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Radiating Efficiency
Frank,
To complete the graphs of Rin + jXin versus length for one radial, I need data for lengths between 0.5 metres and 2 metres at intervals of 0.2 metres. Could you oblige please? The nice smooth graphs I have produced so far are free of 'measurement' errors which could be attributed to your hard, tedious work. The uncertainty due to NEC4 is as yet unknown. In the NEC4 model of a single radial, what is the length of the short bits of radial used to model it? Alternatively, into what number of short lengths is the radial under test divided? ---- Reg, G4FGQ. |
Radiating Efficiency
"Reg Edwards" wrote in message ... Frank, To complete the graphs of Rin + jXin versus length for one radial, I need data for lengths between 0.5 metres and 2 metres at intervals of 0.2 metres. Could you oblige please? The nice smooth graphs I have produced so far are free of 'measurement' errors which could be attributed to your hard, tedious work. The uncertainty due to NEC4 is as yet unknown. In the NEC4 model of a single radial, what is the length of the short bits of radial used to model it? Alternatively, into what number of short lengths is the radial under test divided? No problem Reg, here are the data you requested: 0.5 m -- Radial Z = 167.6 - j 161.0 0.6 m -- Radial Z = 146.6 - j 136.3 0.8 m -- Radial Z = 115.9 - j 102.3 1.0 m -- Radial Z = 101.4 - j 79.1 1.2 m -- Radial Z = 89.4 - j 61.5 1.4 m -- Radial Z = 80.9 - j 57.2 1.6 m -- Radial Z = 74.6 - j 35.0 1.8 m -- Radial Z = 70.2 - j 24.1 2.0 m -- Radial Z = 67.2 - j 14.2 Concerning your previous question about the Smith Chart. It is a powerful visual aid which gives a better understanding of what is really happening to the impedances. Exactly what I got out of graphing the data was really only a confirmation of the expected spiral toward Zo. Also the "zero-crossing" which occurs at quarter-wave multiples. Normalization of the data (Division of each complex datum by the complex Zo), and linear graphing, will also provide the same information; including the gradual approach to the normalized Zo of 1 ohm. Where the Smith Chart really proves its worth is in the design of matching networks involving: L, C, R, and transmission lines. It is hard to imagine how anybody could do such design without this aid. I am not sure if anybody actually uses the paper versions these days, but the software equivalent, combined with programs such as (Now Agilent's) Eagleware, are pretty much design lab standards. In this model all segments are a constant 10 cm in length. The number of segments will therefore be L(m)/0.1. Frank |
Radiating Efficiency
On Wed, 02 Aug 2006 14:03:48 GMT, "Frank's" wrote:
"Reg Edwards" wrote in message ... Frank, snip Concerning your previous question about the Smith Chart. It is a powerful visual aid which gives a better understanding of what is really happening to the impedances. Exactly what I got out of graphing the data was really only a confirmation of the expected spiral toward Zo. Also the "zero-crossing" which occurs at quarter-wave multiples. Normalization of the data (Division of each complex datum by the complex Zo), and linear graphing, will also provide the same information; including the gradual approach to the normalized Zo of 1 ohm. Where the Smith Chart really proves its worth is in the design of matching networks involving: L, C, R, and transmission lines. It is hard to imagine how anybody could do such design without this aid. I am not sure if anybody actually uses the paper versions these days, but the software equivalent, combined with programs such as (Now Agilent's) Eagleware, are pretty much design lab standards. In this model all segments are a constant 10 cm in length. The number of segments will therefore be L(m)/0.1. Frank May I insert a few words about the Smith Chart? During the period between 1958-59 I designed the entire antenna system and matching harness for the World's first weather satellite, TIROS 1, which was launched April 1, 1960. Four transmitters operating simultaneously on separate frequencies fed the antenna that comprised four crossed monopoles radiating right circular polarization from two transmitters and left circular polarization on the other two frequencies. The point concering the Smith Chart is that the only tools I had for the development of both the antenna system and the matching harness was the Hewlett-Packard HP-805 slotted line for impedance measurements, the slide rule for calculations, and the paper Smith Chart to tell me where I was in the desert. The resolution available with the Chart was sufficient to make the system work successfully. Philip Smith was my hero. Incidentally, the matching harness was fabricated entirely of printed-circuit stripline, and that was 47 years ago. Walt, W2DU |
Walt, W2DU, and Tiros
On Wed, 02 Aug 2006 11:18:07 -0400, Walter Maxwell
wrote: During the period between 1958-59 I designed the entire antenna system and matching harness for the World's first weather satellite, TIROS 1, which was launched April 1, 1960. Walt, Could you please tell me a little more about that satellite? Reason I ask is there is a place I am sure you can enlighten us on, called Camp Evans. I know there is still a big dish antenna there, although the wooden structure surrounding it is failing. Supposedly it was used for communicating with Tiros. Is that right? A NJ radio club had a hamfest there in April, and I was able to walk under the antenna and they have some displays there. Supposedly Camp Evans was also the place where the first signals were bounced off the moon, somewhere around 1946. Camp Evans looks like at least parts of it are being renovated. Brookdale Comm. College has some classrooms there, very modern. Oh yes, and on the road leading to Camp Evans (Marconi Road !!) there is a display of the top portion of one of Marconi's towers, and a plaque noting that there were many such towers in the area in the early 1900s. Quite a bit of radio history, in these parts of New Jersey, and I am glad to know one of the pioneers frequents this newsgroup. Not far away, in Holmdel, is where AT&T communicated with Telstar, I believe, about the same time period. The Holmdel facility, home to 6000 Bell Labs employees as recently as1999 has been sold and is going to be demolished. Rick K2XT |
Radiating Efficiency
May I insert a few words about the Smith Chart?
