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Hazards of raised radials
Regarding the potential hazards involved in using raised radials on a
vertical - I'd be interested in comments from readers of this newsgroup. The antenna installation proposed is a vertical installed through the roof of a building. For many reasons it would be preferable to keep the radials inside the attic. My concern is possible danger due to the high voltages incurred at the ends of the radials. The antenna will be a SteppIR vertical for 40-10 meters with the base just under the roof, protruding through the roof. At the base will be a number of resonant radials fanning out throughout the attic. My concern is if this poses a fire hazard due to arcing (corona, whatever) at the ends of the radials. It may not be convenient to suspend the radials over their entire length or provide high quality suspended insulators at the wire ends. So what danger is there in letting radials lay on the floor of the attic, attached to the roof rafters, or even poked down inside the studs of the walls? I think we can assume the attic will be dry, except for normal Seattle humidity !! Rick K2XT |
As a followup to my question, I guess the concept or the question is
no different than if it referred to a dipole instead of radials on a vertical. The concern is protection from the high voltage at the end of the wire, and the potential of it causing a fire. So it is really a very general question, considering the numbers of antennas hams are having to disguise or hide inside their homes these days. Rick K2XT |
Unless you run kilowatts you have nothing to worry about. To be on
the safe side. just use thick plastic covered wire for your radials taking a little extra care at the extreme ends. Inspect every few years. If by some very remote chance arcing should occur your SWR meter will jump about and you will be obliged immediately to investigate whatever is the cause, radials or anything else. ================================== |
If by some very remote chance arcing should occur your SWR meter will jump about Good point, thanks for the info., |
If by some very remote chance arcing should occur your SWR meter will jump about Good point, thanks for the info., ---------------------------------------------------------------------- -- Rick, You are welcome. I have on occasion, for educational reasons and to avoid the many misunderstandings, recommended a change in the name of the ubiquitous SWR meter. It does not measure SWR and usually there is no line on which the SWR purports to be measured. And reflected power is somewhat meaningless or at least useless information. However, where it is located, it is an extremely valuable indicating instrument. I have suggested the name be changed to TLI (Transmitter Loading Indicator) which it actually is. Unfortunately, there are too many old wives in the way and it interferes with their ancient, pre-1950 traditions. ---- Reg, G4FGQ |
Rick K2XT wrote:
As a followup to my question, I guess the concept or the question is no different than if it referred to a dipole instead of radials on a vertical. The concern is protection from the high voltage at the end of the wire, and the potential of it causing a fire. So it is really a very general question, considering the numbers of antennas hams are having to disguise or hide inside their homes these days. In a vertical dipole, you have only one "radial" which carries the same currents and voltages as the upper vertical element. Seems to me, when one has multiple radials, the energy in each radial has to be the total energy available divided by the number of radials. Therefore, the voltage at the ends of 1/4WL radials should decrease as the number of radials is increased. This seems to be another way that distributed networks differ from lumped circuits. We might even be able to calculate the voltage at the ends of the radials, given the number of radials and the total power available to the radial system. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Cec, don't you think you should take diameter of radials as well as
their number into account. Also their angle, and the height above ground, or their distance from the brickwork, roof beams and rafters when in an attic. Do you have an equation for Volts = Function( number, frequency, watts, length, diameter, angle, height, etc ) ? ---- Reg, G4FGQ |
Reg Edwards wrote:
Cec, don't you think you should take diameter of radials as well as their number into account. Also their angle, and the height above ground, or their distance from the brickwork, roof beams and rafters when in an attic. Actually, I was thinking free space when I wrote that. It was a qualitative answer, Reg, not a quantitative one. Do you have an equation for Volts = Function( number, frequency, watts, length, diameter, angle, height, etc ) ? Only a ballpark figure, Reg, which should be good enough. Since balanced radials don't radiate (much), it should be a piece of cake for you to come up with a piece of software that calculates voltage at the tips Vs number of radials. Let me know if you need any help. :-) -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Rick,
One thought - I'd be very concerned about RF getting into the entire house system, especially stereos and tv's, depending on how your "radials" align with house wiring and how proximate they are. I had a dipole 15 feet off the roof of my house and at 1 KW, it wasn't a pretty sight...burglar and fire alarms going off, night lights blinking (the KW is on a separate 220 line), stereo speakers talking donald duck...the whole house rebelled. So now I am repositioning it out in the back pasture. The only alternative is QRP! 73, Greg, N6GK "Rick K2XT" wrote in message ... Regarding the potential hazards involved in using raised radials on a vertical - I'd be interested in comments from readers of this newsgroup. The antenna installation proposed is a vertical installed through the roof of a building. For many reasons it would be preferable to keep the radials inside the attic. My concern is possible danger due to the high voltages incurred at the ends of the radials. The antenna will be a SteppIR vertical for 40-10 meters with the base just under the roof, protruding through the roof. At the base will be a number of resonant radials fanning out throughout the attic. My concern is if this poses a fire hazard due to arcing (corona, whatever) at the ends of the radials. It may not be convenient to suspend the radials over their entire length or provide high quality suspended insulators at the wire ends. So what danger is there in letting radials lay on the floor of the attic, attached to the roof rafters, or even poked down inside the studs of the walls? I think we can assume the attic will be dry, except for normal Seattle humidity !! Rick K2XT |
