+++++++++++++++++++++ Originally treated as an Early April Fools joke, this compromise antenna seems to work, but is very much a compromise... +++++++++++++++++++++ ate: Fri, 29 Mar 2002 21:25:16 -0500 From: Steven Weber To: qrp-l at lehigh.edu Subject: [123552] EH and 20M contest Amazing, couple hours into the big 20 M SSB DX contest and snaged 20 of the big guns so far, using the tiny EH antenna and 30 watts. I wouldn't trade this for a 3 element yagi up 66 ft, or any other "real" antenna, but considering it's made with aluminum foil and some duct tape, and only a friction connection between the wires and the foil, I'd say that's pretty good. I saw some thin sheet aluminum at the hardware store recently, I think I'll go over there tomorrow and get some to rebuild this thing a bit more solidly. I'm almost sold on the darn thing... 72, Steve, KD1JV "Melt Solder" White Mountains of New Hampshire http://www.qsl.net/kd1jv/ +++++++++++++++++++++ From: "W2WU" To: "Dave Benham" , "Low Power Amateur Radio Discussion" Subject: [123560] Physically small antennas Any physically small antenna represents a compromise. Narrow VSWR bandwidth is one compromise. Why not introduce a conjugate match using an ATU to overcome this limitation? Virtually all EH antennas presented are mono band ... it appears we are seeking a multi octave EH antenna. 73, Ron W2WU ----- Original Message ----- From: Dave Benham To: W2WU Sent: 29 March, 2002 18:12 Subject: Fw: Worlds smallest 80 meter antenna > 73, > Dave K8TRF > > ----- Original Message ----- > From: Karl F. Larsen > To: Low Power Amateur Radio Discussion > Sent: Thursday, March 28, 2002 10:40 AM > Subject: Worlds smallest 80 meter antenna > > > > The EH style of antenna can be made at home on easy to find > > materials. I decided to make one that works on 80 meters. Here is what you > > need: > > > > 5 feet of 8 inch diameter PVC sewer line. > > A big roll of aluminum foil. > > A lot of #18 magnet wire ( 80 turns on an 8" diameter form) > > Some RG-58 coax for a feedline. > > A wooden plateform to hold the 8" pipe vertical > > > > The web page that speaks about this antenna is at: > > > > http://www.qsl.net/w0kph/ehtest.html > > > > and you can get all the details from this web page. > > > > For people living in condo housing who feel that getting on 75 > > meters is not in the cards, think again. This antenna works fine and you > > will get out as well as you did with a dipole 130 feet long. > > > > The problem with this antenna is that it has a very narrow > > frequency range for less than 2 to 1 SWR. I suggest that it's easiest to > > tune up using the MFJ antenna analyser. > > > > -- > > Yours Truly, > > > > - Karl F. Larsen, k5di at arrl.net (505) 524-3303 - > > http://www.zianet.com/k5di/ > > +++++++++++++++++++++ : From: Karl F. Larsen [SMTP:k5di at zianet.com] : Sent: Thursday, March 28, 2002 4:39 PM : To: Low Power Amateur Radio Discussion : Subject: The EH Theory and short antenna : : : Some of you have decided this is an April Fools joke. You can rest : assured it's not. But since your far to lazy to bring this up to read I am : sending you the theory of the EH antenna so, if your education is a bit : above High School you can follow this GREATLY simplified presentation. : : Because it doesn't look like a typical Ham antenna does not mean : it doesn't work. In fact I built one of these while in college at New : Mexico State University in 1959. So read this with care and you too will : be convinced. : : ----------------------------------------------------------------------- : THEORY OF THE EH ANTENNA : : Before you read this, please be in a frame of mind to accept : something new about antennas. This does not contradict any theory relative : to antennas you are familiar with. It does not contradict any basic laws of : physics. What it does do is turn back the pages of history to gain a better : understanding of the fundamental cause of radiation as contained in : Poynting s theorem. With that understanding, we can apply those principles : to an antenna. This results in a way to look at antennas in a way that has : not been done previously. In fact, it is a very radical departure from : conventional "wire" antennas concepts and leads us down a path that results : in very small, very high efficiency antennas with very wide bandwidth and - : - - sorry, I am getting ahead of the story. : About the same time (1880 s) as Heinrich Hertz developed the concept : of resonant