[TenTec] Capture area (was 80 meter loops)

[Sinisa Hristov]

Michael Tope wrote:

> If on the other hand, I just tell you that the antenna
> has +3dBi gain in the direction of the incoming plane
> wave and that the incoming plane wave has a power
> density of 10 microwatts/meter^2, you won't be able
> to tell me the level of the received signal (not enough
> information).


If the wavelength is known, as it normally is,
then effective area can be calculated from isotropic gain,
and vice versa:

  Ae = Gi * lambda ^ 2 / (4 * Pi)

  Gi = 4 * Pi * Ae / (lambda ^ 2)


The origin of this topic came from a false assumption
that the "capture area" of a very long wire antenna
is large simply because of the length of the wire,
and regardless of the directivity.

This was shown to be entirely wrong:  effective area
and gain are proportional to each other.
In directions of low gain the effective area is small
regardless of the length of the wire, or countries worked :-)


73,

Sinisa  YT1NT, VA3TTN