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Diversity antennas
Tom Rauch W8JI has added to his home page a discussion about diversity
antennas As a known authority on antennas he presents interesting insights regarding my diversity antenna where I show computer results of different polarity gains. His knowledge of antennas is much greater than mine, so if any have shown an interest in my antenna design it would be worth while to read Tom's aproach as to what exactly is happening and why Regards Art Unwin KB9MZ |
Diversity antennas
On Tue, 27 Apr 2010 11:22:59 -0700 (PDT), Art Unwin
wrote: Tom Rauch W8JI has added to his home page a discussion about diversity antennas A link might be helpful: http://www.w8ji.com/polarization_and_diversity.htm -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
Diversity antennas
On Tue, 27 Apr 2010 16:20:56 -0700, Jeff Liebermann
wrote: On Tue, 27 Apr 2010 11:22:59 -0700 (PDT), Art Unwin wrote: Tom Rauch W8JI has added to his home page a discussion about diversity antennas A link might be helpful: http://www.w8ji.com/polarization_and_diversity.htm That page is a ramble. Example: Can someone tell me which line number offers the meaning for Diversity? I am not interested in interpretations of Tom, nor abstractions culled together from disjoint statements. I want to know where (literally, not figuratively) Tom defines what Diversity is. 73's Richard Clark, KB7QHC |
Diversity antennas
On Tue, 27 Apr 2010 18:40:22 -0700, Richard Clark
wrote: On Tue, 27 Apr 2010 16:20:56 -0700, Jeff Liebermann wrote: On Tue, 27 Apr 2010 11:22:59 -0700 (PDT), Art Unwin wrote: Tom Rauch W8JI has added to his home page a discussion about diversity antennas A link might be helpful: http://www.w8ji.com/polarization_and_diversity.htm That page is a ramble. I don't think it was intended to be much more than a discussion of a specific type of single antenna diversity reception plus something about stereo-like diversity. Example: Can someone tell me which line number offers the meaning for Diversity? 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. I am not interested in interpretations of Tom, nor abstractions culled together from disjoint statements. How about my definition? No matter which scheme is used, a diversity reception scheme must demonstrate an improvement in availability, BER, or SNR over a single antenna, or it's not really diversity. I want to know where (literally, not figuratively) Tom defines what Diversity is. He doesn't. I'm rather confused as to his "stereo diversity" which I guess uses the listeners ears and brain as the decision switch or decoder. I think he might be referring to a direct conversion receiver where one channel is quadrature leading and the other is quadrature lagging, resulting in a stereo-like effect. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
Diversity antennas
On Tue, 27 Apr 2010 21:04:15 -0700, Jeff Liebermann
wrote: Example: Can someone tell me which line number offers the meaning for Diversity? 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. So, this is an example of a "straw man" argument (not yours, Tom's): a solution to a problem that is undefined. There are, thus, many solutions that none can refute and why Tom's is the sine qua non is built on a foundation of sand. 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. Well, to Tom's credit, there is ample discussion of that - but that discussion does not answer the question, which means there is no way to test for validity. I am not interested in interpretations of Tom, nor abstractions culled together from disjoint statements. How about my definition? Sorry, Jeff, but unless you are the author of the Wikipedia reference, I cannot answer your question. No matter which scheme is used, a diversity reception scheme must demonstrate an improvement in availability, BER, or SNR over a single antenna, or it's not really diversity. I presume the statement above is your definition. Reducing S+N/N satisfies what you call diversity and provides an example of a self-referential definition in that you appeal to with "SNR." Self referential definitions are logical nulls. In other words, does increasing capture area qualify as diversity for a single antenna? If so, diversity means less noise or a better signal in comparison. What is diverse about ordinary directivity? What is the profit in having two words describe the same thing? Even with an informal presumption of the meaning of diversity, we can both agree that diversity is not also directivity. Or perhaps it is that, and with one characteristic more. This returns us to the question with some refinement: what is diversity in the face of directivity? I have a hunch directivity is a distraction, but that returns us to the original question. I want to know where (literally, not figuratively) Tom defines what Diversity is. He doesn't. I didn't think so and I was asking because I didn't consider it worth the effort to search for something so obscured by the baggage of peripheral discussion. I'm rather confused as to his "stereo diversity" which I guess uses the listeners ears and brain as the decision switch or decoder. I think he might be referring to a direct