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Cecil, et al:
I think the real key to this mystery is to consider the wave velocity in the loading coil. Admittedly at the beginning of this debate (I have been following the debate since the big W8JI / K3BU shootout on the Topband email reflector) I was squarely in the lumped element camp, but Cecil Moore's thought provoking arguments have begun to give me reason for pause. Here's why: Under the lumped circuit view of things, there is no delay between current going into the inductor and the current coming out the other terminal. There is a 90 deg phase shift between the inductor current and its terminal voltage, but there is no need to introduce the notion of a delay between the input and output currents in order to account for an inductor doing inductor like things. All one needs to get inductor like behavior is a two-terminal black box whose terminal voltage is equal to L times the derivative of the current passing thru it (e.g. L = di/dt). If one could build such a black box (unfortunately, I am afraid it is akin to building an isotropic radiator), it could be used in place of a real inductor in all manner of tuned circuits and impedance matching applications. In fact, we routinely use such a black box to simulate real inductors in programs like Spice, EZNEC, Touchstone, etc. And in many of these applications, the ideal inductor is a reliable proxy for a real inductor. Now let's consider a parallel two-wire transmission line. If I have such a line with a Zo of say 450 ohms, and I open circuit one end of the line and drive the other end with an RF generator, I will get a nice sinusoidal standing wave pattern along the length of the line that bears a striking resemblance to the current distribution on a linear antenna element. At 1/4 wavelength from the open end of this line, I will be at a current maximum where the input impedance is very close to a short circuit ( I am assuming a low-loss line with minimal radiation). If I now break this 1/4 wavelength long line in the middle and remove a section of line and replace it with a pair of my black box ideal inductors (one ideal inductor in series with each leg of the transmission line), I should be able to adjust the value of the inductors such that I can replace the missing section of line and achieve a current maximum/short circuit condition at the input of the line (e.g. resonance). At this point, I should look at the knobs on my two black box ideal inductors, read off the inductance values, and note the readings for future reference. Now, given that my inductors are ideal, there will be no current taper across them as there was in the transmission line section that they replaced. You can verify this with a circuit simulator, like Serenade, Touchstone, or Superstar. This derives from the fact that there is no propagation delay through an ideal inductor. The current going into an ideal inductor is always in-phase (and of equal magnitude) with the current leaving it. Okay now that we have dealt with the ideal case, let's remove the black boxes and replace them with a pair of parallel ganged roller inductors (actual real parts you can buy on Ebay!). As with the black box case, I should be able to adjust the inductance values of the ganged inductors until I achieve resonance (maximum current/minimum impedance) at the input to the parallel wire transmission line. Again, I will note and record the readings on the calibrated turns counters for future reference. Now let's take a close look at the setup. I now have two roller inductors with their axis parallel to the longitudinal axis of the transmission line. The centerlines of the two roller inductors are some distance "d" apart from each other. If I just consider the 4 terminal network formed by these two inductors, it begins to look an awful lot like a parallel two-wire delay line of length, L and some unknown characteristic impedance, Zd and unknown velocity of propagation, Vp. Uh oh!! now we have some delay associated with our "loading coils". A TEM mode wave impinging on the input to this 4 terminal "delay line" network will propagate at some finite Vp. Thus if I terminate the output of the real inductor network with the proper Zo, the input current will be equal to the output current, but with some finite delay between the input current and the output current. Now if I reinsert this delay contraption back into my 450 ohm two-wire line, it will still produce the same resonant condition as before (I didn't change the inductance settings), but now that I know it has some delay associated with it, I should expect to see some taper in the current along its length. Of course, the fact that the Zd of the "delay line" doesn't necessarily match the Zo of the 450 ohm line probably complicates matters. I'll most likely generate reflections at the input to the inductor assembly, and re-reflections at the output (reward traveling wave). Still, I have satisfied the condition for generating a taper across these real inductors. After all, borrowing from Cecil Moore's argument, the delay along a linear mismatched transmission line is what is responsible for the observed taper in the current (e.g. standing wave). Now for the $64,000 dollar question. What