+++++++++++++++++++ See Also Antenna_Rogers-Dobbins_Folded_Conical_Helix +++++++++++++++++++ Date: Wed, 10 Apr 2002 19:13:42 -0500 From: "Stuart Rohre" To: "Steven Weber" Cc: Subject: [124378] Re: Helical Conical working Message-ID: <001501c1e0ed$bd58a9e0$4e100a0a at rohredt2000> Steven, those are good basic questions on the helical conical. OK let me see if I can start at the major points. I just posted an answer to Joe Vicente and the list, which will cover most of your points. Please read that post, and here are more details: You asked why a cone, not a cylinder? Well, the whole key to getting good radiation efficiency, and to not block one part of the monopoles by others, is the cone and the slant winding. As you will notice doing one, you have the outer no. 10 wire in the clear, to radiate the whole way. It is clear on three sides, since the slant of the cone, moves each turn out from the others as you go toward the wide end. You get a short antenna, as a cone surface can contain the four quarter wave elements in a shorter axial height than a full size monopole, but the primary advantage is moving each successive turn of the monopole out where it can radiate on three sides. It would only have one side to radiate on a cylinder. The adjacent monopole would interact more. Now, important point. The feed end is the small cone end, and the no. 10 wire(s) goes to coax shield and the ground plane junction, (or radials junction, if used in place of plane). The small end no. 12 wire(s) all solder together above the coax connector, and you leave one wire longer to make the junction with the center of the coax connector. One of the issues to explore is would it work if you had the smaller wire as the outer wire, I have to ask Rogers if he modeled that. To get a match to 50 Ohms, you HAVE to use no. 10 outer cone wire, and no. 12 for inner cone wire, ie each pair has to have one 10, and one 12 beside it. That sets up the RF impedance transformation needed. And to further match to 50 ohms, there have to be four monopoles, each a pair of one 10 and one 12 gauge. Of course, you can get close with other geometric combinations that preserve the transformation ratio. But, you have higher loss resistance with smaller wires. The type of insulation on the wires is bound to be a factor, I think, but the 10m prototypes at the 13 inch axis height, (12 inch slant height) have used, to date, thick plastic insulation on the no. 10, and magnet wire no. 12 with enamel insulation. (Formvar). Don't worry, all that other insulations will do is affect the resonant length of the monopole wire pair, so that is why I say start with length longer than a quarter wave, trial wind it up the cone, and then check resonance, and cut to band segment you want. I hope you can lay on one monopole, and cut it to resonate, and replicate three identical and still end up close to where you want to be. Many things to still nail down, so it is an experimenters heyday! OK, let us revisit winding on elements. Wind on first turn, lets say start with fold end of monopole one, at wide end of cone at the "North" position. As you spiral up keeping the pair as close to horizontal at the supports as you can, you will get one turn completely around. Now 12 inches around the 16 inch end, (quarter way around the 48 inch circumference) start with fold end of monopole two. That would be at say "East" on the circumference circle. Wind same direction as you went with monopole one, and beside turn one of monopole one, (above it on cone surface) when you reach it. Now advance 12 more inches at the 16 inch end, and start monopole three, turn one. Going in consistent same direction as first two, wind until you pass turn one of no. two, and then turn one of no. one, and turn one of no. three monopole is going to be higher on slant height than turns one of monopole two, and below it monopole one. Hope that is clear, the lines lay next to each other, first turns next to first turns until four are done, and then the second turn of first monopole gets laid up the slant of each support, then the second turn of monopole two, and so on. Don't worry about the inconsistency in spacing of smaller gauges; that will be true if you wind a cone that is only 6 inches high, and we can only suggest prestretching the wires, to get them perfectly straight which is best efficiency, but we are getting 60 per cent with a two monopole 6 inch high model for 10m now, with terrible wire straightness, and done as a pyramid rather than a cone. It just seems to work no matter what. But, for ease of comparing results, you will do better with four monopoles, and make each a nice parallel line by stretching it first. On the tiny model, we