Suppression of harmonics in radio transmitters
14 June 1951
After reviewing briefly prevalent views on the desired amount of harmonic suppression and the methods of calculating and measuring the amplitude of harmonics, several typical power amplifier output circuits are analysed for their harmonic content. It is shown that quite generally a common capacitive coupling of two tuned circuits in the transmitter output stage is more effective than the more popular inductive link coupling. Shielding methods and "spot" filters (open-ended stubs of lambda/4 length to suppress one particular harmonic) are also discussed. A bibliography of 35 items is appended.