archive: Re: SETI Yet another hare-brained scheme for building an antenna

Re: SETI Yet another hare-brained scheme for building an antenna

Corey Ashford ( yeroca@rocketmail.com )
Mon, 31 Aug 1998 15:16:10 -0700 (PDT)

---Jim Glover <psykey@okcforum.org> wrote:
>
> >
> >
> >
> > Picture a round, above-ground swimming pool about
> > 14 feet in diameter, filled about half way with
water
> > and floating on top of that a coating of aluminized
> > ping-pong balls.
>
> Only one point on the surface of each ping-pong ball
> would reflect radiation in the desired direction.
The
> rest of the radiation striking each ping-pong ball
> would be scattered all over the place. Very low
> efficiency.

Though that's seems intuitively correct, I'm not sure
that
in reality it's true because the curvature is much
less than a wavelength. I would think that the
surface would look essentially flat to a 1420 MHz
radiation.

I need to reread my physics notes on this subject,
however.

>
> Suppose you used half a ping-pong ball for each? The
> aluminized surface would be the flat part of the
half-
> sphere, which would be parallel to the surface of the
> water, when the water was at rest. However, even
this
> wouldn't work as you went up the sides of the curve.
> Each ping-pong ball's flat surface would be pointing
> more or less straight up. (And that's assuming it
> didn't decide to flop over.)

If you were to use half spheres, the flat side ought
to be parallel to the surface of the water...
remember that its "gravity" vector is now at an angle
other than straight up and down due to the centripetal
force.

- Corey
KB7KD

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