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On Sat, 24 Sep 2005 06:21:07 +0000 (UTC), "Reg Edwards"
wrote: Makes a change from so-called SWR meters. Ah Reggie! Hardly, SWR was the second most considered technical hurdle in the development of RADAR. 73's Richard Clark, KB7QHC |
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#2
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Makes a change from so-called SWR meters. Ah Reggie! Hardly, SWR was the second most considered technical hurdle in the development of RADAR. 73's Richard Clark, KB7QHC ================================= Ah Rich!, Yet again you deliberately distort my meaning in your amusing game of 0ne-Upmanship. For the benefit of lurkers, there's a great difference between meters which purport to measure SWR at HF, but do no such thing and tell lies, and probes inserted in waveguides at 3 GHz which tell the truth. ---- Reg. |
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#3
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On Sat, 24 Sep 2005 08:04:34 +0000 (UTC), "Reg Edwards"
wrote: Makes a change from so-called SWR meters. Ah Reggie! Hardly, SWR was the second most considered technical hurdle in the development of RADAR. 73's Richard Clark, KB7QHC ================================= Ah Rich!, Yet again you deliberately distort my meaning in your amusing game of 0ne-Upmanship. For the benefit of lurkers, there's a great difference between meters which purport to measure SWR at HF, but do no such thing and tell lies, and probes inserted in waveguides at 3 GHz which tell the truth. Ah Reggie, Yet again, you deliberately distort my meaning in your amusing game of One-Downmanship. For the benefit of lurkers, there's absolutely no difference between meters which purport to measure SWR at any frequency. You are simply fumbling around with one of your conceits, a troll in the lingua franca of the Internet. What you now describe was a flicker in time between bombs and crashing glass that was quickly discarded as an awkward technique when RADAR went into production. Such troglodyte methods were long gone before you even wrapped your mitts around a magnetron. If we pursue this with your absurd reductionist habit of arguing blind absolutes in place of practical reality (something Lord Kelvinator would sneer at as a foppish mannerism); then what you describe as "probes" are measuring nothing about SWR but are doing what any probe could accomplish: measuring a common unit of voltage, or current (and only by inference of the actual through rectification and filtering). The SWR only arrives by a second (or significantly more than two) reading, and then FURTHER only after various calculations. Even then, barring calculations (something no one does except squinty-eyed scientists and trolls), those same METERs employed were marked in SWR. Imagine, within very few months of RADAR emerging from the lab, SWR METERs ruled the production line, and the field kit. And to be sure, did they measure SWR? As much as any instrument and to your fulminating frustration, to no obvious difference that would be observed by Maxwell's demon (or Schrodinger's cat) craftily turned to this mischievously scientific validation. SWR arrived in its full glory of attention with RADAR. They were born simultaneously and absolutely no one gave a fig before on this topic. Further, it taught a generation of engineers the importance of matching production designs (which had been long inbred into the AC power production community - simply a rediscovery of a "truth" that had never been lost). This was probably because the consequence of SWR is so dramatic in the 100s of KW, when it occurs in the locality of the workbench in a system as small as the span of your arms. Even the Old Wives notice it if they, in error, try to microwave a product wrapped in a crumpled foil such as butter is wrapped. Their startled reaction evokes an immediate response, just as my post caused your knee to jerk reflexively beneath your apron. 73's Richard Clark, KB7QHC |
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#4
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Rich, you sure have an extensive vocabulary.
But try as I can, I can't make any sense out of your long message about what can only be a trivial matter of your chosen ideas of gamesmanship. Kaput! I give up. ---- Yours, Punchinello, G4FGQ. |
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#5
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On Sat, 24 Sep 2005 18:07:19 +0000 (UTC), "Reg Edwards"
wrote: But try as I can, I can't make any sense out of your long message Ah Reggie, As Dr. Johnson would paraphrase himself "claims of illiteracy is the last refuge of the troll." [Not to deny that you are in plenty of company - but you would shrug off that association.] This is notable in that you assert: about what can only be a trivial matter which, of course, means you understood enough not to be able to deny Lord Kelvinator harrumphing at your feigned attitude. It is an ill fitted cloak. of your chosen ideas of gamesmanship. This is the truly amusing part, you deliberately raised two topics (nothing had to be said about SWR meters, certainly - that injection is your trademark invitation), and you had two respondents answering to each of them. Even the sewer rats of Rio could see that you considered the more interesting topic as the one that you have now three times pursued. Such are the games being played, bucko! ;-) C'mon, if I hadn't responded you would have been sorely disappointed and would have had to sneer at David as an american suck-up trying to soothe an olde codger. You need a lightning rod to keep your current flowing and your response is the thanks I get. You're welcome, Old Son! 73's Richard Clark, KB7QHC |
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#6
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Reg Edwards wrote:
Makes a change from so-called SWR meters. Ah Reggie! Hardly, SWR was the second most considered technical hurdle in the development of RADAR. 73's Richard Clark, KB7QHC ================================= Ah Rich!, Yet again you deliberately distort my meaning in your amusing game of 0ne-Upmanship. For the benefit of lurkers, there's a great difference between meters which purport to measure SWR at HF, but do no such thing and tell lies, and probes inserted in waveguides at 3 GHz which tell the truth. ---- Reg. Sorry, I don't see any difference between making voltage measurements with a directional coupler and calculating SWR through meter calibration and making voltage measurements on a slotted line and calculating SWR with a calculator or pencil and paper. Best I can tell is you are saying there is no such thing as a SWR meter. That's like saying there is no such thing as an airspeed meter in an airplane; the meter really measures air impact pressure. If that is your point, so what? -- Jim Pennino Remove .spam.sux to reply. |
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#7
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Jim,
