Alt-BEAM Archive

Message #07331



To: beam@sgiblab.sgi.com
From: "Timothy Flytcher" flytch@hotmail.com
Date: Wed, 03 Nov 1999 00:17:19 PST
Subject: [alt-beam] Re: aquabots - 'sealed' motor


>Ever thought about this.
>
>You see algea on everything, including stones, ships and plants. But not on
>fish ! Fish are producing a hormoon/chemical that prevents algea growing on
>them.
Yes and it "is" available in a paint form... the top American cup racers use
it on their boats...

______________________________________________________



7332 Wed, 3 Nov 1999 10:09:54 +0100 RE: directional antenna? beam@sgiblab.sgi.com Wouter Brok [mailto:w.j.m.brok@stud.tue.nl]
Hello Bram,

>An unidirectional antenna would be something like a wire straight up.
>Just think about a car antenna. That's a uni-directional antenna.

In this I totally disagree with you: a wire straight up is much more of an
omnidirectional antenna than a unidirectional one. In fact it broadcasts in
or receives from all direction except this ones in the line of the wire.
Thus there is some directionality, but this isn't usefull to determine the
direction out of which the signal is coming, unless you use the zero (that
is my name for the directions in which the wire is pointing): if you would
rotate the antenna so that it will more and more point to the source you
will detect a rather large signal-gradient, towards no signal. This in
itself could be usefull to determine direction, but it poses some problems
since you don't have a signal from your antenna when it points in the
proper direction.

The straight wire antenna is a so called dipole antenna, of which you can
find specifications in every single book on antennae I think. An antenne
with a better direction-sensitivity would be a quadrupole or octupole
antenna. These are rather hard to construct (at least for me).

-------------
A straight wire isn't a dipole antenna. A dipole is made of two wires and is
already quite directional. You can enhance the directional-sensitivity by
adding elements infront and behind the dipole. btw. this isn't hard to do. I
made many of them in my time as radio amateur
-------------

[snip]

Bram van Zoelen
Robotics, kites, personal and more
http://vsim.freeservers.com
http:/beam.to/vsim

E-mail
vsim@mail.com
vsim@vsim.freeservers.com



7333 Wed, 3 Nov 1999 03:51:04 -0500 [alt-beam] Natural Born Robots "BEAM" "Richard Caudle"
content-transfer-encoding: quoted-printable

Hey, =


Natural Born Robots is on right now on my local PBS station.

Richard Caudle
www.geocities.com/frankendaddy
Home ICQ - Frankendaddy

Guardians of the sacred words: Nee, Ptang, and NeeWhon! =



content-transfer-encoding: quoted-printable



>
Hey,
 

Natural Born Robots is on right =
now on my =

local PBS station.

 

Richard Caudle

href=3D"www.geocities.com/frankendad=">http://www.geocities.com/frankendaddy">www.geocities.com/frankendad=
dy
Home =

ICQ - Frankendaddy

 

Guardians of the sacred words: N=
ee, =

Ptang, and NeeWhon!         =





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