Re: Topband: I need help proofing an Inverted L model I made please. 40
On 12/11/2020 3:55 AM, Rob Atkinson wrote: The only thing about this I advise in the way of a change is something W1BB recommended, Again, I refer to N6LF's monumental work. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
On 12/11/2020 2:02 AM, Artek Manuals wrote: However I have always wondered about elevated radials . The NEC ( both 2 and 4) models (not that those are to always be trusted) show very little (if any) improvement beyond four elevated radials, you have any theories on why that is? Intuitively (also not to be trusted) that is a lot of real estate in the spaces between I refer you to N6LF's definitive work. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Rudy Severns has many plots of elevated radial numbers, lengths, and elevations on his web site antennasbyn6lf.com My "T" showed the expected change in feedpoint Z as I added 125ft long 10ft elevated radials from 2 to the current 8. The last two made no measurable difference. From Rudy's analysis they could/should be a bit shorter than 125ft. Another experiment with a prototype shorty vertical showed a big reduction in Z when two 128' radials were raised from 4ft to 9ft, confirming the NEC4 modeling. Poor dirt here but a little bit better in winter when the ground is totally water saturated. Also, the T is pretty much surrounded with 100ft plus firs and cedars absorbing RF. Another reason to love verticals on the beach :) . Grant KZ1W On 12/11/2020 02:02, Artek Manuals wrote: Jim et all I agree with what you say on all points when it comes to radials on the ground and salt water affects. However I have always wondered about elevated radials . The NEC ( both 2 and 4) models (not that those are to always be trusted) show very little (if any) improvement beyond four elevated radials, you have any theories on why that is? Intuitively (also not to be trusted) that is a lot of real estate in the spaces between Dave NR1DX On 12/11/2020 4:37 AM, Jim Brown wrote: On 12/10/2020 11:14 PM, Raymond Benny wrote: With said, I believe my ground absorption is very high so I feel the higher numbers of radials helps greatly with my vertical efficiency and radiation. Hi Ray, The soil affects us in two important ways. First, poor soil burns transmitter power underneath the antenna and it's near field. We use radials to shield the soil from the field, and to supply a low impedance path for return current. Magnetic fields produced around each radial by virtue of current flow couples loss in the earth into the radials in the form of series resistance. Loss in each radial is 1 squared R; each time we double the number of radials the current in each is divided by two, so the power coupled to the earth by each divides by four. So the more radials, the less power is coupled to the earth. THAT'S why more is better. The result of all this is that loss in the soil under the antenna reduces the total strength of our signal by that amount. The second effect of soil is in the far field, where we field radiate hits the earth and is reflected by it to form the vertical pattern. The better the conductivity THERE, the our pattern will be both stronger and at a lower angle. An antenna with its base just above sea water is the extreme example of this -- the reflection is extremely strong, and it is at a VERY low angle. We can help the first of these two effects with a good radial system, but the only thing we can do about the second (the far field reflection), is to move where there is better soil. Most of us live where we do because we like living there for reasons other than radio. And that includes me and my XYL. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Over really good dirt there isn’t too much difference. The other problem is that the NEC ground approximation coding usually underestimates loss. This is because the ground approximation in the model uses a monolithic ground. Same stuff 100 feet down as at the surface. Real dirt never is. Water tables, etc, yada yada. Or farm dirt plowed, dug for the first two or three feet down, below that undisturbed and thoroughly packed for hundreds of thousands of years. That's not monolithic. Nor are many properties that were leveled for construction, or in ancient lands, built on construction rubble accumulated for millennia. Simple velocity factor measurement of a 152' dipole on ground is monstrously variable, sometimes just varying orientation in the same back yard. That doesn't account for lots of trees, roots where the only way to reduce the increased counterpoise loss from dielectric losses is to reduce the fields from the counterpoise. That's where the FCP comes from. NEC uses monolithic ground in its ground approximation