Radio Broadcast - 1923, August - 86 Pages, 8.5 ... - VacuumTubeEra

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326 <strong>Radio</strong> <strong>Broadcast</strong>inductance is variable by means of a tapswitch mounted on the back panel, whilethe secondary circuit is tuned by three condensers(two variable and one fixed). Theshaft of the variocoupler was lengthened toinclude the shaft of the three-plate verniercondenser which is thus made to rotate withthe coupling coil in such a manner that as thecoupling is increased, the vernier condensercapacity is decreased, thus tending to stabilizethe resonant point of the primary and secondarycircuits and helping to prevent detuningwhen the couplingischanged. In parallelwith this condenser is the main secondary condenserof thirteen plates which is in turnshunted by two .00015 mfd. condensers inseries. When the main secondary condenser isat full scale.set at o, the secondary wavelength is approximately80 meters and increases to 420 meters1If now one of the small mica condensersis cut out by the switch provided, thesecondary wavelength becomes 400 meters ato and increases to about 600 meters at fullscale. This arrangement givesa full verniereffect with a small variable condenser and stillprovides a large range of wavelengths.In case it is desired to use the tuning elementswithout the radio-frequency bank, ajack has been provided which enables a crystalor other detector to be plugged in. The tuningisaccomplished in the usual manner.In addition to the usual jack arrangementwhich enables the signals to be received oneither the detector or the first or second audioamplifiers, an additional jack has been providedso that an external detector can beplugged in on the audio-frequency bank. Thisjack in connection with the one associated withthe loop jack enables crystal reception, utilizingthe tuning elements with or without audiofrequencyamplification and makes an idealarrangement for local reception.A rather extensive system of voltage controlhas been provided and has proved to be anabsolute necessity. A o-io D. C. voltmeteris connected through a two-pole, triple-throw,cam-key switch to three separate circuits, oneof which follows along on a buss under the filamentrheostats, to which is connected six doublepolesingle-throw push-button switches whichare in turn connected, one to each of the tubesocket terminals. With the key in the properposition, pressing any one of the push-buttonswitches shows the voltage on the terminalsof its associated tube. A second circuit fromthe key switch goes to the A battery terminalsRfDIAGRAM OF THE RADIO- AND-
ReceptionDe Luxe327IT IS A PLEASURE TO SEE A HOME-MADE SET AS NEATLY BUILT AS THISso that the condition of the storage batterymay be determined at will. The third circuitgoes through a high resistance to the B batteryterminals and enables a reading of the platevoltage. The amount of this resistance varieswith different makes of voltmeters but shouldbe of such a value that a scale multiplier of 10may be used. That is to say that when thekey switch is thrown to the B battery positionit isonly necessary to make a mental calculationto get B battery-voltage by multiplyingthe scale reading by ib. "Such an arrangementpermits readings up to 100 volts on a lo-voltmeter.Because of the amount of equipment in theset, it was not possible to have the tubes solocated that their filaments could be observedthrough windows or holes, and an auxiliaryindicating system was provided. Above eachrheostat control knob has been placed a smallbullseye, similar to those used in the older typesof telephone switchboards. Behind each bullseyea 2-volt -candle-power i light has beenplaced and connected through a suitable re-AUDIO-FREQUENCYCIRCUITS
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270 Radio BroadcastPREPARING MESSAG
Page 10 and 11: 276 Radio Broadcastis the first tim
Page 12 and 13: 278 Radio BroadcastTHE BOOM IS ON I
Page 14 and 15: 280 Radio BroadcastWest Coast to Ha
Page 16 and 17: DR. MACMILLAN AT THE NEWLY INSTALLE
Page 18 and 19: 284 Radio BroadcastDONALD H. MIX, R
Page 20 and 21: 286 Radio BroadcastHiram Percy Maxi
Page 22 and 23: 288 Radio BroadcastIF AN ESKIMO BAB
Page 24 and 25: . Pioneer'. .*JUNK WORTH A MILLION!
Page 26 and 27: RadioBroadcastTHE RECEIVERAT 2 PMNo
Page 28 and 29: 294 Radio Broadcastsiderable intere
Page 30 and 31: 296 Radio Broadcastof course radio
Page 32 and 33: 298 Radio Broadcastafter trying sev
Page 34 and 35: 30ORadio Broadcastthan he might rea
Page 36 and 37: 3O2 Radio Broadcastcourt was broadc
Page 38 and 39: THE PRIZE-WINNING CONTRIBUTIONS ARE
Page 40 and 41: 306 Radio Broadcast2 transformers a
Page 42 and 43: 308 Radio Broadcastas short as poss
Page 44 and 45: 3io Radio Broadcastfind that the st
Page 46 and 47: 312 Radio BroadcastFROM SAILOR TO '
Page 48 and 49: The Grimes Circuit with OutdoorAnte
Page 50 and 51: Radio Angling and Fisherman's LuckT
Page 52 and 53: 3 i8 Radio BroadcastSOMETHING DOING
Page 54 and 55: circuit,32ORadio Broadcastwound wit
Page 56 and 57: 322 Radio Broadcasthighest sensitiv
Page 58 and 59: 324 Radio BroadcastMR. CROSLEY BROA
Page 62 and 63: 328 Radio Broadcast^^V'VYVNA/VN/Y^^
Page 64 and 65: 330 Radio Broadcasthappens that its
Page 66 and 67: 332 Radio Broadcastin the classroom
Page 68 and 69: 334 Radio Broadcastaudience which i
Page 70 and 71: Sets for the Great OutdoorsBy A.HEN
Page 72 and 73: 338 Radio BroadcastTHE COLIN B. KEN
Page 74 and 75: R\DIOA PracticalSuper-Heterodynewit
Page 76 and 77: 342 Radio BroadcastDL 35
Page 78 and 79: etween344 Radio BroadcastREAR VIEW
Page 80 and 81: 346 Radio Broadcastcompletely. The
Page 82 and 83: 348 Radio Broadcastchanging the rhe
Page 84 and 85: The GridQUESTIONS AND ANSWERSThe Gr
Page 86: RadioBroadcast
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Radio Broadcast - 1923, August - 86 Pages, 8.5 ... - VacuumTubeEra

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