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#21
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Diversity antennas
On Apr 28, 9:19*pm, tom wrote:
On 4/28/2010 6:48 PM, Art Unwin wrote: On Apr 28, 3:42 pm, *wrote: On Apr 28, 3:59 pm, Art *wrote: On Apr 28, 1:53 pm, Michael *wrote: Jeff Liebermann wrote: A link to the Wikipedia page would probably have been sufficient: http://en.wikipedia.org/wiki/Diversity_scheme The problem is that NONE of the diversity schemes mentioned in the Wikipedia article apply to the single antenna example under discussion. *In my never humble opinion, there's no way to provide any form of diversity reception improvement with a single antenna, unless one also has two feeds, going to two different receivers, and ending in either a decision switch, or some form of intelligent combiner. Trying to wrap my mind around this... I wouldn't know how splitting the signal to two receivers would work.. The issue arises at the antenna doesn't it? Indeed, if a single wire antenna would work for diversity reception, wouldn't it then follow that you would not have to use diversity reception? The signal would already be there for you. Seems like a simple test could answer this one. * * * * *- 73 de Mike N3LI - I think the first place to start is to what the actual antenna pattern represents in terms of polarity. For instance, we have two vectors outside the earths boundary thus you must have two vectors inside the arbitrary *boundary. Obviously the gravity vector will be at right angles to the earths surface. The other vector representing the rotation of the earth will naturally be an circular pattern which is the "saucer" pattern portion of the overall pattern, which is what hams mainly use. Thus we have to make the first determination as being what each portion of the pattern represents in terms of polarity, the centre being straight plume field and the bottom circular field which is a rotational vector. Since they are in vector form we can see them as a stream of particles where the two vectors will be additive. It is only then that the problem of different or the same phase factors *can be ascertained. Definitions applied can be approach later. Personally, I view the gravity vector as linear with the other providing a wobberly helical vector i.e circular. but varying angles to the earths surface. Other thinkers will surely disagree, if only to fight over near field over far field! I have no doubt that gravity effects radio waves in the same manner that it has been proven to effect light. The effects are going to be such that unless your signal is passing by a black hole of no practical concern. Have a great day Art. Jimmie Totally wrong! The vector inside the boundary opposes gravity! The particle has a straight line trajectory and does not fall back to earth during that trajectory.The rotary vector supplies spin to the other vector force just as the dimples in an golf ball or the rifling of a firearm barrel. These same vectors are represented by time varying electrical current (straight line) as well as displacement current which generates a vortex by its circular motion. When the current flow is completely outside the surface of the radiator skin depth disappears as does resistance. So the radiator has a skin of tightly bonded particles upon which the straight line trajectory is imposed. Remember, earth gravity has zero effect on propagation inside a arbitrary boundary otherwise straight line projection could not exist. Welcome back, Art! And I'm quite serious. Obviously you are no longer taking your medications or maybe they just let you out. Please keep it up. *I, for one, have missed your lack of connection to reality. *It is very amusing. tom K0TAR Perception is not the same as reality. A mixer in a radio is different than what is required when seeking diversity. The first is the mixing of two different frequencies where diversity requires the mixing of two frequencies of the same except one has a delay. The output of the latter is three traces where the two separate bone vibration of the ears can separate the two and where your middle ear can provide the summation. Your brain supplies the jumper of your choice. Without discovery you can abide with perception and not with change. With discoveries you must accept change. If all is known then one doesn't have to accept change and can exist without a brain by being a follower and not a leader. |
#22
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Diversity antennas
On 4/28/2010 10:52 PM, Art Unwin wrote:
Please keep it up. I, for one, have missed your lack of connection to reality. It is very amusing. tom K0TAR Perception is not the same as reality. A mixer in a radio is different than what is required when seeking diversity. The first is the mixing of two different frequencies where diversity requires the mixing of two frequencies of the same except one has a delay. The output of the latter is three traces where the two separate bone vibration of the ears can separate the two and where your middle ear can provide the summation. Your brain supplies the jumper of your choice. Without discovery you can abide with perception and not with change. With discoveries you must accept change. If all is known then one doesn't have to accept change and can exist without a brain by being a follower and not a leader. Thanks! tom K0TAR |
#23
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Diversity antennas
K1TTT wrote:
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. Yeah, I think I agree with Tom's practical experience/experiment. I certainly do not think that one antenna is going to do this diversity, because if it would, it means that there is no need for any of the diversity systems we know about today, with double antennas, voting and/or dual receivers. Richard's concerns are for the definition, which I think in Art's case, is probably important. 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 side foray here. Did you try binaural receivers? I've heard of them, never had a chance to listen to one. 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. I agree. One of the important factors as far as I know is that the antennas have to be in two different spots, and although I haven't measured, (I will now that I'm really interested) I'll bet that the best performance comes at a distance that is well related to the wavelength. Which is to say the picket fencing I hear on a mobile two meter signal might allow me to determine his velocity by knowing the frequency of the picket, the frequency of the transmission, with a likely but small error via Doppler shift. But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. - 73 de Mike N3LI - |
#24
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Diversity antennas
Michael Coslo wrote:
K1TTT wrote: 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. I agree. One of the important factors as far as I know is that the antennas have to be in two different spots, and although I haven't measured, (I will now that I'm really interested) I'll bet that the best performance comes at a distance that is well related to the wavelength. Which is to say the picket fencing I hear on a mobile two meter signal might allow me to determine his velocity by knowing the frequency of the picket, the frequency of the transmission, with a likely but small error via Doppler shift. But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. - 73 de Mike N3LI - For diversity, something which you can take advantage of has to be different between signals from two antennas. They can be at the same physical location but, for example, have different polarization (polarization diversity). Or they can be physically separate (space diversity). However, a key necessity is that the signals from the two can't be phase coherent if you're combining them. That means you have to separately detect the two signals with receivers that aren't phase coherent -- you can't use a single LO for both -- then combine the signals after detection. If you do try to connect the antennas together or convert/detect them with the same LO, you'll simply have a single phased array antenna system. If you're not combining them, but listening to one or the other but not both at the same time based on some sort of voting system, you can detect/convert them any way you want, including using the same LO. Roy Lewallen, W7EL |
#25
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Diversity antennas
Michael Coslo wrote:
I agree. One of the important factors as far as I know is that the antennas have to be in two different spots, and although I haven't measured, (I will now that I'm really interested) I'll bet that the best performance comes at a distance that is well related to the wavelength. Which is to say the picket fencing I hear on a mobile two meter signal might allow me to determine his velocity by knowing the frequency of the picket, the frequency of the transmission, with a likely but small error via Doppler shift. But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. Actually, the antennas can be co-located, they just have to have different patterns. There are some researchers in France who did a lot of work using an active whip next to an active loop. A pair of crossed dipoles would probably also work, which would have the advantage that you could use one of them to transmit with. |
#26
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Diversity antennas
On Apr 29, 12:30*pm, Michael Coslo wrote:
K1TTT wrote: 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. Yeah, I think I agree with Tom's practical experience/experiment. I certainly do not think that one antenna is going to do this diversity, because if it would, it means that there is no need for any of the diversity systems we know about today, with double antennas, voting and/or dual receivers. Richard's concerns are for the definition, which I think in Art's case, is probably important. * 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 side foray here. Did you try binaural receivers? I've heard of them, never had a chance to listen to one. 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. I agree. One of the important factors as far as I know is that the antennas have to be in two different spots, and although I haven't measured, (I will now that I'm really interested) I'll bet that the best performance comes at a distance that is well related to the wavelength. Which is to say the picket fencing I hear on a mobile two meter signal might allow me to determine his velocity by knowing the frequency of the picket, the frequency of the transmission, with a likely but small error via Doppler shift. But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. * * * * - 73 de Mike N3LI - When I was an ET in the Air Force I had a TDY assignment attached to a project with Hughes. They were attempting to to implement in software what Tom was doing in wetware. The purpose was to send high speed(at the time) radar data over HF SSB . The project was a success but the final implementation was very different from "stereo diversity" basically because they could not program a computer to do what the brain can do very easily. Jimmie |
#27
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Diversity antennas
JIMMIE wrote:
But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. - 73 de Mike N3LI - When I was an ET in the Air Force I had a TDY assignment attached to a project with Hughes. They were attempting to to implement in software what Tom was doing in wetware. The purpose was to send high speed(at the time) radar data over HF SSB . The project was a success but the final implementation was very different from "stereo diversity" basically because they could not program a computer to do what the brain can do very easily. these days, though, it's pretty straightforward.. The whiz-bang MIMO stuff you see in 802.11n, for instance is one flavor of diversity. Two antennas at each end gives you 4 possible paths (A:1, A:2, B:1, B:2) each of which will have different fading and interference properties. |
#28
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Diversity antennas
Jim Lux wrote:
Michael Coslo wrote: But aside from that little foray, I have no doubt that the effects that call for diversity antennas/receivers also call for some physical separation of separate antennas. Actually, the antennas can be co-located, they just have to have different patterns. There are some researchers in France who did a lot of work using an active whip next to an active loop. A pair of crossed dipoles would probably also work, which would have the advantage that you could use one of them to transmit with. Okay, but I'd have to modify (my statement) that as there would have to be some difference in the antennas, even if co located. Some sort of difference that would make one antenna receive some particular signal better than another one. The crossed dipoles are an good example. As Roy pointed out, it depends on the parameter in question. - 73 de Mike N3LI - |
#29
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Diversity antennas
On Apr 29, 4:30*pm, Michael Coslo wrote:
K1TTT wrote: 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. Yeah, I think I agree with Tom's practical experience/experiment. I certainly do not think that one antenna is going to do this diversity, because if it would, it means that there is no need for any of the diversity systems we know about today, with double antennas, voting and/or dual receivers. Richard's concerns are for the definition, which I think in Art's case, is probably important. * 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 side foray here. Did you try binaural receivers? I've heard of them, never had a chance to listen to one. i tried a few combinations of audio high pass/low pass and different ssb in each ear. there are some interesting effects you can get that way that give you spatial effects as you tune across the band. you can get the feeling that the signals come in one ear and out the other as you tune across them... interesting once you get used to it on cw, but probably not much use on other modes. |
#30
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Diversity antennas
On Fri, 30 Apr 2010 16:20:48 -0700 (PDT), K1TTT
wrote: i tried a few combinations of audio high pass/low pass and different ssb in each ear. there are some interesting effects you can get that way that give you spatial effects as you tune across the band. you can get the feeling that the signals come in one ear and out the other as you tune across them... interesting once you get used to it on cw, but probably not much use on other modes. RTTY might have a ping-pong game on acid effect. 73's Richard Clark, KB7QHC |
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