During the period between 1958-59 I designed the entire antenna system and matching harness for the World's first weather satellite, TIROS 1, which was launched April 1, 1960. Four transmitters operating simultaneously on separate frequencies fed the antenna that comprised four crossed monopoles radiating right circular polarization from two transmitters and left circular polarization on the other two frequencies. The point concering the Smith Chart is that the only tools I had for the development of both the antenna system and the matching harness was the Hewlett-Packard HP-805 slotted line for impedance measurements, the slide rule for calculations, and the paper Smith Chart to tell me where I was in the desert. The resolution available with the Chart was sufficient to make the system work successfully. Philip Smith was my hero. Incidentally, the matching harness was fabricated entirely of printed-circuit stripline, and that was 47 years ago. Very interesting Walt. Judging by the type of work you were involved in you must be familiar with the classic text by: Matthaei, Young, and Jones. I am not familiar with the HP-805, but probably because most of my earlier lab work was concerned only with HF. I realize that slide rule, pencil, and Smith Chart was the only way in those days. When I started work any intense analysis was done in FORTRAN on main frame computers. One of the hot topics I remember was mini-computers, but never got to see one. I don't think they lasted long, since soon after programmable desktops started to become available. One thing I remember was a guy designing HF antenna tuners, and he used the Smith Chart. What is interesting is that the charts were very large, about 2 ft X 3 ft, and came in pads. Much greater accuracy than the standard chart. I think they may have been published by a company called K-electronics. I used to needle guys in the lab by telling them that Smith was a ham. I now have a nice high res pdf of the Smith Chart, but usually use an electronic version from the "Berne Institute of Engineering". 73, Frank |
Radiating Efficiency
On Wed, 02 Aug 2006 16:50:39 GMT, "Frank's"
wrote: "Berne Institute of Engineering" Hi Frank, Reverse engineering this clue, I've found the author is Prof. F. Dellsperger, and that his Smith Chart software can be found at: http://www.fritz.dellsperger.net/downloads.htm 73's Richard Clark, KB7QHC |
Radiating Efficiency
"Richard Clark" wrote in message
... On Wed, 02 Aug 2006 16:50:39 GMT, "Frank's" wrote: "Berne Institute of Engineering" Hi Frank, Reverse engineering this clue, I've found the author is Prof. F. Dellsperger, and that his Smith Chart software can be found at: http://www.fritz.dellsperger.net/downloads.htm 73's Richard Clark, KB7QHC Thanks Richard, I had recently tried to locate a source for this program, but could no longer find it. I see he has updated the program so will try the upgrade. I see he also has a lot of other stuff that looks interesting. 73, Frank, VE6CB |
Radiating Efficiency
No problem Reg, here are the data you requested: 0.5 m -- Radial Z = 167.6 - j 161.0 0.6 m -- Radial Z = 146.6 - j 136.3 0.8 m -- Radial Z = 115.9 - j 102.3 1.0 m -- Radial Z = 101.4 - j 79.1 1.2 m -- Radial Z = 89.4 - j 61.5 1.4 m -- Radial Z = 80.9 - j 57.2 1.6 m -- Radial Z = 74.6 - j 35.0 1.8 m -- Radial Z = 70.2 - j 24.1 2.0 m -- Radial Z = 67.2 - j 14.2 ===================================== Frank, Thank you for the above. Can you do 36 radials from 0.6 to 8.0 metres in increments of 0.2 metres? Must be the same input data as before :- F = 8.07 MHz, Ground = 150,16 Radial diameter = 1.64mm, Depth = 25mm. ---- Reg. |
Radiating Efficiency
Reg,