is the Zd and Vp of the ganged roller inductor assembly. Will the Vp necessarily bear some fixed relationship to the inductive reactance of the inductors, or will this depend on the form factor of the inductor assembly. Will the length of the inductor assembly divided by the wave velocity, Vp be equal to the delay of the line section that it replaced, or will this delay depend on the form factor of the inductor assembly (using ferrites versus air core inductors, I can easily envision two pairs of parallel inductors with the same inductive reactance, but very different form factors). Will the value of inductive reactance needed to "resonate" my loaded transmission line vary with the delay and or form factor of the parallel loading inductors, or will this value be fixed and equal to the value of inductive reactance required when I was using the ideal "black box" inductors? Hopefully you alll see where I am going with this. What say, Gents? 73 de Mike, W4EF..................................... "Cecil Moore" wrote in message Jimmy wrote: lumped inductance = lumped change in current. Actually, I think the assertion was that lumped inductance = no change in current. -- 73, Cecil http://www.qsl.net/w5dxp |
Michael Tope wrote:
Will the value of inductive reactance needed to "resonate" my loaded transmission line vary with the delay and or form factor of the parallel loading inductors, or will this value be fixed and equal to the value of inductive reactance required when I was using the ideal "black box" inductors? Hopefully you alll see where I am going with this. What say, Gents? Hi Mike, good posting. I admire open, questioning minds. I just added some information on this subject to my web page. Although there is some relationship between inductance and delay, I hardly had to mention inductance at all. The phases of the forward current and reflected current are changing in opposite directions. Given any delay at all, the magnitude of the net current will change through the coil (given a typical mobile antenna coil). The electrical length of a mobile antenna loading coil can be approximated by finding the angle whose cosine is (net top current)/(net bottom current). Note that this estimate works for loading coils installed in electrical 1/4WL monopoles or electrical 1/2WL dipoles, not for the general case. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Michael, W4EF wrote:
"Cecil Moore`s thought provoking arguments have begun to give me reasonn for pause." It`s been said the key to enlightnent is repetition, repetition, and repetition.. It must be so. A series resonant circuit is the usual form of a standing-wave antenna. Inductance, capacitance, and resistances due to radiation and heat conversion are unevenly distributed along the antenna. As King, Mimno, and Wing say in "Transmission Lines, Antennas, and Wave Guides" on page 86: "Inductance and capacitance as used for near-zone circuits with uniform current cannot be defined, and ordinary circuit analysis does not apply." Best regards, Richard Harrison, KB5WZI |
Cecil, W5DXP wrote:
"I hardly had to mention inductance at all." Imductance equals delay. That`s why inductors are called retardation coils. In a resistor, current varies exactly in the same way and at the same time as the applied voltage. Volts and amps are in-phase. In an inductor, current is delayed and builds from the time that voltage appears across the inductor. In a lossless (pure) inductance, current lags the applied a-c voltage by 90-degrees. When the voltage is maximum, current is zero, and when the voltage is zero, current is maximum. 90-degrees represents some fraction of a second, depending on cycles per second as 90-degrees is the time required for 1/4-cycle. The higher the frequency, the shorter the time represented by 90-degrees. Loss in an inductance makes an impedance composed of inductive reactance and resistance. As current is delayed in reactance by 90-degrees, but is in-synch in a resistance, Pythagoras gives us the total impedance, and the phase angle of the resultant impedance is an "operational vector", not a "field vector". The angle of current in the impure inductance which is made with the applied voltage is easily determined with trigonometry or graphical methods. An operational vector is also called a phasor. Delay can vary from 0 in a pure resistance to 90-degrees in a purely reactive circuit. Inductance makes current lag by 90-degrees. Capacitance makes current lead by 90-degrees. Broadcasters use a T-network called a 90-degree phase shifter. All three reactances have the same impedance as the input and output impedance. For example, two 50-ohm reactance coils are connected in series in the signal path. A 50-ohm capacitive reactance is connected between the junction of the two coils and the other side of the circuit (ground). One of the coils cancels the capacitive reactance, leaving a pure inductive reactance of 50-ohms in series with the circuit to cause a 90-degree phase lag. Often ganged variable inductors are used in the 90-degree phase shifter to produce the exact delay required and this has almost no effect, less than 1%, on output current magnitude from the phase shifter over a plus or minus 15-degree phase adjustment range. It`s simple trigonometry. Best regards, Richard Harrison, KB5WZI |