did group the pairs with nylon ties in between fiberglass triangles which provide the slant surfaces upon which to drill the spacing holes. The jury is still out on how sloppy you can be and have it work as well as Bob's model. OK back to planarity: All the no. 10 wires are on the 'outer cone' surface, all the no. 12 wires are on the imaginary 'inner cone', if that makes sense. Refer to starting sequence above for more clarity. And remember, turn one of monopole one, will be lowest on wide part of cone, then turn one of monopole two higher, turn one of monopole three further up toward narrow end, and finally turn one of monopole four. Then you continue up the slant height in same order until narrow end is reached, where the coax connector is fitted. Each folded monopole turn is made up of side by side wires space 3/8 inches. It is a bit difficult, but in thinking about it, starting at the wide end should help keep wire pairs straight. A trick the student builders are doing now is marking hole pairs with felt tip marker: Red for first monopole, Blue for second, Black for third, and no mark for fourth. Thus the hole pairs are drilled on the slant height, and color coded R, B, Blk, Blank, and Red again, Blue, and so on up the slant. This is done on each support face where you drill wire hole pairs to support the parallel lines. Invert the cone, to have small end down for use, closest to ground plane for operation. That is why I have switched my mechanical design to two interlocked rectangles of insulating material, upon whose diagonals, I can drill mounting holes for wire pairs, to keep the pair parallel to ground plane edge of the support insulator. The 16 inch diameter end is uppermost above the ground plane in use. It will not work if wrong end is up. IE not efficiently. We have used the same size ground plane for all models due to application we are going for. But, Bob Rogers states that a radial plane could be substituted, and as a start, some of the standard radial conventions could be tried. I would say you could try radials of a length to have 0.05 wavelength between the outer ends, (that would be 30 quarter wave radials), but 16 radials might be a good start. It is easy enough to have a ring at the coax connector and clip on hook up wire radials until you see no further effects. This antenna has a wide SWR bandwidth, and it may be tough to see much change at the feedpoint. At this point, since we have a good copper conducting screen, it is just a SWAG to say 16 radials would be sufficient. Another area to explore,and should they be quarter wave? Probably not if placed on top of ground. They should be longer than the antenna is tall, but how much more is needed is open to testing. Hope I have covered all the questions between the two postings today for now. Let me know how further experiments turn out. 72, Stuart K5KVH ++++++++++++++++++++ Date: Wed, 10 Apr 2002 21:09:08 -0400 From: lenny wintfeld To: "[Low Power Amateur Radio Discussion]" Subject: [124384] Helical Conical Antenna Hi Has someone worked up a diagram of this antenna? The "word picture" descriptions of it (no matter how detailed) so far, have got me stumped. Sounds like a fine thing to try for field day. Thanks! 73, Lenny W2BVH ++++++++++++++++ Date: Wed, 10 Apr 2002 20:43:26 -0500 From: "Stuart Rohre" To: , , "Torell Kent-P12255" Subject: [124388] The Conical Antenna monopole wires and the marble track Hey, this is a great group! Thanks Kent! Kent Torell has come up with the best visualization aid yet. The pair of monopole wires that go around the conical shape describe two wire guides like a marble track. If you placed a marble at the wide cone edge, upon A MONOPOLE wire pair, it would spiral down to the narrow end of cone upon the track formed by the no. 10 wire and the no. 12 wire of each monopole. Thus, to continue this analogy, there are four tracks down the face of the cone, one below the other after the first quarter turn. That is, the tracks starting position would be at the wide end, at North, East, South and West looking down on the wide cone end as a compass circle. Hope this aids those building copies. Stuart K5KVH +++++++++++++++++++ Date: Sat, 13 Apr 2002 22:42:17 -0400 From: Steven Weber To: qrp-l at lehigh.edu Subject: [124669] Pic's of Helical Conical antenna Message-ID: <3.0.6.32.20020413224217.007bdbb0 at mailhost.ncia.