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Better for DX: Vertical or dipole?
I am interested in operation primarily on 160, 80, and 40. I have space for a full-size dipole for 160 but I cannot get it up very high, maybe 30 feet, higher than that only at great expense and with great difficulty. I will likely put up a 160-meter dipole at 30 feet and feed it with ladder line and a tuner, and use it for NVIS work on 160-40. For DX, though, I'm wondering if I will be happy with a vertical such as the Voyager DX from Gap Antennas, or if I should bite the bullet and go to the expense and difficulty of getting the dipole up 60-80 feet (which still won't be very high, compared with a wavelength, at 160 or 80). What's your advice? |
Better for DX: Vertical or dipole?
What's your advice?
Get a copy of ON4UN's low band DXing. Search the Topband archives antennas. Measure/estimate your ground conductivity and permittivity and get comfortable with a modeling program. And finally, experiment. I don't mean to be glib but there's really no quick answer to what antenna you'd be happy with for DX on 40,80 and 160. 30 feet for a horizontal antenna *is* too low, generally. Maybe someone can comment on the Voyager DX... I can't, specifically. Verticals are good, short verticals are compromises and must be treated with care. - - - - - - - - - This is what I use: http://www.n3ox.net/projects/sixtyvert I can certainly work more 40&80m DX on this than on the 30 foot high, 100 foot long centerfed wire I used to use on those bands. As far as 160m goes, this is the first time I can work 160 DX at all... 73, Dan |
Better for DX: Vertical or dipole?
On Fri, 12 Jan 2007 00:33:10 -0500, Rick
wrote: What's your advice? Hi Rick, Choose your poison. A 30 foot high 160M dipole is a notable ground hugging air cooled resistor. A GAP is probably worse. A combination of the two might be in order (which does NOT mean buy a GAP to do this). Erect a 30 foot vertical and top load it with what would have been the dipole. I will leave to others what could be done in higher bands (with one word of advice, GAPs don't usually perform very well on their lowest band(s), but have been to be reported as good verticals otherwise). 73's Richard Clark, KB7QHC |
Better for DX: Vertical or dipole?
Dan wrote:
http://www.n3ox.net/projects/sixtyvert I can certainly work more 40&80m DX on this than on the 30 foot high, 100 foot long centerfed wire I used to use on those bands. As far as 160m goes, this is the first time I can work 160 DX at all... 73, Dan Hmm... very interesting... and do-able. I've been thinking myself about erecting a vertical for 80/40 (but didn't want to waste my time). Thanks Dan! 73, Bryan WA7PRC |
Better for DX: Vertical or dipole?
Rick wrote:
I am interested in operation primarily on 160, 80, and 40. I have space for a full-size dipole for 160 but I cannot get it up very high, maybe 30 feet, higher than that only at great expense and with great difficulty. I will likely put up a 160-meter dipole at 30 feet and feed it with ladder line and a tuner, and use it for NVIS work on 160-40. For DX, though, I'm wondering if I will be happy with a vertical such as the Voyager DX from Gap Antennas, or if I should bite the bullet and go to the expense and difficulty of getting the dipole up 60-80 feet (which still won't be very high, compared with a wavelength, at 160 or 80). What's your advice? Hi Rick, As someone has said get a copy of ON4UN's Low band dxing.. I would not particularly recommend the Gap Antenna for Low Bands. Than being said if you and put out a decent radial system for dx Transmitting anyway I'd say you want some sort of vertical. Why not try a Inverted L. Try to get as much vertical as possible. Base tune it with a matching network- The SGC line works well for that application. you can read more about Inverted L's in Cebik's write up at: http://www.cebik.com/wire/ltv.html Good Luck 73, Dave Kc1di |
Better for DX: Vertical or dipole?
Rick wrote:
What's your advice? Check out the Inverted-L antenna. Also check the vertical Vs horizontal noise level at your QTH. My 40m vertical had 2 S-units higher noise than my 80m dipole rendering it useless for weak signal DX. -- 73, Cecil http://www.w5dxp.com |
Better for DX: Vertical or dipole?
