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Folded Unipole Antenna Bandwidth

February 27th Fact-of-the-Day

A folded unipole antenna has significantly wider bandwidth than an unfolded vertical radiator, because its characteristic impedance is lower. Note that the characteristic impedance of a radiator is not the same as its radiation resistance. The characteristic impedance of a radiator is its radio-frequency impedance without the effects of radiation. Folding a radiator to create two adjacent radiators produces an effect equivalent to a substantial increase in radiator diameter which lowers the characteristic impedance while raising the radiation resistance. The length required for resonance becomes less and the reactive component of the antenna impedance is greatly reduced, which significantly increases antenna bandwidth. ©2005 Martek International All rights reserved.

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