From owner-qrp-l@Lehigh.EDU Sat Jan 25 22:28:24 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 WAA21561 for ; Sat, 25 Jan 1997 22:28:23 -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 WAA21561 for ; Sat, 25 Jan 1997 22:28:23 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35181-35570>; Sat, 25 Jan 1997 22:27:35 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34982-20465>; Sat, 25 Jan 1997 22:27:04 -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 WAA37049 for ; Sat, 25 Jan 1997 22:26:59 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id DAA26436; Sun, 26 Jan 1997 03:25:08 GMT Message-Id: Date: Sat, 25 Jan 1997 22:25:07 -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: ANT: NEC4WIN Vert modelling & rambling In-Reply-To: <32EA2B02.505D@worldnet.att.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: Clay N4AOX 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 NEC4WIN is a public domain version of MININEC 3 with a Wondows interface. As such, it is comparable in power to ELNEC, W7EL's DOS-based version of MININEC, or K6STI's MN portion of AO. MININEC 3 is subject to several limitations: 1. It is limited in the total number of segments that may enter into calculations. 2. Horizontal antennas must be at least 0.2 wavelengths above ground for reasonable accuracy. 3. Do not expect accuracy from vertical antenna models, since development of good radial systems is diffiocult at best and plots over perfect ground are highly misleading. 4. Angles of 90 degrees in wires require segment length tapering toward the angled junction for resonable accuracy, making loops, rectangles, quads, and other such antennas more difficult to model accurately. K6STI and W7EL have features that overcome some of these problems. For example, ELNEC has a means of tapering elements segments toward a specified junction that automates the task, but gives the user control over the minimum and maximum lengths. ELNEC also has some ground system provisions. EZNEC, NEC-Wires, and NEC-Win Basic are NEC-2 programs. As such, they are not limited in the ways in which MININEC is limited. It has a high accuracy ground, handles all but the tightest angles well, and has provision for using transmission lines with antennas. However, NEC-2 has its own inherent limits. It does not produce accurate results with adjacent wires of different diameters--and requires special adjustments (automated in some programs) to substitute a comparable single diameter wire. Feedback from experienced users seems to indicate something like the following: ELNEC/EZNEC provides one of the easiest interfaces to use in setting up an antenna model and modifying it, with many shortcuts to adjusting wire angles and lengths. K6STI's programs permit the use of formulas in setting up wire lengths and relationships, which is handy for some. NEC-Win Basic is a Windows-based NEC-2 that makes use of the graphical capabilities inherent in that system. I have used all of the programs (and others). Among new programs is EM Scientific's MININEC for Windows, which is an advanced proprietary version of a totally revised MININEC by Rockway and Logan. It claims to overcome virtually all of the problems of the public domain version of MININEC in a Windows interface. My copy has not yet arrived. Compared to other programs, NEC4WIN's evaluation software is a bit of a toy, relative to serious antenna modeling. We shall see what the fully capable program has to offer when it arrives. However, as an introduction to what is involved in modeling, it may be an inexpensive tutorial. Just do not assume that all output values are accurate to reality until you have done a fairly good load of modeling and get a good feel for the program possibilities and limitations. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Sun Jan 26 17:05:54 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 RAA01374 for ; Sun, 26 Jan 1997 17:05:53 -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 RAA01374 for ; Sun, 26 Jan 1997 17:05:53 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34989-29427>; Sun, 26 Jan 1997 17:04:03 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34872-42992>; Sun, 26 Jan 1997 17:03:07 -0500 Received: from mtigwc02.worldnet.att.net (ns.worldnet.att.net [204.127.129.2]) by nss2.CC.Lehigh.EDU (8.8.5/8.8.5) with ESMTP id RAA39586 for ; Sun, 26 Jan 1997 17:02:54 -0500 Received: from wynncc ([207.146.4.147]) by mtigwc02.worldnet.att.net (post.office MTA v2.0 0613 ) with SMTP id AAA21119; Sun, 26 Jan 1997 22:02:07 +0000 Message-Id: <32EBC357.1A67@worldnet.att.net> Date: Sun, 26 Jan 1997 15:49:27 -0500 Reply-To: wyn@worldnet.att.net Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: Clay N4AOX To: "Low Power Amateur Radio