"Cecil Moore" wrote:
Reg Edwards wrote: Do you have an equation for Volts = Function( number, frequency, watts, length, diameter, angle, height, etc ) ? Only a ballpark figure, Reg, which should be good enough. Since balanced radials don't radiate (much), it should be a piece of cake for you to come up with a piece of software that calculates voltage at the tips Vs number of radials. Let me know if you need any help. :-) ________________ Reg, The 1937 Brown, Lewis and Epstein IRE paper "Ground Systems as a Factor in Antenna Efficiency" include an analysis of the currents in radial ground systems, along with equations and graphs for it in various configurations. All you need to do to apply them to a system of raised radials is to modify these basic equations. Of course, you will have to read the paper first to do that (wink, nudge). But then you might also see why knowledge of ground conductivity was unimportant to the conclusions of this paper, and refrain from saying so in the future. RF |
Richard Fry wrote:
Reg, The 1937 Brown, Lewis and Epstein IRE paper "Ground Systems as a Factor in Antenna Efficiency" include an analysis of the currents in radial ground systems, along with equations and graphs for it in various configurations. All you need to do to apply them to a system of raised radials is to modify these basic equations. Of course, you will have to read the paper first to do that (wink, nudge). But then you might also see why knowledge of ground conductivity was unimportant to the conclusions of this paper, and refrain from saying so in the future. RF Unfortunately, the mathematical analysis in that paper was found to be in error. A search of the literature shows that quite a number of people worked on this problem well after publication of the BL&E paper. Some notable work was done by J.R. Wait and W.A. Pope of the Radiation Physics Laboratory, Defence Research Branch, in Canada. Two papers in particular give equations for the impedance of radial systems which appear to be valid -- "The Characteristics of a Vertical Antenna With a Radial Conductor Ground System", Appl. Sci. Res. B, Vol. 4, 1954; and "Input Resistance of L.F. Unipole Aerials With Radial Wire Earth Systems", Wireless Engineer, May, 1955. The equations involve multiple integral equations which can't be solved in closed form. In papers I've read which do involve equations which can be solved in closed form, even approximately, the results have deviated greatly from BL&E's measured results, making the accuracy of the method doubtful. This holds true for Reg's program, also, which apparently depends on some simplifying assumptions which aren't valid. NEC-2, which is readily available in numerous forms, does about as good a calculation as any of elevated radial systems. Its major limitation, in my opinion, is the inability to deal with stratified ground. Of course, even if it could handle stratified ground, the user would somehow have to determine the properties and locations of the various strata. NEC-4 can, in addition to NEC-2's capabilities, include buried radials in its models. A few tests show reasonable agreement between it and BL&E's results. Incidentally, the equations in the first Wait and Pope paper I mentioned resemble those used in NEC-4, but I haven't studied them in enough detail to determine if they are indeed the same. Elevated radial systems have been somewhat controversial, with some indications that modeled results don't imitate actual results very well, particularly at low frequencies. But there's very little really good measurement data available to make a valid judgement. Besides the possibility of stratified ground, some people have reported difficulty in maintaining equal currents in near-resonant elevated radial wires in real installations. This would have a substantial effect on a system, and would definitely cause deviation between modeled and measured results. There's considerable work to be done in this field, but what really needs to be done is the making of good, well documented and carefully done measurements of elevated radial systems -- not more calculations based on invalid assumptions. Roy Lewallen, W7EL |
On Mon, 08 Aug 2005 12:27:09 -0700, Roy Lewallen
wrote: There's considerable work to be done in this field, but what really needs to be done is the making of good, well documented and carefully done measurements of elevated radial systems -- not more calculations based on invalid assumptions. Hi Roy, That inspired me to reach for The ARRL Antenna Compendium, Volume 2. Within it, the very first article, is "Vertical Antennas: New Design and Construction Data" By Doty, K8CFU; Frey, W3ESU; and Mills, K4HU Their 10M vertical(s) above an elevated radial system of 64 wires presents some interesting results. Albeit, they perhaps do not answer the questions you've offered, but it does reveal the quality of work possible. 73's Richard Clark, KB7QHC |
On Mon, 8 Aug 2005 06:39:47 -0500, "Richard Fry"
wrote: Of course, you will have to read the paper first to do that (wink, nudge). But then you might also see why knowledge of ground conductivity was unimportant to the conclusions of this paper, and refrain from saying so in the future. Hi OM, In fact those authors took great care to consider the condition of ground conductivity and documented it for very good reasons. One of the hallmarks of their work reveals that the phase shift between the RF in the Wire, and that induced into the ground causes the lateral flow of currents, increasing power dissipation. This is a major reason why the density and spacing are important. Elevating the radials creates an entirely different situation. 73's Richard Clark, KB7QHC |
"Richard Clark" wrote
"Richard Fry" wrote: But then you might also see why knowledge of ground conductivity was unimportant to the conclusions of this paper, ... Hi OM, In fact those authors took great care to consider the condition of ground conductivity and documented it for very good reasons. __________________ Nowhere in Brown, Lewis and Epstein's IRE paper titled "Ground Systems as a Factor in Antenna Efficiency" is there ANY documentation of the actual ground conductivity that was measured, or even calculated for the antenna site and/or the propagation path used. It was unimportant for the construct and relevancy of the tests and conclusions which the paper reported. This is the paper I was referring to in my previous posts. RF |
