Re: Topband: New Subject: 160M array feedline question
Roger, Take a look at this. I am thinking of building one this summer and hang it from a tall tree. https://www.yccc.org/Articles/double_l.htm 73 Mark N1UK G3ZZM On 23-Mar-21 6:33 PM, Roger Kennedy wrote: Guy (K2AV) - I really liked your explanation about the function of a radial field on a 160m vertical . . . and how the radials don't actually radiate. But I've often thought about the other extreme . . . I have a homebrew 2m Ground Plane on top of my mast . . . just a quarter wave vertical . . . and 3 quarter wave radials sloping down about 45 degrees. Now if those radials were vertical, it would really be a vertical Dipole . . . i.e. the radials would be radiating. Whereas if they were horizontal, I guess they wouldn't be. You get my question . . . what really is the difference between the 3 different radial situations? And here's another question . . . rather than all the issues of radials and matching, has anyone ever used a Vertical Dipole on 160m ? Sure, you're not going to have a 260 ft vertical . . . but suppose you had a 100ft support, so that you could have 50 ft vertical legs either side of the coax feeder, and then just bend the legs at right angles at the top and bottom to make up the length (linear loading) - maybe running in opposite directions. I would have though that would be quite an efficient antenna? And presumably (just like any dipole) it would work even better if the ground underneath it was very poor (in my opinion) Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
Hi, Roger It sure seems like a lot of confusion arises when folks attempt concise electrical and mathematical thoughts and calculations using words with very broad and fuzzy definitions. Words like radial, vertical, topload, etc. can mean different things and can create remarkably confusing sentences and descriptions. Like “vertical with one elevated radial”. If one is thinking that radials are a specific kind of wire group used as a counterpoise that effectively minimizes radiation, then “with one radial” can’t be called a radial. It simply is one end of a bent dipole, with one wire very close to and parallel to the ground. Less lossy than some constructions, e.g. the horizontal wire actually laying on the ground or buried, but decidedly lossy. But there will be disagreement about a bent, ground-adjacent dipole, quite more than one way of talking about that. Being accused of not having a radial will undoubtedly be defended with "I worked VK9ABCD at noon long path with a vertical over one radial." But that comeback does not pay any attention to whether one can include "one radial" in a precise definition framework for discussion about how radials work and why the commercial gold standard radials work so well. And of course the worst of antennas can sometimes make QSOs in the best of conditions, while the best of antennas can often barely make QSOs in the worst of conditions. How can one possibly have an academic grade discussion with all that flak flying around under the same list-serve thread title? Since it’s not possible to referee a precise dictionary of such terms that everyone will agree on, the answer to questions can’t be precisely formulated with those terms IF what we’re looking for is precise answers or at least answers good enough to risk precious hours, sore backs and monetary expenditures. In the end the answer to what wires and aluminum tubes do is what the antenna modeling says they do, assuming that attempting the actual antenna doesn’t expose a gotcha that requires additional work to produce in the model what the wires and tubes actually individually do. The antenna model is the only device we have that can break down the problem into small pieces, calculate all the micro-interactions, and then add them up into patterns and gain figures. But even the high-priced pro antenna modelers get tricky to do right with conductors very close to or in the ground, especially an issue on 160m. Losses are the two ton elephant in the room on 160. Conversations with fuzzy terms and concepts don't have a chance at accurately telling you about RF losses, other than to warn they need to be dealt with. We estimate efficiency by constructing the idea in a model, comparing average and worst case ground results, and then doing a near field run set to the ground surface. The former tells you how badly ground could affect the performance and the latter shows if the design has created hotspot RF field zones that can excessively induce ground losses, possibly pointing to design improvements without the hotspots. Verbal discussion is good for airing general ideas and concepts, providing mental constructs for at least basically understanding involved principles, if you can get consensus on definitions of terms. But as soon as you want to know dB's, whether A is better than B, or not, you have to do the work to put the idea up in models, avoiding all the gotchas, so all the interactions between conductors, between conductors and ground, can be calculated, added up and presented as loss figures and radiation patterns. As to your mention of a typical VHF ground plane with counterpoise members in a plane perpendicular to the radiating member, far field radiation from those four will be minimized. When those four are "drooped", the four now have a vertical component to their fields which modifies the pattern of the main radiating member. Frankly I think that the VHF "coaxial dipole" has long since replaced that design. Consider the