Re: Topband: elevated radial question
Hi, Grant! Well, sometimes we have to just flower where we're planted and what is IS! I actually think that an 85' high TEE with elevated radials will be an excellent 160 antenna for you!! Actually, I don't expect that you really need 7 radials. Four should do fine! Of course, you could add more later. If you wish! I don't think you'll have much interaction between your radials and the 4 square receive array since it is vertical, but if the 4 square array has radials you might try to keep them separated from your 160 transmit radials. I used to have m y 160 inverted-L radials on my small lot, along with my 80m GP radials and both worked great! I surely would avoid contact between the 160 radials and that metal building. Any contact would substantially alter the current distribution, electrical length and resonance of the radials. All that can be checked with some imaginative work with an antenn analyzer or dip meter.Note that if you connect any two reasonable opposing radials together near the feedpoint, of your TEE, the pair should be 1/2 wave resonant. I absolutely would NOT connect to the building NOR would I run the radias over the metal roof! Just use FEWER radials! High conductivity is GOOD! Just don't connec to it! BTW, you could also hang and 80m quarter wave wire off the flat topof your tee and attach I to the same feed point as the 160 antenna. Of course you would also need to add some 80m radials! Good luck!! Sounds lie it's likely to be a really good 160 transmit antenna! -MUCH better than a delta loop~ Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Grant Saviers Sent: Wednesday, December 12, 2012 7:06 PM To: topband@contesting.com Subject: Topband: elevated radial question I'm finalizing the layout for a tree hung T loaded vertical for TB, about 85' to the top, two x 45' mostly horizontal loading wires, and radials elevated 10' above (much?) better than average soil, at least this time of year when I have standing water among the trees. (Redmond, WA) I'm taking W8JI's advice and going with the top loaded vertical rather than a delta loop, particularly after I determined I can squeeze seven fairly symmetrical 130' radials in (with a cooperative neighbor). I plan a switched series capacitor feed for bandwidth, with the antenna resonant at 1815KHz or so. Now two questions before stringing wire - 1. My new DXE 4 square receive array is outside the radial field, with the center of the square 82' from the radials perimeter. Does it matter if the end of one radial is about 30' from a corner 4sq antenna, or should I pitch the radials to maximize the separation? Even as much as a 90 degree (or more) segment with no radials? At 90 degree pitch the nearest radial ends would be about 80' from their nearest 4sq antenna. 2. Now the unusual circumstance - there is a 56' x 70' steel building entirely inside the radial circle, but at the perimeter. Steel roof, walls, and Ufer grounded to the perimeter footing. My thinking, not sure I'm correct, is to NOT attach any radials to the building (12' to eves, 14' to peak), but nestle it between 2 radials with about 15' feet of minimum clearance. OTOH, I can connect one or more radials to the steel, or run one or more insulated radials over the roof to a support off the perimeter end of the building. And then OTOH, the steel sure makes this part of the radial field pretty high conductivity. This one is definitely not in the handbooks or in ON4UN or in the N6LF QEX articles. btw I have a SteppIR BigIR vertical going on the center of this roof as a secondary/backup HF antenna. Inputs appreciated, Grant KZ1W ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
This is ~true only for a far field analysis (as defined by NEC software) for a vertical monopole -- which includes the propagation losses present in the radiated fields from that monopole, over an infinite, FLAT, real-earth ground plane. However that is not reality. I think what is going here is we have a bunch of anecdotal results based on one unknown compromised system compared to another compromised system when dozens of things are changed, and we are trying to generate physics to support one thing as being the cause. I am 100% sure, based on dozens of comparisons with three stations located not too far from me, that it is pretty difficult to make an antenna of reasonable size and construction -20dB based on ground system shortfalls. Some of this has gone beyond reasonable or logical, and is poisoning our knowledge base. In Toledo, a good friend lived on a small city lot behind a restaurant. His backyard, the only place for an antenna, was just a few feet deep and maybe 100 feet long. He tied in everything he could; heating ducts, plumbing, short radials, a short chain link fence. He was consistently, over many years, within a few dB of my full size quarter wave in an ideal soil and ground system. This was night after night, DX or local, over and over again. Another fellow in a neighborhood had a short TV tower with inverted L, and his radials ran to a sidewalk maybe ten or fifteen feet away. He had radials crossing the ceiling of his basement. His signal was the same way. Another station, W8KWN, just had driven rods. NONE of these stations were even close to 20 dB down. It was more like 5 dB to maybe a just little more at times, and a little less at times. The driven rods were the worse system, but even they were not -20 dB. Now there was one station