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2M + 70cm Open Sleeve Vertical Dipole
Johnny Pedersen (LA3AKA)
on
July 21, 2004
View comments about this article!
2m/70cm Open Sleeve Vertical dipole
I was playing around with the MMANA Antenna analysis software and wanted to design a 2m/70cm vertical antenna. I tried different antenna models, J-pole, half wave dipoles, Ground Planes …. I then remembered a chapter in the 18. edition of the ARRL Antenna Handbook covering Open Sleeve antennas to make Broad band antennas. I thought that this might be useful for making a dual band VHF/UHF antenna.
The Antenna is planned built using 6mm aluminium rods. According to MMANA this will with a distance of 3.2cm between driven element and sleeve elements give an Feedpoint Impdance of 75 ohms on 2 meter and 50 ohms on 70cm. One nice thing with this antenna is that you get a good gain on 70 cm (approximately 3dB over a g Gain:
The Centre Frequencies for the antenna shown is 145 MHz and 435 MHz
Comparison of Far Fields for the antenna at 435 Mhz and 145 Mhz
The antenna shows an SWR less then 1.3 between 430 and 440 Mhz and less than 2:1 between 140 and 150 MHz according to the Model.
This article has expired. No more comments may be added.
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2M + 70cm Open Sleeve Vertical Dipole
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by N6AJR on July 21, 2004
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Is this able to be mounted horizontally for ssb work?? thanks tom N6AJR
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2M + 70cm Open Sleeve Vertical Dipole
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by KF4VGX on July 21, 2004
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Good graphics and information, Now if we can get Hams in the amateur bands to have a discussion on this.
GRIN !
Thanks for the info,
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by W6TH on July 21, 2004
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Will this gadget send morse code?
Just being funny, but good for those that can't copy morse.
.:
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2M + 70cm Open Sleeve Vertical Dipole
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by N6KD on July 22, 2004
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Where did you get the MMANA software? I like the open sleeve design and would like to build a multiband vertical with 1/2 wave element -but for HF. I assume that the distance from the driven element is critical.
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2M + 70cm Open Sleeve Vertical Dipole
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by AL2I on July 22, 2004
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I am looking to install a 2m/70cm base antennna, and this one looks interesting. The article is a little light on construction details, so I guess I'll have to research the open sleeve design.
I take it that the author has not actually built this antenna yet?
Dave McGraw (AL2I)
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KD5RKO on July 22, 2004
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You can download this software at http://www.qsl.net/mmhamsoft/mmana/
or http://www.smeter.net/antennas/mmana.php
And some antena files are at http://www.qsl.net/dl2kq/mmana/4-3.htm
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2M + 70cm Open Sleeve Vertical Dipole
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by LA3AKA on July 22, 2004
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There should be now problems using it as a horizontal antenna for SSB usage. MMANA shows little change in feedpoint impedance between horizontal and vertical polarization. For more information on open-sleeve antennas see page 7-4 ... in the 18th addition of the ARRL antenna Handbook. As for building an open-sleeve antenna for HF there should be no problems. The main critical point is the ratio between the diameter of the antenna elements and the distance between the elements. I have seen an article in CQ magazine describing a 10-18-24Mhz open-sleeve wire dipole(CQ Feb 1995).
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2M + 70cm Open Sleeve Vertical Dipole
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by KB1JCY on July 22, 2004
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Could you post a pic with the completed product? Also show the construction process.
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2M + 70cm Open Sleeve Vertical Dipole
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by AD5PE on July 22, 2004
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What changes would you need to make to move the UHF side to 440-450MHz while leaving the VHF in the 144-148 range.
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2M + 70cm Open Sleeve Vertical Dipole
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by WB2WIK on July 22, 2004
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I'd surely recommend you actually build one and then show (or clearly describe) how you mounted it and how you fed it.
The theoretical design as shown does not depict any transmission line routing, which for such a design is very critical. If you can't keep the transmission line out of the radiation plane, it's part of the antenna and will have severe impact on performance.
Normally, a vertical sleeve dipole like this is fed with the coaxial cable routed through the lower half of the antenna, which is built using hollow tubing. Did you intend that the bottom of the antenna be its mounting point, and if so, is it insulated from its mounting structure?
Also: I don't see how a 0.5WL center fed dipole, which is what this is at 145 MHz, has ~4.6 dBd gain ("gain over a dipole"). Seems impossible for a 1/2WL antenna to have any gain over a 1/2WL antenna, no matter what its design. Maybe I'm missing something...
WB2WIK/6
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by W6TH on July 22, 2004
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I have heard that this type of antenna work, but have not seen any actual gain figures. I do not have much faith in theoretical gain measurements, but would like to see the field gain measurements and also the field patterns. As it now stands thorem is the word.
