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Externet
Antenna-Theory.com Newbie

Joined: 15 Jan 2015
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Location: Mideast U.S.

 Posted: Sun Jan 18, 2015 6:47 pm    Post subject: Radiation resistance... What is radiation resistance of an antenna and how is it calculated ?
helix
Antenna Theory Regular

Joined: 29 Jan 2015
Posts: 64

 Posted: Fri Jan 30, 2015 5:56 am    Post subject: Radiation resistance is concept used when representing an antenna as an equivalent circuit. It accounts for the power that the antenna transmits to free space. As far as the circuit is concerned, the radiated power is gone from the circuit, so a resistor is appropriate (a resistor dissipates, or removes, power from a circuit). You can find general formulas for radiation resistance in any intro antenna text, e.g. Stutzman and Thiele.
Externet
Antenna-Theory.com Newbie

Joined: 15 Jan 2015
Posts: 8
Location: Mideast U.S.

 Posted: Mon Feb 02, 2015 3:18 am    Post subject: Thanks, helix. Is the formula Rr = 1580 * ( He / wavelength)^2 valid ? Rr = radiation resistance, He = effective height, expressed in fractions of a wavelength, of the distributed common-mode current
helix
Antenna Theory Regular

Joined: 29 Jan 2015
Posts: 64

 Posted: Thu Feb 05, 2015 6:49 pm    Post subject: That formula is probably only valid for electrically short dipoles/monopoles. I'd suggest following the derivation of the formula (wherever you got it from) to ensure that the assumptions going into the derivation are valid for your particular case.
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