From owner-qrp-l@Lehigh.EDU Wed May 15 13:19:41 1996 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.1/8.7.1) with ESMTP id NAA18748 for ; Wed, 15 May 1996 13:19:38 -0400 (EDT) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.1/8.7.1) with ESMTP id NAA18748 for ; Wed, 15 May 1996 13:19:38 -0400 (EDT) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <174888-28512>; Wed, 15 May 1996 12:57:07 -0400 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <174849-28512>; Wed, 15 May 1996 12:56:12 -0400 Received: from dragon.ti.com (dragon.ti.com [192.94.94.61]) by nss2.CC.Lehigh.EDU (8.7.1/8.7.1) with ESMTP id MAA78311 for ; Wed, 15 May 1996 12:56:10 -0400 Received: from robin.itg.ti.com ([128.247.31.238]) by dragon.ti.com (8.6.13/ac3i.dseg.ti.com) with ESMTP id LAA00858 for ; Wed, 15 May 1996 11:55:38 -0500 Received: from itg.ti.com (magic.itg.ti.com [128.247.93.50]) by robin.itg.ti.com (8.7.3/8.6.11) with SMTP id LAA26648 for ; Wed, 15 May 1996 11:49:58 -0500 (CDT) Received: by itg.ti.com (4.1/ITG-1.1) id AA27791; Wed, 15 May 96 11:52:23 CDT Message-Id: <9605151652.AA27791@itg.ti.com> Date: Wed, 15 May 96 11:52:23 CDT Reply-To: QLF%mimi@magic.itg.ti.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: QLF%mimi@magic.itg.ti.com To: "Low Power Amateur Radio Discussion" Subject: VERTICAL GROUND SYSTEMS X-To: QRP-L@Lehigh.EDU X-Listprocessor-Version: 7.2 -- ListProcessor by CREN Status: RO From: Brad Bradfield QLF Subj: VERTICAL GROUND SYSTEMS Even though this isn't QRP related per se, it is a topic that continues to come up here on the QRP-L, so let me attempt to give y'all some information to knaw on. Sorry it's so long. Ok now, everybody put away your knives, guns and flame throwers. First off; verticals REQUIRE a ground system of some kind for PROPER operation. Now unless your vertical is installed in the middle of a salt marsh or off shore in the ocean (I've seen broadcast stations like that,) this probably means radials. Everybody's heard some amateur saying "My Butter-Hy-Mos vertical loads fine without radials so I must not need them afterall." In the words of the immortal Sherman T. Potter, "HORSE FEATHERS!" The books will show you that the base impedance of the vertical will not change a whole lot with the addition of any number of radials. Just because it LOADS ok doesn't mean that the radiation efficiency is worth a can of beans. You could be QRPppp without really intending to be. The following will show the relative improvement in radiated field intensity with an increasing number of 1/4 wavelength radials. Each line is referenced to an antenna with two radials.(4) I wish I had a reference showing the intensity with no radials, but I do not. NUMBER FIELD OF INTENSITY RADIALS IMPROVEMENT ------------------------------------ 2 REF 15 2.7 dB 30 3.4 dB 60 3.9 dB 113 4.2 dB The following will show the relative improvement in radiated field intensity with an increasing length of radials on a 1/4 wavelength vertical antenna with 113 total radials. Each line is referenced to a radial length of 0.125 wavelength.(4) LENGTH FIELD OF INTENSITY RADIALS IMPROVEMENT ------------------------------------ 0.125 REF 0.25 2.1 dB 0.375 2.5 dB Common practice in the broadcast industry is to use 120 to 240 (90 minumum) 1/4 wavelength radials, often interspersed with a number of shorter radials. They are typically #10 AWG bare copper, and are plowed into the ground. If you're building a broadcast station, you will, of course, allow enough real estate to install these radials. If you're sitting on a normal city lot, you won't have this luxury. Install as many radials of whatever length is possible. And you can always bend them to get around objects and/or to make them longer. To answer the question that has also been asked in this discussion, I can find no reference in any of my sources that gives me any information on using insulated wire for radials. I've seen it done, and I've done it myself. It works. For more information, check the following: 1) The Amateur Radio Vertical Antenna Handbook by CAPT Paul Lee, N6PL CQ Publishing, Inc [Outstanding reference, but may or may not be still in print] 2) The Complete Broadcast Antenna Handbook by John E. Cunningham TAB Books [Out of print?] 3) Antenna Engineering Handbook by Johnson and Jasik Chapter 25 McGraw-Hill [Expensive!] 4) Ground Systems as a Factor in Antenna Efficiency by G.H. Brown et al Proc. of the I.R.E., June 1957, p. 735 [Find a library that has it] Again, I apologize for the length of this posting, but thought it might answer some of the continueing questions. 73's Brad, WB0CGH ****************************************************************************** Brad Bradfield, PE Electrical Design Engineer (H) 817-321-2960 Texas Instruments, Inc. (W) 214-462-6230 QLF@MSG.TI.COM WB0CGH@WO5H.#DFW.TX.USA.NA ARRL Life Member QRP-L #377 SMIRK #4906 IEEE(M) ARS #72 Collector of wireless and landline Morse keys and accessories. ******************************************************************************