who had bad luck. He had bigger back yard, and it was just full of wires and antennas. He had all these bamboo supports and quads and other things, a yard full of stuff. His signal was so weak he actually would swear and cuss at the other guys and accuse them of illegal power because his antennas were so good in his own mind that there was not way these other guys would beat him so badly unless they were cheating. No amount of conversation could convince him he had the problem. In my experience, it is more about having a neat, clean, uncluttered installation and not doing things grossly wrong, like using coaxial stubs for loading inductance or packing 900 pounds of antennas into a two pound back yard area, than any sort of grounding issue. The only -10 dB or -20 dB things I ever see are people who jam too much in small area, or have some other serious system error they created but just cannot see. My ten foot tall mobile antenna with a pickup truck for a ground is about 20 dB down from my TX antenna. If someone else has that issue with a 50 foot tall inverted L, they better look at something other than a compromised ground system. They have a more serious issue. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
I have already spoken extensively that your assertion is not proved, NOR is the counter-assertion proved. I have no intentions of adding to that. I am not persuaded either way, though BOTH sides of that question have attractive points. I am waiting for something new to emerge, like helicopter measurements out 50 km from operational ceiling down to the ground. Since the near field NEC4 predicts the notchless 3 or 4 km helicopter measured data, we have to get it out where the NEC process predicts the notch and measure it there. That will settle it. If it maintains down to the ground, then we can beat the LLNL people to death with it and they will have to fix NEC. Otherwise, we don't know. To the point in question, you are asserting that if the notch under the typical far field elevation plot was filled in, THAT would account for the 4 dB? I give you that the loss would lessen if the gain at the ground was equal to say 15 degrees and smooth going up, but the integration of the spherical far field data asserts that OVER HALF THE POWER is going to loss. The only way you get that back is to put it over sea water. Anyone experiencing the marvelous increase in vertical performance at the edge of/over sea water will tell you emphatically that you DO get it over sea water and you decidedly DO NOT get that over inland dirt. Frankly the difference seems a lot more than the difference in the plots. Filling up 20 degrees out of 360 will won't get you back to only 3 dB down. The original question still stands. It is not related to your assumption, or not. Anyone wants to tackle the idea that the far field plot of NEC4 is off by 4 dB, in order to keep from acknowledging heavy foreground induced ground loss, have at it. It should be interesting. 73, Guy. On Thu, Dec 13, 2012 at 7:06 AM, Richard Fry r...@adams.net wrote: Guy Olinger wrote: You can model a near perfect commercial grade radial field, with a radial system apparent series resistance of a few tenths of an ohm, and NEC4 will still come back with an overall loss of 3 to 4 dB. This is ~true only for a far field analysis (as defined by NEC software) for a vertical monopole -- which includes the propagation losses present in the radiated fields from that monopole, over an infinite, FLAT, real-earth ground plane. ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
So here's a question. I have a vertical mounted on a cliff side that performs incredibly. My amateur's approach to figuring out why is that I modeled it in EZNEC as being elevated 400 feet. That shows it performing nearly as well as if it were on a tiny island in the great ocean. Is it correct that an elevated feed point greatly reduces the ground losses? On Dec 13, 2012, at 12:35 PM, Guy Olinger K2AV olin...@bellsouth.net wrote: I have already spoken extensively that your assertion is not proved, NOR is the counter-assertion proved. I have no intentions of adding to that. I am not persuaded either way, though BOTH sides of that question have attractive points. I am waiting for something new to emerge, like helicopter measurements out 50 km from operational ceiling down to the ground. Since the near field NEC4 predicts the notchless 3 or 4 km helicopter measured data, we have to get it out where the NEC process predicts the notch and measure it there. That will settle it. If it maintains down to the ground, then we can beat the LLNL people to death with it and they will have to fix NEC. Otherwise, we don't know. To the point in question, you are asserting that if the notch under the typical far field elevation plot was filled in, THAT would account for the 4 dB? I give you that the loss would lessen if the gain at the ground was equal to say 15 degrees and smooth going up, but the integration of the spherical far field data asserts that OVER HALF THE POWER is going to loss. The only way you get that back is to put it over sea water. Anyone experiencing the marvelous increase in vertical performance at the edge of/over sea water will tell you emphatically that you DO get it over sea water and you decidedly DO NOT get that over inland dirt. Frankly the difference seems a lot more than the difference in the plots. Filling up 20 degrees out of 360 will won't get you back to only 3 dB down. The original question still stands. It is not related to your assumption, or not. Anyone wants to tackle the idea that the far field plot of NEC4 is off by 4 dB, in order to keep from acknowledging heavy foreground induced ground loss, have at it. It should be interesting. 