Plans for a 5/8 wave 2M ground plane
Does anyone know where I can get plans for this antenna? Materials needed
to build one? Thanks |
George Cronk wrote:
Does anyone know where I can get plans for this antenna? Materials needed to build one? ARRL Antenna Book -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
MFJ makes a phased 5/8 wave 2 meter antenna that also works as a 1/2 wave
vertical on 6. Sells for $49 at HRO. 73 Dave K4JRB George Cronk wrote in message 54.205... Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks |
George Cronk wrote in message . 154.205...
Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks You would be better off with a 1/4 wave ground plane on 2m. Seriously. And one of those can be as simple as five 19 inch pieces of wire and a So-239 connector. MK |
"Mark Keith" wrote in message om... George Cronk wrote in message . 154.205... Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks You would be better off with a 1/4 wave ground plane on 2m. Seriously. And one of those can be as simple as five 19 inch pieces of wire and a So-239 connector. MK Why would he be better off with a 1/4 wave, with it's large vertical lobe? |
On Sat, 3 Apr 2004 06:36:31 -0500, "Dave VanHorn"
wrote: You would be better off with a 1/4 wave ground plane on 2m. Seriously. And one of those can be as simple as five 19 inch pieces of wire and a So-239 connector. MK Why would he be better off with a 1/4 wave, with it's large vertical lobe? Hi Dave, For any of a couple of reasons, principal among them being simplicity. I have 2M, 220 and 440 versions with drooping radials that match quite easily and couldn't be any cheaper for only the cost of the SO239. As for "it's large vertical lobe," I am not sure what you mean by that. The 5/8ths has more gain, but not so much more in a band and application that is dominated by line of sight communication. If the difference between the two is important to getting into a repeater, getting into the repeater is not the same as full quieting and can be an obnoxious advantage suffered by those who have to listen to a poor connection. Such problems are more simply remedied by elevating the existing antenna than trying to "add gain." 73's Richard Clark, KB7QHC |
The 5/8ths has more gain, but not so much more in a band and application that is dominated by line of sight communication. Funny, it's made a significant difference for me in the decade or so I've been using them. A folded monopole is almost as simple, and has more gain as well. http://www.w4dex.com/kc4fwc/proj_2.htm If the difference between the two is important to getting into a repeater, getting into the repeater is not the same as full quieting and can be an obnoxious advantage suffered by those who have to listen to a poor connection. ?? More gain is worse? I don't follow you. Being able to run into the same machines at lower power is always good for my batteries, and taking me from noisy to quiet on the same power is always a good thing. Such problems are more simply remedied by elevating the existing antenna than trying to "add gain." Altitude is king, as long as you don't throw it all away in the feedline. |
On Sat, 3 Apr 2004 14:35:29 -0500, "Dave VanHorn"
wrote: The 5/8ths has more gain, but not so much more in a band and application that is dominated by line of sight communication. Funny, it's made a significant difference for me in the decade or so I've been using them. Less than 1 dB is significant? Are we talking about VHF FM DXing? If the difference between the two is important to getting into a repeater, getting into the repeater is not the same as full quieting and can be an obnoxious advantage suffered by those who have to listen to a poor connection. ?? More gain is worse? More gain is not always enough gain. Again, if this is about getting into a repeater, the less than 1dB difference that holds it open with a scratchy signal is no panacea. There is nothing your contacts can do to improve your poor S/N ratio; so, in a sense, it being better is only from your point of view and an imposition on others to strain their ears. I don't follow you. Being able to run into the same machines at lower power is always good for my batteries, and taking me from noisy to quiet on the same power is always a good thing. The same logic applies to getting your buddies to push your car to boost your MPG. Better MPG cannot be said to be bad, but then you aren't the one doing the pushing. Such problems are more simply remedied by elevating the existing antenna than trying to "add gain." Altitude is king, as long as you don't throw it all away in the feedline. Adding altitude also overcomes obstructions that could easily strip away the added "loss" of the line. My buddy's 2M repeater is over a nearby hill from me (I am roughly 100 feet below its crest) and 10 miles away. I can hit it with a pocket HT (100mW with a cheesy antenna) from inside my basement, but move into another room and it's a morgue. A "better" antenna is hardly going to do as good a job as the same poor one above ground level. A "better" antenna will not fit in the pocket, so "better" is entirely subjective with its objective analysis not so much very better. 73's Richard Clark, KB7QHC |
