Return-Path: Received: (qmail 20648 invoked from network); 6 Aug 1999 15:39:02 +0100 Received: from magnus.plus.net.uk (HELO magnus.force9.net) (195.166.128.27) by guiness.force9.net with SMTP; 6 Aug 1999 15:39:02 +0100 Received: (qmail 25623 invoked from network); 6 Aug 1999 14:42:14 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnus.plus.net.uk with SMTP; 6 Aug 1999 14:42:14 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11CkzV-0007n8-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 06 Aug 1999 15:29:01 +0100 Received: from [143.179.236.31] (helo=Iguanodon.big-orange.net) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11CkzT-0007n0-00 for rsgb_lf_group@blacksheep.org; Fri, 06 Aug 1999 15:28:59 +0100 Received: from w8k3f0 ([143.179.151.249]) by Iguanodon.big-orange.net (Netscape Messaging Server 3.6) with SMTP id AAA710C; Fri, 6 Aug 1999 16:28:21 +0200 Message-ID: <000e01bee018$b5145c80$f997b38f@w8k3f0> From: "Dick Rollema" To: "LF-Group" Cc: "Koos Fockens, PA0KDF" , "Klaas Spaargaren, PA0KSB" , "Jan Hekkert, PA3HCD" , "Gerrit Jan Huijsman, PA0GJH" Subject: LF: Fw: Antenna Software Date: Fri, 6 Aug 1999 16:33:05 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Sender: To All from PA0SE Some time ago you received via the reflector the following correspondence between PA0SE and W7EL. >-----Oorspronkelijk bericht----- >Van: Roy Lewallen >Aan: Dick Rollema >Datum: dinsdag 20 juli 1999 19:35 >Onderwerp: Re: Antenna Software > > >>Dick, >> >>Only the professional versions of EZNEC (EZNEC-M and EZNEC/4) directly >>report the ground wave. However, a reasonable approximation of the >>ground wave field strength can be gotten by using the EZNEC near field >>analysis. This is because the "near field" analysis actually calculates >>the total field, both near and far, including the ground wave. The near >>field analysis results are available only as numbers; they are not >>plotted as a graphical pattern. >> >>Roy Lewallen, W7EL >> >>> Dick Rollema wrote: >>> Dear Roy, >>> >>> Quite a few countries in Europe now have made the 136 kHz longwave >>> band available to amateurs. >>> >>> Although at night some sky wave propagation may be present most of the >>> contacts are made via the so called surface wave. >>> >>> I wonder whether EZNEC and ELNEC produce proper radiation patterns for >>> that kind of wave propagation? >>> >>> 73, Dick, PA0SE I use the antenna simulation program Antenna Optimizer by Brian Beezley, K6STI. This program also has the possibility to compute the near field and I wondered whether this was also suitable for computing the field strength of the surface wave. I modelled my antenna system and let the computer calculate the electric and magnetic component of the field. As Roy explained this must the total field, near plus far. For antennas on the surface of the earth outside the near field region only the surface wave remains. Only in the far field E/H = 377, in which E = electric component in V/m and H = magnetic component in A/m. So this is a method to check whether you are in the far field region or not. For several distances (in metres) from the antenna I found the following: Distance E/H 500 271 1000 338 1500 358 2000 366 2500 369 3000 371 3500 374 4000 375 This shows that my earlier statement is correct: in order to obtain the EIRP of a transmitter by measuring the field strength with a loop (or ferrite rod) antenna a minimum distance of 3500 m is sufficient for a meaningful result. 73, Dick, PA0SE JO22GD D.W. Rollema V.d. Marckstraat 5 2352 RA Leiderdorp The Netherlands Tel. +31 71 589 27 34 E-mail: d.w.rollema@gironet.nl