Richard,

It should be a fun experiment.

The ideal power transfer for isotropic radiators in free space at one
wavelength separation is given by 1 / ((4 * pi)^2) = 0.00633 or -22 dB.

The specific number, 22 dB, comes with some specific conditions.

Such as:

* Isotropic radiators, i.e., no gain.

* Free space, no modification of fields by the earth or a roof.

* The antennas are in the far-field regions of each other. This usually
means the antennas are small compared to the wavelength. (Automatic for
the isotropic radiator.)


22 dB may be an convenient number to remember, but it is essentially
meaningless for the question at hand.


73,
Gene
W4SZ




Richard Harrison wrote:
Henry Kolesnik wrote:
"How do you get 22 dB down for one wavelength and 6 more for each
doubling?"

Measure it. That relationship is convenient to remember.

Best regards, Richard Harrison, KB5WZI

Gene Fuller wrote:
"The specific number, 22 dB comes with some specific conditions."

Yes, but when you are calculating the decline in field due to distance
from the source, 22 dB is convenient as the reduction within the first
wavelength. Every time the distance doubles after the first wavelength,
the volts per meter are halved. The power per square meter is thus
quartered (decreases by 6 dB).

Best regards, Richard Harrison, KB5WZI