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On Fri, 14 Oct 2005 16:18:04 GMT, Cecil Moore wrote:
Another one of your rounding errors like where light 10 times brighter than the sun is black. I see you understand this subject just as well as you understood that one. Ah! you've seen the light then. |
On Fri, 14 Oct 2005 16:16:39 GMT, Cecil Moore wrote:
Is a zero length of 50 ohm coax sufficient For angels to hold a convention in? You hit a oil patch on that turn in the road, your logic is in the ditch now. |
"Dave" wrote in message . .. "Cecil Moore" wrote in message . com... Tam/WB2TT wrote: "Cecil Moore" wrote: The actual SWR on a lossless line doesn't change. Yet, in another posting, I showed that moving the Bird 1/4WL closer to the load caused a reported SWR change by the Bird from 1:1 to 2.25:1. How could both results possibly be right? The Bird does not know squat about transmission lines, foreward, or reflected. It only cares about impedance. If you connect a 50 Ohm load to it through 1/4 wave of 75 Ohm coax, the impedance the Bird sees will be transformed to 112.5 Ohms; hence the 2.25 SWR. (Actually, a 2.25:1 impedance ratio) Yes, that's exactly what I said in the other posting. But some people seem to believe that inserting a Bird into a transmission line with a Z0 other than 50 ohms magically changes it to a 50 ohm environment. The 40mm of transmission line inside the Bird is supposed to accomplish that miracle. yep, that is true, and that is what the experiment shows. the 50 ohm load, even though it is caused by a 75 ohm line, is far enough away from the sensor that it sees it as 50 ohms. so the 'miracle' length is obviously less than 40mm. Specifically, the "miracle length"is 0. My SWCad simulation assumes 0 length interconnects, 0 spurious capacity, and 0 spurious inductance. Also, I might add, near infinite bandwidth. In fact, it should work at DC. Haven't tried that, but it works the same at 100 Hz as 100 MHz.. It gives generally accepted answers. Tam |
"Cecil Moore" wrote in message m... Richard Clark wrote: On Fri, 14 Oct 2005 00:51:02 GMT, Cecil Moore wrote: Sorry, I am just quoting Owen's results. There is nothing in his entire scope of postings that presents: There was 4.1667 watts of reflected energy flowing back through the Bird. Which is absurd. The SWR on the 75 ohm line is 1.5:1. If 100 watts is delivered to the load, there's 4.1667 watts of energy reflected from the load and flowing back through the Bird. The Bird doesn't see it because the Bird is calibrated for the wrong Z0. Owen has demonstrated quite clearly that your assertion It takes a certain length of feedline to establish a Z0 environment is blarney from one end of your feedline to the other. Really? They why bother with characteristic impedance at all? If Z0 doesn't establish a Z0 environment, then all transmission lines are just alike and transmission theory is hogwash. -- 73, Cecil http://www.qsl.net/w5dxp Cecil, I can't figure out which side you are on. There is no Z0 environment set up; the Bridge is balanced for a chosen Z0, actually R0. Tam/WB2TT |
Richard Clark wrote:
Cecil Moore wrote: Another one of your rounding errors like where light 10 times brighter than the sun is black. I see you understand this subject just as well as you understood that one. Ah! you've seen the light then. Please tell me that you have figured out how the irradiance in the 1/4WL thin-film can be greater than the incident irradiance when reflections are completely canceled. -- 73, Cecil http://www.qsl.net/w5dxp |
On Fri, 14 Oct 2005 18:26:56 GMT, Cecil Moore wrote:
Please tell me that you have figured out how the irradiance in the 1/4WL thin-film can be greater than the incident irradiance when reflections are completely canceled. How amusing. This dovetails with your own proof (sic) - HERE - how the Bird has failed to sense that very lack of cancellation looking into a quarterwave section that offers a perfect match to the Bird. As I said, you lost your logic on the first bump in the road you took. This is an amusing irony of where you have found power where you have always posited there is none, and where you have rejected there is power when it has been shown to exist. Each example exposes your lack of experience in the scale of the error and its relation to the equipment measuring it. And both times it has come at the topic for which you have absolutely no experience with at the bench. Your arguments are exhibits of the failure of third hand-off quotes bolstered by Xeroxed citations. They all come out of books that are suitable catechisms for puttering students and doddering intellectuals, and they fail in the face of obvious results demonstrated at the bench. Of course, this is advanced topics I am speaking of when we get to the reality of actual results, and no doubt it shakes your Sunday school sophistication of faith in a comic book level of practice. I will now leave you with your sputtering attempt to recover. ;-) |
