. QST . THE. -FlaSTIMKLI^4<3l If you would have first-hand knowledge of thesituation, sweep the spectrum from 7350 to 7500kc. on any Sunday afternoon. We have heardharmonics so thick in this region that somestations couldnt be copied because of harmonicQRM from otheis. Granted that a prol)lem exists, what are wegoing to do al)0ut it? Lets begin by asking wherethis unwanted energy comes from. A harmonicfre(iuency is simply an integral multii)le of somegiven frecjuency called the Jundamenlal. Forinstance, if your transmitter operates on :5705 *609 Park Ave., CollinK-swood 7, N. J. kc, the sec
. QST . THE. -FlaSTIMKLI^4<3l If you would have first-hand knowledge of thesituation, sweep the spectrum from 7350 to 7500kc. on any Sunday afternoon. We have heardharmonics so thick in this region that somestations couldnt be copied because of harmonicQRM from otheis. Granted that a prol)lem exists, what are wegoing to do al)0ut it? Lets begin by asking wherethis unwanted energy comes from. A harmonicfre(iuency is simply an integral multii)le of somegiven frecjuency called the Jundamenlal. Forinstance, if your transmitter operates on :5705 *609 Park Ave., CollinK-swood 7, N. J. kc, the second harmonic is at 7410 kc., andthe third is at 3 X 3705 or 11,115 kc. Regardlessof the kind of transmitter you use, whetherhomemade or store-bought, small amounts ofenergy at these harmonic frequencies are presentin your final tank along with the useful energyat the fundamental frequency. Such energy cancreate problems whenever (1) there is a largeamount of harmonic energy generated or (2). —CAM CttEAT& when conditions exist under which the harmonicemergy may be easily radiated. Either conditionalone may be bad; the combination is an invita-tion for FCC action. The files of our station contain quite a numberof letters and comments from the stations towhom we have sent ARRL Official Observercards. These letters show that the chief reasonsfor the harmonics we have heard are, in order,carelessness, ignorance of the situation, and theinability to correct the problem. Lets go throughthe most common mistakes and see whether wecan avoid these pitfalls. Use a Wavemeier The first question in chasing low-frequencyharmonics should be; this: To what band is thefinal tank circuit tuned? Many Novices arebuilding bandswitching rigs. Many others havebuilt rigs in which the final tank capacitor,without any change in the tank inductor, willtune, for instance, to both and Mc. Inthe case of the bandswitching transmitter, thedanger exists that the operator wil
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