[SI-LIST] Re: loop antenna (mis)behavior
- From: "Andrew Ingraham" <a.ingraham@xxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 28 May 2008 22:26:52 -0400
> Here's the problem: there is absolutely no phase change in either RX
> antenna. That is, they are at 0 degrees phase, relative to one another.
> Changing polarity on either RX antenna does not affect the relative phase,
> where the expected phase shift would then be 180 degrees.
Sounds like you've got something like electrostatic coupling between antenna
wires and they're not acting like loops at all. Try shorting out the RX
loop and see if the signal changes.
Are the RX antennas balanced ... are their loads balanced? And the TX
antenna?
Regarding the near-field behavior ... the near-field (in antenna theory)
extends out a considerable distance, tens of meters. I'm guessing that the
very close-in behavior you see has to do with achieving some magnetic
(transformer-like) coupling when they are so close, which overcomes the
electrostatic coupling you see at greater distances.
Andy
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