"Cecil Moore" wrote in message m... Richard Clark wrote: Cecil Moore wrote: Another one of your rounding errors like where light 10 times brighter than the sun is black. I see you understand this subject just as well as you understood that one. Ah! you've seen the light then. Please tell me that you have figured out how the irradiance in the 1/4WL thin-film can be greater than the incident irradiance when reflections are completely canceled. -- ah, back to something only cecil would care about... guess the v/i discussion is over now. |
On Fri, 14 Oct 2005 18:44:06 -0000, "Dave" wrote:
guess the v/i discussion is over now. Hi Dave, It may have been tailored in that vernacular, but it was actually never about that at all. As the last "thin-film" comment reveals, it has always been about how one mind can encompass two contradictory positions (total cancellation - non total cancellation) about the same mechanism (a quarterwave matching section). In other words: A Troll. The humor here is that supposedly the thin-film offers "total" cancellation for the same reason that the quarter wave from this bench test does not. :-) In fact, neither exhibit "total" cancellation, but to maintain the charade one or the other does, then that charade must fail, and these recent arguments have just revealed that fracture. Some time ago I offered results from the bench in just how much light was in fact returned from a thin-film section, and this was rejected as impossible - hence the allusion to brighter than the sun light being rendered as black to satisfy this illusion of "totality" in cancellation. This reflected light was buried in the digits, but still and all, far brighter than the sun (such is the vast range of accommodation that the eye offers as a measuring device). On the flip side, any leakage (reflection back) from a quarterwave section suffers identical issues. Those reflections are buried in the digits too. This is orders of magnitude different from the speculated 4.17 watts which is a farrago. Does a Bird have the same scope of resolution as the eye? Hardly. The inherent error of the meter at ±5% vastly overwhelms such products (the eye does not suffer such error for other reasons - imagine what a driver's eye-check test would be like if it did). So, to advance this itinerant concept of Owen's demonstration not busting the myth of the requirement for line sections, this troll has diverged from the topic to haul out a spurious argument that is in direct conflict with other discussions of the same topic, from the same troll. It necessarily demands a villain to suit the melodrama offered. That villain is the Bird and its failure is to reveal a power. Left unsaid is that actual power is, as I said, buried in the digits and wholly irresolvable. Further, it is NOT the claim of 4.17 watts which was rummaged up. The Bird would be incapable of resolving the actual reflection products from a real quarterwave section. Thus it cannot absorb the sin of this counter-proof (sic). Let's just say that statements that arbitrarily assign ideal concepts like "totality" suffer across the board - and when these forced assignments are used as the link pin to "theories," then they can lead to amusing contradictions and failures of logic like those we've been witness to here. 73's Richard Clark, KB7QHC |
