Radio Antennae
The widespread idea that 50 Ω and 75 Ω nominal impedances are connected with the input impedance of various antennae is, in fact, a myth. It is true, however, that several common antennae are easily matched to these cables. A quarter wavelength monopole has an impedance of 36.5 Ω, and a half wavelength dipole has an impedance of 72 Ω. A half-wavelength folded dipole, commonly seen on television antennae, on the other hand, has an impedance four times that of a dipole, that is 288 Ω. The 0.5λ dipole and the 0.5λ folded dipole are commonly taken as having nominal impedances of 75 Ω and 300 Ω respectively.
Read more about this topic: Nominal Impedance
Famous quotes containing the words radio and/or antennae:
“Now they can do the radio in so many languages that nobody any longer dreams of a single language, and there should not any longer be dreams of conquest because the globe is all one, anybody can hear everything and everybody can hear the same thing, so what is the use of conquering.”
—Gertrude Stein (1874–1946)
“There is no magic decoding ring that will help us read our young adolescent’s feelings. Rather, what we need to do is hold out our antennae in the hope that we’ll pick up the right signals.”
—The Lions Clubs International and the Quest Nation. The Surprising Years, III, ch.4 (1985)