Accession Number : AD0429891

Title :   AN FM TECHNIQUE FOR OBSERVATION OF VLF WHISTLER-MODE PROPAGATION,

Corporate Author : STANFORD UNIV CA STANFORD ELECTRONICS LABS

Personal Author(s) : Carpenter, George B.

Report Date : DEC 1963

Pagination or Media Count : 52

Abstract : Natural whistlers and signals from VLF transmitters were employed in studying whistler-mode propagation. The usefulness of whistler is restricted by the relative lack of information concerning lightning-source parameters, while relatively poor multipath resolution was obtained using the signals of VLF transmitters. A controlled-source experiment intended to overcome these disadvantages is described. When a VLF transmitter is frequency modulated, high resolution of multipath signals is theoretically possible. The FM technique for detecting and resolving whistler-mode signals is based on the observation of amplitude modulation of the direct subionospheric signals due to the presence of whistler-mode signals. Travel time of the whistler-mode signal is associated with the periodicity of the envelope changes of the composite signal. Factors such as signal dispersion, value of modulation parameters, and instrumental effects are considered with regard to their influence on detection and resolution. An actual FM experiment was conducted employing transmissions from NPG (18.6 kc) at Jim Creek, Washington. (Author)

Descriptors :   *VERY LOW FREQUENCY, *PROPAGATION, LIGHTNING, MULTIPATH TRANSMISSION, FREQUENCY MODULATION, RESOLUTION, RADIO SIGNALS, ELECTROMAGNETIC WAVE REFLECTIONS, VELOCITY, TIME, REFLECTION, IONOSPHERE, IONIZATION, ELECTRONS, COMMUNICATION AND RADIO SYSTEMS, DETECTION, EXPERIMENTAL DATA, DEMODULATION, AMPLITUDE MODULATION.

Distribution Statement : APPROVED FOR PUBLIC RELEASE