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"Richard Clark" wrote in message ... On 19 May 2006 03:26:29 -0700, wrote: I do not agree with you on antenna linearity, but that is another subject for another rainy weekend, and I'm not the right person to be discussing that anyway. Hi Glenn, By this very post you are discussing it. Who, in your estimation, does qualify to discuss it? Despite all outward appearances (and certainly the troll inspired name of the topic), this is NOT about one-upmanship competition. 73's Richard Clark, KB7QHC don't you call me a troll... i just set the stage with an aptly named thread to get things started for my own amusement... wait a minute, maybe that does make me a troll! but at least i was open about my motives, and boy am i enjoying it.... especially since its still raining! maybe you guys can keep going through this weekend??? |
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Cecil Moore wrote:
wrote: By 'simple antenna' I mean an antenna such as a wire dipole without traps, baluns or other things that could degrade linearity. Seems the easiest measurement of nonlinearity would be the harmonics (if any) generated by the antenna that do not appear in the source signal. Which wouldn't tell you a single thing about the current distribution along the length of the dipole. 73, Tom Donaly, KA6RUH |
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Richard Clark wrote:
On Fri, 19 May 2006 15:08:11 GMT, "Tom Donaly" wrote: Stokes' law and the Raman effect can be found in physics texts dealing with quantum mechanics. Georg Joos, in his book _Theoretical Physics_ deals with such things. The reading is dense but the underlying concepts aren't too difficult. The difficulty might lie in understanding how they apply to this discussion. Hi Tom, Certainly Joos would give some entry into the field, but finding work as accessible outside of a bookstore or library (in other words, through a search engine) makes for drinking out of a fire hose to quench a sip's worth of thirst. Insofar as HOW this applies, I've spoken to that and Tom shows interest. That alone goes beyond the typical churning that passes for discussion. The point is that these underlying concepts are fairly simple as you imply and they are certainly not remote from the usual topics of consideration here. What they lack is specifics that relate to our common applications, and there too I've offered discussion. However, few seem inspired to travel those paths and that fault can hardly be laid at my doorstep. 73's Richard Clark, KB7QHC Hi Richard, I didn't intend any criticism. People like Cecil, with home-grown theories, don't ever seem to want things considered in depth. That's understandable from a psychological standpoint, but it isn't any help to the rest of us when some of the things the theory ignores become significant. In the case of antennas, practically everything is significant. 73, Tom Donaly, KA6RUH |
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Reg,
Thank heavens there is someone here who knows the Queen's English. Glenn ======================================== The trouble with Richard is that he wraps everything up in Shakespearian prose, verse and poetry. The sonnets. Queen Elizabeth the First's language. ---- Reg. |
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On Fri, 19 May 2006 19:01:23 GMT, "Tom Donaly"
wrote: In the case of antennas, practically everything is significant. Les Mots Juste ;-) |
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Richard Clark wrote:
On Fri, 19 May 2006 15:08:11 GMT, "Tom Donaly" wrote: Stokes' law and the Raman effect can be found in physics texts dealing with quantum mechanics. Georg Joos, in his book _Theoretical Physics_ deals with such things. The reading is dense but the underlying concepts aren't too difficult. The difficulty might lie in understanding how they apply to this discussion. Hi Tom, Certainly Joos would give some entry into the field, but finding work as accessible outside of a bookstore or library (in other words, through a search engine) makes for drinking out of a fire hose to quench a sip's worth of thirst. Insofar as HOW this applies, I've spoken to that and Tom shows interest. That alone goes beyond the typical churning that passes for discussion. The point is that these underlying concepts are fairly simple as you imply and they are certainly not remote from the usual topics of consideration here. What they lack is specifics that relate to our common applications, and there too I've offered discussion. However, few seem inspired to travel those paths and that fault can hardly be laid at my doorstep. 73's Richard Clark, KB7QHC And a web search produced a couple very good links out of the first 20. One was a great discussion of problems in long optical fibers, and some relatively simple ways to work around some of them, or at least to mitigate them. tom K0TAR |
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On Fri, 19 May 2006 14:24:07 -0500, Tom Ring
wrote: And a web search produced a couple very good links out of the first 20. One was a great discussion of problems in long optical fibers, and some relatively simple ways to work around some of them, or at least to mitigate them. Hi Tom, In my early days in this game (late 80s), I sought to turn lemons into quantum-aide. That is, I sought erbium doped fiber optics to amplify nanowatt fluorescence signals with 10 to 50 µS decay times. Not one of those off-the-shelf commodities, however; so I had to amplify in the conventional way with an PMT. For those interested, long haul communications fiber optics (transoceanic grade) met with the same requirements for amplifiers placed along the length to maintain S+N/N. Erbium doped fibers were projected as a solution. You could pulse UV into the fiber to charge it, and a IR data pulse would be amplified, continuously along its length. The IR data pulse would be boosted by the previous charge of energy. This is an example of forward Raman scattering and is called Raman Amplification (which at the time would have been about 30dB and 10% efficient). 73's Richard Clark, KB7QHC |
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Tom Donaly, KA6RUH wrote:
"Actually, it`s supposed to be impossible to represent the current distribution along a dipole using simple mathematical formulas because integral equations have to be solved that are impervious to any solution other than numerical approximation." How many places do you attach to pi? First, what is linearity? It is the absence of nonlinearity. Millman and Seely wrote on page 525 of the 1951 edition of "Electronics" (one of my old textbooks): "Because of this nonlinear characteristic of the dynamic curve over the operating range, the wave form of the output wave differs slightly from that of the grid-exciting-voltage waveshape. Distortion of this type is called "nonlinear" or "amplitude" distortion.." All of the antennas I`ve worked with had no noticeable amplitude distortion. They caused no harmonics or mixing products. On page 235 of Kraus` 1950 edition of "Antennas" he sets out to solve Hallen`s equation for current distribution. On page 239, Kraus writes: "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, and that the phase is constant over a 1/2-wavelength interval, changing abruptly by 180-degrees between intervals." You can take what Kraus says to the bank. Best regards, Richard Harrison, KB5WZI |
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