On Mon, 08 Aug 2005 12:27:09 -0700, Roy Lewallen
wrote: Unfortunately, the mathematical analysis in that paper was found to be in error. A search of the literature shows that quite a number of people worked on this problem well after publication of the BL&E paper. Some notable work was done by J.R. Wait and W.A. Pope of the Radiation Physics Laboratory, Defence Research Branch, in Canada. Two papers in particular give equations for the impedance of radial systems which appear to be valid -- "The Characteristics of a Vertical Antenna With a Radial Conductor Ground System", Appl. Sci. Res. B, Vol. 4, 1954; and "Input Resistance of L.F. Unipole Aerials With Radial Wire Earth Systems", Wireless Engineer, May, 1955. The equations involve multiple integral equations which can't be solved in closed form. In papers I've read which do involve equations which can be solved in closed form, even approximately, the results have deviated greatly from BL&E's measured results, making the accuracy of the method doubtful. This holds true for Reg's program, also, which apparently depends on some simplifying assumptions which aren't valid. snip Roy Lewallen, W7EL Roy, I don't have the Wait and Pope paper for review, but I'm concerned over the validity of their equations that you say render BL&E's measurements invalid. How can their measurements be invalid when field-strength measurements of literally thousands of AM BC antennas agree with BL&E's? Keep in mind that every BC station that uses a directional array is required to prove the performance of the array with field strength measurements that assure the measured values agree with the calculated values. It was only after verifying BL&E's measurements by comparing their data with those obtained from many subsequent measurements of BC antennas that the FCC used the BL&E data in standardizing the requirements for radial systems for new BC stations. Isn't it possible that Wait and Pope's equations relate to some other aspects of BC antennas than those of BL&E? I simply cannot accept the notion that BL&E's data is wrong. Walt,W2DU |
Rest easy, Walt. To my knowledge, no one has ever shown BL&E's
*measurements* to be invalid, or the conclusions reached from those measurements. It's their mathematical treatment of what they expected to happen, in the first part of their paper (Part II: Theoretical Considerations), that wasn't correct. I don't believe I have a paper that details the errors they made, but it was regarded my later authors as being in error, prompting a great deal of more rigorous work. Later authors don't generally even reference that BL&E theoretical mathematical work. Nearly all reference their measurements, however, as they should. Roy Lewallen, W7EL Walter Maxwell wrote: Roy, I don't have the Wait and Pope paper for review, but I'm concerned over the validity of their equations that you say render BL&E's measurements invalid. How can their measurements be invalid when field-strength measurements of literally thousands of AM BC antennas agree with BL&E's? Keep in mind that every BC station that uses a directional array is required to prove the performance of the array with field strength measurements that assure the measured values agree with the calculated values. It was only after verifying BL&E's measurements by comparing their data with those obtained from many subsequent measurements of BC antennas that the FCC used the BL&E data in standardizing the requirements for radial systems for new BC stations. Isn't it possible that Wait and Pope's equations relate to some other aspects of BC antennas than those of BL&E? I simply cannot accept the notion that BL&E's data is wrong. Walt,W2DU |
On Tue, 9 Aug 2005 08:03:53 -0500, "Richard Fry"
wrote: Nowhere in Brown, Lewis and Epstein's IRE paper titled "Ground Systems as a Factor in Antenna Efficiency" is there ANY documentation of the actual ground conductivity that was measured, or even calculated for the antenna site and/or the propagation path used. It was unimportant for the construct and relevancy of the tests and conclusions which the paper reported. This is the paper I was referring to in my previous posts. Hi OM, Both Reg and you would do well to obtain and read a copy. On page 757 is introduced the necessary discussion of: Is = Iw + Ie "The we will denote the total earth current flowing radially inward .... as Is, ... where Iw is the component flowing in the wires, and Ie is the part which actually flows in the earth. The discussion of earth conductivity (quite specifically named as such) within the paper spans pages 757, 758, 759, 760, with numerous citations and graphings against specific conductivity values applied to related figures in page 761, 762, 763, and 764. On page 758: "The actual earth current and the current flowing in the radial wires are given by..." introducing formula (8). Followed on page 759 with: "while the current actually flowing in the earth is...." introducing formula (10). "Thus from (8), (9), and (10), together with Fig. 4. we may obtain the actual current in the earth...." As for explicit conductivity: "Fig. 5 shows the current in the wires for the following conditions .... 0.2X10^-4 mhos per cm cube" "Fig. 6 shows the actual current in the earth for the same conditions." "shown for the following conditions..." and four specifications of conductivity follow. Now, specifically to a comment I offered as to the importance of noting conductivity: "When the earth is of good conductivity, the current leaves the wires and enters the earth closer to the antenna than does when the earth is a poor conductor." There is also a formulation for Fig. 17 (page 766) that is introduced as "The current is flowing toward the antenna through a ring of earth of radius..." which computes the power lost to ground for a known conductivity (with examples abounding). In this short span of 8 pages dedicated to earth conductivity there at least 12 graphs and charts all quite distinctly displaying the variation of measured results as a function of different specified ground conductivities antennas and ground system combinations. The authors were quite aware of the ground beneath their feet and duly reported its contributions in the standard engineering fashion of displaying first principles. 73's Richard Clark, KB7QHC |
Thanks Roy, I'm resting easy now.