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Richard Clark wrote:
"I thought this was dead long ago." So did I. This recent posting is a repetition for me, but sometimes repetition is needed for those who weren`t there in whole or in part for the earlier postings. I don`t expect anyone to accept a statement without proof from me that ordinary circuit analysis does not apply to antennas, but from 3 E.E. Sc. D.`s who were at the time they made the statement giving their very best for victory in WW-2, I would expect some serious consideration and at least a first assumption that the opinion is correct. Best regards, Richard Harrison, KB5WZI |
Richard Harrison wrote:
It`s been said the key to enlightnent is repetition, repetition, and repetition.. It must be so. Drops of water can wear away a rock. Drops of truth can wear away sacred cows, even when embedded in granite brains. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Tue, 02 Dec 2003 16:45:34 -0600, Cecil Moore
wrote: Richard Harrison wrote: It`s been said the key to enlightnent is repetition, repetition, and repetition.. It must be so. Drops of water can wear away a rock. Drops of truth can wear away sacred cows, even when embedded in granite brains. And there are some who **** on your leg and try to convince you its the rain - Judge Judy |
Gentleman,
The point of my post was not to point out the obvious fact that lumped circuit analysis has some limitations when used in the context of antenna loading coils. The debate (at least the one I am familiar with), was whether or not the current magnitude across an antenna loading coil varied as the current would vary in a linear section of antenna having same physical length as the loading coil, or whether the current magnitude would vary as the current would vary in a linear section of antenna have the same physical length as the section of antenna that the loading coil replaced. In either case, distributed effects not accounted for in simple lumped element models are recognized to be at work. For the former scenario to be true, the current retardation through the loading coil is presumed to be roughly equal to that observed in a linear section having the same physical length as the loading coil. In this case the retardation would be Tau = length physical/Vp. This scenario recognizes that distributed effects are at work (hence the small, but finite current taper), but suggests that the dominant factor responsible for the loading of the antenna is the phase shift between the inductor current and the voltage across it. The latter case also suggests that distributed effects are at work, but to a much greater degree than in the former. In this case, the loading of the antenna is presumed to be the result of the large current retardation introduced by the loading coil. In this case, the retardation is presumed to be Tau = length effective/Vp or Tau = length replaced/Vp. In this scenario, the effect of the phase shift between the loading coil current and the voltage across its terminals seems to be considered incidental and is largely ignored. The point of my loaded transmission line example was to show that under either set of assumptions, the loading coil will produce the desired result. That is to say that it will load the physically short structure (in the case of my example, a transmission line) thus bringing it into so-called resonance. Thus the fact that the loading coil produces the desired result (e.g. input impedance match) can't be pointed to as proof that one physical mechanism is dominate and the other is not. The transmission line stub loading network doesn't have to behave the same way as the lumped inductor loading coil to produce the same desired result (e.g. input impedance match, resonance, or whatever you want to call it). What I am getting at, is that both camps may be wrong. The answer may lie somewhere in between these two extremes (e.g. taper equivalent to physical length vs taper equivalent to electrical length), but this isn't attractive because its ambiguous and doesn't make for nice diagrams that can be placed on websites, in textbooks, or in antenna handbooks (not to mention all of the accompanying self-righteous chest beating). 73 de Mike, W4EF................................. P.S. for those of you who have already heard all this please accept my apologies as I missed out on last months debate. "Richard Harrison" wrote in message ... Richard Clark wrote: "I thought this was dead long ago." So did I. This recent posting is a repetition for me, but sometimes repetition is needed for those who weren`t there in whole or in part for the earlier postings. I don`t expect anyone to accept a statement without proof from me that ordinary circuit analysis does not apply to antennas, but from 3 E.E. Sc. D.`s who were at the time they made the statement giving their very best for victory in WW-2, I would expect some serious consideration and at least a first assumption that the opinion is correct. Best regards, Richard Harrison, KB5WZI |
Michael Tope wrote:
What I am getting at, is that both camps may be wrong. The answer may lie somewhere in between these two extremes ... As I understood it, there is an extreme on only one side. One side says the current through a loading coil doesn't change. The other side says that the current through a loading coil does change. You can look at the decrease in the feedpoint impedance of a loaded antenna Vs a wire antenna and prove that the coil doesn't exactly replace that length of antenna. The coil is a more efficient inductor and less efficient radiator than the wire it replaces which results in a higher net current at the feedpoint. To the best of my knowledge, no one has said there is an exact 1:1 correspondence between the coil and the wire it replaces. The correspondence is only approximate. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Mike, W4EF wrote:
"What I am getting at is that both camps may be wrong." One of the arguments is that current into one end of a loading coil equals current out of the other end of the coil. That is not required of an antenna loading coil in the middle of an antenna. Recall the diagram of a center loaded short vertical whip from ON4UN`s Fig 9-22 that Yuri Blanarovich posted early in the dispute. 45-degrees of the 90-degree total antenna length is replaced by the loading coil. Current tapers cosinusoidally from 1A at the drivepoint to 0A at the tip. Cosine of 22.5-degrees = 0.924 Cosine of 67.5-degrees = 0.383 Roy sarcastically referred to "Yuri`s Cosine law". Yuri is right. Current into the bottom of the coil is 0.924 A, and into the top of the coil it is 0.383 A. Roy disappeared from the argument. Yuri seems to have tired of the dispute too. On page 86, King, Mimno, and Wing say: "It is fundamentally incorrect to treat a centerdriven antenna as though it were the bent-open ends of a two-wire line." This is true for a whip as a continuation of a coax line too. The antenna should radiate and the line should not. The difference between an antenna and a transmission line is fundamental. Consider the equivalent circuit of the balanced line. It is made from distributed series-connected inductors with distributed capacitors shunted across the inductor junctions. The two line conductors are closely coupled and enforce balance in the line. The close equal and opposite currents discourage radiation from the line. Attach a non-radiating balanced load across the feedline. The currents into both terminals of the load must be the same. There is much looser coupling between the two sides of a dipole than between the wires of a transmission line. In a transmission line feeding a mismatched load, the reflected energy "sees" Zo as does the incident energy traveling the line. Zo is enforced in both directions by the inductance and capacitance distributed uniformly in the line. Due to energy escape in an antenna, incident and reflected energy can "see" differing impedances on either end of a loading coil. The coil doesn`t enjoy the type of enforced balanced feed imposed by a balanced transmission. The feed at its ends is asymmetrical. Best regards, Richard Harrison, KB5WZI |
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Richard Clark wrote:
"The only points of interest are found in the data and the limits of error that surround it." Richard Clark is among other things an expert in measurements. Others may find other points of interest in things which don`t intrest Richard. For me, a simple go or no-go scale may be good enough. Regardless of precision, the ultimate decision often must boil doewn to a simple yes or no. If my recollection is right, Yuri presented a photo of a loading coil in action which had functioning r-f thermoammeters, one at each coil end. Their readings were significantly different. This may not be conclusive, but were I to see it often in various applications, I`d likely be persuaded that currents are likely different at opposite ends of an antenna loading coil sited in the middle of an antenna conductor. Best regards, Richard Harrison, KB5WZI |
Richard Clark wrote:
This happened more from the basis of others forcing arguments upon them, and then proving those straw men wrong; The original question was pretty clear: For a real-world mobile loading coil, does the current vary from end to end? And if it does vary from end to end, does that violate Kirchhoff's laws? -- 73, Cecil, W5DXP |
Richard Harrison wrote:
Due to energy escape in an antenna, incident and reflected energy can "see" differing impedances on either end of a loading coil. The coil doesn`t enjoy the type of enforced balanced feed imposed by a balanced transmission. The feed at its ends is asymmetrical. If two series coils are installed in a balanced feedline with reflections, the net currents through the coils will also change from end to end. -- 73, Cecil, W5DXP |
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Richard Clark wrote:
As for go/no-go sieves, mine is does it make more than a dB difference? In this case, barely 0.5dB. So as a metrologist, plus or minus a dB is good enough? Do you use the number 3 for Pi? That's only .02 dB off. 73, Jim AC6XG |
Jim Kelley wrote:
Do you use the number 3 for Pi? That's only .02 dB off. Heck, Pi is only 0.63 dB higher than e so they are virtually interchangeable. Some state (Tennessee?) once tried to pass a state law requiring Pi to equal 3.00. -- 73, Cecil, W5DXP |
Cecil Moore wrote in message ...
