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Its all gone quiet. Let's stir it up again.
A TALE OF TWO OLD WIVES
There are two cantankerous old wives: One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that's where the current is strongest and the magnetic field is most concentrated. The other old wife asserts it is obvious radiation occurs mainly from the ends of a dipole because that's where the highest voltages occur and the electric field is most intense. Since the pair of arguments are logically identical in form they are of equal validity. But because it is impossible to reconcile the two women .... they cannot BOTH be right .... only one conclusion can be drawn ... .... both arguments are false! The old wives are telling tales. Citizens - drag 'em off to that old English custom - the ducking stool. |
On Sat, 6 Mar 2004 18:45:48 +0000 (UTC), "Reg Edwards"
wrote: A TALE OF TWO OLD WIVES There are two cantankerous old wives: One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that's where the current is strongest and the magnetic field is most concentrated. The other old wife asserts it is obvious radiation occurs mainly from the ends of a dipole because that's where the highest voltages occur and the electric field is most intense. Then there is our THIRD OLD WIFE who sitting at her kitchen table looking out the window at the first two, takes notes of their argument, sets them aside and returns to measuring mud's recuperative powers and bottling it as a nostrum at the next fair. What is the Q of her mud? When the early English author, Samuel Richardson, wrote his ground breaking novel "Pamela, or Virtue Rewarded" it was met immediately by Henry Fielding's sardonic "Shamela." Fielding was responding to the arrogance of the subtitles in that first work: "Aggressive Chastity" and "Provocative Prudence"; dare I point out the parallels (non resonant) that attract me to these current ironies? 73's, Richard Clark, KB7QHC p.s. for those who take umbrage at favourable quotation of eminent British authors (oddly enough, Brits), please note this missive has been sprinkled with on-topic references of: ground[breaking], Field[ing], parallel[s], resonant, current and one technical enquiry for Q that will no doubt be ignored in favor of off-topic condemnations of these sources. ;-) |
Richard Clark wrote:
"What is the Q of her mud?" First, the Q of mud is likely less useful than antenna Q. That is, not worth much. Second, Q depends on mud consistency, temperature, location, and frequency of interest. The earth behaves like a lossy capacitor. Above 10 MHz, the capacitnce in ordinary soil bypasses the resistance of the soil. Below 10 MHz, conductance of the soil shunts the capacitance making soil capacitance (permittivity) less important. Soil as a lossy dielectric has a dielectric constant which is defined as the capacitance with dielectric material filling the void versus the capacitance without the dielectric material. Thickness of a mud layer is relevant. At medium wave and lower frequencies, where the earth is mainly resistive, r-f renetration of the earth, not sea water, is so deep that rain wetting has little effect on propagation or refleection. But, at h-f, penetration of the earth is shallow. Water and salt content are significant to penetration and loss. An ideal capacitor is lossless. There`s no dielectric leakage nor conductor loss resistance. Earth is not ideal. Capacitor quality is judged by how much its current`s phase angle deviates from 90-degrees lead of the applied voltage. This deviation angle is called the capacitor`s "phase angle". The tangent of this angle is called the "dissipation factor". The reciprocal of this dissipation factor is the Q of the capacitor. As mud is wet soil, it has Q, but not just one Q value. Best regards, Richard Harrison, KB5WZI |
and the Fourth Old wife said "its really the force exerted on a far point,
as you sum up effect of each current in each part of the antenna" as she pulled down the laundry off of the longwire. "It is a summation of all the little ones (she means currents), and then you get a field" says she, walking back the the radio shack with he head just a buzzing with electrons.(yea ... she bonkers) She was my Fields Proff too. "Richard Harrison" wrote in message ... Richard Clark wrote: "What is the Q of her mud?" First, the Q of mud is likely less useful than antenna Q. That is, not worth much. Second, Q depends on mud consistency, temperature, location, and frequency of interest. The earth behaves like a lossy capacitor. Above 10 MHz, the capacitnce in ordinary soil bypasses the resistance of the soil. Below 10 MHz, conductance of the soil shunts the capacitance making soil capacitance (permittivity) less important. Soil as a lossy dielectric has a dielectric constant which is defined as the capacitance with dielectric material filling the void versus the capacitance without the dielectric material. Thickness of a mud layer is relevant. At medium wave and lower frequencies, where the earth is mainly resistive, r-f renetration of the earth, not sea water, is so deep that rain wetting has little effect on propagation or refleection. But, at h-f, penetration of the earth is shallow. Water and salt content are significant to penetration and loss. An ideal capacitor is lossless. There`s no dielectric leakage nor conductor loss resistance. Earth is not ideal. Capacitor quality is judged by how much its current`s phase angle deviates from 90-degrees lead of the applied voltage. This deviation angle is called the capacitor`s "phase angle". The tangent of this angle is called the "dissipation factor". The reciprocal of this dissipation factor is the Q of the capacitor. As mud is wet soil, it has Q, but not just one Q value. Best regards, Richard Harrison, KB5WZI |
