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I’m reading up on the “EH” antenna, and one for the AM bands can be practically built with a total length of under 6 feet inside of some plastic pipe.
I’m reading up on the “EH” antenna, and one for the AM bands can be practically built with a total length of under 6 feet inside of some plastic pipe.
The website his here, I found it by reading through links on this (part15.us) website.
The antenna is designed to not have coax feeding it. (yeah, wrap your mind around that one), and consists of 2 non-ferrous cylinders and a phase shifting L/C system. The cylinders can be small around, but below about 8 inches, the matching coils start to become quite large.
The part about this that matters, is that this antenna can have gain of up to 4 db. That’s right, it can be HIGHER than a 1/4 wave tower with ground radial array! It needs NO ground plane of any kind, but it loses horizontal gain when it’s close to the ground. .1 wavelength from the ground and up is sufficient for good performance (though not the 4 db gain). at 1600khz, that’s about 62 feet off the ground. The efficiency at that height and properly and tuned and constructed would be in the high 90’s.
Even if you’re not that high, the difference in gain between our 10 meter allowed conventional antenna and this thing is astronomical. And I use the word “astronomical” because it fits.
Has anyone tried one of these?
Mark
Total posts : 45366Suggest before much time/money is spent on an E-H for Part 15 that “due diligence” be made in researching how well it lives up to its claims.
A similar concept (the CFA) was said by its proponents to perform as well, or better than a standard 1/4-wave monopole with 120, 1/4-wave radials. But careful field strength measurements made by independent, qualified broadcast consulting engineers on operating CFAs have not shown this to be true. The FCC does not allow them for use by commercial broadcast stations.
The E-H claim to have a gain of 4 dB means nothing unless the reference is stated. If the reference is to an isotropic radiator (gain = 0 dBi) , note that a 1/4-wave, broadcast-type monopole has a gain of about 5 dBi.
If its proponents are saying that the E-H has 4 dB more gain than a 1/4-wave, broadcast-type monopole then they should be able to support that with certified and repeatable measurements that can be duplicated by anyone with the needed test equipment. If they could do that, their E-H would be quickly accepted in the broadcast market.
Information on the E-H website also says that an E-H, like a vertical dipole, cannot be installed close to the ground. But that is incorrect for a vertical dipole — as was shown by Dr George Brown of RCA in 1936, and can be verified easily today using NEC computer modeling. A 1/2-wave vertical dipole with the tip of its lower arm installed 3 feet above the earth has the same gain and pattern as a 1/4-wave, broadcast-type monopole (~5 dBi)
It may be that the stated need to install an E-H well above earth is because that produces considerable radiation from conductors leading from the antenna to an r-f ground — which is a scenario the FCC addressed in 15.219.
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Total posts : 45366Probably an error but to clarify Mark’s post,we are not allowed a “10 meter antenna”!!! I wish we were! Its 3 meters or about 10 feet. I think the EH antenna uses the feedline,since its not shielded coax,as part of the radiating structure,i.e. the counterpoise. Part15 rules address this by including the feedline and ground length in the 3 meter total length allowed. But do not be discouraged from experimenting with different designs,you just may discover something that works better…
Regards,Lee
http://www.freewebs.com/wilcomlabs/index.htm
Total posts : 45366Yeah, that “10 meter” antenna was a nice gaffe. To bad it can’t be real, but, hey, we’re all just playing in a little sandbox here.
Total posts : 45366The due diligence has been done. It works. His information on the website shows that at 62 feet high, the AM broadcast antenna is equal in gain to a 1/4 wave tower w/radials. Go higher, and it exceeds that of the tower.
BTW, the author and inventor is NOT suggesting these antennas are the be all and end all, rather, that they have a specific purpose, where you get MUCH higher gain than otherwise possible from a physically small antenna.
I build my own 5 ghz slotted waveguide antennas, and never cease to be utterly amazed at thier gain. a 1 by 2 inch stick of aluminum tube under 2 feet long, and it has higher gain than a sizeable grid dish.
His discussion of how and why it works makes sense to me. Oh, and being close to ground losing “gain” also makes sense, just read how the antenna pattern changes.
Still, one of these sitting 20 feet up would absolutely blow away the 10 foot anything else.
The question is whether the FCC would balk at the phase shift inductors necessary to make the antenna work. I would like to see a good rf guru’s comments on how to build the phase shift in a physically compact space.
Total posts : 45366markk wrote: BTW, the author and inventor is NOT suggesting these antennas are the be all and end all, rather, that they have a specific purpose, where you get MUCH higher gain than otherwise possible from a physically small antenna.
That is their claim. But has it been confirmed by qualified professionals with calibrated field strength meters, using the same input power to the E-H as to a standard 1/4-wave, broadcast-type monopole when the groundwave of both is measured about 1 km away in the horizontal plane?
If the E-H proponents published such provable and repeatable data then that would take care of all the doubters.
If they can’t or won’t, then this should be an important point to anyone considering this design, as part of their own due diligence.
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Total posts : 45366yes, it has been confirmed by qualified professionals measuring field strength. They actually put one of these up quite close to a standard am broadcast antenna, and operated an AM transmitter under an FCC sanctioned test.