Walt On Tue, 09 Aug 2005 10:51:42 -0700, Roy Lewallen wrote: Rest easy, Walt. To my knowledge, no one has ever shown BL&E's *measurements* to be invalid, or the conclusions reached from those measurements. It's their mathematical treatment of what they expected to happen, in the first part of their paper (Part II: Theoretical Considerations), that wasn't correct. I don't believe I have a paper that details the errors they made, but it was regarded my later authors as being in error, prompting a great deal of more rigorous work. Later authors don't generally even reference that BL&E theoretical mathematical work. Nearly all reference their measurements, however, as they should. Roy Lewallen, W7EL |
"Richard Clark" wrote Both Reg and you would do well to obtain and read a copy. =================================== Until now I have not contributed to this discussion. Neither now and very little in the past. So please leave me out of it. I have produced one small program (I am surprised at the attention drawn to it) which computes radiating efficiency of a short vertical antenna based on a novel analysis of ground loss, ie., shallow buried radial wires which behave as lossy transmission lines. All I have to say is that the program gives the "right" answers. Disprove it if you can. It is as accurate as the ground "constants" are known, that is about plus or minus 30 percent. The answers are forthcoming within milli-seconds. No need to go on a one month training course. And it's free. What more do you want? To prove it wrong you have to create a set up similar to that pruduced by BL&E - only this time don't forget to measure ground coductivity and permittivity! From what Roy says, BL&E were hardly better than bungling amateurs of their era. The only reason their report is considered to be 'The Bible' is because it was the only one ever produced and available at the time. They laid down so many radials it didn't matter what ground conductivity was. ---- Reg. |
On Tue, 9 Aug 2005 19:16:45 +0000 (UTC), "Reg Edwards"
wrote: They laid down so many radials it didn't matter what ground conductivity was. Hi Reg, As usual you both lost track of the intent of the study. The whole point was to insure it doesn't matter. Sorry to rustle your skirts, but this falls under the heading of: "Stating the bleeding obvious" 73's Richard Clark, KB7QHC |
"Richard Clark" wrote
"Richard Fry" wrote: Nowhere in Brown, Lewis and Epstein's IRE paper titled "Ground Systems as a Factor in Antenna Efficiency" is there ANY documentation of the actual ground conductivity that was measured, or even calculated for the antenna site and/or the propagation path used. It was unimportant for the construct and relevancy of the tests and conclusions which the paper reported. Hi OM, Both Reg and you would do well to obtain and read a copy.... the discussion of earth conductivity (quite specifically named as such) within the paper spans pages 757, 758, 759, 760, with numerous citations and graphings against specific conductivity values applied to related figures in page 761, 762, 763, and 764. ... (etc) I have the paper, and have read it carefully, many times. The paper gives equations and graphs for current in the radial wires for a perfectly conducting Earth, and for Earth conductivities of 20 x 10^-15 e.m.u. and 100 x 10^-15 e.m.u. Later, in the experimental data, they report measurements of the currents for various radial configurations during their measurement sequences. But as I wrote, nowhere do they specifically report the actual ground conductivity for the antenna site, or along the 0.3 mile propagation path of the test. If you can find that anywhere in that paper, I will promptly retract my statement, and apologize. Figure 30 in the paper shows that the ground system comprised of 113 radials of 0.412 lambda each resulted in a measured field strength that was about 0.18 dB below the theoretical value for it from a 90 degree radiator against a zero-ohm connection to a perfect Earth. I expect most of us would be quite happy if our measured data agreed that closely with its theoretical value. In any case it does show that the actual value of the ground conductivities for the test site and path had a trivial bearing on the test results, e.g., it was unimportant. In fact the efficiency of AM broadcast vertical radiators per the FCC definition always is based on a perfect ground plane, and two ohms or less of DC resistance in the transmitter connection to it (via the radial ground system). Only then is distant field strength determined, using the radiator efficiency value and applied RF power along with the appropriate FCC propagation curve for the frequency and Earth conductivity for the path. RF |
On Tue, 9 Aug 2005 15:32:22 -0500, "Richard Fry"
wrote: But as I wrote, nowhere do they specifically report the actual ground conductivity for the antenna site, or along the 0.3 mile propagation path of the test. If you can find that anywhere in that paper, I will promptly retract my statement, and apologize. Hi OM, As stated previously: "Fig. 6 shows the actual current in the earth for the same conditions" I hope the word "actual" is not subject to recourse to the IEEE dictionary for clarification. The "same conditions" are explicitly specified with conductivity. One has to trust that engineers did not ask the farmer's wife to make this determination for them in her kitchen. The imputation of distrust would seem to serve another agenda. Figures 7, 8, 9, and 10 also are all quite explicit. The paper offers enough data to render your objections as tedious as my work disproving "total cancellation" - the difference being I did the work instead of simply saying "'t'ain't so." ;-) 73's Richard Clark, KB7QHC |