73, Guy. On Thu, Dec 13, 2012 at 7:06 AM, Richard Fry r...@adams.net wrote: Guy Olinger wrote: You can model a near perfect commercial grade radial field, with a radial system apparent series resistance of a few tenths of an ohm, and NEC4 will still come back with an overall loss of 3 to 4 dB. This is ~true only for a far field analysis (as defined by NEC software) for a vertical monopole -- which includes the propagation losses present in the radiated fields from that monopole, over an infinite, FLAT, real-earth ground plane. ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: Elevated Radials Questions
Grant, you should consider putting in an additional 23 radials and put the radial system on or in the ground. This will eliminate any possible detuning by the big metal building and interaction with the RX 4 square. You said that your vertical T will go up to 85 feet. However, by elevating the radials 10 feet, your effective vertical distance is 75 feet which will allow you to shorten the top hat wires a bit. As an alternate, you could put down 1/8 wavelength radials on the ground but more of them and have a good system too. If you must go with an elevated radial system, I recommend that you read the articles by Dick Weber, K5IU, who strongly advocated elevated radials shorter or longer than 1/4 wavelength. If shorter, then the radials are loaded with a small coil. If longer, then they are tuned out with a capacitor. W5UN uses shortened elevated radials on his 160 meter 4 square with great results. They are about 70% of a quarter-wave in length. 73, Dennis W0JX/8 Milan OH ___ Topband reflector - topband@contesting.com
Topband: The Idiot's Guide To Bi-Directional Two-Wire Beverage Construction...
Good Day All, I wonder if I might prevail upon any all with some first-hand real-world experience as to the criticalness (if any) between the two wires running the length span of a 2-wire bi-directional Beverage...? Just how important is a continuos pre-set distance between the wires, anyway...? And who was it that came up with the necessity of equally-spaced wire...? And how did they determine the optimum distance the wires...? Would a span of power line cord (a.k.a. zip cord) do in a pinch...? Zip cord sure would simplify things greatly for my location here... As I say, any all comments from first-hand experience are not only welcomed, they're solicited, before I plunk down any serious coin for a good run of lamp cord! Hi Hi ~73~ de Eddy VE3CUI - VE3XZ ___ Topband reflector - topband@contesting.com
Re: Topband: The Idiot's Guide To Bi-Directional Two-Wire Beverage Construction...
Eddy, Here are the points I would make for and against zip cord for wire antennas in general and Beverages in particular. Your mileage (kilmeterage) may vary according to your needs, circumstances and applications. 1. Zip Cord is great and not so great for wire antennas on these counts. 2. It is very flexible and great conductivity due to being constructed of multiple tiny copper strands. 3. It is not so great as to strength and cannot be put into long spans with lots of tension. It is easy to split if you want to make single wire Beverages. 4. It is IMO not a good value cost wise, as it is one of the more expensive methods of buying antenna wire. 5. It is great in that it is normally available in 250' rolls at any hardware store. 6. Critters LIKE all varieties of zip cord insulation. It is most often soft, chewy, and apparently very much to their palate's desire. That said in generality, here is my experience with zip cord for 2-wire Beverages from the technical aspect. All other things aside, if you compute the impedance of the particular type of zip cord you are going to use taking into account the size of the conductor, the spacing between the conductors, and the dielectric(insulation) used, AND THEN construct your transformers for both ends to match that impedance to what ever feed line impedance you are going to use, you will have EXCELLENT results when properly grounded at each end. There is no 'optimum' distance between the wires. BUT the distance should remain constant so that the impedance remains constant through out the antenna's length. Lots of things to comment on, BUT the generalities are here. The one best axiom is any Beverage is MUCH better than no Beverage. And the construction of a Beverage is VERY forgiving. Go for it and learn as you experiment. Mis dos centavos, de Milt, N5IA -Original Message- From: Eddy Swynar Sent: Thursday, December 13, 2012 2:08 PM To: topband@contesting.com Subject: Topband: The Idiot's Guide To Bi-Directional Two-Wire BeverageConstruction... Good Day All, I wonder if I might prevail upon any all with some first-hand real-world experience as to the criticalness (if any) between the two wires running the length span of a 2-wire bi-directional Beverage...? Just how important is a continuos pre-set distance between the wires, anyway...? And who was it that came up with the necessity of equally-spaced wire...? And how did they determine the optimum distance the wires...? Would a span of power line cord (a.k.a. zip cord) do in a pinch...? Zip cord sure would simplify things greatly for my location here... As I say, any all comments from first-hand experience are not only welcomed, they're solicited, before I plunk down any serious coin for a good run of lamp cord! Hi Hi ~73~ de Eddy VE3CUI - VE3XZ ___ Topband reflector - topband@contesting.com - No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2805 / Virus Database: 2634/5954 - Release Date: 12/12/12 - No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.2805 / Virus Database: 2634/5954 - Release Date: 12/12/12 ___ Topband reflector - topband@contesting.com
