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--- project:hgg:antenna_design:omidirectional [2012-03-26 09:15] – DTAknfLYYyTEgkdQIt 210.170.35.21
+++ project:hgg:antenna_design:omidirectional [2012-03-26 09:16] (aktuell) – alte Version wieder hergestellt 85.214.34.41
@@ Zeile 1: / Zeile 1: @@
-Hmmm I wonder!  While I don't ralley know very much about SOPA (I've only seen bits and pieces about it), nor very much about  hackers  I am intrigued with the thought of a 2nd alternative to what I'm hearing might become a nightmare when/if SOPA gets fully implemented in the existing internet.  I'm also pretty clueless as to how such a thing could actually be done. It seems the big corporations who own and operate the various infrastructures to process and move all the data that makes the web what it is will likely have lots to say about just who can access and use those resources unless the alternative internet was completely  underground  and available only through risky, illegal channels that somehow ride along  piggy-back  style on the back of the existing web(?).  Sorry this is way over my head I'll put it to rest now. I hope whatever happens just doesn't completely destroy my individual access to what has become a resource that would be difficult to be without.
+====== Omnidirectional Antenna ======
+I've started experimenting with this antenna type because it was proposed by some people as a good sollution as long as we are in Receiving mode. Here's what I found.
+====== Groundplane Antenna ======
+We had already tried this type of Antenna but made an error in the calculations. Since data we gathered is thus worthless, we should redo all things about this antenna type.
+The antenna should be a <m>lambda / 4</m> antenna and thus Wavelength is ~ 275.04 mm, a quarter wavelength is ~ 68,76 mm.
+Thus the antenna should look like this:
+{{:project:hgg:antenna_design:groundplane.png|}}
+The lenght of the antenna should be lambda/4, the lenght of the ground-wires should also be.
+German wikipedia (article [[http://de.wikipedia.org/wiki/Groundplane_(Antenne)|Groundplane Antenna 2011-01-01, 3am]] says, the ground wires should be in a 135 degree angle from the antenna wire to match 50 Ohms.
+TODO: test the antenna.
+====== More Gain ======
+I found out that comercial antennas with high gain often are very long like in 1.2 to 3.5 Meters.
+Omni antennas by definition offer 0 dB gain (1).
+To generate higher gain, one must increase the directionality of the antenna, and therefore make it directional (ie not omni directional).
+The gain of the antenna is given by:
+G = η(πD/λ)^2
+Where:
+η = efficiency (0.65 good initial value)
+D = Diameter
+λ = wavelength of signal being received/transmitted.
+ In the antenna Manuals (eg see [[http://www.scribd.com/doc/20515944/Kathrein-Antennas|Different Types of Kathrein Antennas]], in the section VPol Omnidirectional Antenna 1087 to 1093 Mhz) they talk about decouploed Dipoles. As far as i get it, that means that you put more than one Dipole into an Antenna. To make the antenna not have different gains for different directions, the dipoles are stacked. Since the signal is vertically polarized, the antenna won't become direction-dependent if the dipoles are above each other.
+It's not clear if that also works for groundplane antennas.
+Need plan to build that.
+====== Link-Dump ======
+[[http://www.hindawi.com/journals/ijap/2010/843624/]]