From owner-qrp-l@Lehigh.EDU Fri Nov 29 12:46:42 1996 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 MAA01661 for ; Fri, 29 Nov 1996 12:46:41 -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 MAA01661 for ; Fri, 29 Nov 1996 12:46:41 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34981-14371>; Fri, 29 Nov 1996 12:46:02 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34912-42021>; Fri, 29 Nov 1996 12:45:18 -0500 Received: from dt1.datatamers.com (root@dt1.datatamers.com [140.174.237.1]) by nss2.CC.Lehigh.EDU (8.8.3/8.8.3) with SMTP id MAA182055 for ; Fri, 29 Nov 1996 12:45:09 -0500 Message-Id: Date: Fri, 29 Nov 1996 09:43:34 -0800 (PST) Reply-To: ddm@datatamers.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "David D. Meacham" To: "Low Power Amateur Radio Discussion" Subject: Re: 40-meter Loop MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: ki7mn@dancris.com X-Cc: qrp-l@Lehigh.EDU X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO Hi Bob, My only antenna for 40 meters is a 40-meter Delta Loop. Its a great antenna for DX (low angle of radiation) IF you feed it so the polarization is vertical. The apex on mine is about 37 feet above ground. The horizontal portion is 7 feet above ground. Overall length about 143 feet. It needs only one support in this configuration. Feed it in a lower corner, or, as I do, 1/4-wavelength down from the apex. Feed impedance is about 115 Ohms. Use open-wire line to a balanced tuner. I use 72-Ohm transmitting Twinlead an electrical 1/2-wavelength long to the tuner. If fed in a corner you can use 1/4-wavelength of 75-Ohm coax, then any length of 50-Ohm coax to shack (this scheme for one band only). Another, slightly better configuration is to invert the delta so the horizontal portion is high in the air and the point is near the ground. Radiation angle is lower still. Feed at a corner high in the air, or even better, 1/4-wavelength UP from the point near the ground. For this one use ONLY balanced line (open wire, Twinlead, etc.). Impedance will be a little higher, say 125 Ohms. Needs two support points. Cud be like: * * * * * * * * * *---*-------------------------*----* * * * \ / * * * * \ / * * * \ / * * \ / * * \ / * * \ / * * \/ * * * _______*_______________________________________________*___________________ Anyway, you get the idea! If you want two bands you could nest the 30-meter loop inside the 40 and feed them separately. With a balanced tuner you can easily cover the whole 40-meter band. If you use the 1/4-wave 75-Ohm transformer of coax be sure to cut the coax shorter than an electrical 1/4 wave by the velocity factor of the coax (about 0.66 times electrical length in space). Max lobe is broadside (bidirectional). Off the sides, signal is about 3dB down. Main lobes are broad (beamwidth). For a simple DX antenna for 40 or 30 I don't think you can beat the Delta Loop. 72, es gud luck, Dave, W6EMD p.s. I'll try to dig up another bit of loop info. I sent both to AL7FS some time ago. From owner-qrp-l@Lehigh.EDU Fri Nov 29 12:50:49 1996 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 MAA01780 for ; Fri, 29 Nov 1996 12:50:48 -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 MAA01780 for ; Fri, 29 Nov 1996 12:50:48 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35010-42021>; Fri, 29 Nov 1996 12:49:35 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34941-24102>; Fri, 29 Nov 1996 12:48:29 -0500 Received: from dt1.datatamers.com (root@dt1.datatamers.com [140.174.237.1]) by nss2.CC.Lehigh.EDU (8.8.3/8.8.3) with SMTP id MAA180589 for ; Fri, 29 Nov 1996 12:48:20 -0500 Message-Id: Date: Fri, 29 Nov 1996 09:46:44 -0800 (PST) Reply-To: ddm@datatamers.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "David D. Meacham" To: "Low Power Amateur Radio Discussion" Subject: Re: More 40-meter-loop info MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: ki7mn@dancris.com X-Cc: qrp-l@Lehigh.EDU X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO Hi Bob, If driven in a lower corner the polarization is a mixture of vertical and horizontal. This is OK if you want some close-in coverage (the horiz. component). But, if you are interested in low-angle DX coverage only, as I think you want, the place to feed it is 1/4-wavelength down from the apex (on either slant wire). Break the wire, put in an insulator, and attach the balanced feed line. I support my feed line from a 4X4 post, which also anchors the lower corner of the loop. I run a "messenger line" of guy wire from the post to the shack. From it I hang the 72-Ohm feed line with spaced loops of black tie wraps. You can use 300-Ohm twinlead or open wire line, too. If you don't want the line to act as a transformer, make it a multiple of an electrical 1/2-wave (69.34 feet at 7.05MHz for open wire. Multiply by velocity factor if not open wire). You will need a tuner with balanced output (Johnson "Match Box" or one with a Balun). 