"Richard Clark" wrote
"Richard Fry" wrote: But as I wrote, nowhere do they specifically report the actual ground conductivity for the antenna site, or along the 0.3 mile propagation path of the test. If you can find that anywhere in that paper, I will promptly retract my statement, and apologize. As stated previously: "Fig. 6 shows the actual current in the earth for the same conditions" The "same conditions" are explicitly specified with conductivity. etc __________ Yes, BL&E reported on the currents in the radials and the total ground currents during the test (as I already stated), but that is not the issue. The issue is whether or not not they explicity reported the value of Earth conductivity for the test site and propagation path--and they did not. Nor was it important to the conclusions of the test. RF |
Richard Clark wrote: Hi OM, As stated previously: "Fig. 6 shows the actual current in the earth for the same conditions" I hope the word "actual" is not subject to recourse to the IEEE dictionary for clarification. I agree with Richard Fry. All the references to ground conductivity, including Figure 6, are in Part II, the (erroneous) theoretical treatment. As for the "actual", look back a page, to page 759, at the bottom, where they say, "Thus from [equations] (8), (9), and (10), together with Fig. 4 ["Calculated Values of Total Earth Current"], we may obtain the actual current in the earth and the current in the wires." So the "actual" current is calculated from three equations and a graph of calculated current. Whatever they might have meant by "actual", it doesn't mean that it was measured. The "same conditions" are explicitly specified with conductivity. One has to trust that engineers did not ask the farmer's wife to make this determination for them in her kitchen. The imputation of distrust would seem to serve another agenda. Figures 7, 8, 9, and 10 also are all quite explicit. They are also part of the theoretical treatment and don't represent measured values. Measured values begin with Fig. 25. . . . Brown, Lewis, and Epstein did a good and careful job of measurement. Please be careful not to confuse their not-so-good theoretical treatment with their measurement results. Roy Lewallen, W7EL |
Reg Edwards wrote:
Until now I have not contributed to this discussion. Neither now and very little in the past. So please leave me out of it. I have produced one small program (I am surprised at the attention drawn to it) which computes radiating efficiency of a short vertical antenna based on a novel analysis of ground loss, ie., shallow buried radial wires which behave as lossy transmission lines. All I have to say is that the program gives the "right" answers. Disprove it if you can. Considering that Brown, Lewis, and Epstein's experimental work has held as being valid for about 70 years now, it can be used as a test for various attempts at calculating ground system losses. NEC-4 matches their results quite well; your program produces results which are dismally different. Anyone armed with both the BL&E paper and your program can see for himself. It is as accurate as the ground "constants" are known, that is about plus or minus 30 percent. The answers are forthcoming within milli-seconds. No need to go on a one month training course. And it's free. What more do you want? It's sure a lot easier to create an easy-to-use free program if the results don't have to bear any resemblance to reality. But perhaps you're right -- maybe people who use free software shouldn't expect the author to be honest about the program's accuracy. To prove it wrong you have to create a set up similar to that pruduced by BL&E - only this time don't forget to measure ground coductivity and permittivity! Your program fails badly with any reasonable ground conductivity and permittivity. NEC-4 does pretty well with reasonable assumptions for the ground quality of a field in New Jersey in the wintertime. From what Roy says, BL&E were hardly better than bungling amateurs of their era. Once again, you've crossed the line from your normal pomposity and crankiness to an insult and lie. The only reason their report is considered to be 'The Bible' is because it was the only one ever produced and available at the time. Another untruth. It stands because their measurements took in quite a number of conditions, and have been replicated. They laid down so many radials it didn't matter what ground conductivity was. Those people who have read the paper know this to be untrue, also. They made measurements with 2, 15, 30, 60, and 113 radials. Isn't that kind of a record, Reg, three flatly untrue statements in a single posting? You should record the name of that wine and save it for those special occasions when you feel threatened by the possibility that some Yanks might have done something useful 70 years ago. Hope your favorite store has lots in stock. In vino veritas, indeed. Roy Lewallen, W7EL |
On Tue, 09 Aug 2005 15:07:21 -0700, Roy Lewallen
