Re: Topband: Question - optimum number of radials
Yeah, just a few elevated resonant radials can work wonders as you have discovered, Carl! And rock does get in the way of buried radials!! The models teach that elevated resonant radials should work very well! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Carl Sent: Friday, February 14, 2014 10:46 AM To: Tom W8JI Cc: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials While Tom touched on the subject yesterday the subject of an individuals ground conductivity has to be stressed, continuously it seems. The FCC maps arent perfect and hams usually dont have the options of perfect siting for their verticals as do many of the BC stations. Home developers often remove all of the good topsoil and sell it. They back fill with rocky sand and whatever else is cheap or worthless and finish with a skimcoat of real topsoil just thick enough to grow grass. My own attempt with 60-65 quarter wave radials 30 years ago at another home were dismal since the "ground" was pure sand left behind by the glaciers with a fresh water table about 4' down. Great for mixing concrete and drainage only. After I installed a 2X4" fence mesh around the base and out 50' could I reliably work DX. Going to elevated radials here on a granite hill in the same town saved a lot of work and works very well. Carl KM1H _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
Hi, Bill Well, like you, I also live on a fairly small city lot with way too much bedrock coming up to the surface and a long concrete driveway, so buried radials just aren't feasible for me! So I hung my inverted L in a tall tulip poplar in one corner of the lot and I ran two elevated resonant radials down the fence lines - elevated about 5-6 feet. I worked good stuff all over the world including JA and Indian Ocean, and VK6. If I could hear 'em, I could work 'em! BEST thing I EVER did for myself was to build a KAZ terminated receiving loop for the low-bands 160-30m, so I could HEAR more! Worked great!! And no, I didn't have 100 buried radials, but just a few elevated resonant radials will produce very effective results for the transmit antenna! 73 Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Cromwell Sent: Friday, February 14, 2014 10:02 AM To: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials On 02/14/2014 09:15 AM, Charlie Cunningham wrote: > That's a lot of good information, Richard! Thanks for sharing! > > 73, > Charlie, K4OTV > > The whole topic of radials as it applies to me on my small lot is "put in as many as you can". The same probably applies to others on small lots. On top band I do not have room in *any* direction for a quarter wavelength radial..not even one. In some directions a quarter wavelength radial wire might be bent to fit but that begins the many compromises. Obviously that setup would have the antenna in one corner of the lot so there would be no radials at all in one or two directions. So.. no quarter wave radials at all. I have been buying small spools of wire and will be adding them to whatever puny little radial field I DO have. As soon as the ice and snow is gone (maybe in June?) I will be elevating my wire antenna the rest of the way to the treetops and adding in the radial wires. In the process of elevating the antenna I will learn to be ace with a rod n reel . The whole point of that exercise is to *miss* the tree and go over the top. So far I've only ever tried to *hit* a spot out on the water. It's not hard to hit the water . I didn't do too badly finding a particular spot on the water with the bait. But the tree top is not "over" there. It's "up" there. 73, Bill KU8H _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
While Tom touched on the subject yesterday the subject of an individuals ground conductivity has to be stressed, continuously it seems. The FCC maps arent perfect and hams usually dont have the options of perfect siting for their verticals as do many of the BC stations. Home developers often remove all of the good topsoil and sell it. They back fill with rocky sand and whatever else is cheap or worthless and finish with a skimcoat of real topsoil just thick enough to grow grass. My own attempt with 60-65 quarter wave radials 30 years ago at another home were dismal since the "ground" was pure sand left behind by the glaciers with a fresh water table about 4' down. Great for mixing concrete and drainage only. After I installed a 2X4" fence mesh around the base and out 50' could I reliably work DX. Going to elevated radials here on a granite hill in the same town saved a lot of work and works very well. Carl KM1H _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
On 02/14/2014 09:15 AM, Charlie Cunningham wrote: That's a lot of good information, Richard! Thanks for sharing! 73, Charlie, K4OTV The whole topic of radials as it applies to me on my small lot is "put in as many as you can". The same probably applies to others on small lots. On top band I do not have room in *any* direction for a quarter wavelength radial..not even one. In some directions a quarter wavelength radial wire might be bent to fit but that begins the many compromises. Obviously that setup would have the antenna in one corner of the lot so there would be no radials at all in one or two directions. So.. no quarter wave radials at all. I have been buying small spools of wire and will be adding them to whatever puny little radial field I DO have. As soon as the ice and snow is gone (maybe in June?) I will be elevating my wire antenna the rest of the way to the treetops and adding in the radial wires. In the process of elevating the antenna I will learn to be ace with a rod n reel . The whole point of that exercise is to *miss* the tree and go over the top. So far I've only ever tried to *hit* a spot out on the water. It's not hard to hit the water . I didn't do too badly finding a particular spot on the water with the bait. But the tree top is not "over" there. It's "up" there. 73, Bill KU8H _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
