[Homestead] Communications
Don Bowen
don.bowen at earthlink.net
Sun Feb 7 09:50:40 EST 2010
Lynda wrote:
> So, I don't know about this whole line of site stuff and I don't know about antennaes cause I would never have thought a white box was an antennae! I mean, I was expecting something that looked like my CB whip antennae that I would have to send someone up a tree to make it work
Lower frequencies can bend through the atmosphereand travel long
distances, some all the way around the world. Higher frequencies are
more easily attenuated by obstructions, hills, trees, rain. The higher
the frequency the more easily attenuated. That is why Satellite signals
often drop out in the rain.
Antennas can be directional. The tal verticle whip antenna is
omnidirectional, meaning the signal is about the same all around the
antenna. For something like a CB antenna this is what you want.
Antennas like the satellite dish and the multi element TV antenna are
directional, meaning the signal is stronger in one direction that in
another.
The white box you see is just a weather cover. Inside the box will be a
directional antenna and in those it is a highly directional flat dish.
Sometimes the antenna cover looks like a tube, again the antenna inside
is directional.
For WiFi work I have a Yagi, a directional antenna with greater than 16
dBi gain. The typical base loaded Dipole antenna (The vertical whip)
has a gain of around 1 dBi. In other words the Yagi will receive a
signal about 40 times stronger than the whip.
--
Don Bowen KI6DIU
http://www.braingarage.com/Dons/Travels/journal/Journal.html
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