Measurement of the Frequencies of Distant Radio Transmitting Stations

The equipment installed in the Italian Royal Experimental Institute of the Communications for radio-frequency measurements is described. The measurements are bused upon the utilization of harmonics generated by the Abraham multivibrator controlled by a 1024-cycle tuning fork. The factors which can influence the variation of the tuning fork, with special regard to the action of temperature, are examined. A simple and rapid method is described, which permits of control of the frequency of the tuning fork at the beginning and at the end of each measurement, and determines, with great accuracy, the frequency of the harmonics between which the wavelength to be measured is included. Such a method consists in comparing the frequency of the tuning fork with that generated by an alternator, and in recording, through a chronograph, the beats included between the two frequencies, the number of revolutions, and frequency of the alternator together uwith the time furnished by a pendulum of the Astronomical observatory. Some examples of calibrations are reported, showing that the degree of precision assured varies from 1 to 5 per 100,000.