Re: Topband: Elevated Radials Questions
Thanks for the comments and pointers. The land around the antenna is mixed grass and forested islands so on the ground radials would be partially buried and partially on the surface. Digging through the trees and clearing the brush is not something I want to do. Also, based on prior experience with verticals on metal roofs, I'm a real fan of elevated radials. I am relying on the credibility of the N6LF QEX series for how well/not well elevated radials will work (Mar - June 2012). I realize this work was all analysis with EZNEC PRO, but it seems to be the similar to results of others I've read. Googling K5IU elevated radials I did find the 2008 N6LF article which has the experimental data as well. His analysis shows there isn't much difference in losses with more than 4 radials between 0.15 and 0.27 wavelengths long. I've heard conventional wisdom is to tune radials for resonance, but the analysis for 4 or more radials elevated than a couple of feet seems to indicate it is a lot of work for little benefit. I also found the 2005 thread tuning elevated radials on this reflector quite informative. One thing that stands out is that I may be better off with more than 7 shorter than 130' radials. Grant KZ1W On 12/13/2012 12:06 PM, Dennis W0JX wrote: Grant, you should consider putting in an additional 23 radials and put the radial system on or in the ground. This will eliminate any possible detuning by the big metal building and interaction with the RX 4 square. You said that your vertical T will go up to 85 feet. However, by elevating the radials 10 feet, your effective vertical distance is 75 feet which will allow you to shorten the top hat wires a bit. As an alternate, you could put down 1/8 wavelength radials on the ground but more of them and have a good system too. If you must go with an elevated radial system, I recommend that you read the articles by Dick Weber, K5IU, who strongly advocated elevated radials shorter or longer than 1/4 wavelength. If shorter, then the radials are loaded with a small coil. If longer, then they are tuned out with a capacitor. W5UN uses shortened elevated radials on his 160 meter 4 square with great results. They are about 70% of a quarter-wave in length. 73, Dennis W0JX/8 Milan OH ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
Re: Topband: The Idiot's Guide To Bi-Directional Two-Wire BeverageConstruction...
Just how important is a continuos pre-set distance between the wires, anyway...? And who was it that came up with the necessity of equally-spaced wire...? And how did they determine the optimum distance the wires...? Would a span of power line cord (a.k.a. zip cord) do in a pinch...? Eddy, The transmission line mode of the two wires is what brings the far end of the antenna to the feedpoint. That is what allows the antenna to be reversed. If that line is lossy, or if that line is mismatched by just 2.5:1 SWR and the wrong length, the antenna can easily lose 20 dB of null depth when in the forward (fires away from feedpoint) direction. In the reverse direction, where the antenna fires toward the feedpoint direction, mismatch or loss only affects signal level. SWR or loss does not affect F/B in the reverse directional mode. You can use any impedance of line you desire if transformers are readjusted to the correct ratio, and you can even use coaxial cable for the antenna. The problem comes in when the line has greatly unstable impedance, velocity factor, and/or loss, and the major problem is mostly in one direction. I'd avoid exceptionally lossy lines and lines that significantly change characteristics with weather conditions. It is easier to make good transformers when impedance ratio of antenna mode to transmission line mode is close to unity. That's why 400-600 ohm line spacings are usually best. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
So here's a question. I have a vertical mounted on a cliff side that performs incredibly. My amateur's approach to figuring out why is that I modeled it in EZNEC as being elevated 400 feet. That shows it performing nearly as well as if it were on a tiny island in the great ocean. Is it correct that an elevated feed point greatly reduces the ground losses? That makes sense because the VOLTAGE and CURRENT of the antenna, each of which cause loss problems, are remote from earth in the model. If BOTH the electric and magnetic fields do not have significant intensity in lossy earth, there isn't as much loss. However, the idea behind the GAP antenna falls quickly apart because they did not move the antenna away from earth. They simply moved the feedpoint around. We can move the feedpoint around in a short vertical until we are bleeding from the fingers, and loss remains the same. The only way loss changes is if we move the voltage and current up away from earth. I'm not sure what GAP's policy is now, but when questioned years ago about how the magic