To measure SWR on the line it is necessary to place the SWR meter at the antenna end of the line. Even then it gives the correct answer only when the line impedance is 50 ohms. But the SWR meter is always placed immediately adjacent to the transmitter. Whatever the meter indicates it is not SWR because there is no line on which to measure it. The meter is telling lies. The meter indicates only whether or not the transmitter is loaded with a resistance of 50 ohms. Which is ALL you want to know. It tells you nothing more and nothing less. This is, of course, a very valuable function of the instrument. But it is NOT behaving as an SWR meter. Its name should be changed to Transmitter Loading Indicator (TLI). To use the name "SWR meter" and to imagine it is actually measuring an SWR is seriously misleading and is a source of confusion about what is really going on. It is why there are perpetual arguments and misunderstandings about SWR, tuners and related matters on this newsgroup and in every other place. Change the name to TLI, which is what it really does. Novices will not be lead astray, clear thinking will prevail, false ideas will not take root to remain embedded for the remainder of one's radio career. Air pressure indicators instead of airspeedometers are OK because air pressure actually exists. SWR meters are NOT OK because there is no line for SWR to exist on. (At least not where the meter is imagined or supposed to measure it.) Makes a change from cavity magnetrons. ---- Reg. |
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#8
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On Sun, 25 Sep 2005 03:44:00 +0000 (UTC), "Reg Edwards"
wrote: Ah, Reggie, and Richie---- You two ought to go on the road together--your humor beats Bob Hope's hands down. You'd have em laughing their guts out in the aisles! Walt, W2DU |
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#9
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Reg Edwards wrote:
Jim, To measure SWR on the line it is necessary to place the SWR meter at the antenna end of the line. Even then it gives the correct answer only when the line impedance is 50 ohms. Well, duh. Anyone that doesn't know that SWR is with reference to a stated impedance or that SWR is influenced by the characteristics of a real transmission line just isn't paying attention. But the SWR meter is always placed immediately adjacent to the transmitter. Whatever the meter indicates it is not SWR because there is no line on which to measure it. The meter is telling lies. Errr, no, the meter is telling what it sees at the point of measurement. If the measurer is so opaque that he/she doesn't take line influences into account, it is hardly the fault of the measuring instrument that what is reported is not the SWR of the antenna at the specified impedance. The meter indicates only whether or not the transmitter is loaded with a resistance of 50 ohms. Which is ALL you want to know. It tells you nothing more and nothing less. Basically true given the stated conditions, and all that is probably of interest for the average ham. This is, of course, a very valuable function of the instrument. But it is NOT behaving as an SWR meter. Its name should be changed to Transmitter Loading Indicator (TLI). Uttern nonsense; the instrument is still behaving as a SWR meter but the user is not applying it per spec and not correcting measurement error caused by line position. By this logic we have a lot of names to change. For starters: PAM has to change the name of their cooking spray to: Teenage looser get high in a can. Screwdriver manufacturers have to change the name of their product to: General prying instrument and paint can lid removal tool. You may add others. To use the name "SWR meter" and to imagine it is actually measuring an SWR is seriously misleading and is a source of confusion about what is really going on. Nonsense, the meter is always measuring SWR but the user is obviously not measuring the SWR that would be seen at the end of the line. You can't fault the instrument for it's misuse by the ignorant. What would you call a low impedance voltmeter used by some nimrod to measure voltage in a high impedance circuit? It is why there are perpetual arguments and misunderstandings about SWR, tuners and related matters on this newsgroup and in every other place. That is probably true since most people are opaque as to what goes on on a real transmission line, but not everyone is. Change the name to TLI, which is what it really does. Novices will not be lead astray, clear thinking will prevail, false ideas will not take root to remain embedded for the remainder of one's radio career. Clear thinking would demand that the influences of a real line on the observered SWR at an arbitrary point be explained. Air pressure indicators instead of airspeedometers are OK because air pressure actually exists. Non sequitur; SWR actually exists. Getting an accurate measurment is another issue and a matter of education. SWR meters are NOT OK because there is no line for SWR to exist on. (At least not where the meter is imagined or supposed to measure it.) Nonsense. Makes a change from cavity magnetrons. More nonsense and not even a sentence. About the only difference between microwave and HF is that it is a lot easier to build a line, i.e. waveguide, that approximates a theoretical ideal lossless transmission line for reasonable distances at microwave than it is to build lossless coax as commonly used at HF. All the theory remains the same. Personally, I have never had any problem with understanding what it is that a SWR meter displays. ---- Reg. -- Jim Pennino Remove .spam.sux to reply. |
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#10
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Errr, no, the meter is telling what it sees at the point of
measurement. ===================================== But the meter is not seeing an SWR because an SWR does not exist. Where is the 50-ohm transmission line on which the SWR is imagined or supposed to lie? As you are unable to answer that question, the remainder of your argument (which, as I say, arises because of the SWR meter misleading misnomer) falls flat on its face. You are an intelligent person. I don't doubt you have no problems with understanding what the so-called SWR meter really indicates. But you didn't learn this from observations of the SWR meter - as you already know it tells lies! Just to reiterate, the so-called SWR meter indicates only whether or not the load on the transmitter is a resistive 50 ohms. If it is not 50 ohms it will not tell you what it actually is. Not that you need to know what it actually is because you will readjust your tuner, without thinking about it, to make it equal to 50 ohms. Which corresponds to no deflection of the meter needle. The TLI is a very useful and valuable device. It does not lead novices and old-wives (who ought to know better) into false ideas, or cause confusion and misunderstandings within the amateur fraternity. Professionals dismiss SWR for what it is worth anyway. Goodby to SWR except on lines where it matters and where it can be measured. Which, in practice, are very few. --- Reg, G4FGQ. |
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