On Thu, 11 Jan 2007 22:36:23 -0800, Richard Clark wrote: A 30 foot high 160M dipole is a notable ground hugging air cooled resistor. A GAP is probably worse. Good morning, Richard. Actually, 30 feet is on the low side of "about right" on 160 and on the high side of "about right" on 80, for NVIS work, of which I do a lot. For DX, I agree that it's not of much use. And yet... My current antenna is an inverted V up about 35 feet in the center, 90 feet each leg, fed with ladder line. It started life as a 60-foot-high inverted V, full length for 160, in which configuration it worked rather well. Then a storm came by and knocked a tree down .... well, I digress... :-( I had earlier put up the inverted V via one of those "expensive and difficult" mechanisms I mentioned earlier (hired a 60-foot cherry picker and operator). I couldn't do that again, so I hoisted what was left of the antenna up to the top of my 35-foot tower, and trimmed the legs so that they would stay within the property line. Kept the ladder line feeder, and I tune it with an LDG RT-11 autotuner with the LDG balun. I use that antenna on all bands including 160, with a Yaesu FT-817 running a cloud-burning 5 watts, and it works amazingly well for the power level. But, as usual, I want more. :-) Thanks to you and others here for the feedback on the GAP. I REALLY wasn't up for spending almost half a grand for a vertical. |
Better for DX: Vertical or dipole?
On Fri, 12 Jan 2007 13:57:24 GMT, Cecil Moore
wrote: Check out the Inverted-L antenna. Doesn't the horizontal part of the inverted L need to be as high as possible for best results? I'd run into the same problems I'm running into in putting a dipole or inverted V up high enough. Also check the vertical Vs horizontal noise level at your QTH. My 40m vertical had 2 S-units higher noise than my 80m dipole rendering it useless for weak signal DX. I have a fairly high noise level around here on any of the horizontal antennas I've tried. But, I have an MFJ-1026 "Deluxe Noise Canceling Signal Enhancer" :-) that does an amazing job of cutting down the noise IF the noise is primarily from one general direction (which seems to be the case around here although I haven't been able to pinpoint it). That's one of the reasons I wanted to try some kind of a vertical and see how that worked. I read somewhere that ground mounted verticals with radials on or buried in the ground tend to be noisier. Is that true? That's one of the reasons I was considering the GAP Voyager DX... doesn't require an extensive radial system. |
Better for DX: Vertical or dipole?
Rick wrote:
Doesn't the horizontal part of the inverted L need to be as high as possible for best results? I'd run into the same problems I'm running into in putting a dipole or inverted V up high enough. Not exactly. Make the vertical section of the Inv-L as long as feasible. The vertical section is the highest current section and therefore has the greatest effect. Or instead of an Inv-L, make it a T antenna with a vertical section and a symmetrical top hat. The symmetrical top hat doesn't do much radiating. Here's what EZNEC says using VERT1.ez as the reference. 40m 33' Vert1 has -0.04 dBi gain omnidirectional. 16.5'-16.5'Inv-L has 1.04 dBi gain with some directivity. 16.5'-23.5' T antenna has 0.19 dBi gain omnidirectional. Note: 16.5' = vertical, 23.5' = horizontal top hat. Performance wise, I don't think you could tell the real vertical from the T except for the T's lower feedpoint impedance. -- 73, Cecil, http://www.qsl.net/w5dxp |
Better for DX: Vertical or dipole?
Rick ha escrito: I am interested in operation primarily on 160, 80, and 40. I have space for a full-size dipole for 160 but I cannot get it up very high, maybe 30 feet, higher than that only at great expense and with great difficulty. I will likely put up a 160-meter dipole at 30 feet and feed it with ladder line and a tuner, and use it for NVIS work on 160-40. For DX, though, I'm wondering if I will be happy with a vertical such as the Voyager DX from Gap Antennas, or if I should bite the bullet and go to the expense and difficulty of getting the dipole up 60-80 feet (which still won't be very high, compared with a wavelength, at 160 or 80). What's your advice? High Rick, Easy question, difficult answer. Basically, a vertical antenna has more low elevation radiation with respect to dipoles at h0.25*lambda above ground. However, it is, in most cases, difficult to get a reasonable efficiency in the vertical case. In addition, the amount of low angle radiation depends on the type of soil. Many horizontal dipoles operate better than verticals (on DX). My practical proof is: when I get more signal strength (not S/N ratio) out of an antenna when receiving a station, I will generate more signal strength at the station's receiver. When you are able to do a simulation, simulate your antenna (with perfect ground) and determine the BW. Build your antenna and measure the bandwidth. When your bandwidth has doubled (with respect to simulation), your efficiency is about 50%. Make sure that your wire thickness in the simulation is equal to the real antenna. Regarding horizontal dipoles. Up to h= 0.2*lambda, the radiation pattern does virtually not change; however the efficiency does. A halve