conversion receiver where one channel is quadrature leading and the other is quadrature lagging, resulting in a stereo-like effect. I will admit this was my interpretation too. Strange how you have to sift the diamonds out of the horse-****. I had worked in this field and built quadrature detectors 40 years ago to the same ends as you describe. Analog TV color detection had been doing it for at least 20 years before that. I suppose there is a metaphor of diversity there, but it came with the subject of quadrature detection as a solution, not as a recent invention. The quad detector is a direct conversion receiver as you say. For other readers: The signal is split through two channels each mixed with the same base-band source, with one feed of the source shifted 90 degrees for one channel. I suppose here we could drop the input splitter and simply feed in two antenna drives. The separate mixer outputs feed separate headphone elements (the classic application way back then) and the brain perceives the signal as existing in a literal 2D (binaural) space. The consequence of this perception is a heightened ability to discriminate one signal from the rest within the bandpass of reception. The bandpass is perceived as a physical left-to-right space and because the classic application was through headphones, this space was also between the ears. For the modern reader, this was like having a spectrum analyzer in your head. This is the classic situation of being able to listen to one conversation in a crowded room full of speakers (the cocktail party problem) without becoming overwhelmed by overlapping dialog. A simple test is when you tune to the signal of interest, any off-frequency signals are perceived as inhabiting this 2D space at a literal off-center. As no two transmissions occupy the exact same frequency (Tom explicitly mentions errors as small as a quarter Hertz), then they lose being at the center of attention. The brain supplies a huge computational engine that computers have yet to match. The topic of Quad detection is cool in its own right, but I don't see how tarting it up with the discussion of Diversity (especially when the term is one of dim provenance) really adds anything. Quad detection read more like window dressing than the clincher to the topic at hand. 73's Richard Clark, KB7QHC |
Diversity antennas
On Apr 27, 7:22*pm, Art Unwin wrote:
Tom Rauch W8JI has added to his home page a discussion about diversity antennas As a known authority on antennas he presents interesting insights regarding my diversity antenna *where I show computer results of different polarity gains. His knowledge of antennas is much greater than mine, so if any have shown an interest in my antenna design it would be worth while to read Tom's aproach as to what exactly is happening and why Regards Art Unwin KB9MZ Sly old Art Unwin alludes to his antenna design and initiates a long technical thread which talks about anything but an Unwin antenna. And how useful is the discussion to the average reader of r.r.a.a.? |
Diversity antennas
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"). 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. A paradox. 73's Richard Clark, KB7QHC |
Diversity antennas
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. |
Diversity antennas
Bill wrote:
On Apr 27, 7:22 pm, Art Unwin wrote: Tom Rauch W8JI has added to his home page a discussion about diversity antennas As a known authority on antennas he presents interesting insights regarding my diversity antenna where I show computer results of different polarity gains. His knowledge of antennas is much greater than mine, so if any have shown an interest in my antenna design it would be worth while to read Tom's aproach as to what exactly is happening and why Regards Art Unwin KB9MZ Sly old Art Unwin alludes to his antenna design and initiates a long technical thread which talks about anything but an Unwin antenna. And how useful is the discussion to the average reader of r.r.a.a.? Not only useful, but more practical to boot. - 73 de Mike N3LI - |
Diversity antennas
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 - |
Diversity antennas
Michael Coslo 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 - Depends on how you define "work". The only scenario I can think of would be if the received frequency was changing slightly for some reason and the two receivers were on slightly different frequencies. -- Jim Pennino Remove .spam.sux to reply. |
Diversity antennas
On Apr 28, 1:53*pm, Michael Coslo 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! |
Diversity antennas
On Apr 28, 3:59*pm, Art Unwin wrote:
On Apr 28, 1:53*pm, Michael Coslo 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 |
Diversity antennas
On Wed, 28 Apr 2010 14:53:09 -0400, Michael Coslo