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" For those of you who can't get a mental picture of this antenna, I just put a couple of picutres of my version of the Helical Cone antenna up on my web site. It's not linked from the main page, so use this direct link: http://www.qsl.net/kd1jv/cone.HTM NOTICE! It's almost a meg of pixtals between the two photo's, so if you have a slow dial up, it will take 5 minutes or more to down load. The pic's were taken this afternoon by Seab, AA1MY, who took time out from the contest to shake his head at this silly antenna. We actually made two contacts with it too, I'll let Seab tell you about that later. Might have made more, but he already worked most everyone we could hear with it. The antenna has only one element, as when I tried to add a second one, the return loss went all to heck. I think I need a more obtuse triangle, so the extra elements aren't so nearly directly above each other. Not clearly shown are the three 16 foot radials, which are important to get any kind of match. 72, Steve, KD1JV "Melt Solder" White Mountains of New Hampshire http://www.qsl.net/kd1jv/ ++++++++++++++++++ Date: Mon, 15 Apr 2002 18:27:51 -0500 From: "Stuart Rohre" To: "Steven Weber" Cc: Subject: [124831] Re: Improved frame for Folded Conical Helical Antenna Message-ID: <001801c1e4d5$29b2df80$4e100a0a at rohredt2000> Steve, although the intense field is highest at the wide opening of the cone, the polarization over a ground plane is vertical, with small horizontal component. It will not work properly with large end down, and I am puzzled by the observation with it 90 degrees off horizontal for large cone end, unless it was because it was indoors. (And was that without a ground plane?) It is an integrated antenna, one part does not good without the ground plane by the theory they are modeling. With the 10 and 12 wire, do you have the 10 on the outside of the 12? and spaced 3/8 inch? Sounds like you are making progress. The axis between the two wires in one line lies horizontal (parallel) to the ground plane. You can get a more sturdy support with two notched rectangles as the spaces for the wire. You have greater than 16 inch wide forms, as the bottom of the cone shape with the 10 wire outside should be at the 16 inch diameter. IE, 8 inches from the vertical axis each way. Without a cheap source of fiberglass, I am looking at Masonite for a permanent model support, if I can weatherproof it adequately, (edges and faces.) Of course, this antenna will not have the capture area of a full size dipole, but its purpose is to get good efficiency on the HF bands, in spite of low height, and small diameter. What would be a great comparison would be to the EH, or the Isotron designs. Oh yes, do run it outside. If you want to dispense with aluminum screen, just use those wrong wire sizes as radials. A minimum of 16 to start, 30 seems to be the ideal based on the 6 foot square ground plane Rogers used. In fact, there is another great test, run it with both types of ground alternately. I would make the radials at least the size of the original ground screen plane, but you might experiment with full quarter wave, and drop back to 1/8 wave, etc. Lots of room to play with concepts. 72, Stuart K5KVH +++++++++++++++++++++ Date: Tue, 16 Apr 2002 17:55:33 -0500 From: "Stuart Rohre" To: , , , Subject: [124917] cone Antenna PHOTO of how to wind them Hi Folks, Thanks to Steve Weber for his prototype photo of the folded conical helical antenna on the link below: This is with the one monopole mounted, and ready for more to be wound. I really appreciate his doing this intermediate version, as the four monopole version gets the turns so close together, a picture does not show clearly what is going on. It is not too clear with the insulation on the wires and same color; but the wire toward the slant edge is the no. 10 here, and the wire toward the central axis in each turn, is the no. 12. At the bottom, the no. 10 goes to coax shield, the no. 12 to coax center lead. A few notes about this pair of pictures. The Cone will not normally be used in this configuration, it MUST be over a radial plane or ground plane screen at least 6 feet square to work properly. The wide end of cone must be up and small end closer to ground. The Monopoles must start witht the short, (fold) at the wide end. This wide end is 16 inches diameter for either 10m model or a 20m model. The vertical axis where the coil supports join should be 13 inches high. The slant length of the supports over which you drill holes should be 12 inches long first turn to last. The end of the monopole at the narrow part of cone must go to coax without a balun, and the coax connections must go straight off the narrow end of cone and through the ground screen before making a right angle turn as shown here. Remember the wide end is parallel to ground, and ground plane. Notice the holes predrilled in between turns for the second monopole to be threaded. In a similar manner, for optimum performance and match to 