Celwave Stationmaster, etc, since even barely high angle VHF radiation is lost altogether. One of their improvements in those fiberglass encapsulated collinear antennas is to produce patterns that max out three or even six degrees below perpendicular to the vertical to aim max power "down" to the horizon or nearer service area from their high mounting points. I don't see radials on those things. Still on some simple low VHF antennas. Using "down-angled" elevated radials in a 160 antenna has mild advantages seen on a model. But one's physical construction has to have something handling a loss avoidance need to keep RF off the tower beneath the feedpoint. That seems to discourage that idea from becoming popular, because without defeating RF on the tower beneath, that added loss more than cancels the mild advantage seen in simple models without the tower-to-ground treatment. There actually is a way to accomplish tower loading, without tower base radials using one or two FCP's, a
Re: Topband: New Subject: 160M array feedline question
Ooops, sorry about the cut and paste error. This link should work. http://www.yccc.org/Articles/double_l.htm From: Topband on behalf of W7TMT - Patrick Sent: Tuesday, March 23, 2021 3:41:34 PM To: Roger Kennedy ; topband@contesting.com Subject: Re: Topband: New Subject: 160M array feedline question Called a Double L. This is the earliest article on it I remember. Others out there as well. http://www.yccc.org/http://www.yccc.org/Articles/double_l.ht/double_l.htm Patrick, W7TMT From: Topband on behalf of Roger Kennedy Sent: Tuesday, March 23, 2021 3:33:53 PM To: topband@contesting.com Subject: Topband: New Subject: 160M array feedline question Guy (K2AV) - I really liked your explanation about the function of a radial field on a 160m vertical . . . and how the radials don't actually radiate. But I've often thought about the other extreme . . . I have a homebrew 2m Ground Plane on top of my mast . . . just a quarter wave vertical . . . and 3 quarter wave radials sloping down about 45 degrees. Now if those radials were vertical, it would really be a vertical Dipole . . . i.e. the radials would be radiating. Whereas if they were horizontal, I guess they wouldn't be. You get my question . . . what really is the difference between the 3 different radial situations? And here's another question . . . rather than all the issues of radials and matching, has anyone ever used a Vertical Dipole on 160m ? Sure, you're not going to have a 260 ft vertical . . . but suppose you had a 100ft support, so that you could have 50 ft vertical legs either side of the coax feeder, and then just bend the legs at right angles at the top and bottom to make up the length (linear loading) - maybe running in opposite directions. I would have though that would be quite an efficient antenna? And presumably (just like any dipole) it would work even better if the ground underneath it was very poor (in my opinion) Roger G3YRO _ 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: New Subject: 160M array feedline question
Called a Double L. This is the earliest article on it I remember. Others out there as well. http://www.yccc.org/http://www.yccc.org/Articles/double_l.ht/double_l.htm Patrick, W7TMT From: Topband on behalf of Roger Kennedy Sent: Tuesday, March 23, 2021 3:33:53 PM To: topband@contesting.com Subject: Topband: New Subject: 160M array feedline question Guy (K2AV) - I really liked your explanation about the function of a radial field on a 160m vertical . . . and how the radials don't actually radiate. But I've often thought about the other extreme . . . I have a homebrew 2m Ground Plane on top of my mast . . . just a quarter wave vertical . . . and 3 quarter wave radials sloping down about 45 degrees. Now if those radials were vertical, it would really be a vertical Dipole . . . i.e. the radials would be radiating. Whereas if they were horizontal, I guess they wouldn't be. You get my question . . . what really is the difference between the 3 different radial situations? And here's another question . . . rather than all the issues of radials and matching, has anyone ever used a Vertical Dipole on 160m ? Sure, you're not going to have a 260 ft vertical . . . but suppose you had a 100ft support, so that you could have 50 ft vertical legs either side of the coax feeder, and then just bend the legs at right angles at the top and bottom to make up the length (linear loading) - maybe running in opposite directions. I would have though that would be quite an efficient antenna? And presumably (just like any dipole) it would work even better if the ground underneath it was very poor (in my opinion) Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
Inspect your feedline you plan to use (sounds like it is Heliax) and make sure the jacket is undamaged. If it is okay, you can bury it or just lay it on the ground and it won't matter if water covers it. Of more concern is keeping the junction where the feedline divides dry. If you use enough radials, you won't have to worry about the feedline shield becoming a radial. It will be one, but the RF on it will be minimal because it will be one among many radials. But you have to have a lot of radials. I am taking your description of the field being under water for only a couple of weeks a year into account. If you are concerned about animals chewing on the line, burying it or elevating it may be needed. I've had something chew on my 1/2 inch line but I guess rodents realize the jacket isn't the same as wood so they don't go very far. The line is fine due to the solid copper shield. This is one of the reasons why Heliax is superior to braided shield line and a worthwhile investment. 73 Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