Michael Tope wrote: What I am getting at, is that both camps may be wrong. The answer may lie somewhere in between these two extremes ... As I understood it, there is an extreme on only one side. One side says the current through a loading coil doesn't change. The other side says that the current through a loading coil does change. The current through the coil is not the issue as far as my "camp" is concerned. I can see where the current could taper across the coil in certain setups. The issue as far as I'm concerned is: does this taper drastically cause error in modeling compared to lumped elements? I don't think it does to any great degree, and others data, including Richard Clarks, and also W4RNL, seem to concur. Or at least as far as I can see. The taper of the current through the coil is of no great concern to me. The claim that this variation of current across the coil causes drastic modeling error is what I have problems with. To me, it's trying to explain a problem that doesn't really exist, with something that really doesn't matter that much as far as that problem is concerned. No one yet has shown any examples of large modeling errors that is due to this tapering of current. And THATS what the real issue is. Or at least as Yuri tells it. MK |
On Thu, 04 Dec 2003 13:36:24 -0800, Jim Kelley
wrote: Richard Clark wrote: As for go/no-go sieves, mine is does it make more than a dB difference? In this case, barely 0.5dB. So as a metrologist, plus or minus a dB is good enough? Do you use the number 3 for Pi? That's only .02 dB off. 73, Jim AC6XG Hi Jim, Error is a fact of life. My sieve of "does it make more than a dB difference" is not a statement of error however. A simple example of error is found in That's only .02 dB off. 73's Richard Clark, KB7QHC |
Mark Keith wrote:
The current through the coil is not the issue as far as my "camp" is concerned. Apparently it isn't now, but it was quite an issue for a while there. Initially it seemed the only correct point of view was the one which held that loading coils behave strictly as lumped inductances. Remember that? The issue as far as I'm concerned is: does this taper drastically cause error in modeling compared to lumped elements? I think the answer is essentially, no. For me the issue was always whether current can be unequal at opposite ends of an inductor. I find the fact that it can to be very interesting, and I wanted to understand just how it could be so. I guess I'm just not willing to accept the notion that just because fundamentals such as these may be inconsequential to how well an antenna is modeled, that they are also inconsequential to a thorough understanding of how it works. 73, Jim AC6XG |
Richard Clark wrote: Hi Jim, Error is a fact of life. My sieve of "does it make more than a dB difference" is not a statement of error however. A simple example of error is found in That's only .02 dB off. :-) What decimal fraction of a tenth of a Bel do you think the ratio Pi/3 represents, Richard? Seventy third's de AC6XG |
On Thu, 04 Dec 2003 15:11:29 -0800, Jim Kelley
wrote: I find the fact that it can to be very interesting, and I wanted to understand just how it could be so. Hi Jim, It is simply that Kirchhoff's laws have been corrupted in discussion. The Kirchhoff law of current relates to the flow into and out of "a closed surface" or a point (where any number of components' common leads come together) and not to the components themselves (as they have been incorrectly injected as argument). The corruption is found in that the current law has been expressed in the language of Kirchhoff's voltage law by nearly EVERY correspondent. EZNEC treats loads as lumps, lumps are the metaphor for the "closed surface" or a point. EZNEC conforms to Kirchhoff's current law, but not the physical reality simply because in nature a load cannot exhibit its characteristic within a point (there are no infinitesimal capacitors or inductors). Hence a protocol was offered to decimate the inductor and spread its characteristic across the apparent physical space to achieve the same, virtual response of a true inductor immersed in reality. The result of the protocol exhibits roughly the same characteristics offered by ON4UN's drawings (which are also approximations themselves). 73's Richard Clark, KB7QHC |
Mark Keith wrote:
The claim that this variation of current across the coil causes drastic modeling error is what I have problems with. Try modeling a 180 degree phase shift coil using EZNEC. (I have a 180 degree phase shift coil in my 70cm mobile antenna.) I guarantee you will see drastic modeling errors for such an antenna. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Roy sarcastically referred to "Yuri`s Cosine law". Yuri is right. Current into the bottom of the coil is 0.924 A, and into the top of the coil it is 0.383 A. Roy disappeared from the argument. Yuri seems to have tired of the dispute too. Yuri is not really tired of the dispute, more like he has found enough support for what he was looking for. There are still those who do not believe that current can be different at the ends of a loading coil, there are those who now see that maybe "she's not flat", and then those, who new it all along - what's a big deal. The main confirmation that I am not a F0OL (as certain guru(s) tried to imply) has been achieved, thanks to Cecil and others I have understood the mechanism of the phenomena. I have enough ammunition to do some of my own testing and measurements and as I promised to write it up with other fellow believers, 'splain it, provide facts and outline importance for the loaded antenna design. Hopefully the modeling software will be able to capture and use it properly for better results and understanding. And yes Virginia, it is VERY important for the modeling. If the radiator models no change in current accorss the coil, but there is more like 40 - 60% reduction, THAT is important, because it will throw the whole model off if you add more loaded elements like in parasitic arrays. Right now I am very busy organizing Christmas Concert in NYC/NJ area (www.computeradio.us) by 80 member Ukrainian Ensembles from Toronto. Anyone in vicinity is cordially invited to get in tune with Christmas spirit, away from the shopping fever. It is something to see, like small Mormon's Tabernacle Choir. I managed to play with new TenTec Orion rig in CQ WW and I am also working on writing "contesters" review of the rig. Quite a performance but how "cheap" for $3.6k radio. So, I follow the "coil thing", I just run out of arguments, I want to do my experiments and then put it together in a comprehensive article. So thanks to all pros and cons, I got what I needed and this group is the best! W8JI is WR0NG and one should take his "wisdom" with a grain of salt. His web page has more stuff that is off. Yuri, K3BU.us |
Jim Kelley wrote:
Mark Keith wrote: The issue as far as I'm concerned is: does this taper drastically cause error in modeling compared to lumped elements? I think the answer is essentially, no. So you haven't tried to model an antenna with a 180 degree phase- reversing coil, have you? :-) -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
On Thu, 04 Dec 2003 15:20:06 -0800, Jim Kelley
wrote: Richard Clark wrote: Hi Jim, Error is a fact of life. My sieve of "does it make more than a dB difference" is not a statement of error however. A simple example of error is found in That's only .02 dB off. :-) What decimal fraction of a tenth of a Bel do you think the ratio Pi/3 represents, Richard? Seventy third's de AC6XG It only matters if you put your lips to Pi. 73's Richard Clark, KB7QHC |
Jim Kelley wrote: Richard Clark wrote: Hi Jim, Error is a fact of life. My sieve of "does it make more than a dB difference" is not a statement of error however. A simple example of error is found in That's only .02 dB off. :-) What decimal fraction of a tenth of a Bel do you think the ratio Pi/3 represents, Richard? Seventy third's de AC6XG The difference between .2 and .02 is less than a dB, so that falls below your 1 dB threshold. ;-) 73, Jim AC6XG |
Cecil, W5DXP wrote:
"So you haven`t tried to model an antenna with a 180 degree phase-reversing coil, have you?" Kraus` Figure 23-21(b) has phase-reversing coils used as traps. "Here the elements present a high impedance to the coil which may be resonated without an external capacitance due to its distributed capacitance." Kraus` trap is a self parallel resonant circuit, not just another inductance. However, a center-tapped coil can make an excellent phase inverter as in the vacuum tube type Detroit Electric Company (Delco) Buick car radios of the late 1930`s and early 1940`s. This radio had great sound despite limited frequency response inevitable with choke and transformer coupling. Best regards, Richard Harrison, KB5WZI |
Richard Harrison wrote:
Kraus` trap is a self parallel resonant circuit, not just another inductance. Point is that all real-world coils possess distributed capacitance and distributed resistance as well as inductance. There is capacitance but no capacitor in Kraus' trap. If one replaces the "phase-reversing coil" with a phase-reversing stub, EZNEC gives the correct current distribution. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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