because more complexity results in monstrous increases in run time. And we have to remember that NEC is from a period where mainframe run times cost a lot of money, and some computational methods could result in jobs not completing in a month. Reality skeptics sure of underestimated NEC ground loss include W7EL, EZNEC author. One way to get a better idea is to set ground characteristics in EZNEC to gawd awful (in all compared designs) and rerun. As in (.005,1). I do that routinely on a design to stay away from designs that are more sensitive to poor grounds. E.g. set ground characteristics to (.005,1), then run a ground plane with 4 radials. Repeat with 8. Note the difference. Run at various radial heights. Poor ground qualities happen and definitely appear to be the majority rather than the exception. Designing for least sensitivity to poor ground will protect the poor soul that has gawd awful ground in their backyard and don't know it. We spend thousands of dollars on transceivers and amplifiers and then go cheep, cheep on radials? On 160, ground loss is the two ton elephant in the room. Clean up after the elephant and send it to the zoo before you put down new carpet. 73, Guy K2AV On Fri, Dec 11, 2020 at 5:02 AM Artek Manuals wrote: > Jim et all > > I agree with what you say on all points when it comes to radials on the > ground and salt water affects. > > However I have always wondered about elevated radials . The NEC ( both 2 > and 4) models (not that those are to always be trusted) show very little > (if any) improvement beyond four elevated radials, you have any theories > on why that is? Intuitively (also not to be trusted) that is a lot of > real estate in the spaces between > > Dave > NR1DX > > On 12/11/2020 4:37 AM, Jim Brown wrote: > > On 12/10/2020 11:14 PM, Raymond Benny wrote: > >> With said, I believe my ground absorption is very high so I feel the > >> higher > >> numbers of radials helps greatly with my vertical efficiency and > >> radiation. > > > > Hi Ray, > > > > The soil affects us in two important ways. First, poor soil burns > > transmitter power underneath the antenna and it's near field. We use > > radials to shield the soil from the field, and to supply a low > > impedance path for return current. Magnetic fields produced around > > each radial by virtue of current flow couples loss in the earth into > > the radials in the form of series resistance. Loss in each radial is 1 > > squared R; each time we double the number of radials the current in > > each is divided by two, so the power coupled to the earth by each > > divides by four. So the more radials, the less power is coupled to the > > earth. THAT'S why more is better. The result of all this is that loss > > in the soil under the antenna reduces the total strength of our signal > > by that amount. > > > > The second effect of soil is in the far field, where we field radiate > > hits the earth and is reflected by it to form the vertical pattern. > > The better the conductivity THERE, the our pattern will be both > > stronger and at a lower angle. An antenna with its base just above sea > > water is the extreme example of this -- the reflection is extremely > > strong, and it is at a VERY low angle. > > > > We can help the first of these two effects with a good radial system, > > but the only thing we can do about the second (the far field > > reflection), is to move where there is better soil. Most of us live > > where we do because we like living there for reasons other than radio. > > And that includes me and my XYL. > > > > 73, Jim K9YC > > > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > > Reflector > > -- > Dave manu...@artekmanuals.com www.ArtekManuals.com > > -- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > _ > Searchable Archives: http://www.contesting.com/_topband -
Re: Topband: I need help proofing an Inverted L model I made please. 40
> IMHO, for that number, on-the-ground radials do not need to be anywhere near > that long. Personally, I subscribe to the same-length-as-the-vertical > guideline. The only thing about this I advise in the way of a change is something W1BB recommended, which was that the radials on the ground going out underneath the horizontal L wire should be as long as the horizontal wire. My horizontal component has some bends in it and I routed around 10 radials under it to follow it. It probably doesn't make much difference, but it isn't that hard to run a few that are under the wire all the way out. 73 Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Jim et all I agree with what you say on all points when it comes to radials on the ground and salt water affects. However I have always wondered about elevated radials . The NEC ( both 2 and 4) models (not that those are to always be trusted) show very little (if any) improvement beyond four elevated radials, you have any theories on why that is? Intuitively (also not to be trusted) that is a lot of real estate in the spaces between Dave NR1DX On 12/11/2020 4:37 AM, Jim Brown wrote: On 12/10/2020 11:14 PM, Raymond Benny wrote: With said, I believe my ground absorption is very high so I feel the higher numbers of radials helps greatly with my vertical efficiency and radiation. Hi Ray, The soil affects us in two important ways. First, poor soil burns transmitter power underneath the antenna and it's near field. We use radials to shield the soil from the field, and to supply a low impedance path for return current. Magnetic fields produced around each radial by virtue of current flow couples loss in the earth into the radials in the form of series resistance. Loss in each radial is 1 squared R; each time we double the number of radials the current in each is divided by two, so the power coupled to the earth by each divides by four. So the more radials, the less power is coupled to the earth. THAT'S why more is better. The result of all this is that loss in the soil under the antenna reduces the total strength of our signal by that amount. The second effect of soil is in the far field, where we field radiate hits the earth and is reflected by it to form the vertical pattern. The better the conductivity THERE, the our pattern will be both stronger and at a lower angle. An antenna with its base just above sea water is the extreme example of this -- the reflection is extremely strong, and it is at a VERY low angle. We can help the first of these two effects with a good radial system, but the only thing we can do about the second (the far field reflection), is to move where there is better soil. Most of us live where we do because we like living there for reasons other than radio. And that includes me and my XYL. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector -- Dave manu...@artekmanuals.com www.ArtekManuals.com -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
On 12/10/2020 11:14 PM, Raymond Benny wrote: With said, I believe my ground absorption is very high so I feel the higher numbers of radials helps greatly with my vertical efficiency and radiation. Hi Ray, The soil affects us in two important ways. First, poor soil burns transmitter power underneath the antenna and it's near field. We use radials to shield the soil from the field, and to supply a low impedance path for return current. Magnetic fields produced around each radial by virtue of current flow couples loss in the earth into the radials in the form of series resistance. Loss in each radial is 1 squared R; each time we double the number of radials the current in each is divided by two, so the power coupled to the earth by each divides by four. So the more radials, the less power is coupled to the earth. THAT'S why more is better. The result of all this is that loss in the soil under the antenna reduces the total strength of our signal by that amount. The second effect of soil is in the far field, where we field radiate hits the earth and is reflected by it to form the vertical pattern. The better the conductivity THERE, the our pattern will be both stronger and at a lower angle. An antenna with its base just above sea water is the extreme example of this -- the reflection is extremely strong, and it is at a VERY low angle. We can help the first of these two effects with a good radial system, but the only thing we can do about the second (the far field reflection), is to move where there is better soil. Most of us live where we do because we like living there for reasons other than radio. And that includes me and my XYL. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Yes, Mark, N5OT go back a long way, 80's or so. At my QTH, Arizona high desert 4800ft, the soil is very non-conductive - typically dry shale and small rocks, it's called Caleche. We have very little rain, about 10" - 12" per year. Humidity very seldom goes above 30%, and temps in the summer are in the 90's. The first 6" of soil can be dug with a shovel, but below that it takes a backhoe further. The ground below 2ft has probably not seen water since it was laid down eons ago. With said, I believe my ground absorption is very high so I feel the higher numbers of radials helps greatly with my vertical efficiency and radiation. Ray, N6VR/W7YA On Thu, Dec 10, 2020 at 4:09 PM Jeff Blaine wrote: > N6LF Rudy's web site and associated QEX series has empirical data to > answer all of these questions regarding the number and length of on > ground radials. > > 73/jeff/ac0c > alpha-charlie-zero-charlie > www.ac0c.com > > > On 12/10/20 11:14 AM, Mark - N5OT wrote: > > Yeah. I don't claim to be a radial expert but I do claim to have a > > lot of experience working other stations on 160 meters. > > > > My buddy W9RE told me on a DXpedition once that he built a dipole > > laying on the ground and it resonated on 160 when the wires were about > > 80 feet long. > > > > Ray, with respect (N6VR and I go back a LNG way), I think 80 feet > > is the "new quarter wave radial" on 160, and frankly the only thing I > > really think I understand about verticals is, the more wire on the > > ground, the better, but you can get to a point where adding more is > > not worth the effort, YMMV etc. > > > > My story for the week is: I put up yet another temporary 160 vertical > > for the ARRL 160 last weekend, and only managed 14 radials before it > > got so dark I thought I better be getting on the air. > > > > I worked 970 QSOs that night, including 5 Europeans, and while I was > > out there on Saturday adding more radials, I got a text from K5ZD > > saying I was an alligator, that I was very loud the night before, but > > couldn't hear him calling me for 10 minutes as he needed Oklahoma. > > > > So I stopped adding radials, I was up to 22 radials at 80' long, and > > moved on to listening antennas. > > > > Worked maybe 10 Europeans and counted 10 JAs, so I know my signal was > > getting to those places. > > > > That's really all I know about that. > > > > The vertical is 50 feet tall and has two symmetrical top-load wires > > that bring the resonant frequency to 1.8 MHz. > > > > 73 - Mark N5OT > > > > P.S. Got an email from a guy in South Dakota who worked 376 QSOs > > (including 4 other countries) using an inverted L that was 20 feet up > > and the rest horizontal, fed against 20 radials 25' long in his yard. > > I love stories like that. > > > > > > On 12/10/2020 9:52 AM, Wes wrote: > >> IMHO, for that number, on-the-ground radials do not need to be > >> anywhere near that long. Personally, I subscribe to the > >> same-length-as-the-vertical guideline. > >> > >> My inverted-L is 55 feet of vertical tubing plus the horizontal > >> wire. My insulated, on the ground radials are 55.5 feet (9 radials > >> out of a 500 ft roll of wire). By serendipity, measuring one radial > >> against all of the rest with a VNWA it is resonant at 1.84 MHz. To > >> be fair, I still have fewer radials than planned (18 vs. 36) in which > >> case, shorter is actually better according to Belrose and Severns > >> ( > https://www.antennasbyn6lf.com/files/antenna_ground_system_experiment_4.pdf > ). > >> > >> Wes N7WS > >> > >> > >> On 12/9/2020 7:00 PM, Raymond Benny wrote: > >>> If your vertical is ground mounted you need alot [sic] more. I'd say > >>> atleast 36 > >>> radials, 135ft long. It will make a big difference in your signal > >>> and be > >>> easier to match. > >>> > >>> I have over 100 radials but probably an over kill, but I feel I have > >>> a good > >>> signal on 160m. > >>> > >>> Ray, > >>> N6VR/ W7YA > >>> > >> > >> _ > >> Searchable Archives: http://www.contesting.com/_topband - Topband > >> Reflector > > > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > > Reflector > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
N6LF Rudy's web site and associated QEX series has empirical data to answer all of these questions regarding the number and length of on ground radials. 73/jeff/ac0c alpha-charlie-zero-charlie www.ac0c.com On 12/10/20 11:14 AM, Mark - N5OT wrote: Yeah. I don't claim to be a radial expert but I do claim to have a lot of experience working other stations on 160 meters. My buddy W9RE told me on a DXpedition once that he built a dipole laying on the ground and it resonated on 160 when the wires were about 80 feet long. Ray, with respect (N6VR and I go back a LNG way), I think 80 feet is the "new quarter wave radial" on 160, and frankly the only thing I really think I understand about verticals is, the more wire on the ground, the better, but you can get to a point where adding more is not worth the effort, YMMV etc. My story for the week is: I put up yet another temporary 160 vertical for the ARRL 160 last weekend, and only managed 14 radials before it got so dark I thought I better be getting on the air. I worked 970 QSOs that night, including 5 Europeans, and while I was out there on Saturday adding more radials, I got a text from K5ZD saying I was an alligator, that I was very loud the night before, but couldn't hear him calling me for 10 minutes as he needed Oklahoma. So I stopped adding radials, I was up to 22 radials at 80' long, and moved on to listening antennas. Worked maybe 10 Europeans and counted 10 JAs, so I know my signal was getting to those places. That's really all I know about that. The vertical is 50 feet tall and