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The reception of an em wave by an antenna is greatly enhanced if the length of the antenna is in some way related to the wavelength of the em wave. It is a resonance effect. So for a whip antenna the best reception is when the length of the antenna is slightly less than a quarter of a wavelength and for a dipole it should be slightly less than half a ...


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Radio waves don't penetrate very deeply into metals. The depth to which they penetrate is characterized by a parameter called skin depth. The penetration is practically zero beyond about five times the skin depth, so adding additional thickness beyond five skin depths will make no difference. The skin depth for most metals at 5 GHz is about 1 $\mu$m. So ...


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For a metal, a measure of how far the wave penetrates is determined by its skin depth, $\delta$. Typically $\delta \approx 10 mm$ for metals at around 50 Hz, but becomes much smaller at higher frequencies, at microwave frequencies $\delta \approx 1-10 \mu m$. This means that there's no point in having very thick metals.


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A dipole is fed by a frequency varying voltage [or current] source at the center between the two halves. In theory, you send a sinusoidal signal down the transmission line which will see the dipole two dipole leads as an impedance $Z_{ant}$. For a half-wave dipole, $Z_{ant} \approx 72 + j42.5$ $\Omega$. The classical textbook analysis of the radiation from ...


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Just to add to Jim: Any of the three can be used to to retrieve message by transmitting (a) only the side bands (b) only one side band (c) only carrier frequency. Even, sometimes usually due to economic reasons only the upper or lower side bands of an AM is transmitted. The three waves of different frequency are not incorporated into single carrier ...



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