Richard Clark wrote: On Fri, 14 Oct 2005 18:44:06 -0000, "Dave" wrote: guess the v/i discussion is over now. Hi Dave, It may have been tailored in that vernacular, but it was actually never about that at all. As the last "thin-film" comment reveals, it has always been about how one mind can encompass two contradictory positions (total cancellation - non total cancellation) about the same mechanism (a quarterwave matching section). In other words: A Troll. The humor here is that supposedly the thin-film offers "total" cancellation for the same reason that the quarter wave from this bench test does not. :-) In fact, neither exhibit "total" cancellation, but to maintain the charade one or the other does, then that charade must fail, and these recent arguments have just revealed that fracture. Some time ago I offered results from the bench in just how much light was in fact returned from a thin-film section, and this was rejected as impossible - hence the allusion to brighter than the sun light being rendered as black to satisfy this illusion of "totality" in cancellation. This reflected light was buried in the digits, but still and all, far brighter than the sun (such is the vast range of accommodation that the eye offers as a measuring device). On the flip side, any leakage (reflection back) from a quarterwave section suffers identical issues. Those reflections are buried in the digits too. This is orders of magnitude different from the speculated 4.17 watts which is a farrago. Does a Bird have the same scope of resolution as the eye? Hardly. The inherent error of the meter at ±5% vastly overwhelms such products (the eye does not suffer such error for other reasons - imagine what a driver's eye-check test would be like if it did). So, to advance this itinerant concept of Owen's demonstration not busting the myth of the requirement for line sections, this troll has diverged from the topic to haul out a spurious argument that is in direct conflict with other discussions of the same topic, from the same troll. It necessarily demands a villain to suit the melodrama offered. That villain is the Bird and its failure is to reveal a power. Left unsaid is that actual power is, as I said, buried in the digits and wholly irresolvable. Further, it is NOT the claim of 4.17 watts which was rummaged up. The Bird would be incapable of resolving the actual reflection products from a real quarterwave section. Thus it cannot absorb the sin of this counter-proof (sic). Let's just say that statements that arbitrarily assign ideal concepts like "totality" suffer across the board - and when these forced assignments are used as the link pin to "theories," then they can lead to amusing contradictions and failures of logic like those we've been witness to here. 73's Richard Clark, KB7QHC I think it might also be interesting to discuss the instance in which the Bird is interfaced with a real halfwave section. ac6xg |
Owen wrote:
"The myth that measurements with a Bird 43 of conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself is busted." Bird says the wattmeter can be placed anywhere in the line. That precludes a requirement to have minimum lengths of 50-ohm cable on both sides of the wattmeter. Particular total lengths of line woould be a function of wavelenth. The Model 43 Thruline Wattmeter accurately measures forward or reverse power in transmission lines under any load condition. Regardless of the load impedance, the forward and reflected powers are forced by construction of the coax to conform to Zo. Line volts divided by line amps in either direction has an absolute value of 50 ohms. Bird plug-in elements are designed for insertion into a precision coaxial rigid air line which is a part of the Model 43. Elements are available in a wide variety of frequency ranges and maximum power levels.. Cancellation of response to one direction of power flow while responding to the to the other is accomplished by careful balance of the current and voltage samples within an element. The samples which are in-phase add. The samples for the other direction are out-of-phase and cancel. To make sure cancellation is complete in the undesired direction, Zo must be as specified in the design. Accuracy can`t be expected in the wrong Zo environment. Best regards, Richard Harrison, KB5WZI |
Richard Clark wrote:
This is an amusing irony of where you have found power where you have always posited there is none, and where you have rejected there is power when it has been shown to exist. Each example exposes your lack of experience in the scale of the error and its relation to the equipment measuring it. In exactly the same way that forward power can exceed generated power in a 1/4WL matching section of transmission line, so can the forward irradiance in 1/4WL of thin film exceed the forward irradiance in the air before incidence. That you are still so terribly confused about such a simple fact of light physics is sad. You obviously don't understand the information on the Melles-Groit web page. http://www.mellesgriot.com/products/optics/oc_2_1.htm Please study it until you understand it. -- 73, Cecil http://www.qsl.net/w5dxp |