has two symmetrical top-load wires that bring the resonant frequency to 1.8 MHz. 73 - Mark N5OT P.S. Got an email from a guy in South Dakota who worked 376 QSOs (including 4 other countries) using an inverted L that was 20 feet up and the rest horizontal, fed against 20 radials 25' long in his yard. I love stories like that. On 12/10/2020 9:52 AM, Wes wrote: IMHO, for that number, on-the-ground radials do not need to be anywhere near that long. Personally, I subscribe to the same-length-as-the-vertical guideline. My inverted-L is 55 feet of vertical tubing plus the horizontal wire. My insulated, on the ground radials are 55.5 feet (9 radials out of a 500 ft roll of wire). By serendipity, measuring one radial against all of the rest with a VNWA it is resonant at 1.84 MHz. To be fair, I still have fewer radials than planned (18 vs. 36) in which case, shorter is actually better according to Belrose and Severns (https://www.antennasbyn6lf.com/files/antenna_ground_system_experiment_4.pdf). Wes N7WS On 12/9/2020 7:00 PM, Raymond Benny wrote: If your vertical is ground mounted you need alot [sic] more. I'd say atleast 36 radials, 135ft long. It will make a big difference in your signal and be easier to match. I have over 100 radials but probably an over kill, but I feel I have a good signal on 160m. Ray, N6VR/ W7YA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40
Especially if you have elevated radials you will need a choke otherwise the coax and your shack will become part of the ground plane. . In my case I have a choke ( for common mode currents) and UNUN to match the 25 ohm impedance of the antenna to 50 ohms. In some installations the common modes� can be quite large . The choke on my� 60'-"t" is eight ft-240-31 cores with 4 turns of coax. At 4 cores, the cores would get hot enough after 10 minutes at legal limit that were too hot to touch. With ground mounted radials the common mode problem is usually a lot lower. YMMV Dave NR1DX On 12/10/2020 2:17 PM, Jim Brown wrote: On 12/10/2020 4:33 AM, Rob Atkinson wrote: I've never understood what is gained by using a balun at the feedpoint in this application.�� The feedline is unbalanced as is the load. What's the point of a balun. That's the problem with the word "balun." A CHOKE is needed at the feedpoint so that the feedline does not become a radial. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector -- Dave manu...@artekmanuals.com www.ArtekManuals.com -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40
On 12/10/2020 4:33 AM, Rob Atkinson wrote: I've never understood what is gained by using a balun at the feedpoint in this application. The feedline is unbalanced as is the load. What's the point of a balun. That's the problem with the word "balun." A CHOKE is needed at the feedpoint so that the feedline does not become a radial. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Yeah. I don't claim to be a radial expert but I do claim to have a lot of experience working other stations on 160 meters. My buddy W9RE told me on a DXpedition once that he built a dipole laying on the ground and it resonated on 160 when the wires were about 80 feet long. Ray, with respect (N6VR and I go back a LNG way), I think 80 feet is the "new quarter wave radial" on 160, and frankly the only thing I really think I understand about verticals is, the more wire on the ground, the better, but you can get to a point where adding more is not worth the effort, YMMV etc. My story for the week is: I put up yet another temporary 160 vertical for the ARRL 160 last weekend, and only managed 14 radials before it got so dark I thought I better be getting on the air. I worked 970 QSOs that night, including 5 Europeans, and while I was out there on Saturday adding more radials, I got a text from K5ZD saying I was an alligator, that I was very loud the night before, but couldn't hear him calling me for 10 minutes as he needed Oklahoma. So I stopped adding radials, I was up to 22 radials at 80' long, and moved on to listening antennas. Worked maybe 10 Europeans and counted 10 JAs, so I know my signal was getting to those places. That's really all I know about that. The vertical is 50 feet tall and has two symmetrical top-load wires that bring the resonant frequency to 1.8 MHz. 73 - Mark N5OT P.S. Got an email from a guy in South Dakota who worked 376 QSOs (including 4 other countries) using an inverted L that was 20 feet up and the rest horizontal, fed against 20 radials 25' long in his yard. I love stories like that. On 12/10/2020 9:52 AM, Wes wrote: IMHO, for that number, on-the-ground radials do not need to be anywhere near that long. Personally, I subscribe to the same-length-as-the-vertical guideline. My inverted-L is 55 feet of vertical tubing plus