wave dipole at h=0.1*lambda will put more energy in the earth (and radiates less) with respect to the same dipole at 0.2*lambda. At low height, an efficiency of less then 15% is not uncommon. It is because of the low efficiency (power dissipation in the soil) that most HF dipoles has reasonable bandwidth.... Above h=0.25*lambda the vertical radiation will reduce gradually in favour of the radiation at lower elevation. When you are above bad soil, I would recommend you to try to increase the height (especially for 160m) of your dipole. This is because of a vertical antenna in combination with poor soil will probably have a low efficiency and radiation under low elevation will be suppressed (because of the relative high pseudo Brewster Angle). When you can make h=80ft (24.3m), your 160m dipole will still have an "NVIS" radiation pattern, but with higher efficiency, so finally more radiated power in any direction (therefore also at low elevation). Same is valid for 80m, radiaton pattern will flatten a little bit in favour of lower elevation. At 40m, radiation at high elevation will become less, enhancing radiation at lower elevation. At 20m your will get multiple lobes in the elevation radiation pattern. When you go vertical, your height will be limited too. Probably the height will be far below a quarter wavelength (for 80 and 160, unless you use a kite or balloon....). This will result in a low radiation resistance in combination with a high feed current. This feed current must be drawn out of a ground network. Mostly, the ground network will dissipate lots of the RF power. Of course, the situation is better when you live in an area with heavy, wet, mineral rich ground (like me). Maybe for 40m you can get a (top loaded) vertical into a halve wave resonance. The input impedance will be very high (in the kOhm range), resulting in low feed current. This will reduce ground losses significantly. Another option to force the antenna into halve wave resonance is to add inductance in the middle of the wire. The disadvantage of relative short forced halve wave radiators is the very high end-fed impedance (10 kOhm). Mostly this requires a dedicated tuner. Top-loading the antenna (L, T, square, or multi wire cap) will give more current in the top of the antenna. This increases the radiation resistance (maximum factor 4) and decreases the losses in the ground system (better overall efficiency). It also eases matching. Regarding the ground system. Try to get as much as metal connected to ground from where you feed the (vertical) radiator. More smaller ground rods do better then one very long one. Ground your (asymmetrical) tuner to the ground system and add a common mode coax choke between the tuner and Transceiver. There can be RF voltage on the tuner with respect to the transceiver's ground. If the VSWR of the radiator itself is not that bad, you may put the choke between the tuner and the radiator. Another option is a floating ground (I am planning to do this for the next JOTA for 40m with a halve wave radiator). Two or three ground wires of 0.25*lambda are completely above the ground (some 6 feet). Depending on your back yard, this may be a problem. For a multi-band antenna this will require multiple wires. A complete other option is using a (side-fed) loop. The Voyager DX antenna. I do not have experience with that antenna, however it is also used with a counterpoise kit (I saw on several reviews). If this kit is really necessary to operate the antenna, then it is a more or less asymmetrical antenna that needs ground. The bandwidth of 90 kHz at 160m is rather high. It may be the result of poor efficiency. In brief: #If you have very good ground, you may try a vertical monopole antenna. #In case of very bad ground and no opportunity to make a good ground system, use the horizontal dipoles (as high as possible) and or use a vertical polarized radiator that has high radiation resistance at the feed point (halve wave characteristic prefered). Best Regards, Wim PA3DJS |
Better for DX: Vertical or dipole?
"Rick" wrote in message ... I am interested in operation primarily on 160, 80, and 40. Your passport to the low bands ON4UN's Low-Band DXing http://www.arrl.org/catalog/7040/ Reviews at URL: http://www.eham.net/reviews/detail/2802 CL |
Better for DX: Vertical or dipole?
Cecil Moore wrote: Performance wise, I don't think you could tell the real vertical from the T except for the T's lower feedpoint impedance. -- 73, Cecil, http://www.qsl.net/w5dxp The T is better if he wants it to act like a DX vertical. The L is ok, but if the horizontal wire is fairly long, there will be a good bit of horizontal radiation. This can be good for a mix of NVIS and DX, but for DX only, the T is usually better. The T will have an overhead null the same as a normal monopole. I'd say most peoples L's on 160 have more horizontal wire than vertical... :/ I know mine did. I could only get mine about 45 ft vertical . That left 80-90 ft running across the backyard. I often feed my coax fed dipoles as a top hat vertical on 160 by shorting the coax, and feeding as a vertical. At the moment I have a turnstile on 80m, and a dipole on 40. "6 legs total" The 4 60 ft wires make a good "X" top hat.. MK |
Better for DX: Vertical or dipole?