wrote: Whatever they might have meant by "actual", it doesn't mean that it was measured. .... Brown, Lewis, and Epstein did a good and careful job of measurement. Please be careful not to confuse their not-so-good theoretical treatment with their measurement results. If I compare this with On Tue, 09 Aug 2005 15:25:37 -0700, Roy Lewallen wrote: Considering that Brown, Lewis, and Epstein's experimental work has held as being valid for about 70 years now, it can be used as a test for various attempts at calculating ground system losses. NEC-4 matches their results quite well; your program produces results which are dismally different. Anyone armed with both the BL&E paper and your program can see for himself. .... Your program fails badly with any reasonable ground conductivity and permittivity. NEC-4 does pretty well with reasonable assumptions for the ground quality of a field in New Jersey in the wintertime. leads to amusing circularity which I will set aside. One might well suppose that through fine parsing, "actual" is not, and is code for "might be." All reasonably argued, but reason has been replaced with the rhetoric of argument fighting for air. The authors express that with their formulas (8), (9) and (10) that results would be "accurate" which I presume parses here to "best guess." I also note that what falls within the "theoretical" discussion is couched with the variables set in the "measurement" discussion. The paper, as would be expected, was written iteratively and results were drawn back into the theory. The theoretical discussion of radial counts does not proceed from a natural 15, 30, 60, 113 progression - this is plainly ad hoc determination. Nor does the theoretical discussion of antenna height proceed naturally through 22, 44, 66, 88, and 99 degrees - again arrived at by ad hoc methods. All such "theoretical" considerations are the happenstance of what was available in the field. It is overwhelmingly obvious that Figures 4 through 14 are derived from the 3MHz tests employing antenna sections of 20', 20', 20', 20', and 10' which fall right on the curve at the 1.098 degrees per foot of section used. The text clearly states this: "The antenna heights given here were chosen to conform to later experimental heights." This admission precedes the introduction of ground conductivity, and yet after all of this ad hoc conscription from the field flows the presumption that the ground conductivity is derived. To put it bluntly, the data and system variables inhabit the theoretical discussion like a glove. Like a political promise, the embraced vague genesis of ground conductivity has been heralded for every purpose but what the authors put it to. 73's Richard Clark, KB7QHC |
Whatever little BL&E may have contributed to the theoretical aspects,
it has always been disregarded by broadcasting engineers who always did what they did last time - and laid 120 radials regardless of economics. ---- Reg. |
On Wed, 10 Aug 2005 00:54:35 +0000 (UTC), "Reg Edwards"
wrote: and laid 120 radials regardless of economics. Hi Reg, For a million dollar station investment, I don't think the price for shares in Anaconda have brought any significant attention to anyone. Perhaps you are thinking of the relative price in 1906 when it cost 4 times as much against 5% of what we consume now. Well, maybe only 30 years ago when it cost more than 3 times as much as now. Or perhaps only 10 years ago when it cost twice as much as now. Odd, it seems the price of copper and the value of the Pound have been tracking each other over that same period. Your complaint would be better founded on us planting sterling radials. 73's Richard Clark, KB7QHC |
Richard Clark wrote:
On Tue, 09 Aug 2005 15:07:21 -0700, Roy Lewallen wrote: Whatever they might have meant by "actual", it doesn't mean that it was measured. ... Brown, Lewis, and Epstein did a good and careful job of measurement. Please be careful not to confuse their not-so-good theoretical treatment with their measurement results. If I compare this with On Tue, 09 Aug 2005 15:25:37 -0700, Roy Lewallen wrote: Considering that Brown, Lewis, and Epstein's experimental work has held as being valid for about 70 years now, it can be used as a test for various attempts at calculating ground system losses. NEC-4 matches their results quite well; your program produces results which are dismally different. Anyone armed with both the BL&E paper and your program can see for himself. ... Your program fails badly with any reasonable ground conductivity and permittivity. NEC-4 does pretty well with reasonable assumptions for the ground quality of a field in New Jersey in the wintertime. leads to amusing circularity which I will set aside. Sorry, as so often happens I missed your point entirely. If you're interested in having me understand what "circularity" you mean, you'll have to be more blunt and pedestrian so I'm able to understand it. One might well suppose that through fine parsing, "actual" is not, and is code for "might be." All reasonably argued, but reason has been replaced with the rhetoric of argument fighting for air. Again, I haven't a clue what you're talking about. Arguing semantics, I suppose, in which I'm afraid I have no interest. The authors express that with their formulas (8), (9) and (10) that results would be "accurate" which I presume parses here to "best guess." I also note that what falls within the "theoretical" discussion is couched with the variables set in the "measurement" discussion. The paper, as would be expected, was written iteratively and results were drawn back into the theory. I'm missing this one, too. If you're saying that those three graphs are of measured data, I can present what I believe is a good argument against that premise. But I can't tell if that's what you're saying or not. The