Show about dead spots in some short wave sets the broadcast listener who Is using his bis short wave conver converter er for the first time frequently finds there are one or more points on the dial at which the receiver cannot be made to oscil litte this phenomenon which Is familiar to all amateurs results from tile the fact that the receiver Is tuned to tile the resonant frequency of the antenna a i or to a harmonic of this frequency when the two are resonant reson atit considerable power Is absorbed by tile lie antenna which makes it difficult to produce oscillations in the receiver this trouble la is naver never encountered fit at broadcast frequencies because a very small aperio dle primary ts is used and the natural frequency of the antenna circuit Is very high the trouble may be remedied either by loosening the tha antenna coupling or orby by connecting a small series capacity in the antenna which will shift the resonant frequency to some part of the band which ignot Is not in use um |