I have taken Frank's numbers from NEC-4 (that he sent me) and compared the results with Radials_3. Here is what I found: NEC-4 Parameters (in parens are the values I get with Radials_3, note the differences are LARGE) Height 20 m; Radials 15 m; 24 radials at 15 degree intervals; Radials 25 mm below ground; All wires # 14 AWG copper; (I USED 2mm wire) Gnd. Er = 25, Resistivity 25 ohm-m; Resonant Frequency 3.64 MHz, and; (Radial_3 shows Resonant Freq of 3.750) Zin = 41.32 + j 0.156466 ohms at 3.64 MHz. (34.17 ohms and j -24.6) If I change the Freq in Radial_3 to 3.750, I get Zin = 37.41 and j -0.0. That is 110 KHz difference for the same antenna and ground characteristics. Not very good agreement. ================================================= Now, on to the real question I have been asking for a week: Does the current along the radials fall off as rapidly as Radial_3 predicts? I used the numbers from the above antenna, (supplied by Frank from NEC-4) and compared them to what Radial_3 says for the same length. I do not have numbers showing a 5 meter radial for NEC-4 and a 5 meter radial for Radial_3. What I am presenting is the current along the full radial in NEC-4, vs. the current in a radial of specified length in Radial_3. Length is in meters. Since we are using ratios, I only used the integer and two decimal places for the current in my calculations. All values for current are actually what is presented * 10^-2 Length Current NEC-4 (dB) Radial_3 (dB) 0 9.15 N/A N/A 1 8.37 0.77 6.2 2 6.98 2.35 12.4 3 5.63 4.22 18.6 4 4.55 6.07 24.7 5 3.57 8.17 30.9 6 3.00 9.69 37.1 7 2.54 11.13 43.3 8 2.16 12.54 49.5 9 1.84 13.93 55.7 10 1.60 15.15 61.8 11 1.46 15.94 68.0 12 1.41 16.24 74.2 13 1.36 16.56 80.4 14 1.04 18.89 86.6 14.75 0.26 30.93 91.2 Notice at a lenght of 4 meters, Radial_3 is showing 24.7 dB of attenuation of the current, while NEC-4 is only showing 6 dB...not even close. Notice throughout the lengths from 3 to 11 meters, the difference between Radial_3 nd NEC-4 is a pretty consistent 4X, i.e, Radial_3 is showing four times the attenuation at a given length that NEC-4 is showing. Patterns like this in data are rarely the result of chance. Maybe this will lead to a resolution of the problem. If Reg's threshold of 25 dB attenuation is reasonable (at which point adding additional length is of very little value), then NEC-4 says for this particular set of variables that we don't attain anything near 25 dB current attenuation along the length until we get to greater than 14 meters (and the wire is only 15 meters long!) How could the current in a 4 meter radial drop by 25 dB within its length? So, I'm left with two questions: 1. Extra wire....what extra wire? It looks like one needs the entire 15 meter radial wire, not some 4 meter stubby....at least according to NEC-4. 2. Why such a discrepancy in resonant freq between NEC-4 and Radial_3? Unless someone else can point out an error in the analysis, it appears that the transmission line model that Reg is using to predict rate of current drop along the radial vs. length is either the wrong model, or the wrong application thereof. NEC-4 just doesn't seem to support the rapid current fall-off that Radial_3 predicts. BL&E says it ain't so. Tom, W8JI, says his measurements say it ain't so. NEC-4 appears to say "it ain't so". If I were a betting person, I'd say it ain't so. Back to the drawing board? In the mean time, anyone putting in a radial field woud appear to be better served by the references in this thread to "optimizing radial systems", I think by K3LC...it's in several antenna books. 73, p.s. How all this fits into efficiency someone else can analyze, but it can't be good. ....hasan, N0AN |
Radiating Efficiency
On Wed, 02 Aug 2006 16:50:39 GMT, "Frank's" wrote:
May I insert a few words about the Smith Chart? During the period between 1958-59 I designed the entire antenna system and matching harness for the World's first weather satellite, TIROS 1, which was launched April 1, 1960. Four transmitters operating simultaneously on separate frequencies fed the antenna that comprised four crossed monopoles radiating right circular polarization from two transmitters and left circular polarization on the other two frequencies. The point concering the Smith Chart is that the only tools I had for the development of both the antenna system and the matching harness was the Hewlett-Packard HP-805 slotted line for impedance measurements, the slide rule for calculations, and the paper Smith Chart to tell me where I was in the desert. The resolution available with the Chart was sufficient to make the system work successfully. Philip Smith was my hero. Incidentally, the matching harness was fabricated entirely of printed-circuit stripline, and that was 47 years ago. Very interesting Walt. Judging by the type of work you were involved in you must be familiar with the classic text by: Matthaei, Young, and Jones. I am not familiar with the HP-805, but probably because most of my earlier lab work was concerned only with HF. I realize that slide rule, pencil, and Smith Chart was the only way in those days. When I started work any intense analysis was done in FORTRAN on main frame computers. One of the hot topics I remember was mini-computers, but never got to see one. I don't think they lasted long, since soon after programmable desktops started to become available. One thing I remember was a guy designing HF antenna tuners, and he used the Smith Chart. What is interesting is that the charts were very large, about 2 ft X 3 ft, and came in pads. Much greater accuracy than the standard chart. I think they may have been published by a company called K-electronics. I used to needle guys in the lab by telling them that Smith was a ham. I now have a nice high res pdf of the Smith Chart, but usually use an electronic version from the "Berne Institute of Engineering". 73, Frank Thanks for the nice response, Frank, Walt |
Walt, W2DU, and Tiros
|
Radiating Efficiency
Hasan,
Why don't you look for differences between BLE and NEC4? I'm sure you'll find some. ---- Reg. |
Radiating Efficiency
Frank,
Thank you for the above. Can you do 36 radials from 0.6 to 8.0 metres in increments of 0.2 metres? Must be the same input data as before :- F = 8.07 MHz, Ground = 150,16 Radial diameter = 1.64mm, Depth = 25mm. Reg, Here are the results from the analysis of a 26 radial system. All dimensions and parameters are the same as for the single radial antenna as you defined above: 0.6 m -- Radial Z = 37.3 - j 28.1 -- Efficiency 15% 0.8 m -- Radial Z = 30.5 - j 21.0 1.0 m -- Radial Z = 26.2 - j 16.9 1.2 m -- Radial Z = 23.2 - j 14.2 1.4 m -- Radial Z = 20.9 - j 12.4 1.6 m -- Radial Z = 19.1 - j 11.1 1.8 m -- Radial Z = 17.6 - j 10.1 -- Efficiency 21.0% 2.0 m -- Radial Z = 16.2 - j 9.4 2.2 m -- Radial Z = 15.1 - j 8.8 2.4 m -- Radial Z = 14.0 - j 8.4 2.6 m -- Radial Z = 13.0 - j 8.0 2.8 m -- Radial Z = 12.1 - j 7.7 3.0 m -- Radial Z = 11.3 - j 7.4 3.2 m -- Radial Z = 10.4 - j 7.1 -- Efficiency 24.5% 3.4 m -- Radial Z = 9.7 - j 6.8 3.6 m -- Radial Z = 8.9 - j 6.5 3.8 m -- Radial Z = 8.2 - j 6.2 4.0 m -- Radial Z = 7.5 - j 5.8 4.2 m -- Radial Z = 6.9 - j 5.5 4.4 m -- Radial Z = 6.4 - j 5.1 4.6 m -- Radial Z = 5.8 - j 4.7 4.8 m -- Radial Z = 5.4 - j 4.3 5.0 m -- Radial Z = 5.0 - j 3.9 -- Efficiency 27.8% 5.2 m -- Radial Z = 4.6 - j 3.5 5.4 m -- Radial Z = 4.3 - j 3.1 5.6 m -- Radial Z = 4.0 - j 2.7 5.8 m -- Radial Z = 3.7 - j 2.3 6.0 m -- Radial Z = 3.5 - j 2.0 6.2 m -- Radial Z = 3.3 - j 1.6 6.4 m -- Radial Z = 3.1 - j 1.3 6.6 m -- Radial Z = 3.0 - j 0.9 6.8 m -- Radial Z = 2.9 - j 0.6 7.0 m -- Radial Z = 2.8 - j 0.3 7.2 m -- Radial Z = 2.7 + j 0.01 7.4 m -- Radial Z = 2.6 + j 0.3 7.6 m -- Radial Z = 2.6 + j 0.6 7.8 m -- Radial Z = 2.6 + j 0.9 8.0 m -- Radial Z = 2.5 + j 1.1 -- Efficiency 31.1% .. .. 10.0 m -- Radial Z = 3.0 + j 3.3 -- Efficiency 32.6% Where I have shown the efficiency as sky wave power out. The input impedance is that of all radials, so for a single radial the input Zr must be Ztr * 26. Frank |
Radiating Efficiency
Reg, I meant 36 radials. The 26 is a typo.