wire antennas (1/4 wavelength, 1/2 wavelength, etc) while : working as a college Professor and noted Physicist in Germany, John Henry : Poynting, also a college Professor and noted Physicist, but on British soil, : developed the concept that all radiation, including light waves, is based on : a fixed relationship between electric and magnetic fields. The following are : Poynting s principles from his theorem. They are written in more complex : terms in his theorem, but this is what they mean to a Ham: : a) The Electric (E) field and the Magnetic (H) field must occur : simultaneously, : b) They must be at right angles to each other, : c) they must have the same curvature, : d) they must have a ratio of 377 ohms (same impedance as free space) : when the E field is measured in volts/meter and the H field measured in : ampere turns. : It took great minds many years to figure out how the Hertz antenna : satisfied the Poynting theorem. The approach here is sort of backward - it : starts with the Poynting theorem and finds there is no need for "resonant" : antennas. : Since Poynting s theorem is still valid after all these years, then : it says all we have to do is get a hand full of each field and we are ready : to go. Actually, what Ted Hart (W5QJR) has done is to use two (2) elements : for an antenna and create the radiation between those elements. Here is how : he does it. If the elements are large, they will have a large natural : capacity between them. When a voltage (from the transmitter power) is : applied to the two plates of the capacitor an electric (E) field will be : developed in the capacitor area between the plates. Also, the current : through the capacitor will develop a magnetic (H) field at right angles to : the electric field. The E and H fields exist in the same space and have the : same curvature. : That would seem to satisfy most of the Poynting theorem, but ---when : current flows through a capacitor, the phase of the current leads the phase : of the applied voltage. Therefore, the difference in phase prevents : satisfaction of the Poynting Theorem because the E and H fields do not occur : simultaneously. Why? Glad you ask. If you draw two sine waves that are 90 : degrees apart, while one is maximum the other is minimum. If they are in : phase, they go through their maximums and minimums simultaneously. So - - : -what does Ted do to fix that problem? He simply put a coil between the : transmitter and the antenna. A capacitor causes the current to lead the : voltage in time phase while an inductor (coil) delays the time phase of the : current relative to the voltage. If you want the antenna to operate on a : particular frequency, then you make the reactance of the coil equal the : reactance of the antenna capacity. Now, the current and voltage are in phase : within the antenna, therefore the E and H fields are in phase, and the : Poynting theorem is satisfied. : But - you have to ask - how do you get the E and H fields to satisfy : the requirement that they have a ratio of 377 ohms? My answer is - that is : beyond the scope of this paper. Just believe me when I tell you that if you : do what Ted says, the coax hooked to the antenna (through a link coil) will : see an effective RF resistance at the operating frequency of the antenna. If : you build copies of my antennas you can get a 50 ohm match with link : adjustment. The development of radiation resistance is evidence that the : Poynting theorem is satisfied and radiation is being produced. The actual : value is dependent on the phase between the fields and the impedance : transformation due to the effective L matching network caused by the coil : and antenna capacity, plus the capacity between the antenna and the coil, as : well as the physical configuration of the antenna. That is a lot of stuff, : but it all comes naturally. : There are various physical configurations that satisfy the criteria : for an EH Antenna. By the way, did you note that the name for the antenna : concept came from the fact that the E and H fields are created : simultaneously and exist in the same space? Ted tried to develop a logo by : putting the E and the H in the same space, but it did not look good and was : too hard to type one letter on top the other. You need to look at Ted s web : site for additional technical information. : I do need to tell you that these antennas are exceptional receiving : antennas. They are very quiet in the presence of man