the horizontal wire. My insulated, on the ground radials are 55.5 feet (9 radials out of a 500 ft roll of wire). By serendipity, measuring one radial against all of the rest with a VNWA it is resonant at 1.84 MHz. To be fair, I still have fewer radials than planned (18 vs. 36) in which case, shorter is actually better according to Belrose and Severns (https://www.antennasbyn6lf.com/files/antenna_ground_system_experiment_4.pdf). Wes N7WS On 12/9/2020 7:00 PM, Raymond Benny wrote: If your vertical is ground mounted you need alot [sic] more. I'd say atleast 36 radials, 135ft long. It will make a big difference in your signal and be easier to match. I have over 100 radials but probably an over kill, but I feel I have a good signal on 160m. Ray, N6VR/ W7YA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
> > To model radials, we must use Real High Accuracy Ground, with NO connection > to Ground. Read the EZNEC manual Yes! That is what I need to change. Thank you! Solution: I was connecting the radials to ground using EZNEC. I need to create the radials just above ground. Page 90 of the User Manual. "Buried radials can be directly modeled only with EZNEC Pro/4 using an NEC-4 calculating engine (see Buried Wires). With EZNEC, EZNEC+, and EZNEC Pro/2 they have to be simulated.” Buried radials with EZNEC have to be simulated. “...model buried radials by substituting radials just above the ground surface. This does a moderately good job of predicting the ground system efficiency as well as whatever pattern modification results from the radial system. With this approach, the High Accuracy Real ground type must be used. See Connecting to High Accuracy Ground for more information.” Page 127 of the User Manual "With program types other than EZNEC Pro/4 the best way to approximate a buried radial system is by creating horizontal radials just above the ground, and make the "ground" connection to the radials. A height of between about 1/100 and 1/1000 of a wavelength is suitable, but in any case no less than several wire diameters. If a low impedance connection is required, make the radials about a quarter wavelength or odd multiples long, and avoid lengths approaching a half wavelength or multiples. These aren't free space wavelengths, however, but wavelengths for a wire at the radial height. A half wavelength for a wire very close to the ground will be less than in free space, though. You can determine the wavelength by modeling a dipole at the height of the radials and adjusting its length until it's resonant. Be sure you're seeing the lowest (series) resonance, which for very low wires will occur with a dipole length somewhat less than a free space half wavelength. The best radial length will be about half the resonant dipole length. Radials can easily be constructed using EZNEC's automated radial creation feature. Above ground radials will show resonant effects more sharply than buried radials, but will provide a reasonable approximation of a buried radial system." _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
IMHO, for that number, on-the-ground radials do not need to be anywhere near that long. Personally, I subscribe to the same-length-as-the-vertical guideline. My inverted-L is 55 feet of vertical tubing plus the horizontal wire. My insulated, on the ground radials are 55.5 feet (9 radials out of a 500 ft roll of wire). By serendipity, measuring one radial against all of the rest with a VNWA it is resonant at 1.84 MHz. To be fair, I still have fewer radials than planned (18 vs. 36) in which case, shorter is actually better according to Belrose and Severns (https://www.antennasbyn6lf.com/files/antenna_ground_system_experiment_4.pdf). Wes N7WS On 12/9/2020 7:00 PM, Raymond Benny wrote: If your vertical is ground mounted you need alot [sic] more. I'd say atleast 36 radials, 135ft long. It will make a big difference in your signal and be easier to match. I have over 100 radials but probably an over kill, but I feel I have a good signal on 160m. Ray, N6VR/ W7YA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40
I've never understood what is gained by using a balun at the feedpoint in this application. The feedline is unbalanced as is the load. What's the point of a balun. The wild variations in R and X over the range of the band will likely result in heat and loss at the balun. If the point is to keep RF off the exterior of the feedline, that problem vanishes if you have a lot of radials which are needed regardless. The best solution is to put the matching network at the feedpoint but if you opt to match the line to the transmitter at the shack, the vswr loss for 70 feet of 213 won't be terrible and the dielectric will probably withstand the voltage maxima. 73 Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
