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Diversity antennas
On Apr 28, 6:45*pm, Michael Coslo wrote:
Richard Clark wrote: On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote: how useful is the discussion to the average reader of r.r.a.a.? Hi Bill, Well, diversity antenna work is quite useful to the average reader - I suppose (they haven't actually clamored for the discussion or embroiled themselves in the topic, but you did couch this in terms of "readers"). Sure, at least in a practical sense. I make use of diversity receivers in wireless microphone work. While these are used at UHF frequencies rather than HF, our problems are more multipath, maybe picket fencing a bit. So while I know better than to get into the definitions of diversity antennas, given my meager abilities, *my guess is that if one antenna worked better than two - or merely worked at all, we'd be using just one. Tom's pseudo stereo looks suspiciously like a wetware version of my wireless systems,only that they vote, whereas his signal levels are too low for that, so he does it in his head. Unfortunately, if we divorced the two authors who fail to offer what Diversity means, apart from what is already accepted in convention, then we remove the entertainment value and "readership" would likely decline. That is for certain. A paradox. One of my favorite words. if the pseudo stereo is derived from 2 different antennas then you have diversity reception where the separate antennas provide different signals that may fade at different times due to polarization changes or incident angle changes... that is what tom was driving at as a useful diversity system, albeit at the expense of more complex receiver hardware. when you take a single rf signal and split it through different receive processors to shift the phase, or do different sidebands, or just run through different high/low pass audio filters, you don't really have diversity, you have some kind of a processing system that makes it easier for your brain or some other decoder to sort out the signal from the noise. I played with some simple ones years ago and they can provide interesting effects that can make sorting out signals in pileups easier, or maybe pulling signals out of the noise a bit easier, but none of them will really prevent the multipath, arrival angle, or polarization fading. that is where tom was trying to point out that any way you combine the rf from two antennas into one you lose the advantages of the diversity of the antennas. |
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