From owner-qrp-l@Lehigh.EDU Sat Jan 25 11:19:27 1997 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id LAA26184 for ; Sat, 25 Jan 1997 11:19:26 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id LAA26184 for ; Sat, 25 Jan 1997 11:19:26 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34852-35570>; Sat, 25 Jan 1997 11:18:11 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34829-35570>; Sat, 25 Jan 1997 11:17:28 -0500 Received: from x3.boston.juno.com (x3.boston.juno.com [205.231.100.22]) by nss2.CC.Lehigh.EDU (8.8.5/8.8.5) with ESMTP id LAA101627 for ; Sat, 25 Jan 1997 11:17:25 -0500 Received: (from wb2vuo@juno.com) by x3.boston.juno.com (queuemail) id LSB06027; Sat, 25 Jan 1997 11:14:11 EST Message-Id: <19970125.111006.4663.1.wb2vuo@juno.com> Date: Sat, 25 Jan 1997 11:10:01 PST Reply-To: wb2vuo@juno.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: wb2vuo@juno.com (William K Hibbert) To: "Low Power Amateur Radio Discussion" Subject: The Bow-Tie Antenna X-To: qrp-l@Lehigh.EDU, n2tuk@FRONTIERNET.NET, dakline@sgccva.sunygenesee.cc.ny.us, dkbjstewart@juno.com, EVMAN@IX.NETCOM.COM, bobkowa@netacc.net, billy@FRONTIERNET.NET, djw@cci.com, wfking@kodak.com, kg2f@FRONTIERNET.NET, wb8ygg@juno.com, rindiano@rpa.net, duanekf2jc@aol.com, kf2xc@FRONTIERNET.NET, lievense@FRONTIERNET.NET, n2uio@FRONTIERNET.NET, w2pj@FRONTIERNET.NET, cwells@juno.com, bhunter@FRONTIERNET.NET, k2dv@juno.com, wdrhodes@kodak.com X-Mailer: Juno 1.00 X-Juno-Line-Breaks: 2-3,16-17,25-26,35-36,40-41,46-47,49-56 X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO I saw a reference to a "Bow-Tie" antenna. and I had built a couple of them back in the early 80's, one for the 10 Meter band, and one for 2 Meter FM. The 10 Meter Bow-Tie was hung from a lie that I ran from the TV mast to an oak tree in the back yard, with the antenna braodside to a NE/SW direction. I was living in Niantic, CT, about midway from NYC and Boston, and planned to use it for 10 Meter FM simplex. The array produced a bi-directional, vertically-polarized pattern that outdid the 10 Meter GP by a couple of S-units. I never actually measured the gain. It also produced a nice low-angle signal that was great for DX, especially to Europe. On the longer paths, it outperformed my 2-el Yagi (up 20 ft) by a good margin. I could even hear my own signal on Long-Path when the band was open around the world. (I would hit the key for a short dot, and the Argosy's QSK would switch fast enough to hear it come back 150 (+/-) ms later...) [Where ARE those sunspots when you need them???] The 2 Meter version was installed at my location in Rush, NY, south of Rochester. The NYS Thruway runs E-W by there, and I set the Bow-Tie up E-W to talk to the mobiles on simplex as they drove by. It was made with 1/2 x 1/2 aluminium angle for the vertical sections and #8 aluminium ground wire for the sides, all mounted on a recycled mop handle and mounte above the TV antler with a 5 ft section of closet pole stuffed in the mast. This kept the metal masting out of the center of the array. The feed was direct with 50-ohm coax. Just picture a pair of Vertical Delta Loops, with the feedpoints meeting in the "middle" of the bow-tie. The loops are connected together, top - top and bottom - bottom and fed directly with the coax. I fed with the braid on the bottom, which shouldn't matter either way, but with no balun of any sort. The 10 Meter version was made with equal legs of 11 ft 6 inches, which resonated around 28.9 MHz, and the SWR was below 2:1 on the whole band, 28.0 - 29.7 MHz. It was higher on the CW end than the FM end, but the Argosy didn't care nor did the ComTronix FM80... The 2 Meter version has to be shortened down due to the effective "diameter" of the angle and the #8 wire. The length ended up at 26 1/2 inches per side for 146 MHz, and the SWR was almost flat on the whole band, about 1.4:1 at the very bottom. If you mounted the antenna on it's side, it would display a bi-directional horizontally-polarized pattern, but you would have ot get it up so that the bottom was at least 1/2-wave up for low-angle performance. My 10 Meter Bow-Tie had the center up about 20 ft, so the lower corners would have been about 14 ft up. Keep in mind that the WX WILL improve sometime, and no matter what, it is ALWAYS antennna WX :-) 72/73, Keith, WB2VUO, QRP-L #582, scQRP 40, Tech Specialist (ARRL/WNY), ARRL Life Member, VP/BARK, Beacon Chaircritter, Rochester VHF Group Trustee, KB2YTW/B 10 Mtr QRPp Beacon (250 mW @ 28.2870 MHz) "In the Depths of the Great Bergen (NY) Swamp...FN13ac" Packet - wb2vuo@w2im.