Frank Here are the results from the analysis of a 36 radial system. All dimensions and parameters are the same as for the single radial antenna as you defined above: 0.6 m -- Radial Z = 37.3 - j 28.1 -- Efficiency 15% 0.8 m -- Radial Z = 30.5 - j 21.0 1.0 m -- Radial Z = 26.2 - j 16.9 1.2 m -- Radial Z = 23.2 - j 14.2 1.4 m -- Radial Z = 20.9 - j 12.4 1.6 m -- Radial Z = 19.1 - j 11.1 1.8 m -- Radial Z = 17.6 - j 10.1 -- Efficiency 21.0% 2.0 m -- Radial Z = 16.2 - j 9.4 2.2 m -- Radial Z = 15.1 - j 8.8 2.4 m -- Radial Z = 14.0 - j 8.4 2.6 m -- Radial Z = 13.0 - j 8.0 2.8 m -- Radial Z = 12.1 - j 7.7 3.0 m -- Radial Z = 11.3 - j 7.4 3.2 m -- Radial Z = 10.4 - j 7.1 -- Efficiency 24.5% 3.4 m -- Radial Z = 9.7 - j 6.8 3.6 m -- Radial Z = 8.9 - j 6.5 3.8 m -- Radial Z = 8.2 - j 6.2 4.0 m -- Radial Z = 7.5 - j 5.8 4.2 m -- Radial Z = 6.9 - j 5.5 4.4 m -- Radial Z = 6.4 - j 5.1 4.6 m -- Radial Z = 5.8 - j 4.7 4.8 m -- Radial Z = 5.4 - j 4.3 5.0 m -- Radial Z = 5.0 - j 3.9 -- Efficiency 27.8% 5.2 m -- Radial Z = 4.6 - j 3.5 5.4 m -- Radial Z = 4.3 - j 3.1 5.6 m -- Radial Z = 4.0 - j 2.7 5.8 m -- Radial Z = 3.7 - j 2.3 6.0 m -- Radial Z = 3.5 - j 2.0 6.2 m -- Radial Z = 3.3 - j 1.6 6.4 m -- Radial Z = 3.1 - j 1.3 6.6 m -- Radial Z = 3.0 - j 0.9 6.8 m -- Radial Z = 2.9 - j 0.6 7.0 m -- Radial Z = 2.8 - j 0.3 7.2 m -- Radial Z = 2.7 + j 0.01 7.4 m -- Radial Z = 2.6 + j 0.3 7.6 m -- Radial Z = 2.6 + j 0.6 7.8 m -- Radial Z = 2.6 + j 0.9 8.0 m -- Radial Z = 2.5 + j 1.1 -- Efficiency 31.1% . . 10.0 m -- Radial Z = 3.0 + j 3.3 -- Efficiency 32.6% Where I have shown the efficiency as sky wave power out. The input impedance is that of all radials, so for a single radial the input Zr must be Ztr * 36. Frank |
Radiating Efficiency
Here are the results from the analysis of a 26 radial system.
0.6 m -- Radial Z = 37.3 - j 28.1 -- Efficiency 15% 0.8 m -- Radial Z = 30.5 - j 21.0 1.0 m -- Radial Z = 26.2 - j 16.9 1.2 m -- Radial Z = 23.2 - j 14.2 1.4 m -- Radial Z = 20.9 - j 12.4 1.6 m -- Radial Z = 19.1 - j 11.1 1.8 m -- Radial Z = 17.6 - j 10.1 -- Efficiency 21.0% 2.0 m -- Radial Z = 16.2 - j 9.4 2.2 m -- Radial Z = 15.1 - j 8.8 2.4 m -- Radial Z = 14.0 - j 8.4 2.6 m -- Radial Z = 13.0 - j 8.0 2.8 m -- Radial Z = 12.1 - j 7.7 3.0 m -- Radial Z = 11.3 - j 7.4 3.2 m -- Radial Z = 10.4 - j 7.1 -- Efficiency 24.5% 3.4 m -- Radial Z = 9.7 - j 6.8 3.6 m -- Radial Z = 8.9 - j 6.5 3.8 m -- Radial Z = 8.2 - j 6.2 4.0 m -- Radial Z = 7.5 - j 5.8 4.2 m -- Radial Z = 6.9 - j 5.5 4.4 m -- Radial Z = 6.4 - j 5.1 4.6 m -- Radial Z = 5.8 - j 4.7 4.8 m -- Radial Z = 5.4 - j 4.3 5.0 m -- Radial Z = 5.0 - j 3.9 -- Efficiency 27.8% 5.2 m -- Radial Z = 4.6 - j 3.5 5.4 m -- Radial Z = 4.3 - j 3.1 5.6 m -- Radial Z = 4.0 - j 2.7 5.8 m -- Radial Z = 3.7 - j 2.3 6.0 m -- Radial Z = 3.5 - j 2.0 6.2 m -- Radial Z = 3.3 - j 1.6 6.4 m -- Radial Z = 3.1 - j 1.3 6.6 m -- Radial Z = 3.0 - j 0.9 6.8 m -- Radial Z = 2.9 - j 0.6 7.0 m -- Radial Z = 2.8 - j 0.3 7.2 m -- Radial Z = 2.7 + j 0.01 7.4 m -- Radial Z = 2.6 + j 0.3 7.6 m -- Radial Z = 2.6 + j 0.6 7.8 m -- Radial Z = 2.6 + j 0.9 8.0 m -- Radial Z = 2.5 + j 1.1 -- Efficiency 31.1% . . 10.0 m -- Radial Z = 3.0 + j 3.3 -- Efficiency 32.6% Where I have shown the efficiency as sky wave power out. The input impedance is that of all radials, so for a single radial the input Zr must be Ztr * 26. =========================================== Frank, The input impedance of 26 radials is NOT equal to all 26 connected in parallel. There is a non-linear relationship between the number N and input impedance because they share the same volume of soil at least when they are short. For 26 radials the resonant effects have disappeared which I cannot explain. Yet attenuation is the same, Zo converges on Zin at approximately 8 or 10 metres as before. You appear to have automated the results. Can you do a large number of radials, say around 100, from 0.4 to 8.0 metres? And can you do a small number of radials such as 6 or 8, from 0.4 to 8.0 metres? |