On 12/9/2020 8:51 PM, wi6x...@gmail.com wrote: The radials as modeled have End1 Ground connection and no End 2 connection. Should they be connected to another wire? To model radials, we must use Real High Accuracy Ground, with NO connection to Ground. Read the EZNEC manual carefully about that. With Real High Accuracy Ground, no connection to it is permitted. HOWEVER -- if you're going to simply try to put as much copper on the ground as possible (which I recommend), don't bother to model radials, use the Mini-NEC Ground, connect the bottom of the antenna to Ground (you can with MiniNEC), and put the generator in the bottom segment. 15 on an FCC map is pretty good ground. Unless someone (like Frank) gives you better advice, I'd use Pastoral, Med Hills when you right click in the Ground Description tab. More copper on the ground will reduce the resistive component of the feedpoint Z. If your rig will put full power into the feedline, I'd stop there. 1.4:1 is plenty good for SWR, especially with such a short feedline on 160M, but more copper on the ground will make you a few dB louder. :) 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Thank you everyone. The radials as modeled have End1 Ground connection and no End 2 connection. Should they be connected to another wire? --- WIRES --- No. End 1 Coord. (ft) End 2 Coord. (ft) Dia (in) SegsInsulation Conn. X Y Z Conn. X Y Z Diel C Thk(in) 1 GND0, 0, 0W2E10, 0, 40 #14 17 10 2 W1E20, 0, 40 143, 0, 40 #14 17 10 3 GND0, 0, 00, -100, 1 #14 17 10 4 GND0, 0, 00,100, 1 #14 17 10 5 GND0, 0, 0 -100, 0, 1 #14 17 10 6 GND0, 0, 0 100, 0, 1 #14 17 10 I have a field of 100+ 70’ to 20’ #14 wire radials under my lawn that I will use. I stopped inputing radials in the model at four radials when my numbers seemed off. I’m using EZNEC Ver. 6 (NEC-4). I do not have room for proper elevated radials. I only have room to elevate about six, and they could only be about 5’ above ground. I used Jim K9YC’s Pacificon 160 on Small Lots slideshow to get started with this antenna and his cookbook for the balun. Thanks! FCC’s ground conductivity map indicates 15 millimhos per meter, and I’m on predominantly clay soil. Transmission line is 75’ of RG213, so it is not an issue. Thanks again for helping. Jim WI6X > On Dec 9, 2020, at 1:16 PM, Jim Brown wrote: > > On 12/9/2020 12:00 PM, wi6x...@gmail.com wrote: >> My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but I >> don’t have enough experience to know if what what I am doing is correct or >> not. I’m a neubie, at EZNEC and 160m. > > Those numbers tell you that the antenna is resonant below the band, and the > dimensions also show. It's a common trick to tune the antenna low so that R > is 50 ohms and X is inductive; we can then tune out the inductance with > series C. I'm using this technique with my Tee vertical for 160M. > > Feedline loss on 160M is pretty low unless the line is pretty long, so if > your rig or power amp will drive it, I wouldn't worry about it. > > Another important observation. Four radials isn't enough of a counterpoise > unless they are well elevated -- N6BT, who's done lots with verticals and is > a fine antenna engineer, says at least 16 ft. A lot of the R in your model > could be ground loss. If those radials are on-ground, you need a LOT more > than four; they don't need to be any specific length or even close to the > same, but 100' is pretty close to a quarter wave (thanks to soil modifying > their VF), and more copper on the ground is better. > > Also, soil parameters strongly affect that loss component -- try to learn > what your soil is like, and plug those parameters into the model. In the soil > parameters window, right click on the entry screen to get a list of them. > > Here are slides for a talk I've done at Pacificon, Visalia, and to several > clubs. It's mostly about antennas and counterpoise/radial systems. No > original work, just summarizing a lot of great work by others. > http://k9yc.com/160MPacificon.pdf > > 73, Jim K9YC > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
If your vertical is ground mounted you need alot more. I'd say atleast 36 radials, 135ft long. It will make a big difference in your signal and be easier to match. I have over 100 radials but probably an over kill, but I feel I have a good signal on 160m. Ray, N6VR/ W7YA On Wed, Dec 9, 2020, 3:59 PM Carl Luetzelschwab wrote: > Jim, > > It looks like you connect wires to lossy ground. Do you have the NEC-4 > engine with your EZNEC ver 6.0? > > Carl K9LA > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Jim, It looks like you connect wires to lossy ground. Do you have the NEC-4 engine with your EZNEC ver 6.0? Carl K9LA _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
