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http://nopr.niscair.res.in/handle/123456789/35407
Sat, 22 Feb 2020 01:51:07 GMT2020-02-22T01:51:07ZA new formula for the gain of open-ended rectangular waveguide
http://nopr.niscair.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): 359-362Mon, 01 Dec 1997 00:00:00 GMThttp://nopr.niscair.res.in/handle/123456789/355431997-12-01T00:00:00ZPolarization measurement of low latitude whistlers using crossed loop antenna method
http://nopr.niscair.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<sup>1/2</sup>) 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): 354-358Mon, 01 Dec 1997 00:00:00 GMThttp://nopr.niscair.res.in/handle/123456789/355421997-12-01T00:00:00ZNomogram for sunspot numbers
http://nopr.niscair.res.in/handle/123456789/35541
Title: Nomogram for sunspot numbers
Authors: Upreti, U C
Abstract: Nomogram construction using the parabolic relationship <i>f</i><sub>0</sub>F2=<i>a</i><sub>0</sub>+<i>a</i><sub>1</sub><i>R</i><sub>12</sub>+<i>a</i><sub>2</sub><i>R</i><sup>2</sup><sub>12</sub> between monthly median <i>f</i><sub>0</sub>F2 and running average sunspot number (RASSN) R<sub>12</sub> values has been described; here <i>a</i><sub>0</sub>, <i>a</i><sub>1</sub> and <i>a</i><sub>2</sub> 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><sub>0</sub>F2. Transforming the <i>f</i><sub>0</sub>F2-RASSN relation to the form <i>R</i><sup>2</sup><sub>12</sub>+<i>pR</i><sub>12</sub>+q=0 [where <i>p</i>=<i>a</i><sub>1</sub>/<i>a</i><sub>2</sub> and <i>q</i>=(<i>a</i><sub>0</sub>- <i>f</i><sub>0</sub>F2/<i>a</i><sub>2</sub>), a practical method for the preparation of a single nomogram for <i>f</i><sub>0</sub>F2-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><sub>0</sub>F2, <i>a</i><sub>0</sub>, <i>a</i><sub>1 </sub>and <i>a</i><sub>2</sub> 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): 346-353Mon, 01 Dec 1997 00:00:00 GMThttp://nopr.niscair.res.in/handle/123456789/355411997-12-01T00:00:00ZRadiation of an electric dipole in an anisotropic medium
http://nopr.niscair.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): 340-345Mon, 01 Dec 1997 00:00:00 GMThttp://nopr.niscair.res.in/handle/123456789/355401997-12-01T00:00:00Z