#wny.ny.usa.noam Email - wb2vuo@juno.com From owner-qrp-l@Lehigh.EDU Sat Jan 25 16:04:45 1997 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id QAA09134 for ; Sat, 25 Jan 1997 16:04:43 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id QAA09134 for ; Sat, 25 Jan 1997 16:04:43 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35183-35823>; Sat, 25 Jan 1997 16:04:24 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <35163-35823>; Sat, 25 Jan 1997 16:03:39 -0500 Received: from x3.boston.juno.com (x3.boston.juno.com [205.231.100.22]) by nss2.CC.Lehigh.EDU (8.8.5/8.8.5) with ESMTP id QAA30018 for ; Sat, 25 Jan 1997 16:03:32 -0500 Received: (from wb2vuo@juno.com) by x3.boston.juno.com (queuemail) id QiH06027; Sat, 25 Jan 1997 16:00:41 EST Message-Id: <19970125.155911.4663.0.wb2vuo@juno.com> Date: Sat, 25 Jan 1997 15:59:08 PST Reply-To: wb2vuo@juno.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: wb2vuo@juno.com (William K Hibbert) To: "Low Power Amateur Radio Discussion" Subject: RE: Bow-Tie Antenna, a Dwg of Sorts X-Mailer: Juno 1.00 X-Juno-Line-Breaks: 0-14,16-38,40,42,44-49,51-53,55-66,68,70,72,74,76-77 X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO The Bow-Tie Antenna After getting a couple of questions on the shape and orientation of the Bow-Tie antenna, (Thanks to Tom, WA3REY and Dan, KC5GXL), I decided to try sketching the antler for a better explanation. Kinda limited, but here goes: |\ /| | \ / | | \ / | | \ / | | \ / | | \_._/ | | /-.-\ | The coax connects to the center at the dots. | / \ | Mine was connected with the shield on the bottom, | / \ | center conductor on the top. No balun was used. | / \ | | / \ | |/ \| The distance around each delta is equal to just over a wavelength, L(ft)= 1005/F(MHz), so each "side" of the triangles (6 of them in the Bow-Tie) are equal to around 1/3-wave, L(side) = 335/F(MHz). In a tabular form, for 20 - 2 Meters it will look like this: FREQUENCY LENGTH(ft) SIDE(ft) 14.10 MHz 71.3 ft 23.8 ft 18.10 MHz 55.5 ft 18.5 ft 21.10 MHz 47.6 ft 15.9 ft 24.90 MHz 40.4 ft 13.5 ft 28.40 MHz 35.4 ft 11.8 ft 29.20 MHz 34.4 ft 11.5 ft 52.50 MHz 19.1 ft 76.6 Inches 146.0 MHz 82.6 Inches 27.5 Inches If you want to scale the Bow-Tie to other frequencies, use the formulae above. Say, for example,that your local REACT* group wanted a better antenna to monitor for motorists on a local Interstate. They will be on CB Channel 9 (27.065 MHz). The dimensions will be as follows: Length = 1005/27.065 = 37.1 ft Side = 335/27.075 = 12.4 ft The antenna would be mounted with its long dimension perpendicular to the highway, E-W for the antenna for a Northbound or Southbound highway. The same principle would apply for a 2 Meter Bow-Tie along a busy Interstate Hope this helps to picture the antenna. 72/73, Keith, WB2VUO, QRP-L #582, scQRP 40, Tech Specialist (ARRL/WNY), ARRL Life Member, VP/BARK, Beacon Chaircritter, Rochester VHF Group Trustee, KB2YTW/B 10 Mtr QRPp Beacon (250 mW @ 28.2870 MHz) "In the Depths of the Great Bergen (NY) Swamp...FN13ac" Packet - wb2vuo@w2im.#wny.ny.usa.noam Email - wb2vuo@juno.com * Before you fire up the flames, there are a bunch of Hams in Public Service that STILL use the CB channels in a reasonable, legal method for Public Service work such as REACT. Even the Halloween "Pumpkin Patrols" along the NYS Thruway (I-90) used CB in areas to increase coverage on the overpasses. The real communicators in such a group are far more receptive to assistance rather than brickbats. Think it through before you flame, regardless of the Mode...Keith From owner-qrp-l@lehigh.edu Mon Jan 27 07:00:48 1997 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id HAA12749 for ; Mon, 27 Jan 1997 07:00:47 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id HAA12749 for ; Mon, 27 Jan 1997 07:00:47 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35168-38382>; Mon, 27 Jan 1997 07:00:07 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <35050-38382>; Mon, 27 Jan 1997 06:59:07 -0500 Received: from utkux4.utcc.utk.edu (UTKUX4.UTCC.UTK.EDU [128.169.76.11]) by nss2.CC.Lehigh.EDU (8.8.5/8.8.5) with SMTP id GAA55115 for ; Mon, 27 Jan 1997 06:58:59 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id LAA17997; Mon, 27 Jan 1997 11:56:57 GMT Message-Id: Date: Mon, 27 Jan 1997 06:56:57 -0500 (EST) Reply-To: cebik@utkux.utcc.utk.edu Sender: owner-qrp-l@lehigh.edu Precedence: bulk From: "L. B. Cebik" To: "Low Power Amateur Radio Discussion" Subject: Re: Bow-Tie Antenna Length In-Reply-To: <19970126.160232.4647.6.wb2vuo@juno.