I have seen one made for the HF single band "?" meters, but never seen or heard any results mentioned. This is a great bit of information and would benefit all by having one on display and further the measurements. I won't knock it as I have not tried it.
.:
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by W6TH on July 22, 2004
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I the word "theorem" is the correct spelling.
Should have corrected the spelling, can't win them all.
.:
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KB1LKR on July 22, 2004
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Re: gain at 146, it shows 11.0dBi at 1.4° and 6.7dBi at 3.9° but there are 4 sharp lobes between 0° and 10° wiht minima of about 3 dBi. would not a more realistic measure of the gain be the average gane between 0 and n degrees, say 0-10°, this might be only 6 dBi (guestimating from the small plot), still not bad, but not the 11 dBi that occurs at one (or a couple) very narrow angle(s)?
The 446 curve is a bit less sharply lobed, but the same comment applies. For that matter, it would apply to any high gain design w/ a sharply, narrowly lobed pattern in/near the axis of max gain -- and perhaps explains some of W6TH's distrust of theoretical data vs. real world performance, but you have to start somewhere, and modeling certaintly helps one to understand where a design may touchy and where it is likely to be robust, and how it is likely to perform.
It is an interesting design regardless, and will probably work well, thank you for sharing it. Let us know how it performs when you get it up.
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by WB2WIK on July 22, 2004
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I still don't see how this can be successfully fed by anything, if built using "6mm aluminum rods." A 6mm aluminum rod implies it's solid. The feedpoint is in the center. How's the feedline get there?
The plots imply a mounting height of seven feet, presumably, which happens to be about one wavelength at 145 MHz. What happens when you install this antenna at a useful height for extended horizon, like fifty feet? That big lobe at about 2 degrees isn't going to be there anymore. As it is shown, that lobe isn't very useful anyway, since it's way too narrowly focused -- unless the station you want to work falls exactly on its point, the antenna "gain" falls back to nothing.
I don't see how this is a useful design, any more than a pair of parallel vertical dipoles for 146 and 445 MHz would be. Am I missing something?
WB2WIK/6
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by K5DVW on July 22, 2004
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I was going to say something about the feedline issue too, but I thought surely I must be missing it somewhere?
So, how would you feed this thing? And, specifically, how would you feed it with coax?
K5DVW
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KI6LO on July 22, 2004
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The feedpoint is shown as a single point on the driven element in most antenna modeling software. The actual feedpoint would be at either a standard split in the radiator with the center of coax to one side and shield to other, just as you would do a normal dipole. The other method might be to use a gamma match similar to the ones used on yagi and other 1/2 wave driven element antennas (like beams and such).
Using a gamma might be difficult with this design as it may affect the coupling between the center element and the sleeve elements. You'll have to experiment some.
Gene KI6LO
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KI6LO on July 22, 2004
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I modeled this antenna in the EZNEC 3.0 using the original post's element measurements and the results concur with his. The followup post concerning feedline placement are valid as it would affect the overall results, but if mounted on a standoff arm and fed from the side at 90 degrees to the center element should minimize the effects. The angle of radiation is narrow as noted and this antenna, if fed and mounted in such a way to minimize the effects, should be a good antenna for local VHF/UHF repeater work but with the maximum gain at such a low take off angle, it probably would not be a great antenna for any distance at these frequencies. But you can't beat the design. Very clean and simple to build. Some PVC pipe for insulator and some aluminum rod and your in business.
BTW the original poster's design was 7 METERS in height, not 7 feet.
The EZNEC 3.0 model results are summarized below:
Antenna at 7M high above REAL ground.
2M results:
Gain = 6.02 dBi @ 4.0 deg
SWR less than 1.5 from 144-148 Mhz @ 75 ohm
SWR less than 2.0 from 144-148 Mhz @ 50 ohm
Antenna pattern similar
70cm results:
Gain = 10.35 dBi @ 2.0 deg
SWR less than 1.5 from 430-440 Mhz @ 50 ohm
less than 2.0 from 430-447 Mhz @ 50 ohm
Antenna pattern similar
Think I might build one to see what it really can do.
Gene KI6LO
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by WB2WIK on July 22, 2004
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Gene, I don't see how feeding this antenna (or any vertical dipole) as you describe is practical; in fact, it's so impractical, I'd like to see someone do it!
This is the reason the vertical dipoles are nearly always:
-Built as "ground plane" antennas, instead; or
-Built as coaxial dipoles, which is very similar to that discussed in this article, but where the lower half of the antenna is hollow tubing of sufficient diameter to support routing the transmission line through it; or
-Built as side-mounted folded dipoles, or often "U"-poles, as commonly seen in stacked dipole commercial antenna products.