Interesting page on the subject here ; https://ham.stackexchange.com/questions/3675/what-is-the-effect-of-using-different-number-of-radials-with-ground-plane-antenn On 23/3/21 1:55 pm, Guy Olinger K2AV wrote: A counterpoise is what we do when the full size of a double-ended antenna, dipole, OCF, etc is too large for us to build, maintain, etc. Very simply, we want to jam the energy from the shield of our coax into the counterpoise, and the energy from the center conductor into the radiating element, the vertical, T, inverted L, etc, the aerial wire. Then we want to get all that energy back from the counterpoise, none lost if possible, at the phase reversal. Any you don't get back is mostly outright loss. With commercial high grade radials you can show that the effective series resistance of the counterpoise is 1/2, 1/3 or sometimes even 1/10 of an ohm. That means that the aerial wire is radiating something like 50, 100 times the energy lost/radiated by the radials' connection to ground. The two current destinations taken together MIMIC a circuit, because the current into the counterpoise is the same, but opposite polarity as the current into the radiating part of the antenna. If the currents are equal and opposite, it looks like a circuit, walks like a circuit, quacks like a circuit. You can model it with a fake circuit, and use Maxwell's equations for circuits to predict what is gonna happen. There is no magic circulation, just the ability to convince the coax it is hooked up to a circuit. With the massive parallelism of a commercial grade radial field, the radial's electrons are coupled into the ground as a reservoir, with the push back from extra or missing electrons that will return the current when the phase reverses. The more radials, the more even the radials, the longer the radials, the lower the power lost to current through resistive materials, lost to dielectric loss in dielectric materials, lost to resistance in the wire. Not perfect return, but a nice, high percentage return. In free space, it is possible to construct a counterpoise that NEC4 can accurately predict will radiate power to the far field at a rate 30 dB below the RF current's energy. The essential loss is in the RF resistance of the wire. You are talking about a counterpoise that is 98 or 99+ percent efficient in free space. We are not interested in a counterpoise radiating, or invoking loss in the environment. Talking to the counterpoise, I'm telling it I'm giving it this pile of energy. A half cycle from now I want it all back. No skimming off the top. Maybe just a skoch. A commercial quality radial field beneath a vertical is deliberately intended to be non-radiating. Looking at the current around the base of the vertical, the current to the east is exactly the opposite of the current to the west, as are to the north and south, as are all opposite radial pairs, therefore the fields generated are opposite, intended to be net zero in the far field. That's on purpose, pretty much true, and exactly what the engineers had in mind. It is easy to show that there are unfortunate ham designs and implementations of the counterpoise/aerial concept where not even 10 percent of the power is radiated skyward. That is the 160 meter two ton elephant in the room that gets ignored an awful lot of the time. 73, Guy K2AV _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
A counterpoise is what we do when the full size of a double-ended antenna, dipole, OCF, etc is too large for us to build, maintain, etc. Very simply, we want to jam the energy from the shield of our coax into the counterpoise, and the energy from the center conductor into the radiating element, the vertical, T, inverted L, etc, the aerial wire. Then we want to get all that energy back from the counterpoise, none lost if possible, at the phase reversal. Any you don't get back is mostly outright loss. With commercial high grade radials you can show that the effective series resistance of the counterpoise is 1/2, 1/3 or sometimes even 1/10 of an ohm. That means that the aerial wire is radiating something like 50, 100 times the energy lost/radiated by the radials' connection to ground. The two current destinations taken together MIMIC a circuit, because the current into the counterpoise is the same, but opposite polarity as the current into the radiating part of the antenna. If the currents are equal and opposite, it looks like a circuit, walks like a circuit, quacks like a circuit. You can model it with a fake circuit, and use Maxwell's equations for circuits to predict what is gonna happen. There is no magic circulation, just the ability to convince the coax it is hooked up to a circuit. With the massive parallelism of a commercial grade radial field, the radial's electrons are coupled into the ground as a reservoir, with the push back from extra or missing electrons that will return the current when the phase reverses. The more radials, the more even the radials, the longer the radials, the lower the power lost to current through resistive materials, lost to dielectric loss in dielectric materials, lost to resistance in the wire. Not perfect return, but a nice, high percentage return. In free space, it is possible to construct a counterpoise that NEC4 can accurately predict will radiate power to the far field at a rate 30 