Chapter 22 - Recent V.L.F. Work at The U.S. Army Electronics Research and Development Laboratory

Abstract

This chapter discusses the recent v.l.f. work at the U.S. army electronics research and development laboratory. At laboratory, v.l.f. phase measurements have mostly been carried out with Pierce's photographic recording technique, having a time constant of about 0.1 sec and recently also with automatic phase following receivers having a time constant of about 1 min. In 1960, the feasibility of synchronizing was demonstrated with a flying atomic clock two atomic clocks, one located at Rome, New York and the other on Oahu, Hawaii (8000 km), and keeping them synchronized via v.l.f. transmissions. An error of 3.7 μsec was measured when the flying clock returned to Rome, New York, after 4 days. V.l.f. measurements using the flying clock as a reference revealed a dispersion between 10.2 and 14.2 kc/s signals of 0.3 per cent and between 14.2 and 18.2 kc/s signals of 0.1 per cent with the lower frequency waves travelling the faster. The measurements also indicated a small nonreciprocity, with v.l.f. propagation in east–west direction being about 0.01 to 0.02 per cent faster than propagation in west–east direction. These experiments utilized double frequency transmissions from Haiku on Oahu, Hawaii and Forestport, New York carried out on a time-sharing base with a repetition period of 5 sec.