Discussion" Subject: Re: ANT: NEC4WIN Vert modelling & rambling References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-To: "L. B. Cebik" X-Cc: Low Power Amateur Radio Discussion X-Mailer: Mozilla 2.01E (Win95; I) X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO L. B. Cebik wrote: > > NEC4WIN is a public domain version of MININEC 3 with a Wondows interface. > As such, it is comparable in power to ELNEC, W7EL's DOS-based version of > MININEC, or K6STI's MN portion of AO. MININEC 3 is subject to several > limitations: > 1. It is limited in the total number of segments that may enter into > calculations. > 2. Horizontal antennas must be at least 0.2 wavelengths above ground for > reasonable accuracy. > 3. Do not expect accuracy from vertical antenna models, since development > of good radial systems is diffiocult at best and plots over perfect ground > are highly misleading. > 4. Angles of 90 degrees in wires require segment length tapering toward > the angled junction for resonable accuracy, making loops, rectangles, > quads, and other such antennas more difficult to model accurately. > > > Compared to other programs, NEC4WIN's evaluation software is a bit of a > toy, relative to serious antenna modeling. We shall see what the fully > capable program has to offer when it arrives. However, as an introduction > to what is involved in modeling, it may be an inexpensive tutorial. Just > do not assume that all output values are accurate to reality until you > have done a fairly good load of modeling and get a good feel for the > program possibilities and limitations. > Hi L.B., If you have corresponded with the publisher of NEC4WIN you may understand that the software in public domain is somewhat limited. The purchased version addresses some of the weaknesses you mention, although I am not sure about the auto-optimum-meshing. ORION has a ver. 1.6c which is free for the asking that addresses some of the earlier evaluation version instabilities. Also the authors provide work-arounds for some of the residual problematic areas. You are correct to point out that there are more serious modelers and that NEC4WIN may seem like a toy or an inexpensive tutorial in comparison. This was the point I was trying to make about the term "better". Obviously you get what you pay for unless you share a site license. 72/73, Clay N4AOX From owner-qrp-l@Lehigh.edu Tue Jan 28 07:00:00 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 GAA16833 for ; Tue, 28 Jan 1997 06:59:59 -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 GAA16833 for ; Tue, 28 Jan 1997 06:59:59 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34898-50531>; Tue, 28 Jan 1997 06:59:23 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34840-50531>; Tue, 28 Jan 1997 06:58:29 -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 GAA66766 for ; Tue, 28 Jan 1997 06:58:26 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id LAA02527; Tue, 28 Jan 1997 11:56:17 GMT Message-Id: Date: Tue, 28 Jan 1997 06:56:16 -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: Trimmed 40m dipole to 30m, but... In-Reply-To: <19970127.191354.4951.4.DWink@juno.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: Daniel C Winkler 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 > > Buy EZNEC-- it'll be the best $90 you ever spent. ELNEC is a > little cheaper, but not as accurate, but might do just fine for you. Good ideas on dropping the feedpoint impedance, although 1.7:1 is a perfectly usable SWR if it is advisable by site considerations to keep the ends up. 45 degrees will drop the ends by 20-25'; 30 degrees will drop them by 12' or so--all assuming a center support. Hence, physical feasibility plays a role in what to do. Chief note here is that the NEC-2 engine in EZNEC is more accurate, especially for low wire antennas of the sort most QRPers have an intense interest in. MININEC, the engine in ELNEC grows more inaccurate as the antenna height drops below 0.2 wavelength (which is about 55' on 80 meters). And loops with right angles are easier to directly model on NEC-2. However, NEC-2 has limitations, especially when you want to model antennas with wires/tubes of different sizes. If you get into this are of modeling, consider also have a version of MININEC (ELNEC, AO, or NEC4WIN) on hand also, one with provision for element length tapering preferrably, which is necessary in MININEC for most angular junctions. NEC-4 overcomes most of the limitations of NEC-2, but is proprietary and expensive for ham aquisition--something over $800 for those without a university affiliation ($150 for educational purposes)--and then you receive a TARed UNIX FORTRAN program that requires compilation for use on a PC. For those in engineering circles who may