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isotropic (source) radiator

the point of origin for the purely omnidirectional radiation of electromagnetic energy located at the absolute center of a sphere which radiates energy of equal intensity at all points of the inner surface (effective area) of the sphere. the isotropic radiator exists only in theory since construction is impossible but it is useful as a reference by which to gauge the directivity of electromagnetic radiators.

the directivity of the isotropic radiator is 0 dB. and the power multiplier ratio is 1.

from this reference point it is clear that any effort to concentrate or focus the energy produced by the radiator (for example, the addition of a parabolic reflector) in an effort to increase the intensity of the radiation to any fractional area of the internal surface of the sphere will distract from the intensity of the radiation in the direction of large portions of the sphere's internal surface and will produce an increase in directivity in the favored direction relative to the placement of the reflector element with respect to the radiator.

the antenna does not "multiply" power or signal. the antenna concentrates and focuses energy in a specific direction (azimuthally and / or vertically) at the expense of the loss of radiation intensity in other directions. this is the meaning of the word directivity. this is not automatically translated into "gain" until the radiation efficiency of the antenna has been determined, based primarily upon system values of radiation resistance and loss resistance present at the antenna feedpoint.

there is no antenna that is 100% efficient and as such any legitimately stated "gain" figure will always be less than the calculated and / or measured directivity.

<blockquote data-quote="freecell" data-source="post: 764374" data-attributes="member: 30">isotropic (source) radiatorthe point of origin for the purely omnidirectional radiation of electromagnetic energy located at the absolute center of a sphere which radiates energy of equal intensity at all points of the inner surface (effective area) of the sphere. the isotropic radiator exists only in theory since construction is impossible but it is useful as a reference by which to gauge the directivity of electromagnetic radiators.the directivity of the isotropic radiator is 0 dB. and the power multiplier ratio is 1.from this reference point it is clear that any effort to concentrate or focus the energy produced by the radiator (for example, the addition of a parabolic reflector) in an effort to increase the intensity of the radiation to any fractional area of the internal surface of the sphere will distract from the intensity of the radiation in the direction of large portions of the sphere&#039;s internal surface and will produce an increase in directivity in the favored direction relative to the placement of the reflector element with respect to the radiator.the antenna does not &quot;multiply&quot; power or signal. the antenna concentrates and focuses energy in a specific direction (azimuthally and / or vertically) at the expense of the loss of radiation intensity in other directions. this is the meaning of the word directivity. this is not automatically translated into &quot;gain&quot; until the radiation efficiency of the antenna has been determined, based primarily upon system values of radiation resistance and loss resistance present at the antenna feedpoint.there is no antenna that is 100% efficient and as such any legitimately stated &quot;gain&quot; figure will always be less than the calculated and / or measured directivity.</blockquote>

[QUOTE="freecell, post: 764374, member: 30"] isotropic (source) radiator the point of origin for the purely omnidirectional radiation of electromagnetic energy located at the absolute center of a sphere which radiates energy of equal intensity at all points of the inner surface (effective area) of the sphere. the isotropic radiator exists only in theory since construction is impossible but it is useful as a reference by which to gauge the directivity of electromagnetic radiators. the directivity of the isotropic radiator is 0 dB. and the power multiplier ratio is 1. from this reference point it is clear that any effort to concentrate or focus the energy produced by the radiator (for example, the addition of a parabolic reflector) in an effort to increase the intensity of the radiation to any fractional area of the internal surface of the sphere will distract from the intensity of the radiation in the direction of large portions of the sphere's internal surface and will produce an increase in directivity in the favored direction relative to the placement of the reflector element with respect to the radiator. the antenna does not "multiply" power or signal. the antenna concentrates and focuses energy in a specific direction (azimuthally and / or vertically) at the expense of the loss of radiation intensity in other directions. this is the meaning of the word directivity. this is not automatically translated into "gain" until the radiation efficiency of the antenna has been determined, based primarily upon system values of radiation resistance and loss resistance present at the antenna feedpoint. there is no antenna that is 100% efficient and as such any legitimately stated "gain" figure will always be less than the calculated and / or measured directivity. [/QUOTE]

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