A Precision Method for the Measurement of High Frequencies

A precision method for the measurement of the frequency of an oscillating circuit is discussed. The theory on which the method is based is discussed and there is developed an equation which relates the frequency of the beat note between two oscillators to the natural frequency of a circuit which is loosely coupled to one of them. This equation is considered in some detail and certain of its properties are deduced. Curves are drawn for three typical cases. The cause and avoidance of certain errors are considered. The method is extended to the case of a non-oscillating circuit. Finally there is suggested a method for the measurement of small values of mutual inductance.