dB below the RF current's energy. The essential loss is in the RF resistance of the wire. You are talking about a counterpoise that is 98 or 99+ percent efficient in free space. We are not interested in a counterpoise radiating, or invoking loss in the environment. Talking to the counterpoise, I'm telling it I'm giving it this pile of energy. A half cycle from now I want it all back. No skimming off the top. Maybe just a skoch. A commercial quality radial field beneath a vertical is deliberately intended to be non-radiating. Looking at the current around the base of the vertical, the current to the east is exactly the opposite of the current to the west, as are to the north and south, as are all opposite radial pairs, therefore the fields generated are opposite, intended to be net zero in the far field. That's on purpose, pretty much true, and exactly what the engineers had in mind. It is easy to show that there are unfortunate ham designs and implementations of the counterpoise/aerial concept where not even 10 percent of the power is radiated skyward. That is the 160 meter two ton elephant in the room that gets ignored an awful lot of the time. 73, Guy K2AV On Mon, Mar 22, 2021 at 9:42 PM Adrian wrote: > Recycling signals at the feedpoint sounds more like a mismatch swr > situation. > > The ground radials form half of the antenna, and that radiation from > ground, in phase with the vertical radiation determines the field > strength and take off angle. > > vk4tux > > > On 23/3/21 11:31 am, Charles Moizeau wrote: > > I feel it more appropriate to say that the function of ground-mounted > radials is to harvest the radiation from a vertical antenna that splashes > on the ground and return it to the feed point for recycling. > > > > 72/73, > > > > Charles, W2SH > > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
Recycling signals at the feedpoint sounds more like a mismatch swr situation. The ground radials form half of the antenna, and that radiation from ground, in phase with the vertical radiation determines the field strength and take off angle. vk4tux On 23/3/21 11:31 am, Charles Moizeau wrote: I feel it more appropriate to say that the function of ground-mounted radials is to harvest the radiation from a vertical antenna that splashes on the ground and return it to the feed point for recycling. 72/73, Charles, W2SH _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
I feel it more appropriate to say that the function of ground-mounted radials is to harvest the radiation from a vertical antenna that splashes on the ground and return it to the feed point for recycling. 72/73, Charles, W2SH From: Topband on behalf of Jim Brown Sent: Monday, March 22, 2021 20:40 To: topband@contesting.com Subject: Re: Topband: New Subject: 160M array feedline question On 3/22/2021 2:41 PM, Carl Braun wrote: > Some brought up the idea of my ground mounted radials becoming submerged in > fresh water...however, that would only take place for a week or less during > the spring here and, it would only happen if we had a slow snow pack melt and > rain at the same time. The earth is a big resistor. Connecting to it BURNS transmitter power. What many folks miss is that the function of radials is to SHIELD the antenna's fields and return current from lossy earth, NOT to couple to it. The only part of the earth we want to carry return current or see a transmitting antenna's field is SEA water. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
On 3/22/2021 2:41 PM, Carl Braun wrote: Some brought up the idea of my ground mounted radials becoming submerged in fresh water...however, that would only take place for a week or less during the spring here and, it would only happen if we had a slow snow pack melt and rain at the same time. The earth is a big resistor. Connecting to it BURNS transmitter power. What many folks miss is that the function of radials is to SHIELD the antenna's fields and return current from lossy earth, NOT to couple to it. The only part of the earth we want to carry return current or see a transmitting antenna's field is SEA water. 73, Jim K9YC _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
Topbanders Thanks to all who responded I received a lot of good advice and will be taking it. Specifically, the advice to bury the hardline rather than elevate it. Some brought up the idea of my ground mounted radials becoming submerged in fresh water...however, that would only take place for a week or less during the spring here and, it would only happen if we had a slow snow pack melt and rain at the same time. This happened here two years ago but only lasted for a week or so. I am sure to have more questions as this project matures. In the meantime, I will continue to work with my modified 80/160 Butternut vertical that's stuck in the snow. It uses 4 pieces of 30' irrigation tubing for radials as well as some wayward wires to create the ground screen. No amplifier. This winter I have 22 countries on 160 with it. Looking forward to the array! Thanks again Carl W9LF From: Carl Braun Sent: Sunday, March 21, 2021 3:26 PM To: topband@contesting.com Subject: New Subject: 160M array feedline question Hello Topbanders I am currently awaiting the snow to melt here in the Northwoods of Wisconsin before starting the construction of my low band vertical array. My verticals will be mounted in a low ground area near a lake and the area tends to get wet and sometimes floods in the early spring. Water levels could reach 6" to 12" above ground. My concerns relate to the hardline