[From nobody Thu Jul 3 13:40:48 2003 Return-Path: <owner-lowfer@ns3.qth.net> Received: from mail4.bellatlantic.net ([151.197.0.38]) by immta2.bellatlantic.net (InterMail v4.01.01.00 201-229-111) with ESMTP id <20000202121334.JVRM15638.immta2@mail4.bellatlantic.net>; Wed, 2 Feb 2000 07:13:34 -0500 Received: from ns3.qth.net (ns3.qth.net [207.204.29.187]) by mail4.bellatlantic.net (8.9.1/8.9.1) with ESMTP id HAA10676; Wed, 2 Feb 2000 07:12:37 -0500 (EST) Received: (from majordom@localhost) by ns3.qth.net (8.9.3/8.9.3) id XAA01390 for lowfer-outgoing; Tue, 1 Feb 2000 23:03:00 -0500 Received: from sun4.scgroup.com (ns.scgroup.com [192.55.122.7]) by ns3.qth.net (8.9.3/8.9.3) with ESMTP id XAA01386 for <lowfer@qth.net>; Tue, 1 Feb 2000 23:02:53 -0500 Received: from windev1.scgroup.com (windev1.scgroup.com [192.55.122.104]) by sun4.scgroup.com (8.9.1b+Sun/8.9.1) with SMTP id UAA18648 for <lowfer@qth.net>; Tue, 1 Feb 2000 20:02:35 -0800 (PST) Message-ID: <004c01bf6d32$630186a0$687a37c0@scgroup.com> From: "Stewart Nelson" <sn@scgroup.com> To: <lowfer@qth.net> References: <000801bf6a6f$bda3b580$c74488cd@valuedcu> Subject: Re: [Lowfer] antennas Date: Tue, 1 Feb 2000 20:02:55 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2314.1300 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300 Sender: owner-lowfer@qth.net Precedence: bulk Reply-To: "Stewart Nelson" <sn@scgroup.com> X-Mozilla-Status2: 00000000 Hi all, Thanks to everyone who responded to my query about using a well for grounding. The answers were about evenly divided between "it's wonderful" and "it's useless" :) I suspect that both might be true, depending on how far down the water is. In my case the water comes up almost to ground level, so it seemed promising, and I attempted to make an impedance measurement at 180 kHz. I used an audio generator with the hot lead connected to the well casing, and the cold attached to a shovel driven into the ground about 50 feet away. A current probe showed that I could get about 20 mA p-p to flow. At first, I connected the scope ground to a second shovel, placed about 50 feet away in the opposite direction, and connected the channel 2 input to the well. I saw almost no trace of the 180 kHz. There was about 1.5 volts p-p of (badly distorted) 60 Hz. It makes sense to see some AC, because the house electrical system is grounded to the water piping, but, if my ground resistance estimate of 0.5 ohms is accurate, then about 1 A RMS is flowing. Is this plausible? Then, I put a small capacitor in series with the scope to eliminate the 60 Hz. Now there is about 0.5 V p-p of RF. It's AM broadcast. Again, I would expect some, but this much is inconsistent with the impedance I measured at 180 kHz, below. Is is possible that the house wiring picks up the RF and couples it to the well? Or that the well impedance is many times higher at 1 MHz than at 180 kHz? Or is my impedance measurement grossly invalid? Next, I rigged a parallel L-C across the scope, tuned to 180 kHz, with a suitable series resistor. Now I can see the signal clearly. It's about 100 mV p-p, so the impedance is about 5 ohms. There is more than 45 degrees of phase shift (voltage leading). A rough guess is that there is 3 + j4 ohms. If valid, this is probably much better than ground radials. But I don't want to go to the effort of erecting an antenna here if this is bogus - there are better locations if radials are needed. Also, I noticed that the voltage waveform (using the current for sync) appeared as two waves about 10 degrees apart. Closer inspection showed that the phase was varying at a 120 Hz rate. Could the AC line current flowing cause the RF well impedance to change? Doing something to the generator path? Or is this some artifact of my test setup? I don't see the effect when a resistive test load is used. Finally, thanks to Dick Carroll for warning me about possible lightning damage to the well pump. But I am also worried that a lesser ground could increase the chances of fire or damage to other equipment. How are most lowfer antennas grounded for safety? Any ideas appreciated. 73, Stewart KK7KA To unsubscribe, send to MAJORDOMO@qth.net "unsubscribe lowfer" (Do not send to list!!) Send on list submissions to lowfer@qth.net ]