60 + j19 does seem off. Is this ground mounted or with elevated radials? An EZNEC free-space model reports *36 +j227* at 1800kHz. On perfect GND it reports 166 +j306 ohms. 10' above 0.005/13 GND it reports *37 +j262* ohms with resonance at 1510kHz. Dave KH6AQ On Wed, Dec 9, 2020 at 11:32 AM Jim Brown wrote: > On 12/9/2020 12:00 PM, wi6x...@gmail.com wrote: > > My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but > I don’t have enough experience to know if what what I am doing is correct > or not. I’m a neubie, at EZNEC and 160m. > > Those numbers tell you that the antenna is resonant below the band, and > the dimensions also show. It's a common trick to tune the antenna low so > that R is 50 ohms and X is inductive; we can then tune out the > inductance with series C. I'm using this technique with my Tee vertical > for 160M. > > Feedline loss on 160M is pretty low unless the line is pretty long, so > if your rig or power amp will drive it, I wouldn't worry about it. > > Another important observation. Four radials isn't enough of a > counterpoise unless they are well elevated -- N6BT, who's done lots with > verticals and is a fine antenna engineer, says at least 16 ft. A lot > of the R in your model could be ground loss. If those radials are > on-ground, you need a LOT more than four; they don't need to be any > specific length or even close to the same, but 100' is pretty close to a > quarter wave (thanks to soil modifying their VF), and more copper on the > ground is better. > > Also, soil parameters strongly affect that loss component -- try to > learn what your soil is like, and plug those parameters into the model. > In the soil parameters window, right click on the entry screen to get a > list of them. > > Here are slides for a talk I've done at Pacificon, Visalia, and to > several clubs. It's mostly about antennas and counterpoise/radial > systems. No original work, just summarizing a lot of great work by others. > http://k9yc.com/160MPacificon.pdf > > 73, Jim K9YC > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
On 12/9/2020 12:00 PM, wi6x...@gmail.com wrote: My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but I don’t have enough experience to know if what what I am doing is correct or not. I’m a neubie, at EZNEC and 160m. Those numbers tell you that the antenna is resonant below the band, and the dimensions also show. It's a common trick to tune the antenna low so that R is 50 ohms and X is inductive; we can then tune out the inductance with series C. I'm using this technique with my Tee vertical for 160M. Feedline loss on 160M is pretty low unless the line is pretty long, so if your rig or power amp will drive it, I wouldn't worry about it. Another important observation. Four radials isn't enough of a counterpoise unless they are well elevated -- N6BT, who's done lots with verticals and is a fine antenna engineer, says at least 16 ft. A lot of the R in your model could be ground loss. If those radials are on-ground, you need a LOT more than four; they don't need to be any specific length or even close to the same, but 100' is pretty close to a quarter wave (thanks to soil modifying their VF), and more copper on the ground is better. Also, soil parameters strongly affect that loss component -- try to learn what your soil is like, and plug those parameters into the model. In the soil parameters window, right click on the entry screen to get a list of them. Here are slides for a talk I've done at Pacificon, Visalia, and to several clubs. It's mostly about antennas and counterpoise/radial systems. No original work, just summarizing a lot of great work by others. http://k9yc.com/160MPacificon.pdf 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire. My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but I don’t have enough experience to know if what what I am doing is correct or not. I’m a neubie, at EZNEC and 160m. Thank you in advance for your advice and recommendations. 73, Jim, WI6X SOURCES: Wire #1, 0% From E1 GROUND TYPE: Real/High Accuracy EZNEC ver. 6.0 160m Inv L 12/9/2020 11:38:28 AM --- SOURCE DATA --- Frequency = 1.83 MHz Source 1 Voltage = 314.7 V at 17.19 deg. Current = 4.99 A at 0.0 deg. Impedance = 60.25197 + J 18.63926 ohms Power = 1500 watts SWR (50 ohm system) = 1.470 (75 ohm system) = 1.422 EZNEC ver. 6.0 160m Inv L 12/9/2020 11:21:01 AM --- WIRES --- No. End 1 Coord. (ft) End 2 Coord. (ft) Dia (in) SegsInsulation Conn. X Y Z Conn. X Y Z Diel C Thk(in) 1 GND0, 0, 0W2E10, 0, 40 #14 17 10 2 W1E20, 0, 40 143, 0, 40 #14 17 10 3 GND0, 0, 00, -100, 1 #14 17 10 4 GND0, 0, 00,100, 1 #14 17 10 5 GND0, 0, 0 -100, 0, 1 #14 17 10 6 GND0, 0, 0 100, 0, 1 #14 17 10 _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
