Vhf Whip Antenna
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What is "antenna dimension D" described in Fraunhofer distance equation?
Learning Radio Commuications, Fraunhofer distance , where:
d = 2*D^2/Lamda
They are calling big "D" antenna dimenssion, as in the antenna diameter? As an example, if I have a VHF antenna transmiting at 175Mhz (1.7M wavelength) , and it's a whip type antenna of a diameter of say 10cm (0.1M) , the far field is considered a distance greater than 2*d^2/lamda = 2*(.1^2)/1.7=0.00177M ? thanks
Looking at the antenna and correcting what "antenna dimension" defines, then , it's about a 1/2lamda antenna dimension (1.7/2 = .85), so d = 2*.85^2/1.7 = 0.85M ?
D is the largest physical linear dimension of the antenna. A quarter wave with an adequate ground plane is generally considered the equivalent of a half wave, so I would expect it to be 1.7m.
Tags: antenna, vhf whip antenna