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Dipole antenna orientation


testraub

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Okay, finally got a EDM transmitter and built a dipole antenna for it. I know that I should mount it verticaly, but was wondering about horizontal mounting it (ie: under the eve of the house). Would this effect range, etc? I have no problem mounting it vert, but I'm sure the Wife would like it hidden better. Also, how high should I mount it above ground? Thanks!

Tom Straub

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To answer your question, I would like to teach for a second first. A dipole antenna mental picture is a single line with an interruption in the middle. A feed wire is attached in the middle. now a mental picture how the radiation pattern looks. Remove the wires in the middle but keep the two wires in the same plain. Lets put one end up and the other end down towards the ground. Now from above the wires draw a circle around the wires. This is what is known as an omni-directional pattern. This donut of RF energy is at 90 degrees to the wires and centered on the wires and the gap between the two wires. This is a vertical antenna. Now turn the wires so that they are still in a line with the gap in the middle, but the wires run parallel to the ground. Now we have a horizontal antenna. But the radiation pattern is directional. With most of the power at 90 degrees to the wires and very little power off of the ends of the wires. So, there is only two points that most of the energy will be received. We call this a beam antenna. But with more wires in parallel to the driven elements we can force the back lope to the front and have a true beam. We call those antennas a yagi, much like the old TV antennas on houses a few decades back.

So to answer your question there will be no gain going horizontal. But you will limit the area that will have signal. Also note that there is a signal loss between one antenna vertical and one horizontal (transmitter / receiver).

Edited by Max-Paul
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Tom, stick with vertical, because horizontal polarization will drop your signal about 30dB for cars that use vertical polarization

For home receivers, you would go horizontal.

Greg

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I've been wondering when someone would come along with the Cliffs notes version of that Max said... :D;):D

Edited by George Simmons
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Okay, quick question.  Made dipole out of white PVC, and want to know if painting it will effect things very much?

 

Thanks

 

Tom Straub

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Ah, Ha, there's your range problem. Electrons dont conduct well with plastic. Need some wire there Tom to make them little electrons scream down and make a magnetic wave. :D

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Funny Max :rolleyes:   Okay, new question.  Does anyone know of a way to get the RDS signal to be read in Windows 7?  I do have an TV/FM card installed, but thus far can't really test the RDS feature of the EDM transmitter.  None of my vehicles have this on their radios.

 

Tom Straub

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