That's a lot of good information, Richard! Thanks for sharing! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard Fry Sent: Friday, February 14, 2014 7:00 AM To: topband@contesting.com Subject: Re: Topband: Question - optimum number of radials The r-f loss at the operating frequency in a set of buried radials varies with the conductivity and permittivity of the earth in which they are buried. The NEC4.2 study below shows that for poor earth conditions (within about 1/2WL from the base of the monopole), the number and length of buried radials needed to maintain an r-f loss of a few ohms in the ground return rises from that needed for more conductive earth. In the case of AM broadcast stations, the use of 120 buried radials each 1/4-wavelength (in free space) produces a ground system loss of 2 ohms or less. This is true no matter what are the characteristics of the the earth in which those 120 radials are buried. For a 1/4-wave, unloaded monopole with 35 ohms of radiation resistance and 2 ohms of ground system loss, antenna system radiation efficiency is 35/37 = 95% of the applied power (approx). The FCC requires that a minimum inverse distance groundwave field of 241 mV/m is produced by an applied power of 1 kW at at a distance of 1 km by even the lowest class of AM station (Class C). A perfect 1/4-wave monopole driven against a perfect ground plane produces about 313 mV/m for those conditions. A typical installation using an unloaded 1/4-wave monopole driven against 120 x 1/4-wave buried radials produces about 306 mV/m for those conditions -- which field is consistent with a monopole system with a radiation efficiency of 95%. The 241 mV/m minimum field required for Class C AM stations could be produced by a 1/4-wave monopole+ground system with about 59% efficiency. Class A AM stations such as WLW, WJR, WGN etc are required to generate an inverse distance groundwave field of 362 mV/m at 1 km for 1 kW of applied power. This cannot be done with a 1/4-wave monopole. Most of the Class A stations use monopole heights ranging from 180 to 195 degrees. WJR, Detroit uses a 195-deg monopole system that produces about 403 mV/m at 1 km for 1 kW of applied power. At their licensed transmitter power of 50 kW, that field becomes 403 x SQRT(50) = 2.85 V/m, approx. http://i62.photobucket.com/albums/h85/rfry-100/10m_Vert32Buried_Radials.jpg RF _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
The r-f loss at the operating frequency in a set of buried radials varies with the conductivity and permittivity of the earth in which they are buried. The NEC4.2 study below shows that for poor earth conditions (within about 1/2WL from the base of the monopole), the number and length of buried radials needed to maintain an r-f loss of a few ohms in the ground return rises from that needed for more conductive earth. In the case of AM broadcast stations, the use of 120 buried radials each 1/4-wavelength (in free space) produces a ground system loss of 2 ohms or less. This is true no matter what are the characteristics of the the earth in which those 120 radials are buried. For a 1/4-wave, unloaded monopole with 35 ohms of radiation resistance and 2 ohms of ground system loss, antenna system radiation efficiency is 35/37 = 95% of the applied power (approx). The FCC requires that a minimum inverse distance groundwave field of 241 mV/m is produced by an applied power of 1 kW at at a distance of 1 km by even the lowest class of AM station (Class C). A perfect 1/4-wave monopole driven against a perfect ground plane produces about 313 mV/m for those conditions. A typical installation using an unloaded 1/4-wave monopole driven against 120 x 1/4-wave buried radials produces about 306 mV/m for those conditions -- which field is consistent with a monopole system with a radiation efficiency of 95%. The 241 mV/m minimum field required for Class C AM stations could be produced by a 1/4-wave monopole+ground system with about 59% efficiency. Class A AM stations such as WLW, WJR, WGN etc are required to generate an inverse distance groundwave field of 362 mV/m at 1 km for 1 kW of applied power. This cannot be done with a 1/4-wave monopole. Most of the Class A stations use monopole heights ranging from 180 to 195 degrees. WJR, Detroit uses a 195-deg monopole system that produces about 403 mV/m at 1 km for 1 kW of applied power. At their licensed transmitter power of 50 kW, that field becomes 403 x SQRT(50) = 2.85 V/m, approx. http://i62.photobucket.com/albums/h85/rfry-100/10m_Vert32Buried_Radials.jpg RF _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
For anyone interested in modeling a vertical with a variable number of radials you might refer back to this post: http://lists.contesting.com/archives//html/Topband/2013-04/msg00017.html Near the bottom you'll find a link to download a ".weq" format model for use with AutoEZ. AutoEZ requires Microsoft Excel and EZNEC v5. (Shooting myself in the foot here.) Even using the free demo version of AutoEZ you can still take advantage of the "multi-config" aspect of the model. Manually set the variables to any desired values (such as variable "N" for number of radials) then use the "View Ant" button. That will build a temporary .ez format model and send it to EZNEC. Then switch over to the EZNEC main window and click the EZNEC "FF Plot" button or other buttons as desired. In effect you are using AutoEZ to build the model and EZNEC to process it. If you don't have the Pro/4 (NEC-4) version of EZNEC you can simulate buried radials by putting them ~0.001 wavelengths above ground. For info on that subject see the EZNEC Help Index > Elevated Radial Systems. Dan, AC6LA http://ac6la.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
