Topband: Capture area

Tom Rauch w8ji at
Thu Feb 22 11:24:37 EST 2007

> As one reduces the Antenna Capture Area capabilities, say 
> by an order
> of magnitude for each step, it follows the signal levels 
> ought also
> reduce a similar order of magnitude

"Capture area" or "effective aperture", despite common myth, 
is not determined by physical size. It is also not important 
to receiving.

Capture area is determined by gain and frequency. Gain 
includes efficiency and directivity, but not size.

If I have a 50 foot vertical with 50% efficiency and zero dB 
gain, it has more "capture area" than a typical Beverage 
1000 feet lone, or even a pair of Beverages spaced 350 feet 
that are 1000 feet long. A large Rhombic often has less 
capture area than a stack of 4 element Yagi's because it 
often has less gain.

The only thing that is important for receiving is the 
antenna directivity and the direction and level of noise, 
once we have enough signal to make external noise limit the 

Size doesn't matter.

73 Tom 

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