[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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