NOPR Collection:

Complex Permittivity of Sand & Sandy Loam Soils at Microwave Frequency

1982-08-01T00:00:00Z

Title: Complex Permittivity of Sand & Sandy Loam Soils at Microwave Frequency Authors: Vyas, A D Abstract: Permittivity and dielectric loss of sand and sandy loam soils have been measured in laboratory conditions at X-band microwave frequency. With the help of permittivity data the emissivity of samples has been calculated. Page(s): 169-170

Equatorial Radio Scintillations of ATS-6 Beacons-Phase I: Huancayo 1974-75

1982-08-01T00:00:00Z

Title: Equatorial Radio Scintillations of ATS-6 Beacons-Phase I: Huancayo 1974-75 Authors: Rastogi, R G Abstract: The temporal variations of the amplitude fluctuation of the radio beacons signals on 41,140 and 360 MHz transmitted from the ATS-6 satellite (at 94°W longitude) received at Huancayo, Peru (lat., 12.0°S; long., 75.3°W, dip lat. ION) during the first phase of the ATS-6 programme have been described. Scintillations on 360 MHz were observed only during the nighttime with the maximum average value of about 2 dB peak-to-peak fluctuations. The average scintillations on 140 MHz were very low (less than 0.1 dB) during the sunrise and sunset periods, with a midday maximum of about 0.7 dB and of a premidnight (2100-2400 hrs L1) peak of about 3.5 dB peak-to-peak fluctuations. The general features of scintillations on 41 MHz were similar to those for 140 MHz, the minimum value of scintillation index around sunrise and sunset periods being about 2 dB and the daytime and nighttime peaks being about 5 dB. Scintillations during the nighttime were mostly very low and on some occasions very high, whereas the daytime scintillation values varied randomly around the mean value. The nighttime scintillations were strongest during December (summer) months while the daytime scintiIlations were strongest during the equinoxes. Assuming the scintillation index (SI) to vary with frequency (as S1 f^-n, it was found that the exponent, n, was about 1.3 and 1.4 for weak scintillations and systematically approached 0.0 for increasing magnitude of scintillation. Page(s): 159-168

An Analysis of Radiation Patterns of Corrugated Corner Reflector Antenna Systems

1982-08-01T00:00:00Z

Title: An Analysis of Radiation Patterns of Corrugated Corner Reflector Antenna Systems Authors: Vasudevan, K; Nair, K G Abstract: A theoretical analysis of the effects of corrugated reflector elements on the radiation characteristics of corner reflector antennas has been attempted and experimental results in support of the theory have been presented. The results with respect to radiation patterns and half power beam width (HPBW) of the system, show remarkable agreement between theoretical predictions and experimental data. Page(s): 156-158

Some Features of Annual Variation in the Equatorial Geomagnetic Field

1982-08-01T00:00:00Z

Title: Some Features of Annual Variation in the Equatorial Geomagnetic Field Authors: Rangarajan, G K Abstract: Analysis of mean hourly values of H field from Trivandrum (dip 0.3°S) based on data derived for all days and for quiet and disturbed days, restricted separately, reveals the fine structure of the local time dependence of the annual component in the electrojet region. Comparison with the result for Alibag (dip 24°N) shows that (i) the local time variations of amplitude for quiet days at Alibag and Trivandrum are broadly similar; (ii) there is no equatorial enhancement in the amplitude for hours close to local noon, indicating absence of ionospheric conductivity contributions; (iii) at Trivandrum, a significant secondary peak centred at 1700 hrs LT, especially in the data for quiet days, is observed. (This component is nearly in phase opposition to that at 1200 hrs LT, with minimum in June.); (iv) the amplitude of the secondary component, derived from 3-yr data at a time, shows an inverse linear dependence on solar activity whereas the local noon component is nearly independent of solar activity; and (v) local time variation in the amplitude at Trivandrum derived from disturbance field is dissimilar to that observed at Alibag. (The dissimilarity persists even in the semi-annual component of the disturbance field and is indicative of different generating mechanisms). Page(s): 152-155