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In view of the nil replies to the following posting it's safe to say that's
another old wives' tale which bites the dust. The next ingrained tale on the list is the so-called SWR meter nonsense versus the TLI. ========================= A TALE OF TWO OLD WIVES There are two cantankerous old wives: One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that's where the current is strongest and the magnetic field is most concentrated. The other old wife asserts it is obvious radiation occurs mainly from the ends of a dipole because that's where the highest voltages occur and the electric field is most intense. Since the pair of arguments are logically identical in form they are of equal validity. But because it is impossible to reconcile the two women ..... they cannot BOTH be right .... only one conclusion can be drawn ... ... both arguments are false! The old wives are telling tales. Citizens - drag 'em off to that old English custom - the ducking stool. |
"Reg Edwards" wrote in message ... In view of the nil replies to the following posting it's safe to say that's another old wives' tale which bites the dust. The next ingrained tale on the list is the so-called SWR meter nonsense versus the TLI. ========================= A TALE OF TWO OLD WIVES There are two cantankerous old wives: One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that's where the current is strongest and the magnetic field is most concentrated. The other old wife asserts it is obvious radiation occurs mainly from the ends of a dipole because that's where the highest voltages occur and the electric field is most intense. Since the pair of arguments are logically identical in form they are of equal validity. But because it is impossible to reconcile the two women .... they cannot BOTH be right .... only one conclusion can be drawn ... ... both arguments are false! The old wives are telling tales. Citizens - drag 'em off to that old English custom - the ducking stool. |
Reg:
Compared to current, voltage is just so ephemeral.... Voltage is a line integral, it depends upon the path over which one evaluates the integral. While current is something more substantial... one does not have to plan the path of integration to know the current. What? -- Peter K1PO "Reg Edwards" wrote in message ... In view of the nil replies to the following posting it's safe to say that's another old wives' tale which bites the dust. The next ingrained tale on the list is the so-called SWR meter nonsense versus the TLI. ========================= A TALE OF TWO OLD WIVES There are two cantankerous old wives: One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that's where the current is strongest and the magnetic field is most concentrated. The other old wife asserts it is obvious radiation occurs mainly from the ends of a dipole because that's where the highest voltages occur and the electric field is most intense. Since the pair of arguments are logically identical in form they are of equal validity. But because it is impossible to reconcile the two women .... they cannot BOTH be right .... only one conclusion can be drawn ... ... both arguments are false! The old wives are telling tales. Citizens - drag 'em off to that old English custom - the ducking stool. |
Reg Edwards wrote:
In view of the nil replies to the following posting it's safe to say that's another old wives' tale which bites the dust. Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. We know from field strength measurements that a mobile antenna with a balanced top hat can radiate as well (or better than) an antenna equipped with a radiating high voltage top section. If you keep the high voltage portion of the antenna and replace the high current portion with an antenna tuner, the field strength falls by some 12 dB. Lengthening the high current section under the loading coil has a much greater effect than lengthening the high-voltage section on top of the loading coil. -- 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! =----- |
Cec, I don't doubt your experimental results. It's your extrapolated
imagination and logic which worries me. ;o) ---- Yours, Reg. |
Reg Edwards wrote:
Cec, I don't doubt your experimental results. It's your extrapolated imagination and logic which worries me. ;o) I didn't imagine those experimental results, Reg, and all I did was report those results. My logic tells me that there is a grain of valid circumstantial evidence in there somewhere. What you need to do to prove your point is present an antenna where the high-current portion is prohibited from radiating yet still yields a high field strength. Example #1: The top half of an electrical 1/4WL antenna is prohibited from radiating by a balanced top hat. Field strength results are similar to a 1/4WL monopole. This has already been presented. Example #2: The bottom half of an electrical 1/4WL antenna is prohibited from radiating by _________________. Fill in the blank and prove that field strength results are similar to a 1/4WL monopole. That's all you need to do to make a believer (instead of a doubter) out of me. -- 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! =----- |
Its the voltage parts of the antenna which do the radiating.