coaxial cable that will run from my lighting arrestor panel at the outside of my shack to the center of the two element vertical array which is 250' away. I will be using 1 5/8" hardline that I was able to snag for a very good deal but am concerned about having the cable lying on the ground and possible become submerged should we get significant rain with the snow melt. My plan is to elevate the feedline approximately 24" above the ground using old sections of Rohn 25 tower spaced every 10' or so. Each vertically mounted 5' chunk of Rohn 25 will be buried 2' into the ground have a 3' 2x6 board laying horizontally across the tower that would act as a coaxial "shelf" that will keep the hardline out of the water and prevent any significant drooping between these Rohn support sections. My question for the forum is related to the fact that I will have an elevated coaxial feedline with two ground mounted vertical antennas. I plan to use an UNUN or similar line isolator/choke that would keep the hardline from becoming a extra radial. Any thoughts from the forum on this set up? Any extra precautions I should take to keep return currents from flowing on the feedline? Thanks in advance for any suggestions. Carl W9LF _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: New Subject: 160M array feedline question
If the radials have a good chance be being submerged in fresh water, I would consider elevating the radials. Had an experience here where my 40 radials on each of my 4 square verticals were often times below the water level and radiation efficiency dropped like a rock. Great receive performance but transmit signal was poor (think boiling the water). When I raised about 20 radials out of the water and disconnected the ones now trapped in mud, etc. the 4 square started to play well. Regards, Mark, K1RX > On Mar 22, 2021, at 9:54 AM, Wes wrote: > > What's the perceived problem with the cable being submerged? > > Wes N7WS > >> On 3/21/2021 1:25 PM, Carl Braun wrote: >> Hello Topbanders >> >> I am currently awaiting the snow to melt here in the Northwoods of Wisconsin >> before starting the construction of my low band vertical array. My >> verticals will be mounted in a low ground area near a lake and the area >> tends to get wet and sometimes floods in the early spring. Water levels >> could reach 6" to 12" above ground. My concerns relate to the hardline >> coaxial cable that will run from my lighting arrestor panel at the outside >> of my shack to the center of the two element vertical array which is 250' >> away. I will be using 1 5/8" hardline that I was able to snag for a very >> good deal but am concerned about having the cable lying on the ground and >> possible become submerged should we get significant rain with the snow melt. >> >> My plan is to elevate the feedline approximately 24" above the ground using >> old sections of Rohn 25 tower spaced every 10' or so. Each vertically >> mounted 5' chunk of Rohn 25 will be buried 2' into the ground have a 3' 2x6 >> board laying horizontally across the tower that would act as a coaxial >> "shelf" that will keep the hardline out of the water and prevent any >> significant drooping between these Rohn support sections. >> >> My question for the forum is related to the fact that I will have an >> elevated coaxial feedline with two ground mounted vertical antennas. I plan >> to use an UNUN or similar line isolator/choke that would keep the hardline >> from becoming a extra radial. Any thoughts from the forum on this set up? >> Any extra precautions I should take to keep return currents from flowing on >> the feedline? >> >> Thanks in advance for any suggestions. >> >> Carl W9LF >> >> _ >> 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: New Subject: 160M array feedline question
What's the perceived problem with the cable being submerged? Wes N7WS On 3/21/2021 1:25 PM, Carl Braun wrote: Hello Topbanders I am currently awaiting the snow to melt here in the Northwoods of Wisconsin before starting the construction of my low band vertical array. My verticals will be mounted in a low ground area near a lake and the area tends to get wet and sometimes floods in the early spring. Water levels could reach 6" to 12" above ground. My concerns relate to the hardline coaxial cable that will run from my lighting arrestor panel at the outside of my shack to the center of the two element vertical array which is 250' away. I will be using 1 5/8" hardline that I was able to snag for a very good deal but am concerned about having the cable lying on the ground and possible become submerged should we get significant rain with the snow melt. My plan is to elevate the feedline approximately 24" above the ground using old sections of Rohn 25 tower spaced every 10' or so. Each vertically mounted 5' chunk of Rohn 25 will be buried 2' into the ground have a 3' 2x6 board laying horizontally across the tower that would act as a coaxial "shelf" that will keep the hardline out of the water and prevent any significant drooping between these Rohn support sections. My question for the forum is related to the fact that I will have an elevated coaxial feedline with two ground mounted vertical antennas. I plan to use an UNUN or similar line isolator/choke that would keep the hardline from becoming a extra radial. Any thoughts from the forum on this set up? Any extra precautions I should take to keep return currents from flowing on the feedline? Thanks in advance for any suggestions. Carl W9LF _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