elevated feedpoint with the yellow lightning bolt worked, they handed out a paper about a very tall broadcast tower. They said the paper shows how an elevated feedpoint reduces loss. The paper actually said nothing of the sort. The paper said a halfwave tall AM broadcast tower, operating on the low end of the AM broadcast band, had just very slightly less field strength when it was converted from an end fed half wave with 120 radials to a groundplane with eight radials 1/4 wave above ground. Somehow they thought moving the feedpoint eliminated the need for radials with an electrically short antenna, when the real mechanism was a 1/2 wave vertical was converted to a 1/4 wave groundplane 1/4 wave above ground and it only got a tiny bit weaker. The groundplane still had 8 radials, but they were hundreds of feet in the air. There was some more stuff about offsetting the feedpoint in that handout, but nothing that remotely applied to a fractional wavelength vertical just sitting on the dirt with a few radials laying directly on the lawn. They got rid of lossy traps and loading coils by using even lossier coax and some folded wires for a loading system. This is all why, as frequency increases and the current and voltage moves up the antenna, the GAP on most bands isn't terribly bad. This also why it is a real dog of an antenna on 160 and 80, where it is very short electrically, has no ground system, has an exceptionally poor loading method, and where it folds the radiator back and forth which suppresses radiation resistance. This is why a ten foot mobile antenna can tie it or beat it on 160, and why it is reasonably on par with anything else on most bands above 80 meters. 73 Tom ___ Topband reflector - topband@contesting.com
Re: Topband: Fw: GAP VERTICAL QUESTION
Short version: *** WARNING: Most locations do not have the fortunate circumstances to support sparse or miscellaneous radial systems without exaggerated loss, and the builder with constrained circumstances should attempt counterpoise solutions designed specifically for those circumstances. Long version: I think the main point is being missed here. First of all RBN is showing changes well in excess of 6 dB with the removal of loss by replacing a faint radial system with an FCP. Remember that an FCP HAS NO GAIN. It only reduces loss. If the signal went up ten dB, it's because 10 dB of loss was removed from the system. Doesn't matter if we don't know how to calculate it with our stuff. IF it was a complex change, involving changing the wire overhead (other than adding the FCP and moving the feed to 8 feet in the air), or moving the location of the antenna, then the answer clearly cannot be cleanly attributed to any one issue. Some reported changes added together MULTIPLE loss remediations plus improvements to the radiator and produced what can only be termed stark improvements in overall performance. A few of these are easily in excess of 20 dB because of everything that was done at the same time. I certainly do not count those as pure ground loss improvements. But neither is there any reason to throw away reported results, calling them anecdotal with a condescending tone of voice as if that were some kind of disease. Anytime one can clean up that much cr*p at one time, one deserves congratulations, not being hounded on the reflector, as has happened to some. Nor should starting out with a cr*ppy situation disqualify the report, or make its numbers poison. *I* would fairly agree with a 6 dB limit to the possible change, in situations that were absent a long list of troublesome loss contributors linked to ground coupling. I would agree, given such pristine conditions as I would expect to measure on your cleared out, flat, expansive, lovely rural acres of electrically unpolluted farm land. Nor would I disagree that there are some with severely restricted radials on small lots that get away with it to some degree, simply due to serendipitous or deliberately cleaned-up backyard circumstances. WX7G I believe has done that and is getting away with it using NINETY 12 to 24' radials. But we should note there are many situations where there is not enough space or the circumstances to attempt WX7G's successful enough limited method. What is going wrong is that current ADVICE is telling people that ANY radials, and even merely a ground rod, will NEVER exceed six dB down from full size. And with that guidance, they are putting down faint imitations of a commercial radial field, expecting with a 1500 watt amp they will be equal to you, if they could only get you to reduce power to 375 watts. There should be SOMEBODY out there like that, as in the story you tell. There is a law of averages. But there are many, many more who have drunk the koolaid, followed the advice, and had very disappointing results. Some here maintain that disappointing can't be measured in dB, therefore doesn't count, and should be ignored, poisons the database. Disappointing is abstract or conjectural unless it has happened to oneself. Then one bristles when accused of purveying disinformation. Once someone's backyard has stuff from the list of troublesome loss contributors, the chances of being penalized ONLY six dB with a faint radial imitation are getting slim. The loss contributors include dirt quality from the poorer end of the spectrum, particularly in urban circumstances, or where the land has been leveled out for construction with dirt or even rubble useless for anything