50 ohms, you should have one turn pair of the first monopole, then allow 3 pairs of holes for the other monopoles. Thus, when all are threaded, you have a pair terminated at the top of the cone wide part, and then wind the next pair starting 90 degrees from the first start, and so on, so each succeeding pair is below the pair above, pair 1, 2, 3, 4. Since they start 90 degrees apart around the wide part, they should end 90 degrees apart around the narrow end, but you are going to solder all the no. 12's to coax center lead, and solder all no. 10's to coax shield and ground screen, (or radials). Now that you have a picture, if you have any questions, please write: http://www.qsl.net/kd1jv/cone.HTM +++++++++++++++++++ Date: Wed, 17 Apr 2002 13:52:02 -0500 From: "Stuart Rohre" To: , "LORONA,AL AA-USA,ex3\"" , Subject: [124973] Re: [TenTec] cone Antenna PHOTO of how to wind them which band? Message-ID: <003f01c1e640$f649c650$4e100a0a at rohredt2000> Well, I do not disagree that capture area is all important to great antennas. But for the condo owner with antenna restrictions, he is never going to see the antenna farms that Tom and I love to build of horizontal Vee beams, rhombics, Double Extended Zepps, and giant loops. This Cone antenna is for the patio or balcony of the apartment/ condo or deed restricted zero lot line homes. It is better than a no antenna, a mobile whip or other attempts to radiate in such a volume. Nothing more nor less than maintaining reasonable antenna efficiency in the face of the obstacles of modern living. Stuart K5KVH ++++++++++++++++++++ Date: Wed, 17 Apr 2002 18:58:36 -0500 From: "Stuart Rohre" To: , , , Subject: [124988] Re: [TenTec] cone Antenna PHOTO of how to wind them which band? URL and testing raised over ground. Here is the photo link published yesterday: "Did you look at the pictures? http://www.qsl.net/kd1jv/cone.HTM" That is the start of one, with one parallel line element wound, and holes drilled for a second. Thanks again to Steve Weber for this shot. Note: In USE, You MUST turn the antenna so that the narrow cone end is against the ground, with ground screen under it, or 30 radials, or it will not work as efficiently. ( Steve's picture was taken with the antenna supported so that we could see the construction of how to wind the elements and for his first test before he knew to have the wide cone end pointed up.) This is a vertically polarized antenna, I think a misstatement that it was horizontally polarized might have crept into an early post in my excitement and late night hours. :-) Today we tested a 10m model that is a more narrow cone, but still made of no. 10 wire paired with no. 12. This one has only two parallel line elements. However, it has greater than 60 per cent efficiency with the Wheeler Cap test chamber. We are still tweaking its length and height, so I will publish those when it is set as a tuned model. We determined that raising the antenna above the ground, and ground plane, moves it significantly away from resonance. You would have to mount it on a solid cylinder of aluminum if you raise it above the ground plane. We had it working in air at 27 MHz. We put it in the buoy chamber, a plastic pipe affair. It moved it down to 25 MHz. Trimming over a foot moved it to a point where we wished to test today in 10m band. But, it never regained zero reactance on the Smith Chart. You trim from the shorted end of each two wire element, then reshort the wires. It is really fun watching Smith Charts being plotted in real time. We had 100 ohms impedance and 2:1 SWR, and about 150 pf capacitive reactance at best with the antenna raised some three feet or so above ground. Lowering (inductance) of the connections to ground plane helped, but the best thing is to have the antenna at the ground plane. This could be with tuned radials; we did a demo with Ham stick radials to prove that. We think tuned shorter radials would work as well, and that is the direction we take next in tests. What this means it works BEST at ground level on a ground screen, or on a patio/ balcony floor with 6 foot square screen under it, with feedline going thru the middle of the ground plane, NOT on top of it. Bring the feedline off under the plane, by putting low feet on the plane. We are feeding the prototypes with RG 58 coax. If ground mounted, move conductors away as you should for any vertical antenna. If on a roof, you mount it with cone wide end up, on a 6 foot square ground screen. We started with copper screen, but aluminum will work if you get solid low inductance connections to it. This might be a bolted connection with metal washers for improved lowered resistance. Thanks for the continued interest, Stuart