Frequency measurements in electrical communication

J. W. Horton: A comment in connection with the frequency measuring work of the Bureau of Standards may be of interest. From time to time they have transmitted standard frequencies from the radio station at the Bureau. On several occasions these have been compared with our standard as follows: The transmitted wave was received in the usual manner, amplified in a radio frequency amplifier and impressed upon a detector circuit which was loosely coupled to a variable frequency oscillator. This oscillator was adjusted, in accordance with our base frequency, to the frequency scheduled to be transmitted by the Bureau. Any difference between the two sources, one in Washington and the other in New York, appeared as a low frequency in the output of the detector. Comparisons made on frequencies of from 500,000 to 1,000,000 cycles per second showed in no case a difference of more than 2500 cycles. On one occasion, at a frequency of 1,000,000 cycles per second, the observed difference was about 25 cycles, being below the audible range.