A few interesting designs at this web site
[http://members.tripod.com/~KE4UYP/index-22.html] may help you. One is a a linear loaded 1/2 wave inverted L fed at the top of the L rather than the base. Another is a top & bottomed hatted, bottom fed L. Neither design requires radials. Author includes theoretical radiation patterns & SWR curves. 73 Terry W9EJO |
Better for DX: Vertical or dipole?
That's W8EJO, not 9.
Typo. Harry7 wrote: A few interesting designs at this web site [http://members.tripod.com/~KE4UYP/index-22.html] may help you. One is a a linear loaded 1/2 wave inverted L fed at the top of the L rather than the base. Another is a top & bottomed hatted, bottom fed L. Neither design requires radials. Author includes theoretical radiation patterns & SWR curves. 73 Terry W9EJO |
Better for DX: Vertical or dipole?
wrote:
Cecil Moore wrote: Performance wise, I don't think you could tell the real vertical from the T except for the T's lower feedpoint impedance. The T is better if he wants it to act like a DX vertical. The L is ok, but if the horizontal wire is fairly long, there will be a good bit of horizontal radiation. This can be good for a mix of NVIS and DX, but for DX only, the T is usually better. The T will have an overhead null the same as a normal monopole. You're right but I wasn't talking about the Inv-L above. When I said "real vertical", I was talking about a normal 1/4WL monopole. The T and the 1/4WL vertical have about the same performance if the T's vertical section is not too short. -- 73, Cecil http://www.w5dxp.com |
Better for DX: Vertical or dipole?
Harry7 wrote:
One is a a linear loaded 1/2 wave inverted L fed at the top of the L rather than the base. We also haven't mentioned the half-square which resembles the above. -- 73, Cecil http://www.w5dxp.com |
Better for DX: Vertical or dipole?
On 11 Jan 2007 22:29:52 -0800, "
wrote: What's your advice? Get a copy of ON4UN's low band DXing. Search the Topband archives antennas. Measure/estimate your ground conductivity and permittivity and get comfortable with a modeling program. And finally, experiment. I don't mean to be glib but there's really no quick answer to what antenna you'd be happy with for DX on 40,80 and 160. 30 feet for a horizontal antenna *is* too low, generally. Maybe someone can comment on the Voyager DX... I can't, specifically. Verticals are good, short verticals are compromises and must be treated with care. - - - - - - - - - This is what I use: http://www.n3ox.net/projects/sixtyvert I can certainly work more 40&80m DX on this than on the 30 foot high, 100 foot long centerfed wire I used to use on those bands. As far as 160m goes, this is the first time I can work 160 DX at all... 73, Dan Your sixtyvert antenna has me rethinking my vertical plans. I have a forty foot utility pole laying on the ground while I plan the details for a taller vertical. In spite of my aversion to guys I think this pole is light enough to be workable for me. My current vertical is a 45 foot wire off the side of the tower tuned with an SGC-237. It seems to be working well in spite of a minimal ground. It appears to me that the guy anchors could be as simple as a few five gallon buckets of sand. I sure hate to pay that much shipping though! John Ferrell W8CCW |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREES ARE ADDED
What if you have a lot of 50 to 80ft tall pine trees on the acreage? I
live on a 500ft hill that slopes down agressively from a 2 acre flatter spot at the top. The hill is covered in trees. I have a 70ft tower on the highest knobe that I can load up well with a gama match on 40m, 80M and 160m. The wire ground plane I has 45x 120ft wires which run down the hill through the woods. The Top-Band seems OK. On 160M I worked all states in one weeked last winter (contest). But on 80m and 40m I have had very little luck working anything. I suspect the trees are grabbing all the RF energy. Because the trees are virticle conductors I'm thinking that a horozontal dipole might work better. I'll only be able to get it as high as the tree tops. Maybe an average of 55ft high near the edge of an east facing clift. Since I live on the West Coast this might give me good coverage on the States on 40 and 80 meters for next falls Salmon Run? What do you think? Bob AC7PN |
Better for DX: Vertical or dipole?
For what it may be worth ..