wrote: I wouldn't know how splitting the signal to two receivers would work. The issue arises at the antenna doesn't it? Ah! The nut of the problem. To my knowledge, diversity forces you to find the signal elsewhere, not in the same spot because it isn't there anymore, or at least not in the same polarization. This last diversity (polarization) is but one of many. It may be solved at the antenna that features multiple polarization capability - here Tom's ramble throws EZNEC against the wall to see what sticks, and he introduces new issues that distract. There is space diversity, time diversity, phase diversity, frequency diversity (and there are more if we consider more modulations) and all we get is the all encompassing "diversity" being hung out to dry. The distractions that I see discussed are problems of combining signal, not in finding signal. Interesting problem there, but hardly something noted to being an issue with an antenna. Someone will correct my misapprehension in this thread if there is one. 73's Richard Clark, KB7QHC |
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. |
Diversity antennas
On Apr 28, 3:42*pm, JIMMIE wrote:
On Apr 28, 3:59*pm, Art Unwin wrote: On Apr 28, 1:53*pm, Michael Coslo 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. |
Diversity antennas
On Wed, 28 Apr 2010 15:51:35 -0700 (PDT), K1TTT
wrote: that any way you combine the rf from two antennas into one you lose the advantages of the diversity of the antennas. I saw that bold statement as well, and then it was treated to a fog of support. At some point, the RF from two antennas must combine by the time it hits our ears. That, or diversity reception means two people listening to two sources and then matching notes - which means the RF from the two antennas combine on the final page draft. So, let me put this forward. Two antennas feeding two separate RF chain amplifiers both chains mixed from a single LO two separate mixers into IF chain amplifiers --- somewhere they have to combine ---- two IFs into two detectors two detectors into two separate audio chain amps each audio chain driving a speaker element. I have (gasp!) interpolated, interpreted, simply guessed, guessed wrong, guessed right, about this single LO. Maybe it was in the detector at the end of the IF chain. Whatever. So, with this duality extending from antenna(s) to speaker(s), is the prohibition against combining the RF from two antennas merely a syllogism? OK, backing up that chain to the concept of two separate RF chain amplifiers. Lets just call it one RF chain amplifier or no RF amplifiers and straight to a mixer. Is the prohibition at the combining of RF from two antennas located at the mixer input? No parallel connection? This is getting ugly because it is not about diversity, and it is not about antennas. 73's Richard Clark, KB7QHC |
Diversity antennas
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 |
Diversity antennas
On 4/28/2010 12:11 PM, Bill wrote:
On Apr 27, 7:22 pm, Art wrote: Tom Rauch W8JI has added to his home page a discussion about diversity antennas As a known authority on antennas he presents interesting insights regarding my diversity antenna where I show computer results of different polarity gains. His knowledge of antennas is much greater than mine, so if any have shown an interest in my antenna design it would be worth while to read Tom's aproach as to what exactly is happening and why Regards Art Unwin KB9MZ Sly old Art Unwin alludes to his antenna design and initiates a long technical thread which talks about anything but an Unwin antenna. And how useful is the discussion to the average reader of r.r.a.a.? It's the amusing part. Totally useless technically, but often comprises nearly 100% of the traffic on this group for days or weeks. tom K0TAR |
Diversity antennas
On Apr 28, 5:51*pm, 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. 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. Tom From my viewpoint which may well be unconventional, may I point out that both elements as well as the array as a whole is resonant and in equilibrium. Thus in reality, you have two separate antennas that are additive and go to the same receiver. The receiver uses the addition of the two current flows or two separate flows thus picking up both linear and non linear signals. So I would suggest that the antenna is therefore sensitive to both . phases( ie in phase and out of phase fields). Ww8ji is of the opinion that the program is in error by virtue of the statement it makes since it is unable to print the truth but doesn't provide evidence of same.I believe he is looking at an array that is not in equilibrium to arrive at his viewpoint. Both elements pick up the same message with one having a delay in time due to phase change regardles of what created it, deflection or other wise. This is no different to viewing both elements as mechanically vibrating and because the array as a whole is in equilibrium both will vibrate in unison Regards Art |
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. |
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 |
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 - |
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 |
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. |
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 |
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. |
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 - |
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. |
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 |
Diversity antennas
On Apr 30, 6:51*pm, Richard Clark wrote:
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 Qrz forum has a new posting that states the USN changed their antennas on the west coast to those tipped from the horizontal for superior results. This is 60 years ago before the advent of antenna computers. I would like to think that they saw the advantages of using two vectors as opposed to just the single one for gravity, which in a way confirms the diversity antenna shown on the unwinantennas page which is sensitive to multi polarities. Ofcourse many on this net will disagree in order to avoid change. Cheers |
Diversity antennas
Jeff Liebermann wrote:
"In my never humble opinion, there`s no way to provide any form of diversity reception improvement with a single antenna, unless one also uses two feeds, going to different receivers, and ending in either a decision awitch or an intelligent combiner." That is my experience too. Space diversity requires 2 or more antennas and receivers. One antenna can serve separate receivers which are connected to cross-polarized feeds using a single reflector for polarization diversity. Or, multiple receivers can be used on a single receiving antenna, but transmission of more than one copy of the desired signal is required, This is how frequency diversity is usually achieved. Two copies of the same program may be modulated on the same carrier if it is shown that the medium treats the sidebands differently so that when one is treated badly the other may be solid. I`ve seen this done with selection of upper or lower sideband from a double sideband transmission. Best regards, Richard harrison, KB5WZI |
Diversity antennas
On May 1, 7:00*pm, Art Unwin wrote:
On Apr 30, 6:51*pm, Richard Clark wrote: 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 Qrz forum has a new posting that states the USN changed their antennas on the west coast to those tipped from the horizontal for superior results. This is 60 years ago before the advent of antenna computers. I would like to think that they saw the advantages of using two vectors as opposed to just the single one for gravity, which in a way confirms the diversity antenna shown on the unwinantennas page which is sensitive to multi polarities. Ofcourse many on this net will disagree in order to avoid change. Cheers well, why don't you just go there and spew your bafflegab about how you can prove that they were right to do that! |
Diversity antennas
someone once wrote:
Qrz forum has a new posting that states the USN changed their antennas on the west coast to those tipped from the horizontal for superior results. This is 60 years ago before the advent of antenna computers. Having been in the navy on both coasts, years ago before the advent of antenna computers, (alert: reality intrudes here) nothing is vertical or horizontal aboard a ship. We had absolutely no antennas that were "tipped from the horizontal" - whatever that means. 73's Richard Clark, KB7QHC |
Diversity antennas
On Apr 29, 1:07*pm, JIMMIE wrote:
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- Hide quoted text - - Show quoted text - I was in the US Navy from 1962 to 1982 and encountered the venerable R-390A receiver on many occasions. By design, the -390 was equipped for diversity if you manipulated some straps on the rear panel. However, the one time that I tried to use a pair of -390s in diversity mode the results were less than spectacular. I was on a ship and we copied an RTTY broadcast that was being keyed on several frequencies, all subject to QSB. I suspect that the combined audio signal, even though it sounded better (less apparent QSB), was degraded by differing path lengths for the two signals, causing timing jitter on the recovered TTY signal. Whatever the reason, performance was worse, not better. "Sal" (KD6VKW) |
Diversity antennas
Sal, KD6VKW wrote:
"Wharever the reason, performance was worse, not better." Sal, thank you for your U.S. Navy service. My experience with diversity was different. At Radio Free Europe we relayed broadcast programs by HF radio before communications satellites existed. We used Hammarlund SP-600 receivers in triple diversity. We found most other receivers deficient. Our receiving sites were remote ffrom our transmitting sites to avoid interference. We used UHF for short haul relay. For HF triple diversity each of the SP-600s was connected via an isolation amplifier with a separate rhombic antenna aimed at its transmitter. Outputs of the three receivers was fed into a Crosby or Pioneer combiner which elected the best signal and rejected the other two. The horizontal rhombics each required four towers because they were laterally spaced about ten wavelengths apart for space diversity at one of the lower allocated frequencies. We, at times resorted to frequency diversity too. The receiver operator listened to both of the sidebands of each transmitted frequemncy and selected the better of the two for reception manually. By selecting the cleanest frequencies and sidebands and using the output combiners to select the instantaneously best of three signals, broadcast quality programs usually prevailed. Best regards, Richard Harrison, KB5WZI |
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