made noise. : I am pleased to present various EH antennas I have experimentally : developed. I will also tell you some tricks I have developed to assist you : in making your own. : : : -- : Yours Truly, : : - Karl F. Larsen, k5di at arrl.net (505) 524-3303 - : http://www.zianet.com/k5di/ : +++++++++++++++++++++ Date: Sat, 30 Mar 2002 05:53:52 -0700 (MST) From: "Karl F. Larsen" To: "Lofgren, Charles" Cc: Low Power Amateur Radio Discussion Subject: [123575] RE: EH Test antenna Hi Charles, please be more explicit about how you made these antannas. How did you tune them to frequency? My copy of the one from the web page is very narrow good SWR range. If your not tuned up the loss can be very high. Your claim of 20-30 DB below a dipole makes your antenna close to a dummy load. Not saying it isn't true, but if it is then your design is not working well. On Fri, 29 Mar 2002, Lofgren, Charles wrote: > A couple of months ago, I made two different versions of the EH--that is, > with different (supposed) phasing networks--and sized one for 30 meters and > the other for 40 meters. I found that in most cases the EH antennas were > about 20-25 dB below the reference antenna on receiving. But I didn't do > any comparisons for different paths/distances. > > The EH antennas were up approximately 20 feet. The reference antenna was a > 40 meter horizontal loop, fed with 300 ohm line and z-match, up about 25 > feet. I judged the performance by switching in and out the 20 dB front-end > attenuator in my QRP+, and/or a resistive SWR bridge for which I knew the > attenuation--along with an A-B switch for the antennas. (A two-handed > operation.) And interpolation with ears and s-meter. Really exact! > > My results were in line with several I saw mentioned on the > rec.radio.amateur.antenna newsgroup. I'm no scientist or engineer, but the > discussion there seemed to me to pretty well discredit the theory of the > design, short of the inventors coming up with replicable test results > showing a lot better performance. > > Still, if I'd had a few instances of the sort Steve mentions in the case of > the DX, I might have played further. But I quickly lost interest. > > Charlie Lofgren, w6jjz > > > > -----Original Message----- > > From: Steven Weber [mailto:kd1jv at moose.ncia.net] > > Sent: Friday, March 29, 2002 2:13 PM > > To: Low Power Amateur Radio Discussion > > Subject: EH Test antenna > > > > [snip] > > > Well, the thing does actually work. I just made a contact > > (21:45 Z) with > > HE3MY (5X5) and Z33Z (5X4) with it. 30 watts SSB though. > > State side signals > > are way down compaired to the dipole on the roof, but DX > > stations are about > > the same with either antenna. The vertical polerization of > > the EH no doubt > > makes the difference. The appex of the roof mounted fan > > dipole is maybe 10 > > feet higher than the top of the EH antenna. > > > > So, this little thing just might be a half decent DX > > antenna. Will have to > > tune it down lower in the band and see what it does with 5 > > watts CW. I'm > > not quite a beliver yet, but these quick results are encouraging! > > > > > > 72, > > Steve, KD1JV > > "Melt Solder" > > White Mountains of New Hampshire > > http://www.qsl.net/kd1jv/ > > > ########################################### > > This message has been scanned by F-Secure Anti-Virus for Microsoft Exchange. > For more information, connect to http://www.F-Secure.com/ > -- Yours Truly, - Karl F. Larsen, k5di at arrl.net (505) 524-3303 - http://www.zianet.com/k5di/ +++++++++++++++++++++ Date: Sat, 30 Mar 2002 08:58:19 -0700 From: "James R. Duffey" To: Subject: [123581] Short Antenna Efficiency (long) I found that the material posted by Karl (K5DI) on the EH antenna to be inadequate to explain the good performance claimed for it. I do not blame Karl for this, he was merely bringing the material to our attention. I should mention that I am somewhat handicapped by having both undergraduate and graduate courses in electromagnetics. :^) As others have pointed out, there is a wealth of information on the web complaining about the deficiencies of this explanation, so I will not repeat my concerns here. I find the actual construction details of an EH antenna described on W0KPH's web page to be informative. There is enough information there to calculate the efficiency of this antenna. The efficiency of an antenna is given by: Radiation Resistance Efficiency =__________________________________________ Loss Resistance + Radiation Resistance Kraus in Chapter 5 his book "Antennas" shows how to calculate the radiation resistance for a variety of antennas, including electrically short ones. For a very short antenna with a triangular current distribution, which the antenna described by W0KPH is, the radiation resistance is given by: Radiation Resistance = 197*(L/wavelength)**2 Now this is calculated by integrating the Poynting vector over all space in the far field so it should be consistent with the EH theory. Now the antenna described by W0KPH is about 14 inches long, so L/wavelength is 0.018. This makes the radiation resistance 0.064 Ohms, a small value indeed. The main contribution to loss resistance is from the 22 gauge wire used in the coil. There appears to be 88 inches of 22 gauge wire in the antenna, which will have a resistance of about one Ohm at 14.06 MHz. There is also the resistance of the aluminum foil which is about 0.06 Ohms. So the efficiency is efficiency = 0.064/(1 + 0.06 + 0.064) =0.057, call it 6% This corresponds to 12 dB down on a 100 % efficient antenna. For a dipole made from 22 gauge wire, the radiation efficiency is 73 Ohms, and the resistance of the wire will be about 4.55 Ohms for an efficiency of 94%. Based on these numbers, I would not say that the EH antenna has the potential to get out as well as a full size dipole. These numbers are consistent with Ed Hare's observations of the EH antenna being 4 to 5 S units weaker than an inverted Vee. The efficiency is still better than Charlie measured, but still poor by most standards. To put the efficiency in perspective, it is about equal to a 160 M mobile antenna based on a base loaded 8 foot radiator. So I would say that contacts could be made with the EH antenna on 20 M, but I do not believe one would be very happy with it after using a bigger antenna for 20 M, say a Hamstick or Hamstick dipole. I have neglected contact resistance and ground losses, and this could account for even more loss. I am somewhat at a loss to understand how this antenna has a 50 Ohm feed point impedance unless there are other large losses elsewhere in the system. If someone can measure the bandwidth of the antenna, the loss resistance can be calculated more exactly, and a more exact number for the efficiency obtained. Now there are some things that can be done to improve the efficiency. If end loading is used instead of center loading, the current distribution on the antenna will be essentially uniform and the radiation resistance will increase to 0.25 Ohms This can be easily done by placing large discs at the end of the antenna. Large Pizza pans should be a good start. This should be consistent with the EH theory of a capacitive antenna. Add inductance between the ends of the aluminum foil and the disk to bring the antenna back into resonance. Using a larger diameter wire for the inductor should help. The model shown at W0KPH's web site has no way to prevent feed line radiation. I would add a choke balun at the feed point. Of course, if the feed line is radiating, it is likely to be a more efficient radiator than the antenna it is feeding. I hope that I have not muddied the waters with this simplistic explanation. I would welcome a similar explanation, using sound electromagnetic theory from an EH antenna proponent that shows how a significantly higher efficiency is obtained from this antenna than what I have calculated above.. There is no free lunch. - Dr. Megacycle KK6MC/5 -- James R. Duffey KK6MC/5 Cedar Crest, NM DM65 +++++++++++++++ Date: Sat, 30 Mar 2002 12:40:47 -0500 From: Steven Weber To: qrp-l at lehigh.edu Subject: [123600] More EH observations Hi there antenna gurrus. So, last night I made 23 contacts, in about as many different countries, with the silly little EH antenna on 20M durring the WPX contest. (30 watts) I was constantly being stomped on by other stations and those poor fellows on the other end definatly had to struggle some to hear me. Occasionally, I'd flip to the dipole and get through quickly, where I'd been calling and calling on the EH. I don't have a choke on the end of the coax, so who know how much feed line radiation is a factor. I just went to the hardware store and bought a roll of 6" x 10' aluminum flashing for $3.29 and will rebuild the antenna this afternoon with that instead of the foil. Maybe I'll add some ferrite cores to the end of the coax while I'm at it, but I'll have to take the PL-259 connector off the