. QST . ableon all bands. Although not shown in the schematic,a parasitic suppressor is used in the plate lead ofthe 4-65A, to rid the transmitter of the parasitic. The final-amplifier tube, a 4-65A, was chosenbecause of its reputation for stability and rug-gedness, and its ability to operate efficientlj atplate voltages from 600 to 3000 volts. At a platevoltage of 2000 volts, it is possible to load thefinal to an input of 300 watts. Li4 is a rotary inductor whose origin is mi-known, but whose inductance turned out to bejust what was needed. It is considerably larger,physicall
. QST . ableon all bands. Although not shown in the schematic,a parasitic suppressor is used in the plate lead ofthe 4-65A, to rid the transmitter of the parasitic. The final-amplifier tube, a 4-65A, was chosenbecause of its reputation for stability and rug-gedness, and its ability to operate efficientlj atplate voltages from 600 to 3000 volts. At a platevoltage of 2000 volts, it is possible to load thefinal to an input of 300 watts. Li4 is a rotary inductor whose origin is mi-known, but whose inductance turned out to bejust what was needed. It is considerably larger,physically, than is necessary in a transmitter ofthis size, and one of the smaller commercial vmitscould be used instead. Lu, an air-wound inductor,constitutes nearly all of the tank inductance whenthe transmitter operates on 10 meters, and itsinclusion shifts the shunt capacitance of the ro-tary inductor to the output side of the pi network, * Grammer, Pi-Network Tank Circuits for Higli Power,QST, October, tending to keep the Q of the tank circuit down at10 meters. This has been explained in QST.*The output capacitors are Type CM-45mica units, switched in and out of the circuit bySz, a progressively-shorting rotarj^ switch. RFCiis a National type R-175 choke which has beenmodified to be effective on all amateur bandsfrom to 30 Mc. Since this transmitter wasbuilt, the National Company has announced anew shunt-feed choke, the R-175 A, that isfree from holes, and is usable in this type of rigwithout modification. As one of the preventives against TVI, aseries-resonant circuit, consisting of a lOO-M^f-mica capacitor, Cie, and a few turns of wire, Lis,is connected across the output of the transmitter,at the output connector. This series-tuned circuitis adjusted to resonate at the frequency of thetelevision channel most likely to be interferedwith in a given locahtj, and is effectively a shortcircuit across the transmitter output at this fre-quencj. Thus, any harmo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