Jerry Sevick, W2FMI, has an interesting comment about the "120" number in his book, "The Short Vertical Antenna and Ground Radial." At the end of the first chapter he notes: "...it should be mentioned that the world standard for the number of radials to be used with verticals in the AM broadcast band is 120. This number was based on the classic paper published in 1937 by Brown, Lewis, and Epstein. During the course of a business meeting with Dr. Brown, I asked him how he and his colleagues arrived at the 120 radial figure--because I was quite sure 100 would work as well. His answer was interesting. "He said that he and the others had been thinking in terms of 100 radials, but the farmer who plowed in 100 radials had wire left over because copper is soft and stretches easily. When he asked what to do with the extra wire, the farmer was told to plow it in. The result was a world standard of 120 radials." That's an interesting story, but the story-teller must never have looked at the papers. BL and E used 113 radials maxium, not 120. Brown, Lewis, and Epstein's papers are all over the web, if you search for them. The FCC says: "At the present development of the art, it is considered that where a vertical radiator is employed with its base on the ground, the ground system should consist of buried radial wires at least one-fourth wave length long. There should be as many of these radials evenly spaced as practicable and in no event less than 90. (120 radials of 0.35 to 0.4 of a wave length in length and spaced 3° is considered an excellent ground system and in case of high base voltage, a base screen of suitable dimensions should be employed.)" So you see, the FCC requires 90 radials unless you prove you can make efficiency with fewer. They do not say 120 quarter wave radials, they require 90 1/4 wave or longer, and say 120 radials .35 to .4 wl is "considered excellent". _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
Jerry Sevick, W2FMI, has an interesting comment about the "120" number in his book, "The Short Vertical Antenna and Ground Radial." At the end of the first chapter he notes: "...it should be mentioned that the world standard for the number of radials to be used with verticals in the AM broadcast band is 120. This number was based on the classic paper published in 1937 by Brown, Lewis, and Epstein. During the course of a business meeting with Dr. Brown, I asked him how he and his colleagues arrived at the 120 radial figure--because I was quite sure 100 would work as well. His answer was interesting. "He said that he and the others had been thinking in terms of 100 radials, but the farmer who plowed in 100 radials had wire left over because copper is soft and stretches easily. When he asked what to do with the extra wire, the farmer was told to plow it in. The result was a world standard of 120 radials." H! Brad, KV5V On Thu, Feb 13, 2014 at 7:49 PM, Tom W8JI wrote: > > > I understand that 120 radials is the golden standard. At what point is > there no significant improvement?>>> > > 120 radials never was a gold standard. > > The FCC said if a AM BC station uses something like 110 radials, I forget > the exact number, they can avoid doing a radial system proof of > performance. I think Hams assumed that somehow meant 110 radials or > whatever the exact number was were somehow "perfect". > > There is no improvement here on 40M at about 20-30 radials. YMMV. > > This will be different on different bands at the same location, and > different on the same bands at different locations, and even different with > different antennas. So what happens in one cause is probably not true in > others. > > Read carefully, and you will see even Rudy Severns says that, so his gold > standard isn't gold. > > 73 Tom > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
I understand that 120 radials is the golden standard. At what point is there no significant improvement?>>> 120 radials never was a gold standard. The FCC said if a AM BC station uses something like 110 radials, I forget the exact number, they can avoid doing a radial system proof of performance. I think Hams assumed that somehow meant 110 radials or whatever the exact number was were somehow "perfect". There is no improvement here on 40M at about 20-30 radials. YMMV. This will be different on different bands at the same location, and different on the same bands at different locations, and even different with different antennas. So what happens in one cause is probably not true in others. Read carefully, and you will see even Rudy Severns says that, so his gold standard isn't gold. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
N6LF has done quite a bit of actual testing of various in ground and elevated radial systems. See: http://www.antennasbyn6lf.com/ K3LC has done extensive modeling of both in ground and elevated radial systems: http://www2.gcc.edu/dept/elee/Faculty/Christman.htm However, if the majority of your on/in ground radials are only 0.1 wave you won't need many before the point of diminishing returns. 73, ... Joe, W4TV On 2/13/2014 6:12 PM, DALE LONG wrote: I understand that 120 radials is the golden standard. At what point is there no significant improvement? How much worse is 60 radials? How much worse is 24 radials (4 of 1/4 lambda and 20 or 1/10 lambda)? This may have been discussed in the past, but if there is any engineering reference or field testing that has been done, I would like to know the results. Thanks Dale - N3BNA _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Question - optimum number of radials
w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html Check the links on that page to N6LF, Rudy Severns' pages. His work has been called the gold standard of radial science. 73, Mike www.w0btu.com On Thu, Feb 13, 2014 at 5:12 PM, DALE LONG wrote: > I understand that 120 radials is the golden standard. At what point is > there no significant improvement? > > How much worse is 60 radials? How much worse is 24 radials (4 of 1/4 > lambda and 20 or 1/10 lambda)? > _ Topband Reflector Archives - http://www.contesting.com/_topband
