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Radiation resistance...

 
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Externet
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Joined: 15 Jan 2015
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PostPosted: Sun Jan 18, 2015 6:47 pm    Post subject: Radiation resistance... Reply with quote

What is radiation resistance of an antenna and how is it calculated ?
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helix
Antenna Theory Regular


Joined: 29 Jan 2015
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PostPosted: Fri Jan 30, 2015 5:56 am    Post subject: Reply with quote

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.
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Externet
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PostPosted: Mon Feb 02, 2015 3:18 am    Post subject: Reply with quote

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
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helix
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Joined: 29 Jan 2015
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PostPosted: Thu Feb 05, 2015 6:49 pm    Post subject: Reply with quote

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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