72, Dave, W6EMD From owner-qrp-l@Lehigh.EDU Fri Nov 29 17:22:00 1996 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 RAA07845 for ; Fri, 29 Nov 1996 17:21:59 -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 RAA07845 for ; Fri, 29 Nov 1996 17:21:59 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34935-24102>; Fri, 29 Nov 1996 17:21:35 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34844-42021>; Fri, 29 Nov 1996 17:21:09 -0500 Received: from utkux4.utcc.utk.edu (UTKUX4.UTCC.UTK.EDU [128.169.76.11]) by nss2.CC.Lehigh.EDU (8.8.3/8.8.3) with SMTP id RAA184866 for ; Fri, 29 Nov 1996 17:21:05 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id WAA25216; Fri, 29 Nov 1996 22:21:06 GMT Message-Id: Date: Fri, 29 Nov 1996 17:21:06 -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: 40-meter Loops: which way is up? In-Reply-To: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: "David D. Meacham" 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 In the various exchanges about full-wave loop antennas, replies often omit the crucial fact: whether they are referring to a horizontally oriented loop or to a vertically oriented loop. The difference makes a great difference in performance and construction ease. Among vertically oriented loops are the delta and the quad (usally square rather than diamond for the low bands. Square loops or quad loops of 1 wl generally show a lower take-off angle than dipoles set at the height of the lower quad wire--simply because the upper wire contributes to that angle. And they have a little gain over the dipole, but the exact amount depends on comparative heights between dipoles and quad loops. Vertically oriented deltas give the operator two options. Fed up one leg (precisely where depends on the nature of the triangle), they become phased verticals with a very low take-off angle, but lesser gain. Fed at the bottom or top center, they become dominantly horizontally polarized antennas similar in performance to the square quad loop--allowing for differences in how much wire is high and how much is low. Horizontally-oriented delta and quad loops perform much like dipoles at the same height, with essentially the same take-off angles and only a little gain (or broader lobes, depending upon actual layout). Just as with a dipole, the key word for improvement is height, the higher, the better, as the take-off angle (or lobe of maximum radiation) gets lower. I have modeled dozens of configurations of horizontally-oriented 1 wl loops and can find no especial good reason to prefer one layout (square, triangle, hex, octagon, etc.) over another. Unless one can get a non-vertically polarized antenna at least one-half wl up, expect a high angle of maximum radiation, good for short skip paths. If you are stuck below the half-wl level for the horizontal, consider one of the vertical antenna options for a second, low take-off angle antenna for longer skip paths on the lower HF bands. Among such antennas are the inverted L, 1/4-wl vertical, vertical dipole, the sloper (fed at the bottom or the top of the wire, the delta (equilateral or right angle) fed as phased verticals, and the half square. All models presume flat, uncluttered terrain. Peculiarities of local terrain can modify antenna properties and make an antenna work well (or poorly) beyond its modeled performance. However, the peculiarities of terrain are not transferrable to other locations. Equally non-transferrable (but teachable) is operator performance--some of us can work the world while loading up a single human hair; some of us have difficulties working the guy next door with rhombics at both locations. When passing along ideas about what works and what does not with antennas for the lower HF bands, we should all try to sort out what is generally true and thus forms the basis for good expectations on the part of others--and what is true because of the peculiarities of my own situation and thus might not work as well elsewhere. Case in point with another type of antenna. I have just finished a study of off-center-fed (OCF) dipoles (1/2 wl). They perform just as OCFs should perform, but about 80% of what has been said of them in print (especially ads for kits) is simply false or misleading. A lot of OCF "data" has come from individual "experience" and wishfully simplified formulas, but little of it prepares the OCF builder with the right expectations. Where antennas can be vertically or horizontally oriented, I hope we can keep our reference points straight in the exchanges so that we the readers and learners can apply the right information to the right antenna. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Fri Nov 29 21:10:30 1996 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 VAA12424 for ; Fri, 29 Nov 1996 21:10:29 -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 VAA12424 for ; Fri, 29 Nov 1996 21:10:29 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34929-42021>; Fri, 29 Nov 1996 21:10:02 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34851-42021>; Fri, 29 Nov 1996 21:09:06 -0500 Received: from mail.bright.net (brutus.bright.net [205.212.123.10]) by nss2.CC.Lehigh.EDU (8.8.3/8.8.3) with ESMTP id VAA65192 for ; Fri, 29 Nov 1996 21:09:03 -0500 Received: from rhodes1 (waba3-cs-9.dial.bright.net [205.212.158.172]) by mail.bright.net (8.8.3/8.6.12) with ESMTP id CAA01875; Sat, 30 Nov 1996 02:10:05 GMT Message-Id: <199611300210.CAA01875@mail.bright.net> Date: Fri, 29 Nov 1996 21:07:47 -0500 Reply-To: weightdn@bright.net Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "Mike Rhodes" To: "Low Power Amateur Radio Discussion" Subject: Re: 40-meter Loops: which way is up? MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-To: , "Low Power Amateur Radio Discussion" X-MSMail-Priority: Normal X-Priority: 3 X-Mailer: Microsoft Internet Mail 4.70.1155 X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO Ok, so far I've seen mention of feed points everywhere except at the point that will be easisest for me to feed. I want to put up a Delta loop for 10mHz with the apex near the top of my tower (about 55 ft) simply because that's the easiest way for me to put it up. Likewise, I would like to feed it at the apex for the same reason. The top will be closest to the tower which also gives a convenient path for the feedline, down to the antenna switch. The bottom 'corners' will be pulled out to whatever is convenient for tie-off points. I get the impression that this is possibly the most UNdesirable feed point. Why so, and what am I likely to end up with if I do it that way? Thanks. 72/73 de Mike / W8DN weightdn@bright.net ---------- > From: L. B. Cebik > To: Low Power Amateur Radio Discussion > Subject: Re: 40-meter Loops: which way is up? > Date: Friday, November 29, 1996 5:21 PM > > In the various exchanges about full-wave loop antennas, replies often omit > the crucial fact: whether they are referring to a horizontally oriented > loop or to a vertically oriented loop. The difference makes a great > difference in performance and construction ease. > > Among vertically oriented loops are the delta and the quad (usally square > rather than diamond for the low bands. Square loops or quad loops of 1 wl > generally show a lower take-off angle than dipoles set at the height of > the lower quad wire--simply because the upper wire contributes to that > angle. And they have a little gain over the dipole, but the exact amount > depends on comparative heights between dipoles and quad loops. > snip < From owner-qrp-l@Lehigh.EDU Sat Nov 30 13:19:12 1996 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 NAA13408 for ; Sat, 30 Nov 1996 13:19:11 -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 NAA13408 for ; Sat, 30 Nov 1996 13:19:11 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35182-36679>; Sat, 30 Nov 1996 13:18:41 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <35129-41800>; Sat, 30 Nov 1996 13:18:07 -0500 Received: from dt1.datatamers.com (root@dt1.datatamers.com [140.174.237.1]) by nss2.CC.Lehigh.EDU (8.8.3/8.8.3) with SMTP id NAA50934 for ; Sat, 30 Nov 1996 13:18:03 -0500 Message-Id: Date: Sat, 30 Nov 1996 10:16:26 -0800 (PST) Reply-To: ddm@datatamers.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "David D. Meacham" To: "Low Power Amateur Radio Discussion" Subject: Re: 40-meter Loops: which way is up? In-Reply-To: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: "L. B. Cebik" X-Cc: Low Power Amateur Radio Discussion X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO LB, My delta loop is vertically polarized as mentioned in the first sentence of my first posting. 72, Dave, W6EMD