Richard Clark wrote:
As the last "thin-film" comment reveals, it has always been about how one mind can encompass two contradictory positions (total cancellation - non total cancellation) about the same mechanism (a quarterwave matching section). In other words: A Troll. If the incident irradiance is a single frequency coherent signal, the requirement for TOTAL CANCELLATION OF REFLECTIONS is still that the index of refraction of the 1/4WL thin-film be the square root of the medium upon which it is deposited. QED -- 73, Cecil http://www.qsl.net/w5dxp |
On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote:
It was previously reported that the path through the Bird is 40mm. The path through the Bird is actually about five Cecil, If you are referring to my statement in another thread, it was that the sampling element is about 40mm inside the 50 ohm Thruline section (ie that there is about 40mm of 50 ohm transmission line between the Bird 43 terminals and the sampling element), not as you have stated above. Owen -- |
Jim Kelley wrote:
I think it might also be interesting to discuss the instance in which the Bird is interfaced with a real halfwave section. If the Bird is inserted at a point where the net voltage divided by the net current is equal to 50, apparently a 50 ohm Z0-match is achieved at that point and any length of lossless 50 ohm coax can be inserted without altering the forward/reflected conditions in the adjacent transmission lines. -- 73, Cecil http://www.qsl.net/w5dxp |
Owen Duffy wrote:
On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote: It was previously reported that the path through the Bird is 40mm. The path through the Bird is actually about five If you are referring to my statement in another thread, it was that the sampling element is about 40mm inside the 50 ohm Thruline section (ie that there is about 40mm of 50 ohm transmission line between the Bird 43 terminals and the sampling element), not as you have stated above. I'm sorry, Owen, I took your statement to mean that the total length of path through the Bird is 40mm (1.5") which is not enough length to force a 50 ohm environment. I downloaded the Bird manual this morning and discovered that, unlike an MFJ, the path through the Bird is about 5 inches and coaxial. I apologize to Bird and you Bird experts for that bad assumption. -- 73, Cecil http://www.qsl.net/w5dxp |
That explains why my new tuner failed to work. I have a rotary switch that
selects 40mm of 50, 75,300, 450, and 600 ohm coax. I thought it should match anything! Now I see I have to go to 5" lengths. I should know better than to build anything before all the errata sheets are in. I can use some additional diversion as almost all the soldering iron burns have healed. "Cecil Moore" wrote in message m... Owen Duffy wrote: On Fri, 14 Oct 2005 16:22:39 GMT, Cecil Moore wrote: It was previously reported that the path through the Bird is 40mm. The path through the Bird is actually about five If you are referring to my statement in another thread, it was that the sampling element is about 40mm inside the 50 ohm Thruline section (ie that there is about 40mm of 50 ohm transmission line between the Bird 43 terminals and the sampling element), not as you have stated above. I'm sorry, Owen, I took your statement to mean that the total length of path through the Bird is 40mm (1.5") which is not enough length to force a 50 ohm environment. I downloaded the Bird manual this morning and discovered that, unlike an MFJ, the path through the Bird is about 5 inches and coaxial. I apologize to Bird and you Bird experts for that bad assumption. -- 73, Cecil http://www.qsl.net/w5dxp |
On Wed, 12 Oct 2005 22:09:51 GMT, Owen Duffy wrote:
The myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. All, Can I offer the suggestion that the key to understanding why this is so, it to understand the sampler. I don't have the detail of the physical and electrical parameters of the Bird sampler, however I suspect that like so many other reflectometers, it comes down to a device that samples independently the net current and the net voltage associated with any travelling waves, and those RF samples are in proportion and phase relationship that when algebraicly added and rectified, they produce a DC voltage that is proportional to the power flow in one direction only (provided that Zo is real). The proportions calibrate the instrument for a specific V/I ratio. Apart from mentioning that Zo must be real, and I will address that in another thread, Zo in the region where the sample is unimportant to the "proportion and phase relationship..." bit. Zo of the through line is important only to the extent that you would generally: - not want a significant transformation of impedance between the load terminals and the calibrated sensor at that calibrated V/I ratio. - not want a significant transformation of impedance between the generator and load terminals at that calibrated V/I ratio to minimise disruption to the system being measured. Everyday we use instruments to measure something, somewhere and apply that knowledge to infer something else, somewhere else using appropriate other knowledge. For example, you might measure the voltage drop across a cathode resistor and make some reasonable inference about anode current using appropriate other knowledge. Making measurements with a Bird 43 in one place and inferring the situation somewhere else using appropriate other knowledge is reasonable. For example, I may have an antenna system (say a loop) that uses a transmission line transformer (TLT) to transform the loop terminal Z to 50 ohms. I can attach the generator end of the TLT to the Bird 43, attach the Bird 43 via 50 ohm cable to a transceiver that is rated for a nominal 50+j0 ohm load, and proceed to adjust the antenna / TLT for zero reflected power indication on the Bird 43 knowing that I can reasonably infer that the load presented to the transceiver will be approximately 50+j0 ohms using the knowledge that Bird readings indicate Z at that point is 50+j0 and there will be insignificant transformation on the 50 ohm cable to the transceiver. This is a proper and sound application of the instrument. Did I get that wrong? Did I need to mention environments? Owen -- |
THERE ARE ABOUT 4.17 WATTS OF REFLECTED ENERGY FLOWING BACK THROUGH THE BIRD AND THE BIRD COMPLETELY IGNORES IT. So the Bird is not even yielding valid readings for forward and reflected power through itself. That's exactly what I have been saying all along. If it were calibrated for 75 ohms, it would indicate the correct values. -- 73, Cecil http://www.qsl.net/w5dxp Cecil, With a 1/2 wl of 75 ohm line terminated with 50 ohms at both the source and load end, the 4.17 watts reflected energy does not flow back thru the Bird. With 100 watts incident on the source (Bird), 100 watts will be either radiated, or consumed as heat at the load end. 4.17 will be reflected back to the source. When it reaches the source, a portion will be reflected back towards the load, and a portion consumed as heat. ect. The small portion consumed by heat might account for the 1/2 needle deflection Owen observed on reflected power. 4.17 watts does not flow back thru the Bird as reflected power, and the Bird, of course acknowledges. I don't think the Bird ignores that. I acknowledge that the Bird does not report the actual forward/reverse power in this example Gary N4AST |
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On Fri, 14 Oct 2005 21:23:25 GMT, Owen Duffy wrote:
that when algebraicly added and rectified, they produce a DC voltage that is proportional to the power flow in one direction only (provided that Zo is real). The proportions calibrate the instrument for a Sorry, that should be: "that when algebraicly added and rectified, they produce a DC voltage that is proportional to the square root of power flow in one direction only (provided that Zo is real). The proportions calibrate the instrument for a..." Owen -- |
On Thu, 13 Oct 2005 01:43:48 GMT, Cecil Moore wrote:
and not to be a myth at all. There's 104.17 watts of forward power through the Bird and 4.17 watts of reflected power back through the Bird. Why does the Bird ignore those actual power values? I did not report or even measure such a thing. It is your report based on something that you know or something that you measured without evidence of either measurements or detail of construction. With respect Cecil, the statement is more an elaboration of the myth than convincing support for it. This unsubstantiated premise seems the basis for nearly a hundred posts by many. Owen -- |
Owen Duffy wrote:
On Wed, 12 Oct 2005 22:09:51 GMT, Owen Duffy wrote: The myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Can I offer the suggestion that the key to understanding why this is so, it to understand the sampler. Again Owen, your own experiment using 75 ohm coax on each side of the Bird proved why the above is not a myth. The Bird didn't read the correct forward power on the 75 ohm coax. The Bird didn't read the correct reflected power on the 75 ohm coax. The SWR calculated using the Bird's readings does not represent the SWR on the 75 ohm coax. The proportions calibrate the instrument for a specific V/I ratio. Yes, that ratio is 50 ohms for the Bird. Only a piece of 50 ohm coax will guarantee that Vfor/Ifor=Vref/Iref=50 ohms. You proved that a piece of 75 ohm coax will not do it. Did I need to mention environments? No, but you should have. The Bird gives the correct forward and reflected power readings on the attached coax only in a 50 ohm environment. Your experiment proved that to be true. -- 73, Cecil http://www.qsl.net/w5dxp |
Richard Clark wrote:
Who would approach a Bird and expect it to in the first place? Someone who says that the environment surrounding the Bird doesn't matter? -- 73, Cecil http://www.qsl.net/w5dxp |
Owen Duffy wrote:
Cecil Moore wrote: and not to be a myth at all. There's 104.17 watts of forward power through the Bird and 4.17 watts of reflected power back through the Bird. Why does the Bird ignore those actual power values? I did not report or even measure such a thing. Since I realized the Bird forms a Z0-match at its output that statement should be ammended to say: There 104.17 watts of forward energy flowing in the 75 ohm coax on each side of the Bird and 4.17 watts of reflected energy flowing in the 75 ohm coax on each side of the Bird. Why does the Bird ignore those actual power values existing in the actual system? 100W--tuner---75 ohm coax---Bird--1/2WL 75 ohm coax--50 ohm load Pfor=104.17W-- Pfor=104.17W-- 100W delivered --Pref=4.17W --Pref=4.17W The Bird is not reading the proper values of forward and reflected power on the 75 ohm coax because it is embedded in a non-50 ohm environment. -- 73, Cecil http://www.qsl.net/w5dxp |
On Sat, 15 Oct 2005 03:27:43 GMT, Cecil Moore wrote:
Who would approach a Bird and expect it to in the first place? Someone who says that the environment surrounding the Bird doesn't matter? On Sat, 15 Oct 2005 03:25:26 GMT, Cecil Moore wrote: If the Bird is embedded in something other than a 50 ohm environment, it does not report the actual forward/reverse power on the coax on either side of the Bird. Who would approach a Bird and expect it to in the first place? |
On Sat, 15 Oct 2005 03:37:16 GMT, Cecil Moore wrote:
The Bird is not reading the proper values of forward and reflected power on the 75 ohm coax Who would approach a Bird and expect it to in the first place? |
Richard Clark wrote:
Who would approach a Bird and expect it to in the first place? Someone who says that the environment surrounding the Bird doesn't matter? -- 73, Cecil http://www.qsl.net/w5dxp |
Richard Clark wrote:
Who would approach a Bird and expect it to in the first place? Someone who thinks reflections cannot be eliminated by 1/4WL of thin-film? -- 73, Cecil http://www.qsl.net/w5dxp |
On Sat, 15 Oct 2005 03:58:22 GMT, Cecil Moore wrote:
Someone who says that the environment surrounding the Bird doesn't matter? On Sat, 15 Oct 2005 03:25:26 GMT, Cecil Moore wrote: If the Bird is embedded in something other than a 50 ohm environment, it does not report the actual forward/reverse power on the coax on either side of the Bird. As you are the only one who maintains your own statement above, do you really need a roll-call to differentiate yourself? |
On Sat, 15 Oct 2005 04:00:14 GMT, Cecil Moore wrote:
Who would approach a Bird and expect it to in the first place? Someone who thinks reflections cannot be eliminated by 1/4WL of thin-film? Certainly one who thinks it does. And both having been disproved, it stands to - well, let's just say that fulfilling that trite expression with "reason" fulfills the cliche - but not the tenor. ;-) |
On Sat, 15 Oct 2005 03:37:16 GMT, Cecil Moore wrote:
Owen Duffy wrote: Cecil Moore wrote: and not to be a myth at all. There's 104.17 watts of forward power through the Bird and 4.17 watts of reflected power back through the Bird. Why does the Bird ignore those actual power values? I did not report or even measure such a thing. Since I realized the Bird forms a Z0-match at its output that statement should be ammended to say: There 104.17 watts of forward energy flowing in the 75 ohm coax on each side of the Bird and 4.17 watts of reflected energy flowing in the 75 ohm coax on each side of the Bird. Why does the Bird ignore those actual power values existing in the actual system? 100W--tuner---75 ohm coax---Bird--1/2WL 75 ohm coax--50 ohm load Pfor=104.17W-- Pfor=104.17W-- 100W delivered --Pref=4.17W --Pref=4.17W The Bird is not reading the proper values of forward and reflected power on the 75 ohm coax because it is embedded in a non-50 ohm environment. This has nothing to do with the stated myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Nothing in the myth stated or implied direct application of the measured conditions on the thruline section to any other connected (or disconnected for that matter) transmission line, that is entirely your construction. It is a diversion Cecil. Owen -- |
Sorry, that should be: "that when algebraicly Actually, that should be "algebraically" :) Interesting thread though. BYW, is the Bird using the Bruene type bridge or some other topology? Alan |
On Sat, 15 Oct 2005 18:26:30 +1000, Alan Peake
wrote: Sorry, that should be: "that when algebraicly Actually, that should be "algebraically" :) Thanks. There were some other typos along the way, but that was clearly a spelling mistake and the spell checker didn't find it. Interesting thread though. BYW, is the Bird using the Bruene type bridge Is that BTW? I understand that the Breune type bridge is one of the bothways detector designs with a untapped toroidal current transformer. I doubt the Bird sampler element is of that type. It appears to have a flat section of line that is parallel to the coax centre conductor and is presumably capacitively and inductively coupled, and it uses some form of frequency compensation to give it broadband response. You rotate the sampler element for measurement of the opposite direction. Someone here may have dismantled one to see how it works. I suspect that all of these probe designs try to sample net V and I at a point, and the extent by which they depart from a point sample limits their upper frequency of usefulness. Though there are several designs, they seem to broadly fall into two main types, those where the sampler response is inherently proportional to frequency (though they may be compensated as in the Bird elements) or those where they are inherently broadband (as the Bruene circuit). Trust you are well. I heard you on 40m the other day, but only just! Propagation has been pretty shabby. Owen -- |
Richard Clark wrote:
Cecil Moore wrote: Someone who thinks reflections cannot be eliminated by 1/4WL of thin-film? Certainly one who thinks it does. And both having been disproved, ... I guess you will take that delusion to your grave. -- 73, Cecil http://www.qsl.net/w5dxp |
Owen Duffy wrote:
Nothing in the myth stated or implied direct application of the measured conditions on the thruline section to any other connected (or disconnected for that matter) transmission line, that is entirely your construction. It is a diversion Cecil. No, it is the point that Reg and I were discussing long before you entered the thread. Reg made the same same point a couple of days ago. -- 73, Cecil http://www.qsl.net/w5dxp |
Alan Peake wrote:
Interesting thread though. BYW, is the Bird using the Bruene type bridge or some other topology? The Bird 43 manual is available at http://www.bird-electronic.com -- 73, Cecil http://www.qsl.net/w5dxp |
Owen Duffy wrote:
This has nothing to do with the stated myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Would you be willing to make the same statement about an MFJ wattmeter? -- 73, Cecil http://www.qsl.net/w5dxp |
Mythbusters: V/I ratio is forced to Z0
"Cecil Moore" wrote in message om... Owen Duffy wrote: This has nothing to do with the stated myth: Measurements with a Bird 43 of the conditions on the Thruline section are invalid unless it has some minimum length of 50 ohm line on both sides of itself. Would you be willing to make the same statement about an MFJ wattmeter? now your are just trying to muddy the waters... i wouldn't trust an mfj to measure anything! |
Mythbusters: V/I ratio is forced to Z0
On Sat, 15 Oct 2005 14:26:43 GMT, Cecil Moore wrote:
I guess you will take that delusion to your grave. Yet more guessing? |
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