end first. I've got some big cores that came off video monitor cables that should work okay. I noticed I get different readings on the MFJ analyzer depending on if my hand touches the metal case or not, so not sure which is the real reading, or what that means. Nothing good, I'm sure of that! Maybe the choke will help with that. This is with the antenna set up out back and using the analyzer in the shack. Okay, so these aren't very scientific tests. A properly loaded 6" clip lead might work just as well. So might a 100 watt light bulb,10 feet in the air at the end of the coax. (might have to try that, hi) If you can radiate any kind of signal, chances are good those 20M contest stations can hear it. You know thier using real antennas! Getting anyone to talk to you under casual, non-contest situations maybe quite a different story. I have a feeling using this EH antenna on lower bands woudn't be nearly as effective. The 20 M and higher bands are so much more forgiving to inefficent antenna designs. The bottom line is this thing does indeed sort of work, but it's definatly no super antenna. Fantastic claims of performance are just that, fantastic claims. You ain't goona be busting pile-ups with this thing! But it's cheap and easy to build and maybe suitable where you need a very small antenna - but it does have to be out in the clear as much as possible to work. Using it inside your condo/apartment may not work too good. If James Duffey's shirt cuff calculations of efficiency are in the right ball park, you may want to run a lot more power than 5 watts into it! Okay, I'm going to rebuild the antenna with the flashing, add the choke to the coax and see what happens later this afternoon and evening. Film at 11. After that, it most likely will be scraped. 72, Steve, KD1JV "Melt Solder" White Mountains of New Hampshire http://www.qsl.net/kd1jv/ ++++++++++++++++++ Date: Sat, 30 Mar 2002 14:07:18 -0500 From: "Paul Christensen" To: "Low Power Amateur Radio Discussion" Subject: [123604] Re: More EH observations It appears you can now purchase a variant of the EH from GAP Antenna Products. Take a look. How would like this as your only "trail friendly" antenna? http://www.gapantenna.com/superc.htm Anyone want to be an early adopter? -Paul, W9AC +++++++++++++++++++++ Date: Sat, 30 Mar 2002 17:29:39 -0500 From: Steven Weber To: qrp-l at lehigh.edu Subject: [123614] Theory triumps! So, I rebuilt this EH test antenna with the flashing, solder lugs and #14 wire for the coil. Hey, what's this? Can't get nearly as good a match as the quick tin foil jobbie, with the connecting wire just wrapped under a layer of foil. It seems without all the losses of sloppy construction, this thing doesn't work! Isn't that what you guy's were saying? It does look like this "EH" antenna, at least the version shown by W0KPH, is a less efficent way of building an Isotron. At least the Isotron has a much larger radiating surface. I gave up on the idea and decided to try making it into a classic short, center loaded dipole. I cut a couple of 1 foot lengths of the flashing, wrapped them around a piece of 1 1/4" ID PVC (since the 6" width of the flashing woudn't quite go all the way around the 1 1/2" pipe), wound some loading coils between the flashing and man, now the tuning is sharp! We'll see if we can double our score with this version tonight. Then it's back to a *real* antenna. Enough with wasting time and matterials 72, Steve, KD1JV "Melt Solder" White Mountains of New Hampshire http://www.qsl.net/kd1jv/ +++++++++++++++++++ Date: Sat, 30 Mar 2002 15:39:40 -0700 (MST) From: "Karl F. Larsen" To: qrp-l at lehigh.edu Subject: [123617] GAP Short antenna It will be interesting if their patent works. I doubt that anyone will change it but they can. They don't call it a EH antenna but it's what they have been calling them in other places. And they have been very careful not to say how well they work as radiators. They say they hear as well as a 1/4 wave vertical. Well that's not all that good since a vertical picks up all the noise. When they say how they did in a Fox Hunt, I'll be more interested. -- Yours Truly, - Karl F. Larsen, k5di at arrl.net (505) 524-3303 - ++++++++++++++++++++++ Date: Sat, 30 Mar 2002 19:09:55 -0500 From: Steven Weber To: qrp-l at lehigh.edu Well Gang, I made a half dozen contacts with the 2 foot center loaded dipole and it was still a struggle to be heard. Then I though, hey, why not set up the 20M tent pole vertical? So