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: William K Hibbert X-Cc: Low Power Amateur Radio Discussion X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO I have seen two types of antennas called bow ties listed. One is a pair of triangles, closed, on each side of a feed point. This is a true bow tie and it amounts to a dipole that is shortened by using the spread of wires as a very fat wire. For 10 meters, I have modeled and made on as short as 0.22 wavelengths long and the same wide. These are also called fans, but there is also the practice of fanning multiple dipoles from on feedpoint, so that is no less confusing. Fan dipoles (or bowties) can be set up vertically or horizontally. They perform like dipoles. The other consists of two elements in the horizontal plane with a gap between the ends of the the side wires. Most common is feeding the rear wire and using the forward wire as a director. This arrangement is also called the folded X-beam and goes back into the 1960s in CQ, as well as appearing in the ARRL Antenna Compendium Volume 1 and a couple of issues of the ARRL HB just before the major revision in 1995. It is dervied from, but is superior to, a true X and a Roman X, and is much more compact. When installed 1/2 wavelength up and higher, the pattern gives a forward gain about 1/2 dB less than a standard 2-element Yagi, or about 3 dB better than a dipole in the same position. The rear lobe can have, with precise length adjustment of the wires, a deep null to the immediate rear, but with 2 quartering rear lobes down by only abut 10 dB from the forward lobe. However, the feedpoint impedance in this arrangement is about 25 ohms, calling for something like a beta match. If arranged for 50 ohm feed impedance, the rear lobe expands to a broad oval down about 8-10 dB. You can also lengthen the director and place a capacitor at its center, tuning the antenna pattern by that means. For 10 meter portable use, I used 1/2 wl of 450 line from the director center and placed the capacitor down where I could tune it on the run. The setting change across the wide 10 meter band. You can also set the element relations for more gain, but the feedpoint impedance goes down to 10 ohms and the rear lobe expands very rapidly--in my view, the better F-B is worth more than the extra half dB of forward gain. For a detailed analysis of the folded X-beam, see Communications Quarterly for Winter, 1995, page 33 ff. A future issue of Com Quart will have an article on making 2 element beams from true fan and bowtie elements. In the meantime, if you want to try a folded X-beam, be careful of dimensions. The ones analyzed, following W9PNE's work, use aluminun tubes with copper end wires. If you go to all wire construction, dimensions will change, and I'd suggest modeling the antenna first to get you in the ball park for end separation and overall element lengths. For all wire, you can use NEC-2, but if you use a combination of al tube and cu wire, use MININEC and taper element segment lengths toward the acute angles. If you merely cut to formulas, odds are that this slightly finnicky configuration (and all antennas with very acute angles along elements get finnicky) will not perform better than a shortened dipole--too many variables in the parasitical relationships for "slap it up and call it good" methods of construction. For example, my portable 10-meter model with a tunable director and a beta match on the driven element ended up with the director being longer than the driven element. Drove some folks crazy who only saw the physical elements, but made eminent electrical sense: you lengthen an element--making it inductive--to tune it with a capacitor and to match a driven element with a beta match, you shorten it to make is a bit capacitive. I hope these notes are useful, but suspect they may add to the confusion. There is an old habit in amateur radio antenna experimenting of trying to reduce antennas, however complex, to a set of "L=12345/f" formulas for scaling frequency. With simple antennas, this technique works ok as a starting point for your own experiments. With more complex antennas and changes in element diameter, the technique tends to give the impression that one can simply erect the antenna as a cookbook exercise and the result is a poor performer (although the user may not realize this). This is especially true when we put the antenna below 1/2 wavelength up. It is better to a. first understand how the antenna works, including all the varables involved, and then b. try to model or get it modeled for your own installation set-up, and c. know in advance what the best experimental moves are for tweaking it to just where you want it. For example, suppose you want to put up a simple 2-element Yagi. You see some formulas or lengths. But what are the varables you can control? a. Driven element length; b. reflector length, and c. spacing. Do you know what is likely to happen if you change each of these by a little? By a lot? -73- LB, W4RNL