That is proved by cutting off the top part of the antenna and replacing it with a top hat which has a much larger capacitance so it radiates the power harder. --- Reg. |
Reg Edwards wrote:
Its the voltage parts of the antenna which do the radiating. That is proved by cutting off the top part of the antenna and replacing it with a top hat which has a much larger capacitance so it radiates the power harder. Reg, let's say we have an elevated antenna system where the radial system and top hat system are identical and balanced. Energy flows back and forth between the radials and top hat. Very little energy is radiated from either the top hat or the radials since they are balanced. Virtually all of the radiated energy comes from the high-current vertical portion of the antenna. Such antennas are described in Appendix II - Short Ground-Mounted Verticals in _Building_and_Using_Baluns_and_Ununs_ by Jerry Sevick, w2fmi. -- 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! =----- |
Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me
at present. --- Reg. |
Cecil Moore wrote: Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG |
Reg Edwards wrote:
Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me at present. He's accepted by most as *the* ham balun guru. Some disagree. -- 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! =----- |
Jim Kelley wrote:
Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. A balanced top hat doesn't radiate much because the currents in the opposing elements are 180 degrees out of phase with each other. It doesn't matter if they are traveling waves or standing waves. If they are 180 degrees out of phase with each other, they are more like a transmission line than they are like 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! =----- |
Cecil Moore wrote:
Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG ============================ Jim, are you one of the crackpots who think that it's the voltage parts of the antenna which do the radiating which is proved by replacing the top portion of the antenna with a top hat which has a large capacitance so that the voltage has a greater effect. ;o) --- Reg, G4FGQ |
Reg Edwards wrote:
Cecil Moore wrote: Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG ============================ Jim, are you one of the crackpots who think that it's the voltage parts of the antenna which do the radiating which is proved by replacing the top portion of the antenna with a top hat which has a large capacitance so that the voltage has a greater effect. ;o) --- Reg, G4FGQ Hi Reg, Were it not for this group, I would never have known the full extent of my crackpottedness! My colleagues and associates have been keeping it a secret from me all these years evidently. With that in mind, yes. Nevermind Farady. The size of the hat should indeed determine the size of the effect. I wear a 7 3/4. 73, Jim AC6XG |
On Wed, 10 Mar 2004 13:43:05 -0800, Jim Kelley wrote:
Reg Edwards wrote: Cecil Moore wrote: Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG ============================ Jim, are you one of the crackpots who think that it's the voltage parts of the antenna which do the radiating which is proved by replacing the top portion of the antenna with a top hat which has a large capacitance so that the voltage has a greater effect. ;o) --- Reg, G4FGQ Hi Reg, Were it not for this group, I would never have known the full extent of my crackpottedness! My colleagues and associates have been keeping it a secret from me all these years evidently. With that in mind, yes. Nevermind Farady. The size of the hat should indeed determine the size of the effect. I wear a 7 3/4. 73, Jim AC6XG Have you guys ever considered that since the infinitesimally short dipole radiates only 4 percent less than a resonant dipole, the only reason for having any longer length than infinitesimally short is to make it resonant? So what do you think the relation between voltage and current is in the short dipole? Does that bring to mind whether the max radiation occurs at the max voltage or max current portion of the dipole? Walt, W2DU |
On Wed, 10 Mar 2004 14:34:38 -0600, Cecil Moore
wrote: Reg Edwards wrote: Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me at present. He's accepted by most as *the* ham balun guru. Some disagree. Yeah, I'm one who disagrees! Walt, W2DU |
He's accepted by most as *the* ham balun guru. Some disagree.