Radiating Efficiency
Frank,
The input impedance of 26 radials is NOT equal to all 26 connected in parallel. There is a non-linear relationship between the number N and input impedance because they share the same volume of soil at least when they are short. For 26 radials the resonant effects have disappeared which I cannot explain. Yet attenuation is the same, Zo converges on Zin at approximately 8 or 10 metres as before. You appear to have automated the results. Can you do a large number of radials, say around 100, from 0.4 to 8.0 metres? And can you do a small number of radials such as 6 or 8, from 0.4 to 8.0 metres? Reg, I suspected as much concerning the input impedance of a number or radials. Note that my model was 36 radials, not 26. 26 was simply a typo. Believe me there is no automation involved in running NEC, although the work is trivial. The 36 radial model was taking 13 minutes per run as I approached 8 m length radials. I can certainly model the small number of radials, which should not take too long. As for 100 radials; this exceeds the maximum number of junctions limit in NEC. This does not mean it cannot be done, there are work-arounds. Due to excessive computer time I will have to develop a model with a more realistic run time. I am interested in doing this for my own benefit, but it will take some time. I will be very busy for the next few weeks, but will be able to squeeze some time in occasionally. Frank |
Radiating Efficiency
The input impedance of 26 radials is NOT equal to all 26 connected in
parallel. There is a non-linear relationship between the number N and input impedance because they share the same volume of soil at least when they are short. For 26 radials the resonant effects have disappeared which I cannot explain. Yet attenuation is the same, Zo converges on Zin at approximately 8 or 10 metres as before. You appear to have automated the results. Can you do a large number of radials, say around 100, from 0.4 to 8.0 metres? And can you do a small number of radials such as 6 or 8, from 0.4 to 8.0 metres? Reg, Here is the analysis of an 8 radial system. All other parameters the same: 0.4 m -- Radial Z = 65.4 - j 58.1 -- Efficiency 11.2% 0.6 m -- Radial Z = 48.7 - j 55.4 0.8 m -- Radial Z = 39.8 - j 29.6 1.0 m -- Radial Z = 34.2 - j 23.5 1.2 m -- Radial Z = 30.2 - j 19.2 1.4 m -- Radial Z = 27.2 - j 16.1 1.6 m -- Radial Z = 24.9 - j 13.7 1.8 m -- Radial Z = 23.0 - j 11.7 -- Efficiency 19.4% 2.0 m -- Radial Z = 21.3 - j 10.0 2.2 m -- Radial Z = 19.9 - j 8.5 2.4 m -- Radial Z = 18.7 - j 7.1 2.6 m -- Radial Z = 17.7 - j 5.9 2.8 m -- Radial Z = 16.7 - j 4.6 3.0 m -- Radial Z = 15.9 - j 3.5 3.2 m -- Radial Z = 15.2 - j 2.3 -- Efficiency 22.4% 3.4 m -- Radial Z = 14.7 - j 1.1 3.6 m -- Radial Z = 14.3 + j 0 3.8 m -- Radial Z = 14.0 + j 1.1 4.0 m -- Radial Z = 13.9 + j 2.2 -- Efficiency 23.2% 4.2 m -- Radial Z = 13.9 + j 3.2 4.4 m -- Radial Z = 14.1 + j 4.2 4.6 m -- Radial Z = 14.4 + j 5.0 4.8 m -- Radial Z = 14.7 + j 5.7 5.0 m -- Radial Z = 15.2 + j 6.3 -- Efficiency 23.0% 5.2 m -- Radial Z = 15.6 + j 6.7 5.4 m -- Radial Z = 16.1 + j 7.1 5.6 m -- Radial Z = 16.5 + j 7.3 5.8 m -- Radial Z = 16.9 + j 7.4 6.0 m -- Radial Z = 17.2 + j 7.5 6.2 m -- Radial Z = 17.5 + j 7.5 -- Efficiency 22.5% 6.4 m -- Radial Z = 17.8 + j 7.5 6.6 m -- Radial Z = 18.0 + j 7.4 6.8 m -- Radial Z = 18.1 + j 7.4 7.0 m -- Radial Z = 18.3 + j 7.4 7.2 m -- Radial Z = 18.4 + j 7.3 7.4 m -- Radial Z = 18.4 + j 7.3 7.6 m -- Radial Z = 18.5 + j 7.2 7.8 m -- Radial Z = 18.6 + j 7.2 8.0 m -- Radial Z = 18.6 + j 7.2 -- Efficiency 22.4% Note that after 4 m the antenna efficiency starts to drop, which is not the case for large numbers of radials. Now I have to figure out the best way to model a 100 radial system. Frank |
