http://nopr.niscpr.res.in/handle/123456789/35407 2026-10-09T03:29:39Z http://nopr.niscpr.res.in/handle/123456789/35543 Title: A new formula for the gain of open-ended rectangular waveguide Authors: Selvan, K T; Das, Sisir K Abstract: A new, simple formula is presented for the gain of the open-ended rectangular waveguide (OEG). The formula is derived by expressing the gain of the OEG in terms of the gains of its two constituent parallel waveguides, one supporting TEM mode and the other supporting TE10 mode. This new formula offers an improvement of about 1-2 dB over Schelkunoff’s formula and compares with the more complicated formulas of Yaghjian to an accuracy of about 0.5 dB. Page(s): 359-362 1997-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35542 Title: Polarization measurement of low latitude whistlers using crossed loop antenna method Authors: Singh, Raghuraj; Singh, Birbal Abstract: The crossed loop antenna method has been developed at the low latitude ground station Bichpuri, Agra (Geomagn. Lat., 17°1´N; <i>L</i>=1.15), to study the ionospheric transmission characteristics of whistlers and VLF emissions observed at this station by measuring their polarization characteristics. In this paper, the details of this technique is described and some initial result of polarization characteristics. In this paper, the details of this technique is described and some initial results of polarization measurements for the case of multiflash whistlers and tweek atmospherics are presented. It has been shown that the multiflash whistlers (D~18 s^1/2) recorded at this observing station were transmitted from the ionosphere 200 km away and reached the station with elliptical polarization. The tweeks recorded on the same day reached with linear polarization within 18°-30° from north-south direction. Page(s): 354-358 1997-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35541 Title: Nomogram for sunspot numbers Authors: Upreti, U C Abstract: Nomogram construction using the parabolic relationship <i>f</i>₀F2=<i>a</i>₀+<i>a</i>₁<i>R</i>₁₂+<i>a</i>₂<i>R</i>²₁₂ between monthly median <i>f</i>₀F2 and running average sunspot number (RASSN) R₁₂ values has been described; here <i>a</i>₀, <i>a</i>₁ and <i>a</i>₂ are the best fit coefficients. The nomogram can give required local effective sunspot number (LESSN) values corresponding to any observed value of <i>f</i>₀F2. Transforming the <i>f</i>₀F2-RASSN relation to the form <i>R</i>²₁₂+<i>pR</i>₁₂+q=0 [where <i>p</i>=<i>a</i>₁/<i>a</i>₂ and <i>q</i>=(<i>a</i>₀- <i>f</i>₀F2/<i>a</i>₂), a practical method for the preparation of a single nomogram for <i>f</i>₀F2-RASSN has been described and the problem of very high and very low values of the variables has also been dealt with successfully. A single nomogram for large range of variables, namely, <i>f</i>₀F2, <i>a</i>₀, <i>a</i>₁and <i>a</i>₂ has been obtained so that one easily find LESSN values at any location, season, and time. The nomogram tends to minimize the errors in LESSN calculations at all levels of solar activity. Page(s): 346-353 1997-12-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35540 Title: Radiation of an electric dipole in an anisotropic medium Authors: Kai, Li; Weiyan, Pan Abstract: The radiation of an electric dipole in an infinite anisotropic plasma medium is analyzed. A three-dimensional fourier transform is employed to compute the field and it is shown that the far field can be expressed as some of two separate spherical waves. As an example, radiation patterns of the dipole parallel to the geomagnetic field in two different frequency regions are calculated. Page(s): 340-345 1997-12-01T00:00:00Z