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Old 1-Apr-2011, 7:11 PM   #3
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Join Date: Mar 2011
Location: anaheim, ca
Posts: 13
Originally Posted by Dave Loudin View Post
You are onto something, but don't think of it as a match to the transmission line. Think about how the signals received by the different elements add up in strength and in phase (the underlying principle of antenna design.) This page at Ken Nist's site has excellent pictorial descriptions of what you're after.
Just to clarify what I said. I looked at Ken Nist's site and he does discuss why larger antenna sometimes don't work any better. It's due to the non-uniform field. Imagine that you are transmitting from your antenna. What signal do I have to feed it to produce all those multiple multipath signals coming from different directions? A very complex signal with significant imaginary components along with the real components. This implies the antenna impedances vary significantly. Based on reciprocity, the reception of the multipath signals also has the same complex impedances. If there is a poor match to the 300 ohms or 75 ohms transmission line then there is reflection (known as high VSWR). This was what I was trying to say in my original post.
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