Radiating Efficiency
Reg, Here is the analysis of an 8 radial system. All other parameters the same: 0.4 m -- Radial Z = 65.4 - j 58.1 -- Efficiency 11.2% 0.6 m -- Radial Z = 48.7 - j 55.4 0.8 m -- Radial Z = 39.8 - j 29.6 1.0 m -- Radial Z = 34.2 - j 23.5 1.2 m -- Radial Z = 30.2 - j 19.2 1.4 m -- Radial Z = 27.2 - j 16.1 1.6 m -- Radial Z = 24.9 - j 13.7 1.8 m -- Radial Z = 23.0 - j 11.7 -- Efficiency 19.4% 2.0 m -- Radial Z = 21.3 - j 10.0 2.2 m -- Radial Z = 19.9 - j 8.5 2.4 m -- Radial Z = 18.7 - j 7.1 2.6 m -- Radial Z = 17.7 - j 5.9 2.8 m -- Radial Z = 16.7 - j 4.6 3.0 m -- Radial Z = 15.9 - j 3.5 3.2 m -- Radial Z = 15.2 - j 2.3 -- Efficiency 22.4% 3.4 m -- Radial Z = 14.7 - j 1.1 3.6 m -- Radial Z = 14.3 + j 0 3.8 m -- Radial Z = 14.0 + j 1.1 4.0 m -- Radial Z = 13.9 + j 2.2 -- Efficiency 23.2% 4.2 m -- Radial Z = 13.9 + j 3.2 4.4 m -- Radial Z = 14.1 + j 4.2 4.6 m -- Radial Z = 14.4 + j 5.0 4.8 m -- Radial Z = 14.7 + j 5.7 5.0 m -- Radial Z = 15.2 + j 6.3 -- Efficiency 23.0% 5.2 m -- Radial Z = 15.6 + j 6.7 5.4 m -- Radial Z = 16.1 + j 7.1 5.6 m -- Radial Z = 16.5 + j 7.3 5.8 m -- Radial Z = 16.9 + j 7.4 6.0 m -- Radial Z = 17.2 + j 7.5 6.2 m -- Radial Z = 17.5 + j 7.5 -- Efficiency 22.5% 6.4 m -- Radial Z = 17.8 + j 7.5 6.6 m -- Radial Z = 18.0 + j 7.4 6.8 m -- Radial Z = 18.1 + j 7.4 7.0 m -- Radial Z = 18.3 + j 7.4 7.2 m -- Radial Z = 18.4 + j 7.3 7.4 m -- Radial Z = 18.4 + j 7.3 7.6 m -- Radial Z = 18.5 + j 7.2 7.8 m -- Radial Z = 18.6 + j 7.2 8.0 m -- Radial Z = 18.6 + j 7.2 -- Efficiency 22.4% Note that after 4 m the antenna efficiency starts to drop, which is not the case for large numbers of radials. Now I have to figure out the best way to model a 100 radial system. Frank ================================================== === Frank, Thank you very much for the results on 8 radials. As expected, it seems that for small numbers of radials the resonance effects are begining to appear again. I have ideas as to why this should happen. It's to do with the geometry of the system and the fact that the ends of the radials are not terminated with true open-circuits when calculating input impedance. ( As is assumed by program Radial3.) I look forward to receiving results for 100 or more radials which may allow me to improve, in the mathematical model, the function of N which describes the system's input impedance in terms of the number N of radials. ---------------------------------------------------------------------- ----------------------- But, let's face it, a good understanding of what's going on under the soil surface, without investigating input impedance at say 25 MHs, and without investigating input imedance at soil resistivities of say 2000 ohm-metres, will be known only crudely. Is it all worth the trouble? After all, we already know enough quite enough about radial systems at HF to design one which will work good enough, performance-wise, to keep anybody happy. ( BL&E's work, as good as it may be, does not apply at HF.) Just lay one or two dozen radials, in ordinary soils, with lengths equal to about half antenna height. Which is a good enough rule-of-thumb for anybody who doesn't expect to win contests because he has the advantage of 0.05 S-units. And extremely few people know what their local soil resistivity is within +/- 40 percent. It's largely guesswork! But please keep up the good work with NEC4 in which I have great confidence. ---- Reg, G4FGQ |