Roy Lewallen wrote: The T is simply a top loaded vertical. The top portion radiates an insignificantly small amount for the same reason ground plane radials don't radiate. (Hey, wonder if they act as an "image" mirror to reflect the signal into the ground?) (That was a joke.) The horizontal portion of an L antenna radiates like any end fed horizontal wire. If it's low, most of the radiation is at a high elevation angle. Roy Lewallen, W7EL wrote: Cecil Moore wrote: Performance wise, I don't think you could tell the real vertical from the T except for the T's lower feedpoint impedance. -- 73, Cecil, http://www.qsl.net/w5dxp The T is better if he wants it to act like a DX vertical. The L is ok, but if the horizontal wire is fairly long, there will be a good bit of horizontal radiation. This can be good for a mix of NVIS and DX, but for DX only, the T is usually better. The T will have an overhead null the same as a normal monopole. I'd say most peoples L's on 160 have more horizontal wire than vertical... :/ I know mine did. I could only get mine about 45 ft vertical . That left 80-90 ft running across the backyard. I often feed my coax fed dipoles as a top hat vertical on 160 by shorting the coax, and feeding as a vertical. At the moment I have a turnstile on 80m, and a dipole on 40. "6 legs total" The 4 60 ft wires make a good "X" top hat.. MK For a long number of years I used a square loop antenna down low to the ground on HF. It was not fed in the 'usual' place, at the mid-point on the horizontal wire, either at the bottom of the square loop or on top. I chose to feed it half way up one of the vertical sides so as to obtain the best results I could from the vertical radiation for it. That so as to do the best job I could for 40 and 80 meter DX work without going after formal ground plane enhancement and working the feed point against that, as in ground plane verticals with radials. In the 40 meter case the lowest horizontal wire was about ten feet or so above ground level. The actual loop was fed from a coax cable with the ground braid of the coax tied directly to the loop wire, and the feed match as a gamma match section using six inch open wire feed insulators for that, plus a series capacitor made from a cut off piece of coax cable the braid connected to the braid connect point end of the center wire of the feed coax and the inside coax wire connected to the gamma match line section. I had pair of three element quads made this way, with a pair of switched in or shorted wire stubs made from the same six inch open wire feed lines which if shorted, made that loop a director, and if opened, made it a reflector. They were supported at right angles to each other so I had four-way aiming capability here. You can laugh all you want, but about 270 countries on 40CW confirmed from it wasn't too bad. And it placed way up there in the DX test single band entries for a long time from W5 land, which isn't really the easiest place from which to compete against the East and West coasts of the USA on low bands. Yes, it was replaced by a four element phased vertical array, with elevated tuned radials. Which is definitely noisier on receive. But it has the advantage of being directionally switchable without going outside and getting on a step ladder four times just to change the fire direction in the middle of the night, or rain or .. even .. TRW's and twisters in this area of Texas. Of which there were only twenty tornadoes on the ground in a single day just a couple weeks ago right around here. ;) For years now I've wanted to build a low three element rotary vertically fed 40 meter quad to test this against the four square switched phased vertical array I've used to romp the confirmed 40CW only card count to 321 now. That with about a level 5 or 6 ground level quality here in sandy pine tree country. But age, funds, want-to and other more important computer programming work in my preference list have gotten in the way. If I ever can get this done I'd dearly love to post the comparative figures on a real-time real=workem romp! If it wouldn't be too much trouble for someone interested in this, making a 40 meter wire loop is pretty easy. You only need a pair of poles to support the top wire. I think you will be pleasantly surprised how quiet it is and how effective it is, if vertically fed, for working low band DX stations.... Mike - W5WQN |
Better for DX: Vertical or dipole?