I did and man, what a difference - now I can be heard! Might have to throttle the rig back down to 5 watts and make those guys work again for my one lousy point So, the conclusion of all this foolisness is what everyone knew all along - well, most everyone- sure short antennas work, but if you can use anything else - anything at all, by all means, please do so! 72, Steve, KD1JV "Melt Solder" White Mountains of New Hampshire http://www.qsl.net/kd1jv/ ++++++++++++++++++ Date: Sat, 30 Mar 2002 18:25:04 -0700 (MST) From: "Karl F. Larsen" To: Steven Weber Cc: Low Power Amateur Radio Discussion Hi Steve, I'm sort of the start of the EH antenna and it played out as a hoax for the most part. So let me again say if you want a really good pedestian antenna go to: www.qsl.net/w3ff and get his instructions for an end loaded dipole that I have on a 10 foot painters foldable pole that I used for last summers's Fox Hunt. In the front yard with a Argonaut 509 I worked all the Foxes I tried for! It's a great antenna that fits in a small box and can be back packed. On Sat, 30 Mar 2002, Steven Weber wrote: > Well Gang, > > I made a half dozen contacts with the 2 foot center loaded dipole and it > was still a struggle to be heard. Then I though, hey, why not set up the > 20M tent pole vertical? So I did and man, what a difference - now I can be > heard! Might have to throttle the rig back down to 5 watts and make those > guys work again for my one lousy point > > So, the conclusion of all this foolisness is what everyone knew all along - > well, most everyone- sure short antennas work, but if you can use anything > else - anything at all, by all means, please do so! > > > 72, > Steve, KD1JV > "Melt Solder" > White Mountains of New Hampshire > http://www.qsl.net/kd1jv/ > -- Yours Truly, - Karl F. Larsen, k5di at arrl.net (505) 524-3303 - http://www.zianet.com/k5di/ +++++++++++++++++++ Date: Sat, 30 Mar 2002 20:02:17 -0600 From: "George, W5YR" To: jamesd1 at flash.net Cc: Low Power Amateur Radio Discussion Subject: [123640] Re: Short Antenna Efficiency (long) Thanks for the work, Jim. Your results ring true for me. Unfortunately, the EH inventor argues to the contrary in that he asserts that the radiation resistance of the EH is 377 ohms which is a perfect match to "free space" which is why the efficiency can approach 100% very closely - they use "over 90%" in their claims in order to be "conservative." Your mumerical approach would confirm that *IF* one could verify the actual radiation resistance of the antenna. Hart claims that the unique method for generating the E and H wave components and then combining them optimally accounts for the theoretically perfect radiation resistance value and the resultant efficiency. For my money, I go with your analysis - far less smoke and mirrors your way! <:} After months of intense discussion on r.r.a.a. no one, including the EH supporters, has been able to present any semblance of a factual theoretical basis for their claimed performance. Somehow we keep getting back to this requirement for the current through a capacitor and the voltage across it to be in time phase for EH wave generation . . . 73/72/oo, George W5YR - the Yellow Rose of Texas +++++++++++++++++ Date: Sat, 30 Mar 2002 21:13:19 -0500 From: Bruce Muscolino To: jstamper at shentel.net Cc: Low Power Amateur Radio Discussion Subject: [123646] Re: Battle of the shor antennas, final results It should be clear to everyone that there is a lot of controversy about short antennas. From personal experience I can say the only antennas that seem to work well are the traditional designs. Yes, I am sure there are new and exciting ways to interpret Maxwell, but the old tried and true designs work best in my opinion. I have built two short antennas and had very good results with both of them. Some design guidelines that came from my work are don't bother to try to shorten the antenna by much more than 60%, Yes, shorter antennas can be made, but they are a bear to tune up and have such small bandwidths as to be unusable! My 40 meter helically wound dipole was about 7 meters end to end. My 20 meter helically wound dipole was 3 meters end to end. They were both mounted inside and gave a good account of themselves. I's stick to something like a dipole, it could be helically wound or it could be the W3FF design. I think you'll find them easiest to put up and use! Sorry, MAGIC ANTENNA'S don't work around here! 73 +++++++++++++++++++