Dave VanHorn wrote:
?? More gain is worse? Depends on the TOA. Around Phoenix, we had a mountaintop repeater that we could hit better with a 1/4 wave than with a 5/8 wave when we were close to the base of the mountain upon which it resided. That's where we camped out a lot. -- 73, Cecil, W5DXP -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"Cecil Moore" wrote in message ... Dave VanHorn wrote: ?? More gain is worse? Depends on the TOA. Around Phoenix, we had a mountaintop repeater that we could hit better with a 1/4 wave than with a 5/8 wave when we were close to the base of the mountain upon which it resided. That's where we camped out a lot. I'm aware that there are off cases where the normal rules don't apply, but in general, higher gain and a flatter pattern, is always better than lower gain and heating the clouds.. I've not seen many hairpins out there, and they are just a small bit more to build than the GP. Why is that? Are they just not well known? |
Looking over the replies to this post makes me wonder where the helpful
ham hand is lurking these days. This poor guy just wants to know about plans and materials for an antenna to build and all but one reply tells him he doesn't want one or you should buy this one or he's stupid for considering one or I can get into this repeater with that antenna, bla, bla bla. It can be made with the same components as an SO-239 1/4 wave ground plane but with a little more wire with a cork screw turn at the bottom. Doesn't anyone have the simple plans for this guy? George Cronk wrote: Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks |
On Mon, 05 Apr 2004 00:54:06 GMT, Mike wrote:
Looking over the replies to this post makes me wonder where the helpful ham hand is lurking these days. This poor guy just wants to know about plans and materials for an antenna to build and all but one reply tells him he doesn't want one or you should buy this one or he's stupid for considering one or I can get into this repeater with that antenna, bla, bla bla. It can be made with the same components as an SO-239 1/4 wave ground plane but with a little more wire with a cork screw turn at the bottom. Doesn't anyone have the simple plans for this guy? George Cronk wrote: Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks Actually I do have plans for a colinear 5/8 over 5/8 2 meter antenna; all you'd have to do is omit the phasing coil and top radiator. This one is built from wire on an SO-239. To the original poster - I can scan the sketch & email it to you, let me know if you'd like that & it's a done deal. Howard KE6something or other |
"Dave VanHorn" wrote in message ...
"Mark Keith" wrote in message om... George Cronk wrote in message . 154.205... Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks You would be better off with a 1/4 wave ground plane on 2m. Seriously. And one of those can be as simple as five 19 inch pieces of wire and a So-239 connector. MK Why would he be better off with a 1/4 wave, with it's large vertical lobe? Cuz it's easier decoupled with it's 1/4 wave radials, and is less likely to have feedline radiation than the funky 5/8 antenna with 1/4 wave radials. In direct comparisons here, the 1/4 GP was a good bit better than the 5/8 with 1/4 radials. The maximum gain of an elevated 1/4 wave GP on 2m, mounted at 35 ft at the base, is appx 6.2 dbi at 3 degrees. The maximum gain of a 5/8 GP with horizontal 1/4 wave radials, at the same height, is about 4.7 dbi at the same angle. And this does not yet take into account any decoupling problems! If the feedline radiates, any gain on the horizon is likely lost as the pattern is skewed up off the horizon. The average 5/8 antenna is ruined by using 1/4 wave radials. A 5/8 should be paired with a mirror image 5/8 to function properly. IE: dual 5/8 collinear such as the isopole, etc... And decoupling must still be used even on those. I agree with one thing Richard said about height and a 1/4 wave..If you get the tip of the 1/4 GP at the same height as the tip of a tall dual 5/8 collinear, there is little real difference between the two. And the dual 5/8's collinear is better than a 5/8 GP. 2m is real critical as far as the low angles used, and also to the effects of feedline radiation lowering the gain at those low angles. Now on 10m, many times I do prefer a 5/8 GP over a 1/4 GP, but there the angles used are less critical. If your 5/8's works, I wouldn't worry much, but in comparing them in A/B tests, "at appx 35 ft" I've never seen a 5/8 GP with 1/4 radials beat a 1/4 wave GP with 1/4 radials. I once built a fancy 5/8 GP with a nice larson coil, lots of 1/4 wave radials, etc...Was a super dud...I tore it up the 1st day and went back to a 1/4 wave. The 1/4 wave was an average 3-4 S units better on local rptrs, and simplex. About the same difference as comparing a undecoupled ringo ranger, to a decoupled ringo ranger 2... MK |
Mike wrote in message .com...
