. QST . region. In such a transmitter it is some-times possible to tune a multiplier stage to thethird harmonic around Mc, instead of theintended second harmonic near Mc. Again,it sometimes happens that the output of adoubler stage tuned to Mc. may containsufficient energy at Mc. to drive a final sothat it will show a pronounced dip at resonanceat Mc. What can be done to make sure the final istuned to the right band? The FCC regulationsprovide that the frequency of the transmittermust be checked from time to time. Unfor-tunately, we cant rely on the receiver to tell usabout
. QST . region. In such a transmitter it is some-times possible to tune a multiplier stage to thethird harmonic around Mc, instead of theintended second harmonic near Mc. Again,it sometimes happens that the output of adoubler stage tuned to Mc. may containsufficient energy at Mc. to drive a final sothat it will show a pronounced dip at resonanceat Mc. What can be done to make sure the final istuned to the right band? The FCC regulationsprovide that the frequency of the transmittermust be checked from time to time. Unfor-tunately, we cant rely on the receiver to tell usabout harmonics. If we have a trans-mitter right next to the receiver, we will probablyhear a signal every Mc. right up the instrument we need to be sure of the rightband is called a wavcmeter. An unitthat can be built for just a few cents was de-scribed in QST recently, comiilete with a cut-outdial.^ A more elaborate and more sensitiveinstrument was described by another author. in the February issue of this year. The lattercan be used to indicate the presence of very smallamounts of harmonic energy at and 11 Mc. Tank-Circuit Q If we find that the final tank is not tuned tothe right band, the necessary correction is easyenough. If the tank is tuned to the right placebut there is enough unwanted energy to give anindication on the wavemeter, this is anotherproblem. Then we must find out whether theunwanted signal is coming from the final or fromsome previous stage. Always correct the troubleon the lowest power level. High-Q tank circuits will minimize harmonicsin lower-level stages. Harmonic generation inampUfier stages can be minimized by reducingdrive to the lowest practical level. Consult 1 Smith, The Measuring-Cup Band-Spotter, QST,Sept., 1952. 2 McCoy, The Baking-Pan Wavemeter, QST, Feb.,1955. 3 Also see McCoy, A 5-Band Antenna Coupler, QST,April, 1955. * Although the minimizing of the number of turns in thelink coils is desirable in reducing h
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