Cecil Moore wrote: The T and the 1/4WL vertical have about the same performance if the T's vertical section is not too short. -- 73, Cecil http://www.w5dxp.com The closer to a 1/4 wave for the combined vertical plus top hat wire , the better. You can even improve farther as far as current distribution if you make it longer. IE: 3/8 wave total length. That will raise the max current point up into the vertical section more towards the top, rather than the bottom. Course, if you do this, you will need a cap to tune out the reactance. Like Roy says, the hat radiates little. Even just two wires is a pretty clean vertical pattern with little radiation from the hat unless the total length is so long as to place the current max at the apex or into the horizontal wires . So I wouldn't get too carried away with the total length past a 1/4 wave if I wanted a strictly vertical pattern. When I ran both an L and a T, the L would often do better at close to medium distances in the early PM. But the T was usually better once it stretched out a bit. So most of the time, I preferred the T. At that time, I also had a Z dipole, which was better for NVIS than the L. Now all I have is the "coax dipole" T. I did away with the others.. The Z dipole was generally the worse of the three as far as DX. Course, I don't work too much DX on 160m. I can't hear most of them with my micky mouse receiving antennas... :/ I've heard W8JI working stuff that didn't exist here on my radio.. I've pretty much faced the fact I won't be having a killer 160 setup until I can get out in the boondocks. MK |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREES ARE ADDED
On 13 Jan 2007 09:23:32 -0800, "AC7PN" wrote:
Because the trees are virticle conductors I'm thinking that a horozontal dipole might work better. I'll only be able to get it as high as the tree tops. Maybe an average of 55ft high near the edge of an east facing clift. Since I live on the West Coast this might give me good coverage on the States on 40 and 80 meters for next falls Salmon Run? What do you think? What do you think about a vee beam? Look over http://www.cebik.com/gup/gup42.html to see if you think that might work for you. S.T.W. |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREES ARE ADDED
Sum Ting Wong wrote: What do you think about a vee beam? Look over http://www.cebik.com/gup/gup42.html to see if you think that might work for you. S.T.W. I would have to run the wires down the face of the cliff to make one of those. Using NEC I just don't know how to simulate the ground effects when the land falls away at a 30-50 degree angle. At one place there is a 60 ft shear verticle drop. My unterminated beverage off the cliff headed East works well on receive but it is terrible on transmit. |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREES ARE ADDED
On 13 Jan 2007 17:46:15 -0800, "AC7PN" wrote:
I would have to run the wires down the face of the cliff to make one of those. Using NEC I just don't know how to simulate the ground effects when the land falls away at a 30-50 degree angle. At one place there is a 60 ft shear verticle drop. My unterminated beverage off the cliff headed East works well on receive but it is terrible on transmit. Beverages aren't supposed to work for transmitting so don't be discouraged by that. I would think that the ground falling away would be an advantage. Maybe Roy would care to comment on this, but I'd just model it using the slope on those wires as if you have a really high support point on the apex of the vee. Keep in mind that if you don't terminate the legs of the vee then it will be bi-directional, so if you're in the San Juans and point that sucker toward Florida you should do equally well into Asia. Gee, I wish I had your problem! ; ) S.T.W. |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREESARE ADDED
Sum Ting Wong wrote:
On 13 Jan 2007 17:46:15 -0800, "AC7PN" wrote: I would have to run the wires down the face of the cliff to make one of those. Using NEC I just don't know how to simulate the ground effects when the land falls away at a 30-50 degree angle. At one place there is a 60 ft shear verticle drop. My unterminated beverage off the cliff headed East works well on receive but it is terrible on transmit. Beverages aren't supposed to work for transmitting so don't be discouraged by that. I would think that the ground falling away would be an advantage. Maybe Roy would care to comment on this, but I'd just model it using the slope on those wires as if you have a really high support point on the apex of the vee. Keep in mind that if you don't terminate the legs of the vee then it will be bi-directional, so if you're in the San Juans and point that sucker toward Florida you should do equally well into Asia. Gee, I wish I had your problem! ; ) S.T.W. NEC is of course limited to perfectly flat ground of infinite extent. If the ground slope is constant for a great distance, you can simulate it by tilting the antenna model the opposite direction then tilting the resulting pattern. But that's about all you can do. I still use Brian Beezley's TA program for analyzing the effects of non-flat ground, but it's long been unavailable and I don't know of any program since which does the same thing. Roy Lewallen, W7EL |
Better for DX: Vertical or dipole? --- REVISED QUESTION IF TREES ARE ADDED
Roy Lewallen wrote:
NEC is of course limited to perfectly flat ground of infinite extent. If the ground slope is constant for a great distance, you can simulate it by tilting the antenna model the opposite direction then tilting the resulting pattern. But that's about all you can do. I still use Brian Beezley's TA program for analyzing the effects of non-flat ground, but it's long been unavailable and I don't know of any program since which does the same thing. N6BV's HFTA program is supplied with all recent ARRL Antenna Books, and is updated and improved in each edition. For anyone who doesn't live on perfectly flat ground of infinite extent, HFTA can provide a lot of answers to the old question: "How good is my QTH?" However, HTFA is limited to horizontal antennas, and I don't know of any program that does the same for verticals (it's a much more difficult problem). -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
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