else and merely coated with enough good dirt to support grass. They include conductors in the ground, or any conductor close to antenna or radials that couples dirt, the list goes on. Getting the bottom of the vertical up 8 feet to an FCP decreases coupling to all that stuff. Faint radial systems on/in the dirt do not shield an antenna from heavily coupling earth made of whatever in the immediate region underneath the feed. Since an FCP provides no shielding of ground, as there is with a proper radial installation, there is a last dB or two of ground loss from the vertical conductor that it cannot mitigate. So if as you put forth, the depth of that trouble can ONLY be 6 dB, then the absolute mitigation of loss from an FCP would be 4 dB, at best 5. However, RBN changes are 7, 10, 12, 15 and some larger which I keep in the reserved for watching column. 7 to 10 is common. This far exceeds the 4 or 5 db, meaning that back yards are COMMONLY nastily lossier than the ideal. Since I can run models that give ridiculous loss figures approaching 20 dB over average ground that is perfectly homogenous without any of the nasties around, there is nothing to keep me from simply hearing people's stories just as they tell it, with no reason to
Re: Topband: Elevated Radials Questions
Not to hijack the thread, but anyone have a general idea how much improvement one would get by going from 8 to 12 gull wing resonant elevated radials on a 60 foot base loaded vertical? 73, Bob AA6VB N7LF's work also shows that more elevated radials are better than fewer. Since the losses are a function of the square of the field intensity, spreading the E field more evenly over a larger area reduces losses by decreasing the peak field intensity. ___ Topband reflector - topband@contesting.com
Re: Topband: Elevated Radials Questions
HI, Grant! A couple of things to think of. First, as reported in the IEEE paper mentioned earlier, increasing the number of elevated radials to more than four , yields a rather limited benefit, This work was done by professional antenna engineers with plenty of equipment and resources. The point of the investigation was the development of a viable replacement of degraded buried radial systems under broadcast towers with elevated radials and did involve measurement of radiated field intensity. As for our 160 antenna with elevated radials - think of it as a ground-plane antenna! In the case of the inverted-L the vertical monopole element is simply bent at a convenient height to take advantage of available supports. In the case of the tee, this can be very convenient for supporting the upper end of the shortened monopole. Additionally, in the case of the TEE any residual horizontally polarized radiation from the flat-top of the TEE will be pretty much cancelled by the equal and opposite currents flowing in opposite directions in the flat-top wires. Unless you are very space limited, the major advantages of RESONANT radials are that the current maxima in the radials will occur at the antenna feed-point. That allows the driving-point impedance to approach pure real in a well-behaved manner - being something less than 70 ohms. (More like 35-50 ohms if you have a good radial system. Short radials introduce a reactive component into the antenna feed that needs to be dealt with. I expect that using many short radials acts more like capacitive coupling to the underlying soil and its losses to provide and image for the vertical monopole. Dig, if you wish, but there is nothing magic about dirt! And it can be a bit lossy! I think you are on a good track! I'll be interested to see how it turns out! I'm very much in favor of your elevated resonant radial approach! It has worked very well for me! The closest I ever came with a direct ground system was in another location where I had a very tall pine on dam (that I owned) of as good-sized lake! I drove an 8-foot copper ground rod at the edge of the lake, at the base of the inverted-L, and using my canoe, I ran several quarter-wave radials out into the water. Worked pretty well! - With a fairly well behaved driving-point impedance! I could see the drop in the driving-point impedance when I ran the radials out into the water. (Turned out that some copper sulfate had been added to the lake to kill off some vegetation! I expect that helped!) Since then, I've done quite well with elevated resonant radials and an inverted L - Until a hurrlcane tilted the tall oak that was supporting the far end of the inverted L and we had to have it taken down.) My elevated radials ran around the perimeter of my lot and had 90 degree bends in them 60-70 feet from the antenna feed point! Good luck!! If you build it, they will come! :) Regards, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Grant Saviers Sent: Thursday, December 13, 2012 5:28 PM To: Dennis W0JX Cc: topband@contesting.com Subject: Re: Topband: Elevated Radials Questions Thanks for the comments and pointers. The land around the antenna is mixed grass and forested islands so on the ground radials would be partially buried and partially on the surface. Digging through the trees and clearing the brush is not something I want to do. Also, based on prior experience with verticals on metal roofs, I'm a real fan of elevated radials. I am relying on the credibility of the N6LF QEX series for how well/not well elevated radials will work (Mar - June 2012). I realize this work was all analysis with EZNEC PRO, but it seems to be the