Return-Path: Received: (qmail 17246 invoked from network); 14 Jul 2001 08:28:56 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 14 Jul 2001 08:28:56 -0000 Received: (qmail 2987 invoked from network); 14 Jul 2001 08:27:32 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 14 Jul 2001 08:27:32 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.16 #2) id 15LKZi-0003T7-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 14 Jul 2001 09:14:54 +0100 Received: from rubellite.lion-access.net ([212.19.217.4]) by post.thorcom.com with esmtp (Exim 3.16 #2) id 15LKZg-0003T2-00 for rsgb_lf_group@blacksheep.org; Sat, 14 Jul 2001 09:14:53 +0100 Received: from w8k3f0 (1Cust226.tnt61.rtm1.nl.uu.net [213.117.40.226]) by rubellite.lion-access.net (I-Lab) with SMTP id 5016A2A5D for ; Sat, 14 Jul 2001 08:13:25 +0000 (GMT) Message-ID: <000b01c10c3d$d6f7ffc0$e22875d5@w8k3f0> From: "Dick Rollema" To: "LF-Group" Subject: LF: Near filed of 9kHz antenna III Date: Sat, 14 Jul 2001 10:19:13 +0200 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2314.1300 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit

To All from PA0SE

A few additional remarks about the info in my earlier massages are necessary.

1. I stated the field computation was based upon a radiated power of 1kW.

That is not correct. The power fed to the antenna is 1kW. Computer program AO gives the efficiency of the antenne as 26.4%. So the radiated power is 264W.

I modelled the antenna as an 180m high vertical copper tube of 15mm diameter.

AO computes the feedpoint impedance as 0.042 - j16189 ohm.

Because efficiency is 26.4% the radiation resistance is 0.264 * 0.042 = 11 milli-ohm.

To pump 1000W into the antenna the current must be SQR( 0.042 * 1000) = 6.48A.

The voltage on the antenna is then 6.48 * 16189 = 105kV.

2. Maker K6STI of AO has told me that the near field option actually calculates the total power, so it includes the far field.

At 2km from the antenna the phase difference between H and E is 88.8 degrees, still near the 90 degrees of the real near field. (In the far field it would be zero degrees).

Also E/H = 872 ohms; it would be 120 * pi = 377 ohms in the far field.

3. I will try to model a loop, as suggested by Rik, ON7YD. I will send the E and H field figures as attachment to separate e-mail messages.

73, Dick, PA0SE