K5KVH +++++++++++++++++ Date: Wed, 17 Apr 2002 20:40:50 EDT From: IamSF5 at aol.com To: MarkD at mfwi.org, qrp-l at lehigh.edu Subject: [124991] Re: [TenTec] cone Antenna PHOTO of how to wind them which band? In a message dated 4/17/02 6:35:24 PM Eastern Daylight Time, MarkD at mfwi.org writes: << Possibly http://www.coneantenna.com/. Didn't catch the original post, but this one (check the Stealth link on the site) might be what is referenced. >> Hi Mark, Thanks MUCHO for the URL. I don't think it's what I was looking for but the pictures were hard to see what it really looked like. I received my machined parts today to modify the B&W window job. One 1 foot rod will be added under the coil and a three foot section that is slotted for adjustment will be part of the window mount. I'm on the 4th floor anf my window frames are steel. I'm clamping it to the top of the window and that will keep the whole antenna in open unrestriced space. Not antenna restricted here. Just have fun trying to improve and play and see how much DX I can get. No down under hams yet but getting close and this is on 4 watts from 12 volts on the MFJ rig 40 Meters. I bagged most of the Europe DX Countries above the Northen part of Africa. I seem to have a pipe line in that direction. Right now my best is Turkey and Egypt. With the antenna placed higher and in the open space, I'm hoping to see some of my RF go South. For you antenna restricted hams reading this the bad thing about the B&W window antenna is that it is an eye catcher. I think the coil form and the mount should be painted some sort of subdude color,something in the bluish or rust/light brown(Judging from other items on the building.) But it does work and i'm really impressed how well it hears. Will keep the list posted. 73/72 Bob AF2Qrp ++++++++++++++++++ Date: Wed, 17 Apr 2002 19:49:04 -0500 From: "Stuart Rohre" To: Cc: Subject: [124992] Loop efficiency at 80m? Perhaps the widely quoted small loop efficiency of 10 per cent is for lowest bands, 80 and 160 only? Stuart K5kVH We are not yet ready to do the folded conical helix at 80 m, but Bob Rogers and I plan to eventually, and estimate we can do 160m in an 8 foot tall cone. Well, the efficient loop for 20m probably is bigger than our present 16 inch diameter, and 13 inch high cone. The guys building them down here are using 5 FEET wide copper tubing loops. And you have to deal with a tuning capacitor in most cases and its losses. 73, Stuart K5KVH +++++++++++++++++++ Date: Tue, 4 Jun 2002 20:39:41 -0400 (EDT) From: kc4kgu at ENTERZONE.NET To: Vic Rosenthal Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] easy simple portable antennas? On Tue, 4 Jun 2002, Vic Rosenthal wrote: > Trevor Day wrote: > > > > Funnily enough, I have just been playing with a pole antenna (courtesy > > W0KPH web site) just to prove to myself that its surely not possible to > > radiate a decent signal on 20m using an antenna that is: > > > > contained within a tube of 2 inches diameter by 14 inches long, > > fed with 4 feet of coax, > > and leaning against the inside of my shack window!!! > > The link is http://www.qsl.net/w0kph/ if anyone's interested. What he's done, > it seems to me, is make a dipole with a large amount of capacity between the > (small) halves and resonate it with a coil. This dipole would be expected to > have a very low radiation resistance, which he matches via a link. Probably the > circulating current in the coil is quite high, which means that for reasonable > efficiency it should be made of copper strap or tubing. > > I think I'll try it -- I'll use tubing for the coil and put a capacitor in > series with the link to simplify tubing. If it works at all, its small size > makes it interesting! > > 73, > Vic, K2VCO > Fresno CA Vic, et all: I looked into this antenna a few weeks ago. From everything I can find with testing, it acts like any other short, fat dipole. IE; It is not a very efficient radiator. Sure, it will load up. That is a function os the loading coil and the capacitance between the two elements. It doesn't appear to radiate nearly as well as a *low* half-wave dipole though. Additionally, I think if you do some searching at google or whatever other search engine you desire on the EH and the CFA antennas (the EH design is apparently the prior work of Dr. Fathi Kabbary on his way to designing the CFA antenna) you'll find that there has been NO real-world testing done that shows results anywhere NEAR the claimed performance of either EH Antenna Systems or CFA Limited. Take a look at this article from Radio World Newspaper: http://www.rwonline.com/reference-room/special-report/rw-antenna3.shtml 73 de John - KC4KGU K2/100 #2490 ++++++++++++++++++