want NEC-4 and have resources to register, but not want to spend the time preparing it for use in a PC (and who do not have a mainframe to use it on), look for a commercial implementation in the near future. You will still have to register for NEC-4 and pay for the interface/implementation, but the aches and pains of set-up will be relieved. NEC-4, incidentally, not only allows all that NEC-2 does, but also handles wire junctions of different diameters and permits radial systems underground (for vertical antenna system developers). Rockway and Logan, the original developers of MININEC, have rebuilt the algorithms and now offer a range of revolutionized MININECs for basic through broadcast engineering users with apparently none of the restrictions of standard MININEC. The student/hobbyist version is over twice the cost of ELNEC or AO and 50% higher than EZNEC. Program is set up for windows. With NECWin Basic and Pro, EZNEC and EZNEC-M, and NEC Wires in the NEC-2 category; ELNEC, AO, and NEC4WIN in the older MININEC category, and MININEC (for Windows or Professional or Broadcast) in the new MININEC category, selection of software is likely to be more difficult than ever. Not long ago, W7EL and K6STI were the only two developers in the game (with shortlived items like Antenna Model, an interesting MININEC with some attempts to replicate early Windows features in DOS). And do not forget that there are also some interesting special purpose non-NEC modeling programs out there. As with all software, odds are that your first modeling program will end up being your favorite--whatever the direction of its evolution and upgrade. This has been the antenna modeling equivalent of someone else answering the question, "What's available in 40-meter QRP kits?" except it is shorter, since there are fewer. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Tue Jan 28 08:57:57 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 IAA20214 for ; Tue, 28 Jan 1997 08:57:55 -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 IAA20214 for ; Tue, 28 Jan 1997 08:57:55 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35072-19556>; Tue, 28 Jan 1997 08:57:31 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34910-50531>; Tue, 28 Jan 1997 08:56:22 -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 IAA28195 for ; Tue, 28 Jan 1997 08:56:12 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id NAA22895; Tue, 28 Jan 1997 13:54:04 GMT Message-Id: Date: Tue, 28 Jan 1997 08:53:58 -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: Vertically-radiating dipoles and antenna modeling MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: QRP-L List X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO I have had a couple of questions about vertically radiating dipoles, those dipoles for 80 or 40 meters with an isolating device installed 1/4 wavelength down the coax feed. Since antenna modeling has been the subject of some interest recently, I thought I might share some notes as a lesson in how not to model unless you are selling a product or idea. Supposedly the VRD gives improved low angle performance to a dipole from the radiation off the outer braid of the coax and also improves performance off the ends. I have seen numbers (misexpressed as dBi, when they should have been plain dB) of 17 to 20 dB improvement in these categories. Patterns are nice ovals--nearly circles. But how did they get this way? 1. Take-off angle: one source uses 10 degrees as the angle for making comparisons. However, the CAPMAN propagation charts in the ARRL Antenna book show that on 80 meters (the test band), the most common DX angle for all directions is over 15 degrees. So, to get good patterns, whatever the reality, use an artificially low angle of radiation. 2. Wire loss: one article specifies lossless wire. Although the difference between copper and lossless wire is not much for 80 meters, it is a difference; and most of us must use copper. 3. Ground: one article uses perfect ground; another source uses very good ground within the ELNEC selections. However, few hams have even average ground to work with. But in moving from very good to average ground, all those smooth ovals disappear. Here are some numbers for 80 meters, using a dipole, an inverted Vee, and a VRD. All are at 60' max height, use copper wire, an elevation angle of 15 degrees, and average ground. Gain is the gain in dBi. Since the dipole pattern has pattern indents off the ends of the antenna, let's call one left and the other right and specify how much down the signal is in dB. Gain Left indent Right indent Dipole -1.3 -10 -10 VRD -0.8 -2.5 -6 Vee -2.0 -4.5 -4.5 What happened to those big wire-end gain numbers? They got lost in realistic ground conditions. What