Looking over the replies to this post makes me wonder where the helpful ham hand is lurking these days. This poor guy just wants to know about plans and materials for an antenna to build and all but one reply tells him he doesn't want one or you should buy this one or he's stupid for considering one or I can get into this repeater with that antenna, bla, bla bla. It can be made with the same components as an SO-239 1/4 wave ground plane but with a little more wire with a cork screw turn at the bottom. Doesn't anyone have the simple plans for this guy? Sure, if he really wants to use an inferior antenna, I can tell him how to build it. It's simple. A 5/8 wave radiator, and about 4-5 turns of coil on a one inch form for matching will get him fairly close. But I don't recommend one. You wouldn't get me running a 5/8 GP on 2m for anything. It's like G5RV's on 80m...They usually suck...So do most 5/8's GP's on 2m...:/ But don't take my word for it. Compare them with an antenna switch and see. The only time I ever see a 5/8's beat a 1/4 on 2m, is if they are nearly on the ground. And I think thats just a line of sight deal... MK |
"Mark Keith" wrote in message om... "Dave VanHorn" wrote in message ... "Mark Keith" wrote in message om... George Cronk wrote in message . 154.205... Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks You would be better off with a 1/4 wave ground plane on 2m. Seriously. And one of those can be as simple as five 19 inch pieces of wire and a So-239 connector. MK Why would he be better off with a 1/4 wave, with it's large vertical lobe? Cuz it's easier decoupled with it's 1/4 wave radials, and is less likely to have feedline radiation than the funky 5/8 antenna with 1/4 wave radials. In direct comparisons here, the 1/4 GP was a good bit better than the 5/8 with 1/4 radials. Interesting. You obviously have developed a far superior measurement technique than most antenna engineering firms, and maybe even NIST. Your results disagree with pretty much everyone who measures antenna gain professionally, and the ARRL handbooks, but hey they must all be wrong then. Though it's entirely done in the HF spectrum, a pretty detailed analysis is presented he http://www.cebik.com/58-3.html A good ground, and cleaner near-field space, is easier to come by at VHF and UHF, so I would expect results to be somewhat better than what was seen here even at the high end of the HF spectrum. If you google a bit, you'll probably find some articles on converting a CB antenna to a 5/8 2 meter antenna. |
Dave VanHorn wrote,
lobe? Cuz it's easier decoupled with it's 1/4 wave radials, and is less likely to have feedline radiation than the funky 5/8 antenna with 1/4 wave radials. In direct comparisons here, the 1/4 GP was a good bit better than the 5/8 with 1/4 radials. Interesting. You obviously have developed a far superior measurement technique than most antenna engineering firms, and maybe even NIST. Your results disagree with pretty much everyone who measures antenna gain professionally, and the ARRL handbooks, but hey they must all be wrong then. Though it's entirely done in the HF spectrum, a pretty detailed analysis is presented he http://www.cebik.com/58-3.html A good ground, and cleaner near-field space, is easier to come by at VHF and UHF, so I would expect results to be somewhat better than what was seen here even at the high end of the HF spectrum. If you google a bit, you'll probably find some articles on converting a CB antenna to a 5/8 2 meter antenna. In volume 1 of the Antenna Compendium series is an article entitled "The 5/8-Wavelength Antenna Mystique" by Donald K. Reynolds, K7DBA. I don't think Reynolds would disagree with Mark too much. 73, Tom Donaly, KA6RUH |
"Dave VanHorn" wrote in message