In any case, the modeling is flawed in that the "gain" exhibited exists only in narrow spikes which may or may not be at useful angles, and this can be pretty broadly stated since there are sharp and deep nulls between those spikes. If you take the mean of the radiation at, say, zero to 20 degrees above horizon, the antenna exhibits no gain, just like any other vertical dipole.
WB2WIK/6
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by G5FSD on July 23, 2004
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what's the problem? Isn't this just a normal 2m dipole with two extra RODS (halfwaves on 70cm) each side? - i.e. the diagram isn't a slice through.. the uhf parts aren't a cylinder! The feed would be on the 'z-axis' - coming out of the screen.
I'd expect this to be practically pretty similar to a 2m dipole on 2m, and if it tunes up on 70cm with 3dB of gain up there relative to a dipole then all well and good. I'd have no trouble stringing one up in the loft and such a simple design would have it's uses I suppose - if you're going to chuck up a dipole for 2m and you've got a dual-band radio you might as well try the extra elements for 70cm too.
73
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KD5UJX on July 23, 2004
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This same antenna is in the Oct 2000 issue of QST. I built one and it has great bandwidth and works well on both bands.
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2M + 70cm Open Sleeve Vertical Dipole
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by WA2JJH on July 24, 2004
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TNX AGN FER UR design. I use MATLAB for simulations and design. Do you know if there is a MATLAB code for this type of design?
MATLAB is similar to basic,fortran, and C.
I guess I can look at the code used and simply do a cut and paste into MATLAB. MATLAB uses the internet when it runs code that is not MATLAB.
I would like to run a few MATLAB simulations on your design.
Yes, the feed point issue is not that clear to me either.
Problem when you do a tech artical for EHAM, people expect EVERYTHING! You did not do this or that. Yes, the point of a photo is a good one. A picture speaks a thousand words.
As one of my prof's said....Yes it is easy to point out any flaw. That is your EGO working." DO NOT TELL ME WHY IT WILL NOT WORK. DO THE RESEARCH, AND FIND A WAY SO IT WILL!" QUOTED FROM DR G. He invented polymer
delivery for glail cell carcinoma.
DR G. is my supervisor. I am not at liberty to give his full name on a public post.
I will have a secure email site soon. I will be glad to share scientific stuff and ham radio.
The HUGHS organisation(Howard HUGHs' think tank/tax write off) only deals with idea's that conventional science thought was useless.
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2M + 70cm Open Sleeve Vertical Dipole
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by WA2JJH on July 24, 2004
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I have to add something for context. What I posted today is right after your great artical.
WHY DID EHAM CHANGE THE ORDER OF THE POSTINGS!
It makes me look silly. It also ruins the continuity
and context of the thread.
My comment about MATLAB should be at the bottom.
If it is a computer glitch no problem.
In the mean time. it is prudent to check date of posting, before sending feedback.
TNX MIKE
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KA4KOE on July 25, 2004
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How can we apply this data re: the ole reliable fan dipole?
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RE: 2M + 70cm Open Sleeve Vertical Dipole
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by KI6LO on July 27, 2004
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In my previous posts, all I was trying to do was state that I had used an alternate modeling software pkg and come up with the same basic results. I wasn't stating that this antenna would do exactly what was shown in the model. That would require building and real world testing, which I have not done, but may someday when time permits.
To those opposed to this design, all I will say is "Don't try it if you don't like it". If you do like the possibilities, by all means, use it as a basis to start experimenting and see what you can develop from there. Experimenting and adapting others' designs to ones use is one of the major underlying premises of ham radio. No one is holding you responsible for the design.
And yes, antenna models are just that, MODELS. There are a myriad of real world influences that affect the realization of a model's potential, but it is nice to be able to start somewhere other than cutting aluminum tubing (or rods in this case)!
73
Gene KI6LO
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2M + 70cm Open Sleeve Vertical Dipole
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by WA2JJH on July 29, 2004
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JOHNNY, do not give up.Problem as i see it is that many hams do not even now how to use simulation software.
Albert Einstein said.....If at first your idea seems impossible........Try anyway!
In the US the face of ham radio is changing.
We one one hand have more hams that are no-code techs.
By my standards,the test is too easy.
We also have old timers, that do not experiment.
OT's hat have an ego too
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2M + 70cm Open Sleeve Vertical Dipole
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by WA2JJH on July 29, 2004
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JOHNNY, do not give up.Problem as i see it is that many hams do not even now how to use simulation software.
Albert Einstein said.....If at first your idea seems impossible........Try anyway!
In the US the face of ham radio is changing.
We one one hand have more hams that are no-code techs.
By my standards,the test is too easy.
We also have old timers, that do not experiment.
OT's hat have an ego too
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