happened to the VRD oval? It turned into a gentle kidney bean shape. The VRD gain at best is a half dB over the dipole (about 1/12th of an S-unit) at this angle, but is less than the dipole at higher (shorter skip) angles. Although the gain of the VRD at 15 degrees over the Vee is about 1.2 dB, raising only the center of the Vee will yield an oval superior to the VRD over all ground conditions. Note that the performance of the Dipole and the Vee are the same whether fed with coax or 450-ohm line. With the ladder line, one can use the dipole or Vee on all bands. The VRD is limited to 80 (in this model), since the coax and outer braid radiation terminating device are not multiband items. I have not presented these numbers to encourage or discourage any types of purchases. Instead, my purpose is to forewarn newer antenna modelers against overly optimistic modeling practices that violate the reality of your situation. Magazine articles have been as bad as advertisements in this regard, since some folks live by selling ideas. Choose a realistic ground for your area--odds are it will be no better than average. Choose realistic elevation angles--look up info in resources to find what is common to each major category of your operating. A modeling program is a supplement to, not a substitute for, all the other resources that help us understand antennas. Choose real wire--copper or aluminum are most common, and copperweld is copper. Then make a bunch of variations on your models, changing ground conditions up and down by a grade, changing elevation angles and making comparative elevation as well as azimuth plots, etc. One model at one angle is only the start of the process. But in the end, be honest with yourself, since the antenna will not operate any better because the parameters have been altered optimistically. That will put you in a position to model commercial antennas to find the reality behind the advertising and to model for yourself what you read in the magazines. Also strive to understand clearly what differences make a difference in antenna figures. Finally, disregard all user testimony that does not emerge from good antenna ranges and well-designed A-B switching tests using freshly and carefully installed antennas of the types compared. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Sun Feb 2 10:06:02 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 KAA17676 for ; Sun, 2 Feb 1997 10:06:01 -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 KAA17676 for ; Sun, 2 Feb 1997 10:06:01 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <36079-23274>; Sun, 2 Feb 1997 10:05:49 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <36049-29929>; Sun, 2 Feb 1997 10:04:51 -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 KAA75458 for ; Sun, 2 Feb 1997 10:04:40 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id PAA12819; Sun, 2 Feb 1997 15:04:57 GMT Message-Id: Date: Sun, 2 Feb 1997 10:04:57 -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: NEC antenna models MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: QRP-L List X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO At the request of the NECWin Basic/NECWin-Pro folks, I have about 3 dozen antenna model files which can be downloaded at their web site: http://www.nittany-scientific.com/examples.htm The files range from 80/40 meter wire antennas to upper HF antennas to a few 2 meter items. Unfortunately for EZNEC users, they are in standard NEC card-file format, but with a little practice, you can extract the data to create an EZNEC input file. NEC-2 programs that can read ASCII card files can use the models directly as inputs. These are samples only--not guaranteed to be optimized to the nth degree. But they do illustrate a number of modeling techniques and cautions to avoid exceeding the limits of NEC-2. They will be adding further sample models, some common, some esoteric, as time goes on. Unfortunately, a tutorial in NEC card reading would be too long for this forum, but the basic scheme is in NOSC TD-116, Volume 2, Part III Users Guide (January, 1981). Reading NEC cards is only distantly related to reading tarot cards, but I wish you good fortune anyway. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Fri Feb 7 08:31:23 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 IAA10546 for ; Fri, 7 Feb 1997 08:31:23 -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 IAA10546 for ; Fri, 7 Feb 1997 08:31:23 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <34958-37651>; Fri, 7 Feb 1997 08:30:01 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34899-29458>; Fri, 7 Feb 1997 08:27:26 -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 IAA86240 for ; Fri, 7 Feb 1997 08:27:08 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id NAA05477; Fri, 7 Feb 1997 13:26:44 GMT Message-Id: Date: Fri, 7 Feb 1997 08:26:43 -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: NEC-4 and EZNEC Pro MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: QRP-L List X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO For antenna modelers leaning toward the professional end of the scale: I have just received from Roy Lewallen, W7EL, a copy of EZNEC Pro/EZCALC4, which is his adaptation of NEC-4 to his well-known interface (common to EZNEC and ELNEC). NEC-4 overcomes limitations found in MININEC and in NEC-2. MININEC limits include inaccuracy for antennas below about 0.2 wl up and difficulties in wires that join at angles. NEC-2 limitations include inaccuracy for adjoining wires of different diameters and the inability to model ground planes below the ground surface. NEC-4 has none of these limitations, but handles otherwise like NEC-2 (the calculation engine in EZNEC). Unfortunately, the system is expensive. EZNEC-M, v. 2 (which is the virtually no-limit to segments version of EZNEC (NEC-2) and uses the EZNEC Pro interface now) runs $425, wih a $325 price for upgrading from EZNEC itself. EZNEC/4, with the NEC-4 engine runs $600 (but contains both NEC-2 and NEC-4), with a $550 price tag for upgrading from EZNEC. However, NEC-4 is still under both government and proprietary control, and Roy cannot ship NEC-4 until you independently register for NEC-4 with LLNL/Un. Cal. This cost $150 educationally (meaning having an acceptable academic affiliation), but otherwise runs $800 or so. You receive from LLNL a TARed copy of uncompiled FORTRAN NEC-4, plus very extensive documentation. When opened and compiled for a PC (a version for MAC is also available), this version of NEC-4 will also run with the EZNEC Pro interface or with other interfaces that may allow you to implement some of the features not implemented in EZNEC Pro. All this makes EZNEC/4 most applicable to universities and engineering departments of business and industry. Nonetheless, I wanted folks to know that NEC-4 is available, and in the EZNEC interface format, several months before the news hits the magazines. I suspect Roy will carry a copy to the next ACES meeting. He showed a very preliminary copy at Dayton next year, before working out all the intricacies of the interface. This will also let QRPers know what one of its Hall of Famers has been up to for the last year or so. -73- LB, W4RNL From owner-qrp-l@lehigh.edu Thu Mar 13 20:45:00 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 UAA24734 for ; Thu, 13 Mar 1997 20:44:59 -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 UAA24734 for ; Thu, 13 Mar 1997 20:44:59 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35100-34409>; Thu, 13 Mar 1997 20:44:39 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34940-52331>; Thu, 13 Mar 1997 20:43:38 -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 UAA63420 for ; Thu, 13 Mar 1997 20:43:35 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id BAA24280; Fri, 14 Mar 1997 01:43:04 GMT Message-Id: Date: Thu, 13 Mar 1997 20:43:02 -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: [TowerTalk] Antenna Modeling Programs In-Reply-To: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: Big Don , towertalk@contesting.com X-Cc: QRP-L List X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.1 beta -- ListProcessor(tm) by CREN Status: RO > How about something that models the difference between stranded wire and > solid wire (for the same length of wire), or doesn't the scientific > community feel any such RF-radiation differences exist? > > Big Don Don, To the best of my knowledge, at HF most sources hold the view that there is no significant difference between solid and stranded wires. Certain stranded wires are constructed in such a manner that a given nominal wire size may not be true to the diameter charts. However, unlike Litz wire--which is effective below about 0.5 MHz, stranded bare stranded wire at HF is considered by most to have the same properties as comparably sized solid wire. Wire contact and field intensity would place the maximum RF current on the exposed surface of the wire. I have found no source that accounts for any possible differential in exposed surface area. If a difference did exist, NEC could not model it. Wires closer than 0.001 wl are considered connected at junctions, and overlapping wires are generally considered illicit and produce erroneous results, enless error-trapped by a particular implementation. If there is any significant difference between stranded and solid wire, it would take a pre-calculation diameter adjustment to the solid size with the closest performance. -73- LB, W4RNL