Some Fading Characteristics of Regular VHF Ionospheric Propagation

Some short-term fading characteristics of a type of ionospheric propagation first described by Bailey, et al. are presented and discussed. Continuous wave transmissions from Cedar Rapids, Iowa, on 49.8 mc were received at Sterling, Virginia, on either rhombic or Yagi antennas directed toward the transmitter. The second detector output of a linear receiver was used to provide a voltage proportional to the envelope of the received signal. This fluctuating voltage was recorded, edited, and then analyzed to determine the probability distribution and autocorrelation function of the signal envelope. The correlation of the envelopes of signals received on spaced antennas was similarly determined for antennas spaced both normal and parallel to the transmission path.