theoretical discussion of radial counts does not proceed from a natural 15, 30, 60, 113 progression - this is plainly ad hoc determination. Nor does the theoretical discussion of antenna height proceed naturally through 22, 44, 66, 88, and 99 degrees - again arrived at by ad hoc methods. All such "theoretical" considerations are the happenstance of what was available in the field. It wouldn't surprise me a bit if the theoretical work was written or modified after the measurements were made, which I believe is what you're saying. That doesn't alter the fact that the graphs of Part II are from calculated rather than measured results. It is overwhelmingly obvious that Figures 4 through 14 are derived from the 3MHz tests employing antenna sections of 20', 20', 20', 20', and 10' which fall right on the curve at the 1.098 degrees per foot of section used. I'm not sure what you mean by "derived from", but they sure aren't graphs of measured data. For starters, some of those graphs are for 1 MHz, while according to the paper all measurements were made at 3. For another thing, I'm sure they didn't have the ability to change the ground conductivity; some of the graphs are for different ground conductivities than others. Finally, compare Figures 7 and 8 with Figure 42. The latter is from measured results, as explained on p. 781. It's quite different from the theoretical results for Figures 7 and 8. Incidentally, the theoretical analysis, including Figures 7 and 8, seems to assume infinite radial length, which is another difference between the theoretical and measured conditions (besides ground conductivity and, in some cases, frequency). The text clearly states this: "The antenna heights given here were chosen to conform to later experimental heights." That's a very reasonable thing to do, when presenting both theoretical and measured results. I believe you're drawing conclusions from it which are well beyond its straightforward intent. (Perhaps this is due to your English literature background? It certainly was one of the activities overwhelmingly emphasized and encouraged in all English lit courses I ever took.) This admission precedes the introduction of ground conductivity, and yet after all of this ad hoc conscription from the field flows the presumption that the ground conductivity is derived. ? To put it bluntly, the data and system variables inhabit the theoretical discussion like a glove. Even that isn't blunt enough for me. Sorry. I did badly in English. Like a political promise, the embraced vague genesis of ground conductivity has been heralded for every purpose but what the authors put it to. If you say so. Whatever you said. Roy Lewallen, W7EL |
On Tue, 09 Aug 2005 18:43:19 -0700, Roy Lewallen
wrote: Like a political promise, the embraced vague genesis of ground conductivity has been heralded for every purpose but what the authors put it to. If you say so. Whatever you said. Hi Roy, It must have taken great effort of will to come to that conclusion. Your achievement is noted as has all the groaning along the way. 73's Richard Clark, KB7QHC |
On Tue, 09 Aug 2005 18:43:19 -0700, Roy Lewallen
wrote: Sorry, as so often happens I missed your point entirely. If you're interested in having me understand what "circularity" you mean, you'll have to be more blunt and pedestrian so I'm able to understand it. Hi Roy, You consistently demur expertise in English, and you are equally troubled in Blunt, but the plea for help cannot go unanswered. Let's see, we have a premise that the ground conductivity was concocted from formula for the BL&E paper. If we proceed along the lines this is true, then we immediately are faced with the conundrum: ground quality of a field in New Jersey in the wintertime. How was this determination made? When was this determination made? What was the determination made? Oh well, all such quantitative discussion is missing so the statement appears to have as much basis as a guess, but we are faced with the complaint holding Reggie to a higher standard: Your program fails badly with any reasonable ground conductivity and permittivity. compared to what determination? Where? of What? by Whom? This appears to be a war of wills between the best guessing software. Can we presume the answers lie with: Brown, Lewis, and Epstein did a good and careful job of measurement. which, by the leading hypothesis contains no measure of conductivity? So the objection to Reggie's software not conforming to results offered by NEC-4 is proven by: NEC-4 does pretty well with reasonable assumptions for the ground quality of a field in New Jersey in the wintertime. a strained appeal through BL&E, NEC-4 matches their results quite well which, by the leading hypothesis contains no measure of conductivity. Which from FCC charts would suggest it to be uniformly dismal. I've seen no discussion of actual quantifiable results against these claims offered, so there is every chance that they are pinned together by the evident circularity: 1. There has been no measurement of ground conductivity by BL&E 2. Reggies model for ground conductivity counters NEC-4 3. NEC-4's model for ground conductivity conforms to BL&E 4. There has been no measurement of ground conductivity by BL&E I would like to see: Your program fails badly with any reasonable ground conductivity and permittivity. supported by something other than appeals to dead white engineers - Reggie has a patent on that method already. 73's Richard Clark, KB7QHC |
Reggie has a patent on that method already.
