Physics question

> Whoa Nelly. Hang on a sec. I have a fundamental physics question. In
> my previous post I was using the inverse square law as a measure of
> power lost in transmission, but is it more correct to say that it is
> power lost per given area.
>

The inverse quare law does not apply to a focussed beam.

The equation of beam spreading is a function of the transmitting antenna
aperture versus the frequency.

The bigger the aperture, the tighter the beam.

Beam spreading does not cause significant power loss. The size of the
antenna is set to precisely match the dimensions of the beam as it
intersects
the Earth's surface.

A little bit of energy is lost due to sidelobes which are caused by
diffraction. It is typically not worth it to make the receiving antenna
large enough to catch all the sidelobes.

>
> The inference from the last question, is that all of the power can
> be captured by having a rectenna that, in the case of the 180 degree
> separation, is the inverse of 9%, namely 11.1 times larger than the
> transmitter. And in the case of the 120 degree separation, the
> inverse of 24%, namely 4.166 times larger than the area of the
> transmitter?
>

I do not understand your numbers, but they do not appear correct.

>
> If the above is correct, then my doubts about the feasability of
> space power sharing may have to be reconsidered. It is my

You need to read up on antenna design, and terms like sidelobes and
diffraction. Inverse square law does not really apply.

>
> understanding that rectennas are constructed of less expensive
> components than the SPS. Maybe it could work?
>

Rectennas are certainly cheaper than transmitting antennas and PV
arrays.