Cuz it's easier decoupled with it's 1/4 wave radials, and is less likely to have feedline radiation than the funky 5/8 antenna with 1/4 wave radials. In direct comparisons here, the 1/4 GP was a good bit better than the 5/8 with 1/4 radials. Interesting. You obviously have developed a far superior measurement technique than most antenna engineering firms, and maybe even NIST. Maybe so if using a simple antenna switch to A/B test is superior... Your results disagree with pretty much everyone who measures antenna gain professionally, and the ARRL handbooks, but hey they must all be wrong then. No, they do NOT disagree with most who have a clue. BTW, those "results" I gave you with gain numbers were from modeling. Though it's entirely done in the HF spectrum, a pretty detailed analysis is presented he HF? Thats the problem....You can't apply the performance shown on HF, and expect it to pan out on 2m. The decoupling problem will rear it's head on VHF. http://www.cebik.com/58-3.html A good ground, and cleaner near-field space, is easier to come by at VHF and UHF, so I would expect results to be somewhat better than what was seen here even at the high end of the HF spectrum. A good ground is not the whole answer. Decoupling is more important at those higher frequencies. If you google a bit, you'll probably find some articles on converting a CB antenna to a 5/8 2 meter antenna. Why would I need to do that? I already done that before. I've built enough 5/8 antennas to choke a horse. Maybe two or three. Thats why I'm fairly comfortable with what I say. I'd like to ask one question. Have you ever actually compared the two types at the same time using a switch? MK |
"Dave VanHorn" wrote in message
If you google a bit, you'll probably find some articles on converting a CB antenna to a 5/8 2 meter antenna. One note...There is only one case on VHF where I often prefer a 5/8 over a 1/4 , and that is on a car when roof mounted. The 5/8 will usually "picket fence" less, if you are in an area that is all flat terrain. But as far as elevated ground planes at the house, I prefer the 1/4 wave anyday. If I use 5/8 elements at home, it will always be a dual 5/8 collinear of some type. Not a GP with 1/4 wave radials. MK |
"Mark Keith" wrote in message om... "Dave VanHorn" wrote in message If you google a bit, you'll probably find some articles on converting a CB antenna to a 5/8 2 meter antenna. One note...There is only one case on VHF where I often prefer a 5/8 over a 1/4 , and that is on a car when roof mounted. The 5/8 will usually "picket fence" less, if you are in an area that is all flat terrain. And that's exactly where I use them. Not much problem with ground planes or decoupling. |
Hustler makes a 5/8 wave 2M antenna they call the SF-2. HRO sells them for
$14.95. At that price the only reason to make one is "for fun" but that's worthwhile. 73, K3DWW "George Cronk" wrote in message 54.205... Does anyone know where I can get plans for this antenna? Materials needed to build one? Thanks |
"Dave VanHorn" wrote in message
Though it's entirely done in the HF spectrum, a pretty detailed analysis is presented he http://www.cebik.com/58-3.html A good ground, and cleaner near-field space, is easier to come by at VHF and UHF, so I would expect results to be somewhat better than what was seen here even at the high end of the HF spectrum. It's more decoupling than anything. Although the usual 5/8 GP with 1/4 wave radials is a flawed animal from the git-go. I think the best article to describe the effect is from a Dr. Reynolds , "I think thats the name anyway", that wrote an article for AEA about this problem. They put out a small brochure with the article and some pictures. They described the problems with most of the common verticals used. IE: 1/2 waves, 5/8's, and collinears. The result of all that led to the development of the AEA isopole. Probably the best decoupled dual 5/8 collinear ever designed. And thus , the highest performing compared to less well decoupled competitors. Thats why cushcraft modified their ringo ranger, and added a decoupling section, and renamed it the ringo ranger 2. The effects of a lack of decoupling was glaring when compared to an antenna of the same appx size, using good decoupling. The RR was also an appx dual 5/8, although slightly perverted in dimensions...The RR2 is a good antenna. But the isopole will still usually beat it. The 5/8 GP or other poorly decoupled antenna does have the rare chance of the feedline currents adding in phase and creating some gain, but this is like a one in twenty chance...Like going to Vegas...Doesn't usually work out that way for most people. Never did for me...I've never had an elevated 5/8 GP on 2m that was worth a hoot. Not a one... Only on a car were they ok. But you look at a car...It's large