Author :
Tewari, R.K. ; Swarup, S. ; Roy, Manujendra N.
Abstract :
A radio wave attenuation measurement survey program was undertaken for the tropical rain forests of India. Measurements were taken at frequencies from 50 to 800 MHz, for antenna heights from 1.5 to 16.5 m above the ground with both horizontally and vertically polarized emissions, and at various separation distances varying from 40 to 4000 m. There were 96 combinations of system parameters for each selected distance between transmitting and receiving locations. In addition to the copolar measurements, cross-polar measurements were carried out to study cross-polar phenomenon in the presence of vegetation. The results of the studies are discussed, covering scatter of the data, lack of homogeneity of the foliage, variation in foliage proximity of the antenna, scattering of radio waves, effect of antenna beamwidth, effect of changes in wind velocity, frequency and polarization dependence of the basic transmission loss, seasonal variation of the loss, effect of climate and type of vegetation, foliage loss, specific attenuation, and effect of increased antenna height in the forest. An empirical model derived from these measurements is proposed
Keywords :
electromagnetic wave absorption; electromagnetic wave polarisation; radiowave propagation; tropospheric electromagnetic wave propagation; 40 to 4000 m; 50 to 800 MHz; India; UHF; VHF; antenna beamwidth effect; antenna height effect; attenuation measurement; basic transmission loss; climate effect; copolar measurements; cross-polar measurements; foliage; frequency dependence; horizontally polarised emissions; polarization dependence; radiowave propagation; scattering; seasonal variation; tropical rain forests; vegetation; vertically polarized emissions; wind velocity effect; Antenna measurements; Antennas and propagation; Attenuation measurement; Frequency measurement; Polarization; Propagation losses; Rain; Scattering; Transmitting antennas; Vegetation;
