages of regeneration this circuit was devised it to Is a of won ivell gants ants X circuit tile tho so elliett divided videl li circuit tind and embodies it stage of tuned radio frequency tuned detector input coupled regeneration in the detector and two steps of transformer coupled couple d audio preventing radiation this circuit hns has ns as minall n tent tendency lency to radiate as any of tho the regenerative hookups hook ups will radiation may inny bo effectively prevented tod by connecting a midget condenser between tile grid ind pante 1 0 o p posts 0 8 0 of 1 ali I 1 II 11 V tube u tile the ono at extreme left the setting rotting of t tills ills c condenser 0 Is varied until tho the signal la Is irely barely audible or inaudible ahen the it V F tubo tube Is barely tit lit then tho the setting of this small condenser dot shown Is left in that position the hookup hook up in performance Is 13 as at distance getting tho file pres prea or of regeneration much inore than up for the absence of tin nn extra ube tube this Is true absolutely it if a tood outdoor aerial la Is used but it if nn fin adoor antenna Is employed or even i t plug for tile the light socket the circuit idill will perform exceedingly well lyel he distance being cut down somewhat the volume but the quantity if f sound being all for speak r operation tile ground con connection nay he be made to tile radiator thus ho he cir circuit cult while primarily working etter under the more generally avail ible advantages will do its duty with ideality under makeshift condition nich men as used in hotel rooms on od coun ry trips etc the set was operated ill last winter in n local hotel and luring the summer weeks to late the round ground connection being made to a adulator ad lator and a plug used in the lighting main for an aerial selectivity yas splendid even less than halt half a mile away being tuned out within iio five degree degreed of the dial and ashly separable from nn an eighth f a mile farther away both bogli powerful very few outside tile the metropolitan area were heard but the receiving conditions one must admit are about as an bad as in any part of at the united states condensers used to facilitate tuning on the low waves 14 lt Is well to use condensers that are modified so 80 ay to cause tile dial redings redi nga to be wider apart for given stations on higher frequencies th these would be what are termed straight line wave length straight line frequency or like condensers I 1 the usual condenser varies its s to capacity which tends tend to crowd tho the stations close together in dial position on tho lower divisions due to the changes in capacity at those points representing so much greater frequency difference the idea may be popularly expressed by saying that an ounce of capacity at the lower end makes ten times as great a difference in frequency as a pound of capacity fit at the upper end of the dial the alie condenser used in tile bet act was the twin notor which when properly connected eliminates body capacity effects in tuning the rotor of the condenser tuning tile the 11 F F stage should go to minus A the stator of the detector input tuning condenser should go to grid condenser and the rotor of the feedback condenser should go to plus A constructional data on colls coils in choosing the colts colls for tile the set one may be guided by his own particular pre preference ferance in design or may follow the directions for making the diani diamond ond weave colls coila shown these are wound on forms having an odd numbered group of removable radiating arms or spokes 1 3 lg IG inch dowel sticks on a circular hub bulb 2 inches in diameter using no 22 double silk covered wire I 1 wind ten turns halt then pick up twelve feet nt nf the same kind of if wire and wind this along alone with the remain 1 I 1 der of tile othar or secondary vand ind tug ing leave four inches slack for con coil elections inside tile the sot set up to this point you will have wound ten tea plus about eleven or about twenty one turns of ilio secondary and will have completed tile lie tile the twelve foot length now contin tio winding the secondary second nry until thirty more inore turns uro tire wit iut on oil M whereupon this winding too Is thus you will havo finished it coll coil with ith lit iiii eleven cloven turn mari nuil it 11 fifty 1 ft one olio turn tura secondary one inore turn or less on tile secondary will liot not gifter tito secondary la in to lu lie tanned liy by n inal variable nr lullu condenser that was 1112 now wind whid exactly tile the slime binno wily except that when you reach tile fortieth turn pick up ton ten fort feet or of tile alio anino kind of wire mul and wind tills this us its if it were it special primary nry stile by stile aldo with tile con coil secondary then go gi it alone with tile secondary to the end now you have ALS tho the aerial transformer Is connected so M that tile adjacent terminals lull hub ond end of primary und and huh hill end 0 of secondary go to ground and minus A respectively ively the hub side that Is inside terminal of 13 go goes to it II plus 67 volts olta and this I 1 it battery should bo be it i separate se ono for best results although the w set will work well on oil ft co coi ninon on 11 II battery block th alio 0 minus a 1 nu of this GT oti volt block by the wily way i goes to plus A too tito terminal of the lie secondary TA LI that roes goes to the grid condenser Is tile end at the he outside dIni diameter neler while the outside terminal of TZ LB goes to plate pinto tho circuit di diagram agrain shows how the condensers tire aro connected to these colts colla tho the tickler LB 15 Is not ro notable table of course and that explains why it Is possible to chart the alio regeneration control hotti audio tubes have lieve grids biased 41 volts volta negative tills this usually means the volt post of oc it standard a 0 battery will bo be used its as tile the nearest approach if tha exact 4 volts arent accessible there Is it ono one volt negative blas bias imparted by the grid return to minus A say sia B volts nt at this point as co compared with tile five avo volts nt at tile the other side of the rheostat fila minus when chenco c e all al voltage rock aning onan pr cepas indeed tile tho drop in tho the rheostat tny bo be a little more than 8 13 volt vence fence only tarco extra or external volts volta aro are needed in figuring the plate pinto potentials the common lead A plus and 11 elnua ln must be count counted ed too as adding the voltage of the A battery to vint that of the n B battery at the plate tito the series connection Is obvious minus six nix to plus sir Is six sh volts hence with B minus connected here you start off with a premium of six volts A volt tap off tho the it II battery would real ly bo be 2811 volts volta these allowances roust must bo be made especially when using tubes that are critical ns an to plate v voltage olt especially tile the 0 and UV the most sensitive detector tubes known though they do draw one whole undisputed ampere audio hookup la Is standard tile the audio hookup hook up Is standard except for the filament control jack those not familiar with its operation will see from the diagram that adjoining springs of tile the jack are connected respectively to B D plus and plate when the plug la Is inserted it pushes up tip tile the springy leaf already connected na as the other ono one to la the very stiff frame notice that there la Is a piece of insulation between the plate spring and the ao joInIng one above abobo it this Is in both the safeguard against short circuit and the lover lever used to close the fila filament luent cIr circuit cult it will be seen that the other otherwise tilso cont continuous lincous filament minus leadin lead in la Is interrupted by being passed front from detector tube to the see ond spring from froin top la in F I 1 0 J the switch S may be used for turning the set on and off as a unit As an the three amplifier tubes one radio und and two audio are operated from one control it should be a power rheostat if wire bound otherwise one of tile compression or decompression type tho the ordinary run of rheostat 0 ohms will heat up under this heava current A double circuit jack J to la used in tile the first audio output ns this ta in a good place to listen to DX stations in winter arid an U lit in sum summer nier when if and where possible and provides duill dent client speaker volume from some bome locals the change from first to second audio audin output Is made simply by pulling tile the plug out of the one jack and inserting sert ing it t in the filament control jack which lights the last audio tube and taps plate plat and B plus tile the C and UV tubes are best for tills this c circuit although uny of the dry cell tubes may be used to we NY cellena advantage |
