Spaced antenna diversity in temperate latitude meteor burst systems operating near 40 MHz: Variation of signal cross-correlation coefficients with antenna separation

We have studied 37-MHz signals received over an 800-km temperate latitude path using 400-W continuous wave transmissions. Signals collected during a 9-day period in February 1990 on two antennas at separations of 5λ, 10λ, and 20λ were analyzed. Three signal categories were identified (overdense, underdense, and not known (NK)) and cross-correlation coefficients between the signals received by the two antennas were calculated for each signal category. No spatial variation, and in particular no decrease, in average cross-correlation coefficient was observed for underdense or NK signals as the antenna spacing was increased from 5λ to 20λ. At each antenna separation the cross-correlation coefficients of these two categories were strongly dependent on time. Overdense signals, however, showed no cross-correlation time dependency at 5λ and 10λ, but there was a strong time dependency at 20λ. Recommendations are made in regard to the optimum antenna spacing for a meteor burst communication system using spaced antenna diversity. Our measurements support the views of Bartholomé and Vogt [1968], who suggested that a 4λ spaced antenna diversity configuration contributed to the exceptional signal throughput of the COMET meteor burst communication system.