PENETRATION OF THE IONOSPHERE BY VERY-LOW-FREQUENCY RADIO SIGNALS INTERIM RESULTS OF THE LOFTI I EXPERIMENTS
Abstract
LOFTI I is the first of a series of Navy satellite experiments designed for determination of the degree and extent of very-low-frequency (VLF) radio-wave penetration of the ionosphere. The LOFTI I telemetry records show relatively strong signals in the ionosphere from 18-kc transmitters on the terrestrial surface. The signals were attenuated less at night and appeared as far away as Australia, 10,000 miles from the transmitter. Statistical treatment of the data so far reduced shows that the attenuation of magneticfield intensity of the 18-kc time pulses from Naval Radio Station NBA, as measured near extreme line-of-sight distances to the north of the station, was less than 13 db 50% of the time at night and less than 38 db 50% of the time during the daylight hours. The data studied so far show very little effect of altitude on signal intensity, an observation which agrees with the theoretical treatment based on a model ionosphere. The observed time delays of the 18-kc signals range from 10 to 200 milliseconds, indicating that VLF propagation velocity in the ionosphere is much lower than in free space. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1961
- Accession Number
- AD0268726
Entities
People
- J.p. Leiphart
- R.w. Zeek
Organizations
- United States Naval Research Laboratory