similar to results of others I've read. Googling K5IU elevated radials I did find the 2008 N6LF article which has the experimental data as well. His analysis shows there isn't much difference in losses with more than 4 radials between 0.15 and 0.27 wavelengths long. I've heard conventional wisdom is to tune radials for resonance, but the analysis for 4 or more radials elevated than a couple of feet seems to indicate it is a lot of work for little benefit. I also found the 2005 thread tuning elevated radials on this reflector quite informative. One thing that stands out is that I may be better off with more than 7 shorter than 130' radials. Grant KZ1W On 12/13/2012 12:06 PM, Dennis W0JX wrote: Grant, you should consider putting in an additional 23 radials and put the radial system on or in the ground. This will eliminate any possible detuning by the big metal building and interaction with the RX 4 square. You said that your vertical T will go up to 85 feet. However, by elevating the radials 10 feet, your effective vertical distance is 75 feet which will allow you to shorten the top hat wires a bit. As an alternate, you could put down 1/8 wavelength radials on the ground but more of them and have a good system too. If
Re: Topband: Elevated Radials Questions
The only place Ive found tuned elevated radials being discussed so much is on ham forums. A bit over 20 years ago I installed a slanted wire 1/4 wave vertical for 160 coming off the top guy wire of a 160' tower and about 10' out. Started with 4 radials of roughly 130', trimmed the radiator for best match with zero reactance and measured the 2:1 bandwidth. Added 4 more radials and the BW narrowed, added 8 more and it narrowed a bit more. Added another 16 and no change in BW so I assume the sweet spot is somewhere in the 20's at this location and the radials starting at 12' and slowly sloping to 20' and then thru tree branches. Just the way they were placed likely precludes any chance of resonance. That antenna worked so well I added another, and used nothing but coax phasing lines to switch directions or fire a figure 8 broadside. Cheap, simple and effective unless you like throwing away money for a mailorder solution. YMMV depending on ground effects and surrounding objects. OTOH I believe people spend way too much time analyzing and relying on some questionable answers and too little time doing some basic construction work and testing. Carl KM1H - Original Message - From: Grant Saviers gran...@pacbell.net To: Dennis W0JX w...@yahoo.com Cc: topband@contesting.com Sent: Thursday, December 13, 2012 5:27 PM Subject: Re: Topband: Elevated Radials Questions Thanks for the comments and pointers. The land around the antenna is mixed grass and forested islands so on the ground radials would be partially buried and partially on the surface. Digging through the trees and clearing the brush is not something I want to do. Also, based on prior experience with verticals on metal roofs, I'm a real fan of elevated radials. I am relying on the credibility of the N6LF QEX series for how well/not well elevated radials will work (Mar - June 2012). I realize this work was all analysis with EZNEC PRO, but it seems to be the similar to results of others I've read. Googling K5IU elevated radials I did find the 2008 N6LF article which has the experimental data as well. His analysis shows there isn't much difference in losses with more than 4 radials between 0.15 and 0.27 wavelengths long. I've heard conventional wisdom is to tune radials for resonance, but the analysis for 4 or more radials elevated than a couple of feet seems to indicate it is a lot of work for little benefit. I also found the 2005 thread tuning elevated radials on this reflector quite informative. One thing that stands out is that I may be better off with more than 7 shorter than 130' radials. Grant KZ1W On 12/13/2012 12:06 PM, Dennis W0JX wrote: Grant, you should consider putting in an additional 23 radials and put the radial system on or in the ground. This will eliminate any possible detuning by the big metal building and interaction with the RX 4 square. You said that your vertical T will go up to 85 feet. However, by elevating the radials 10 feet, your effective vertical distance is 75 feet which will allow you to shorten the top hat wires a bit. As an alternate, you could put down 1/8 wavelength radials on the ground but more of them and have a good system too. If you must go with an elevated radial system, I recommend that you read the articles by Dick Weber, K5IU, who strongly advocated elevated radials shorter or longer than 1/4 wavelength. If shorter, then the radials are loaded with a small coil. If longer, then they are tuned out with a capacitor. W5UN uses shortened elevated radials on his 160 meter 4 square with great results. They are about 70% of a quarter-wave in length. 73, Dennis W0JX/8 Milan OH ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2634/5457 - Release Date: 12/13/12 ___ Topband reflector - topband@contesting.com
Topband: gap voyager a users perspective
In a little over 4 months of owning a gap voyager I have worked on 160 meters: 31 states and 3 countries So does it work? Yes Is it as good as a 1/4 wave vertical with 10 miles of radials? No Is it better than a dummy load? Yes Is it the best antenna in the world? No It is a compromise antenna. It works for me. YMMV WO4R Jeff ___ Topband reflector - topband@contesting.com
Topband: Length of 'T' Top Hat wires?
