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

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342 Radio BroadcastDL 35
A PracticalSuper-Heterodyne withwhich is a frequency of 100 kilocycles. Now be used, and coupled, in any fashion. One convenientarrangement is the use of a three-coilsuppose a signal is coming in at a wavelengthof 400 metres, which is a frequency of 750 honeycomb mounting which allows trying differentcoils and a great range of wavelengths tokilocycles. If we adjust the heterodyne tubeto oscillate at a frequency of 850 kilocycles, be received. These three coils are connectedthen the difference between the heterodyne as shown in the circuitfrequency and diagram, Fig.i. Thethe signal frequencyis 100 D. L. 35 and the tickler coils should be thekilocycles, and this is just right to be fed to movable ones.the long-wave amplifier. On the other hand, As the only two adjustments in tuning areif the heterodyne oscillated at 650 cycles, the the two variable condensers here shown, it isdifference would again be 100 kilocycles. well worth while to get the very best condensersfor the purpose. The receiver tunesThus there are always two possible settings forthe condenser that adjusts the frequency of the very sharply, and a list of stations with theheterodyne oscillator, either of which will bring exact settings of the condensers cannot be keptin the same station. Sometimes it will be unless the construction is so rigid that a certainfound better to use one than the other, but setting always gives the same capacity. Forusually it makes no difference.this reason it is inconvenient to use condensersIn building a frequency-changing unit, the with separate verniers. The General Radiochief points are: use as high a "B" battery voltage condenser, with a small knob turning the condenserthrough a reduction gear, is completelyas available on both the frequency changingtube and the heterodyne; in the grid circuit of satisfactory.the heterodyne oscillator put a grid condenser There should be no difficulty in building aand leak that will allow the tube to oscillate good frequency-changing unit, and once made,most strongly (say .002 mfd. or more and 5000-it can be used without change in connectionohm leak) in the; grid circuit of the frequencychangingtubeputanamountof "C" long-wave amplifierwith any new or improvedbattery that that may later be put on the market or described.The scheme, mentioned earlier in thiscan best be determined by experiment (if 90voltsof "B" battery are used, loor i2voltsof"C" article, of gearing the two condensers togetherbattery will be about right); and, finally, adjust so as to have only one knob to turn, is not recommendedto the average constructor. Na-the coupling between the heterodyne oscillatorand the frequency-changing tube so as to get ture has given us two hands, and after a littleplenty of the heterodyne frequency supplied practiceit is not difficult to turn the two condenserssimultaneously, keeping their relativeto the frequency-changing tube. Up to a certainpoint, the more the better, because the values about right.output of the frequency-changer tube is proportionalto the product of the signal and the build, the long-wave amplifier. Before takingWe now come to the more difficult unit toheterodyne voltages.up the question of the best type, a very easyAny sort of heterodyne oscillator circuit can type to make will be described. The reason it343FIG. 2The intermediate-frequency amplifier is coupled to the frequency changer by two DL 75 o coils shunted by .001 variablecondensers. The amplifier itself is made with UV-.i7i6 transformers and each stageisthoroughly shielded as shown bythe dotted lines
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270 Radio BroadcastPREPARING MESSAG
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276 Radio Broadcastis the first tim
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278 Radio BroadcastTHE BOOM IS ON I
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280 Radio BroadcastWest Coast to Ha
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DR. MACMILLAN AT THE NEWLY INSTALLE
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284 Radio BroadcastDONALD H. MIX, R
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286 Radio BroadcastHiram Percy Maxi
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288 Radio BroadcastIF AN ESKIMO BAB
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. 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 60 and 61: 326 Radio Broadcastinductance is va
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 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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