Radiating Efficiency
On Sat, 5 Aug 2006 19:11:17 +0100, "Reg Edwards"
wrote: Thank you very much for the results on 8 radials. As expected, it seems that for small numbers of radials the resonance effects are begining to appear again. I have ideas as to why this should happen. Hi Reggie, You "should" if you had read Brown, Lewis, and Epstein. They discussed this nearly 70 years ago. Radial3 appears to miss that mark by various amounts ranging from 6 to 60dB. It's to do with the geometry of the system Duh. And the problem you injected in that you abstract one wire to many. and the fact that the ends of the radials are not terminated with true open-circuits when calculating input impedance. ( As is assumed by program Radial3.) Given Hassan's and other's reports of the outrageous departures between Radial3 and BLE/NEC4 (with your concurrence): But please keep up the good work with NEC4 in which I have great confidence. there are at least two of us who find your contradictions would warrant another fling of chalk off your noggin from Lord Kelvin. 73's Richard Clark, KB7QHC |
Radiating Efficiency
On Sat, 5 Aug 2006 19:11:17 +0100, "Reg Edwards"
wrote: After all, we already know enough quite enough about radial systems at HF to design one which will work good enough, performance-wise, to keep anybody happy. ( BL&E's work, as good as it may be, does not apply at HF.) Just lay one or two dozen radials, in ordinary soils, with lengths equal to about half antenna height. Which is a good enough rule-of-thumb for anybody who doesn't expect to win contests because he has the advantage of 0.05 S-units. And extremely few people know what their local soil resistivity is within +/- 40 percent. It's largely guesswork! Reg, G4FGQ Hi Reg, You're saying that BL&E's work doesn't apply at HF. I believe that's an overstatement. They've shown that with about 100 radials of 0.4 lamba length the result is almost perfect ground, regardless of the ground conditions beneath the radials. I contend that using the radial setup as described above will always result in a near-perfect ground at any HF frequency, with close to 100 percent efficiency. Would you not agree? Walt, W2DU |
Radiating Efficiency
Richard Clark wrote:
On Sat, 5 Aug 2006 19:11:17 +0100, "Reg Edwards" wrote: Thank you very much for the results on 8 radials. As expected, it seems that for small numbers of radials the resonance effects are begining to appear again. I have ideas as to why this should happen. Hi Reggie, You "should" if you had read Brown, Lewis, and Epstein. They discussed this nearly 70 years ago. Cut 'im a break Richard! He was just a little kid at the time! ;^) `73 de Mike KB3EIA - |
Radiating Efficiency
They've shown that with about 100 radials of 0.4 lamba length the result is almost perfect ground, regardless of the ground conditions beneath the radials. I contend that using the radial setup as described above will always result in a near-perfect ground at any HF frequency, with close to 100 percent efficiency. Would you not agree? Walt, W2DU ====================================== My dear Walt, I haver never disagreed. How can one disagree with a statement of the bleeding obvious? Indeed, my program RADIAL3 confirms it. And so will NEC4 if you will allow it time to generate some results. ----- Reg, G4FGQ. |
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