The Precision Frequency Measuring System of R.C.A. Communications, Inc.

A frequency measuring system is described wherein transmitter frequencies are accurately compared with the harmonics from a precision, piezo-electric frequency standard. Through the medium of a system of multivibrators and a synchronous clock the frequency of the standard oscillator is referred to the time interval defined by the rotational frequency of the earth. Harmonics from a 100-kc crystal oscillator are fed into a frequency measuring receiver along with the transmitter signals. The receiver is equipped with a small vernier condenser having a micrometer scale which is used to make the measurements. The position of a signal in the frequency spectrum relative to known harmonics from the standard oscillator is obtained by direct interpolation from the micrometer readings of the tuning points of the signal and the adjacent harmonics between which it lies. To allow greater precision in making measurements, harmonics 10 kc apart are used. Methods used in measuring broadcast, high, and ultra-high frequencies are described. A discussion of errors is given. The total probable maximum error of a routine measurement at 20,000 kc (15 m) with this system is ±59 cycles or 0.0003 per cent. At broadcast frequencies a measurement can be made to 0.2 cycle. The operating aspects of the system are discussed. The number of measurements made each month is indicated and the various uses to which these measurements have been put are described.