73's Richard Clark, KB7QHC ================================ Yes! It doesn't take much to get Roy to lose his temper and resort to a frustrated attempt at character assassination. Well, sadly, that's the end of the Bible. Between you, after 68 years, you experts have finally shredded it. ;o( ---- Reg, G4FGQ |
"Richard Clark"
I've seen no discussion of actual quantifiable results against these claims offered, so there is every chance that they are pinned together by the evident circularity: 1. There has been no measurement of ground conductivity by BL&E 2. Reggies model for ground conductivity counters NEC-4 3. NEC-4's model for ground conductivity conforms to BL&E 4. There has been no measurement of ground conductivity by BL&E _________________ At least now you admit that BL&E didn't measure ground conductivity. That's progress. First things first. The goal of BL&E's experimental work was to relate the 'efficiency' of MW vertical radiators of various electrical heights to radial ground systems of various configurations. It did not state or find that ground conductivity had any significant bearing on this, and, as shown by their measured results, it did not. The entire theoretical section of this paper where ground currents are calculated, and the references to ground currents that were measured during the experimental work could have been omitted both from consideration and measurement without changing the conclusions of the paper. None of that was significant to their measured results for field strength vs system configuration, which was the purpose of their efforts. And omitting it would have spared you your confusion. The FCC considers every non-sectionalized AM broadcast vertical radiator of a given electrical height using a given radial ground system to have a given efficiency. Period. Ground conductivity at the radiator site has nothing to do with that. It doesn't matter whether that site is in the middle of Kansas with 30 mS/m conductivity, or on Long Island with 0.5 mS/m, radiation emitted from a given antenna+radial ground system will be the same. The purpose of the BL&E field work was to determine those efficiency values, and it did so with high accuracy. Their findings have been a benchmark confirmed at many hundreds (probably thousands) of AM broadcast station applications since 1937. By the way, even NEC-2 can be used to confirm the results of BL&E's study, by inserting at the bottom of the vertical radiator a low-value DC resistance simulating the resistance of the radial ground system connection with a perfect ground plane. This again shows that ground conductivity is insignificant in determining the radiation 'efficiency' of a MW broadcast vertical and its radial ground system. RF |
"Richard Fry" wrote At least now you admit that BL&E didn't measure ground conductivity. That's progress. ================================ Admit it ? You got me wrong! I was the FIRST to point it out many months ago. I did it politely by blaming BL&E's poor memory. ---- Reg, G4FGQ |
"Reg Edwards"
"Richard Fry" wrote At least now you admit that BL&E didn't measure ground conductivity. That's progress. Admit it ? You got me wrong! I was the FIRST to point it out many months ago. I did it politely by blaming BL&E's poor memory. ___________________ Note that my post responded to the comments of Richard Clark, not to yours. Now if YOU will admit that there was no reason for BL&E to have measured ground conductivity for this study, and quit saying that they "forgot" to do it--that will be another victory for reality. RF |
On Tue, 09 Aug 2005 19:41:54 -0700, Richard Clark
wrote: Let's see, we have a premise that the ground conductivity was concocted from formula for the BL&E paper. On Wed, 10 Aug 2005 07:33:37 -0500, "Richard Fry" wrote: At least now you admit that BL&E didn't measure ground conductivity. That's progress. Hi OM, Admission indeed, this is a consistent strain of interpretation along with the remaining embellishment that is unresponsive to the post. 73's Richard Clark, KB7QHC |
"Richard Clark"
Admission indeed, this is a consistent strain of interpretation along with the remaining embellishment that is unresponsive to the post. _____________ So you say, but what I have written is a relevant commentary on the applicablity of the content and conclusions of the BL&E paper. You have offered nothing to disprove my comments. Nor can you disprove them, because objectively stated reality will not support whatever attempt you might make. RF |
On Wed, 10 Aug 2005 10:31:57 -0500, "Richard Fry"
wrote: "Richard Clark" Admission indeed, this is a consistent strain of interpretation along with the remaining embellishment that is unresponsive to the post. _____________ So you say, but what I have written is a relevant commentary on the applicablity of the content and conclusions of the BL&E paper. You have offered nothing to disprove my comments. Nor can you disprove them, because objectively stated reality will not support whatever attempt you might make. Hi OM, What you have written is called bloated prose. It is suitable for ad copy and trade show handouts that tout insignificant advantages only because there is nothing substantial to present. Eight pages of discussion from the report covering the conductivity of earth has been rendered a foot note by your diminution of attention. Your absurd conclusion that ground conductivity had no bearing on the outcome is glaring contradiction to the scope and purpose of the entire enterprise. To reduce this focus of efficiency to copper loss is a toothpick in the forest of effort by these men. 73's Richard Clark, KB7QHC |
"Richard Clark"
What you have written is called bloated prose. It is suitable for ad copy and trade show handouts that tout insignificant advantages only because there is nothing substantial to present. Eight pages of discussion from the report covering the conductivity of earth has been rendered a foot note by your diminution of attention. Your absurd conclusion that ground conductivity had no bearing on the outcome is glaring contradiction to the scope and purpose of the entire enterprise. To reduce this focus of efficiency to copper loss is a toothpick in the forest of effort by these men. __________________ You still provide no proof that what I wrote is incorrect or inapplicable, I see. I'm content to let objective readers decide for themselves which of us has made the correct evaluation. RF |
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