enough to usually provide a lower 5/8's of sorts, and also there is no feedline radiation to skew the pattern upwards. The feedline radiation if any, is shielded by the car body. HF is a whole different story. On 10m, a 5/8 GP is best over both a 1/4 wave and a 1/2 wave. I've tested this many times in the real world... HF is less critical as far as using a real low wave angle, and also the average angle used , even locally, is probably slightly higher. But it doesn't apply to VHF or UHF. It's a whole different world there, and feedline decoupling is by far the most critical part of a good antenna. Not brute gain numbers. It won't do any good if the gain is not where you need it. And thats under 5 degrees for local VHF. MK |
Mark makes a good point. Those with EZNEC or other modeling program
might try this -- build a model of a ground plane antenna, and do an elevation plot. I'll describe the process with EZNEC, but you can do the same with other programs. With EZNEC, start with the example description VHFGP.EZ, and change the Plot Type to Elevation. Click FF Pat to run a pattern. In the 2D window, select Save Trace As, enter a name, and click Save. Then, from the junction of the ground plane and vertical wire, extend a wire downward for 3/4 wavelength, by adding a wire (in the Wires Window) with end coordinates 0,0,5 and 0,0,4.25 wavelengths. Give the new wire 15 or so segments. Change the Units to Inches or Millimeters, and make the diameter about equal to the outside diameter of your feedline coax. Do a pattern calculation on the new antenna. In the 2D window, select Add Trace, and enter the name of the trace you just saved to show the original pattern for comparison. The distortion of the pattern is due to current induced on the outside of the feedline by the antenna -- the radiating feedline is as much a part of the antenna as the intended radiator. (Those of you enamored with with CFA, EH, or other small antenna take note!) In fact, feedline radiation can actually contribute more to the overall field than radiation from the supposed "antenna". You can see this current in the View Antenna display after doing a calculation. You'll find that very small changes in the length of the feedline wire make profound differences in the pattern. (The phenomenon is similar to what happens when you change the length of a Yagi element.) This open ended feedline of course doesn't do a good job of representing most real feedlines, and the length was chosen to be nearly resonant. The real feedline is likely to be longer, and take a circuitous path, perhaps through the mains wiring, eventually ending at ground, and might or might not resonate. The pattern you'll actually get depends on this path and length, which are often hard to predict or quantify. But the program shows that pretty severe pattern distortion is possible for some feedline lengths, so you might or might not experience it. It also illustrates that the ground radials do an ineffective job of isolating the outside of the feedline from the antenna. I believe it's very possibly a reason people have such varying opinions about ground planes of various lengths and of J-poles -- and why people seem pretty uniformly satisfied with the AEA Isopole. It's not spectacular, but it's consistent, and independent of the feedline. To further your education, try different ground radial angles and lengths in the model antenna, and different radiator lengths. Another fun experiment is to put a "balun" -- a resistive or reactive load of about 1000 ohms -- at the "coax" feedpoint connection (wire 6, 0% of the way from end 1), and see what that does to the current and pattern. Try moving it, and adding a second one at various spacings. Interesting, isn't it? The conclusion you should reach is that a description of the vertical and ground plane wires alone isn't an adequate description of the actual radiating structure -- the feedline is an integral part of the system and has to be included if you're to have any idea of how the antenna will really work. Hopefully, this exercise will help you understand why, when you ask a question about how well a "simple" antenna will work, some of us hem and haw and answer "It depends". Roy Lewallen, W7EL |
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