I have a 67 ft base coil fed vertical, 4, 3 2 irrigation pipe with two 50 ft top hat wires that I use on 160m. I have about 100 - 135 ft radials on the ground. So far I have been pleased with it. Last week Herb, KV4FZ mentioned the 25% rule, which I think means, the top hat 'T' wires should be cut to about 25% of the vertical height. I have not heard of this rule and wonder how it may have come around? I can certainly shorten my top hat wires to abt 17 ft, then re-tap the base loading coil to bring the SWR and resonate point to 1.830 Mhz or so but I'm wondering if its worth it? Is there any theory to the 25% rule? If I mis-interpreted the rule, I like to know what it means. Tnx, Ray, N6VR Chino VAlley, AZ ___ Topband reflector - topband@contesting.com
Re: Topband: Length of 'T' Top Hat wires?
On 12/13/2012 8:37 PM, Ray Benny wrote: I have a 67 ft base coil fed vertical, 4, 3 2 irrigation pipe with two 50 ft top hat wires that I use on 160m. I have about 100 - 135 ft radials on the ground. So far I have been pleased with it. On a 60 foot vertical, I need two 75 foot wires to resonate near 1.830 On a 90 foot vertical, I need four 30 foot wires to resonate near 1.830 These wires slope down at about a 45 degree angle Just some data points Rick N6RK ___ Topband reflector - topband@contesting.com
Topband: PreStew Results
The results for the PreStew event from October are now posted. Many thanks to the 200+ people who sent in their log. You can find the results and rules for the BIG Stew coming up in a couple of weeks here: http://www.kkn.net/stew 73 Tree N6TR t...@kkn.net ___ Topband reflector - topband@contesting.com
Re: Topband: Length of 'T' Top Hat wires?
If I mis-interpreted the rule, I like to know what it means. Many times the top hat wires are not horizontal but come down at an angle like the top set of guy wires on a tower or vertical. Is there any theory to the 25% rule? The 25% rule says the ends of the top hat wires should not extend more than 25% down the vertical. The thought is that the wires shield the main vertical ... that the currents on the top hat wires cause cancellation. Once the tips of the top hat wires get 25% down the vertical, the theory is that the cancellation/reduced radiation resistance offset any gains from the added electrical height. N6LF made reference to this phenomena in one of his studies - unfortunately I don't have the link at hand but Rudy's site is well worth exploring. 73, ... Joe, W4TV On 12/13/2012 11:37 PM, Ray Benny wrote: I have a 67 ft base coil fed vertical, 4, 3 2 irrigation pipe with two 50 ft top hat wires that I use on 160m. I have about 100 - 135 ft radials on the ground. So far I have been pleased with it. Last week Herb, KV4FZ mentioned the 25% rule, which I think means, the top hat 'T' wires should be cut to about 25% of the vertical height. I have not heard of this rule and wonder how it may have come around? I can certainly shorten my top hat wires to abt 17 ft, then re-tap the base loading coil to bring the SWR and resonate point to 1.830 Mhz or so but I'm wondering if its worth it? Is there any theory to the 25% rule? If I mis-interpreted the rule, I like to know what it means. Tnx, Ray, N6VR Chino VAlley, AZ ___ Topband reflector - topband@contesting.com ___ Topband reflector - topband@contesting.com