BTW, the author himself is a qualified professional. But he has confirmation from a qualified third party as well. He has a long .pdf on the site that details the testing and results, and also his presentation to the NAB on that site.
Total posts : 45366Could you please refer us to such measured data, including the techniques and conditions used to produce it?
The EH website has no PDF document with field strength measurements, or field strength comparisons to a 1/4-wave broadcast-type monopole that I could find.
Without publicly available proof of performance, all people will have to consider are the claims of E-H proponents.
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Total posts : 45366I haven’t any interest in arguing with you. If you find it threatening to your peace of mind in some way, that some oddball antenna design allows a physically small antenna, then don’t believe it, it really won’t matter. However, nothing you can say will actually change whether it works or not, and even if I believe the inventor, it really has no detriment to your well being. In other words, I don’t care if you accept the data measured and provided or not, and it would probably not matter how much you doubted, it won’t influence the audience.
As far as the rest of us are concerned, however, it would be nice to hear from someone who’s dealt with the FCC and how they view tuning inductors for matching to small physical length antenna. However, before I attempt to build a simple homebrew one, I’d like some kind of POV in dealing with an FCC inspector, should it be necessary.
Thanks
Mark
Total posts : 45366I don’t care if you accept the data measured and provided or not,
The data could be acceptable to everybody if it exists and has been published. A link or reference to that is what I’m hoping you can supply.
Like most, I expect, I’d like to learn more facts about the E-H.
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Total posts : 45366Well, read, specifically, through the two pdf’s that make up the presentation to the NAB. His introduction pdf, which is long, and the presentation, which is short, tell you a lot.
The presentation names the individual who did the testing and describes the test conditions and the results, for AM broadcasting test.
I’d like to build one, but I need someone with more experience, to help me create the antenna and measure the results. I can handle the physical construction, no sweat. I could probably muddle through the inductor design, too, but I’d prefer not to sabotage my efforts with my now rusty and mostly forgotten half-knowledge 🙂 I intend to build it using fabbed up stuff from Home Depot to make a demonstration antenna, and compare how it works to a simple long wire. I have been away from the electronics stuff for so long that I do not remember the math or even all the terminology anymore. Many years ago in my youth, I studied up to pass my Ham Radio licensing, and ended up being stuck at the code test. Despite many many hours of study and effort, I proved to be utterly deaf to decoding Morse. Instead, I went on to other interests.
Even today, I think I could pass the no-code test with minimal study. I just can’t find the time to do it, as to do so means considerable travel, and my interest in being a licensed ham operator is no longer very high. The “wow” factor’s no longer there, sadly.
I was thinking of building an SSTran 3000 kit for the trial. Anyone gotta spare they want to part with cheap? 🙂 No? heh, didn’t think so.
Total posts : 45366Mark wrote:Well, read, specifically, through the two pdf’s that make up the presentation to the NAB. His introduction pdf, which is long, and the presentation, which is short, tell you a lot. The presentation names the individual who did the testing and describes the test conditions and the results, for AM broadcasting test.
Thanks, but I have read those PDFs already, and they don’t have any field strength measurements, or even calculations of field strength produced by an EH at any elevation above the ground.
The technical numbers shown there appear to be calculated design parameters for components of an EH antenna — not its measured radiation performance.
Its great if you want to experiment with any kind of antenna, and I don’t want to discourage/anyone you from doing that. I’m just trying to supply a little perspective from a practical engineering background for you to consider, if you wish to do so.
As to how an FCC inspector would view a Part 15 AM, EH antenna — that will depend on the inspector. I have read documents from highly placed FCC officials stating that even the length of wire in a conventional loading coil used with a linear radiator (whip) is part of the total 3-meter length of 15.219. Other Part 15 users report no problems with that.
So essentially, you are on your own as far as risk vs reward :).
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Total posts : 45366I guess I’m curious as to why you’d be skeptical. Some people just don’t believe anything until it’s proven in their presence, if that’s you, no problem.
Otherwise, he has obviously built and tested them himself, seeing as how much of the notion of how they work is his own invention/design.
I have no cause to disbelieve, not even doubt, what he says. BTW, did you miss the pictures in the presentation of his antenna and the broadcast AM antenna in the background, and the commentary about how the testing procedure, and how they even made sure that soil conditions would be the same?
It would seem unlikely that the FCC would be disturbed by putting the matching LC network inside a metal box with the transmitter board. I think it would be even more likely to pass muster if we can figure out how to make it all physically smaller…
Total posts : 45366markk wrote: I have no cause to disbelieve, not even doubt, what he says.
No problem, then, if all it takes is personal faith in the undocumented and unproven statements of those OEMs and supporters promoting “EH” (and “CFA”) antennas.
Hope those doing so will be able to convince their FCC field inspectors that such an antenna configuration complies with the FCC rules applicable to their class of service.
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Total posts : 45366It seemed strange to me that the real proof numbers were not presented anywhere,like maybe they are trying to protect some information. I wonder if they have applied for a patent or are otherwise trying to profit from their design? I think so…
It is also VERY INTERESTING that the FCC DID NOT approve this antenna for licensed broadcast use. Read into that what you will. As for me,like Rich,I remain skeptical about their claims. I could embrace the concept if the real proof was there for all to see. It is not.
Regards,Lee
http://www.freewebs.com/wilcomlabs/index.htm
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