====================== How can anybody make himself a guru about such a simple, inactive, mundane device as a balun? Now if it was a conjugate match! |
Walter Maxwell wrote:
Cecil Moore wrote: He's accepted by most as *the* ham balun guru. Some disagree. Yeah, I'm one who disagrees! Well, wait until you find out exactly what the disagreement was. I said a balanced set of elevated radials or a balanced top hat doesn't radiate much RF. What do you say? -- 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 Wed, 10 Mar 2004 22:57:01 GMT, Walter Maxwell wrote:
|On Wed, 10 Mar 2004 14:34:38 -0600, Cecil Moore |wrote: | |Reg Edwards wrote: | Cec, who's Jerry Sevick. I don't seem to have a copy of his works around me | at present. | |He's accepted by most as *the* ham balun guru. Some disagree. | |Yeah, I'm one who disagrees! But he is certainly prolific. Can't pick up a magazine without another same-o-same-o article. Latest in Feb. "High Frequency Electronics." Wes |
Walter Maxwell wrote:
Have you guys ever considered that since the infinitesimally short dipole radiates only 4 percent less than a resonant dipole, the only reason for having any longer length than infinitesimally short is to make it resonant? The total field radiated should be proportional to the product of the voltage and the current applied to the radiator. The size and shape of the radiator will determine the impedance and radiation pattern. Neither issue speaks to the "exact location of the point of max radiation". Any point along the radiator in which traveling wave currents are flowing will radiate. The amount of radiation emanating from any given point would be proportional to the rate at which energy traverses that point. Does that bring to mind whether the max radiation occurs at the max voltage or max current portion of the dipole? The existance of a max radiation point along a radiator should first be shown before we begin to argue about its exact location. In my opinion. 73, Jim AC6XG |
"Walter Maxwell" wrote in message ... On Wed, 10 Mar 2004 13:43:05 -0800, Jim Kelley wrote: Reg Edwards wrote: Cecil Moore wrote: Reg, we have a clear example of where the high voltage part of the antenna is not allowed to radiate (much). That would be a balanced top hat. Not allowing the high voltage part of the antenna to radiate leaves the high current part to do most of the radiating. Cecil, Reg makes a good point. We know that the same amplitude (less ohmic losses) of current travels the entire length of the antenna in both directions. The relative phase of forward and reverse currents simply makes the superposition of the two currents greater at one end than another. We might measure the standing wave current with an ammeter, but it is the traveling wave currents which radiate. 73, Jim AC6XG ============================ Jim, are you one of the crackpots who think that it's the voltage parts of the antenna which do the radiating which is proved by replacing the top portion of the antenna with a top hat which has a large capacitance so that the voltage has a greater effect. ;o) --- Reg, G4FGQ Hi Reg, Were it not for this group, I would never have known the full extent of my crackpottedness! My colleagues and associates have been keeping it a secret from me all these years evidently. With that in mind, yes. Nevermind Farady. The size of the hat should indeed determine the size of the effect. I wear a 7 3/4. 73, Jim AC6XG Have you guys ever considered that since the infinitesimally short dipole radiates only 4 percent less than a resonant dipole, the only reason for having any longer length than infinitesimally short is to make it resonant? Now that makes radiation efficiency per unit length hard to calculate, but it does provoke thought regarding antenna designs based on wavelength dimensions. Input impedance on a parallel circuit based radiators gathers momentum in importance. Art So what do you think the relation between voltage and current is in the short dipole? Does that bring to mind whether the max radiation occurs at the max voltage or max current portion of the dipole? Walt, W2DU |
On Thu, 11 Mar 2004 00:33:07 GMT, "aunwin"
wrote: Input impedance on a parallel circuit based radiators gathers momentum in importance. Hi Art, Only if 0.02% to 5% is all you need. Such is the legacy of eh designs in comparison to full size antennas: more than 30dB down (0.1% efficient if one is to be generous). 73's Richard Clark, KB7QHC |
Reg, G4FGQ wrote:
"One old wife asserts it is obvious radiation occurs mainly from the middle portion of a dipole because that is where the current is strongest and the magnetic field is most concentrated." All sections of a dipole are needed to establish the wave launcher / grabber. Seems to me the old wife quoted above is right. Radiation from a dipole is concentrated in a doughnut pattern around the middle of the wire. What influences are sensed at a distance point perpendicular to the middle of the dipole? There are electric fields, plus and minus, which cancel. The current on one side of the dipole flows into the source while the current on the other side of the source flows out. This places current on both sides of the dipole in the same direction. The magnetic fields from both sides of the dipole are additive because the currents producing them are in-phase. Never mind that an electromagnetic wave must have an electric field as well as a magnetic field. The emerging magnetic field generates an electric field which generates a magnetic field ad infinitum. Best regards, Richard Harrison, KB5WZI |
Jim, AC6XG wrote:
"The amount of radiation emanating from any point woulf be proportional to the rate at which energy traverses that point." Amperes are the measure of current flow. Best regards, Richard Harrison, KB5WZI |
Walt, W2DU wrote:
"Have you guys ever considered that since the infinitesimally short dipole radiates only 4 percent less than a resonant dipole, the only reason for having any longer length than the infinitesimally short is to make it resonant." I`ll assume Walt`s infinitesimally short dipole is the same as Terman`s elemental dipole. If so, I`ll quibble over the 4% . Terman`s table 23-1 on page 871 of his 1955 edition gives the directive gain of the elementary doublet as 1.5 over the isotropic. The resonant dipole has a 1.64 gain . The difference is 0.14 or about 10% more from the 1/2-wave dipole. Still no big deal. Current is in the same direction in both halves of the elementalary dipole no matter how short it is. Opposite charge polarities occupy both elements and their effects tend to cancel on charges equidistant from the middle of the antenna. The field radiated in any direction is the vector sum of fields radiated from infinitesimal elements, and field strength is proportional to current. Directional gain ignores losses. That`s the rub with the tiny antenna of high capacitive reactance (the capacitance is small) and low radiation resistance. The gain ratios are only valid with equal powers in comparison antenna and subject antenna. To get the large current required in the infinitesimal antenna to radiate the same power as the 1/2-wave dipole would be extremely difficult without enormous loss in the match and load circuits. Best regards, Richard Harrison, KB5WZI |
On Thu, 11 Mar 2004 08:38:07 -0600 (CST),
(Richard Harrison) wrote: Seems to me the old wife quoted above is right. Radiation from a dipole is concentrated in a doughnut pattern around the middle of the wire. Hi Richard, This is from an infinite perspective where all contributions of radiation sum to form the shape you describe. If you were actually sitting at the middle of that "doughnut" you would see a pattern more like three poached eggs bigger than the size of the structure. Examples of near field patterns (evidenced through their imposition of a Z other than 377 Ohms upon the vicinity of the antenna) may be observed at: http://home.comcast.net/~kb7qhc/ante...elds/index.htm with: http://home.comcast.net/~kb7qhc/ante...pole/index.htm showing a distinct activity at BOTH the middle AND at the ends. 73's Richard Clark, KB7QHC |
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