X-GM-THRID: 1202173441387390069 X-Gmail-Labels: rsgb lf X-Gmail-Received: fe8b2e2518748903366dac07f10b7ce32fe43e62 Delivered-To: daveyxm@gmail.com Received: by 10.54.72.15 with SMTP id u15cs16129wra; Mon, 1 May 2006 13:16:51 -0700 (PDT) Received: by 10.48.203.20 with SMTP id a20mr437595nfg; Mon, 01 May 2006 13:16:49 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id q28si1539141nfc.2006.05.01.13.16.47; Mon, 01 May 2006 13:16:49 -0700 (PDT) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Faek7-0001WT-2Q for rs_out_1@blacksheep.org; Mon, 01 May 2006 21:11:39 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Faek6-0001WK-GF for rsgb_lf_group@blacksheep.org; Mon, 01 May 2006 21:11:38 +0100 Received: from imo-d03.mx.aol.com ([205.188.157.35]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1Fag9R-0002Jh-HE for rsgb_lf_group@blacksheep.org; Mon, 01 May 2006 22:41:57 +0100 Received: from WarmSpgs@aol.com by imo-d03.mx.aol.com (mail_out_v38_r7.5.) id l.253.a04dd5e (3866) for ; Mon, 1 May 2006 16:11:25 -0400 (EDT) From: WarmSpgs@aol.com Message-ID: <253.a04dd5e.3187c56d@aol.com> Date: Mon, 1 May 2006 16:11:25 EDT To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 9.0 for Windows sub 5055 X-Spam-Flag: NO X-Spam-Score: -0.8 (/) X-Spam-Report: autolearn=disabled,AWL=-0.987,HTML_30_40=0.056,HTML_MESSAGE=0.001,NO_REAL_NAME=0.178 Subject: Re: LF: EMF sensitivity? Content-Type: multipart/alternative; boundary="-----------------------------1146514285" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.3 required=5.0 tests=HTML_MESSAGE,NO_REAL_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Status: O X-Status: X-Keywords: X-UID: 6036 -------------------------------1146514285 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Marek, I am not aware of effects like yours being reported from exposure to much stronger LF fields at LORAN sites and other transmitting facilities. The magnetic field 2 meters from a loading coil handling 500 watts might be near or slightly above accepted limits for human exposure at low frequencies, but not greatly in excess. However, as you surmise, you are not just being exposed to LF alone. The two middle items on your list are, far and away, the most likely sources. In addition to the normal high-frequency components of the switching waveform, it is possible for there to be surprising amounts of UHF energy from parasitic oscillations during the on/off transitions of the FETs. This depends a lot on circuit layout. Your symptoms sound very much like a story I heard in my younger days of an amateur radio operator whose unshielded high-power HF rig was emitting parasitic oscillations in the high UHF range. He, too, experienced a rash and other allergy or flu-like symptoms, and eventually developed eye problems. I would very much encourage you shield the rig adequately before further operation! John -------------------------------1146514285 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Marek, I am not aware of effects like yours being reported from exposur= e to much stronger LF fields at LORAN sites and other transmitting facilitie= s. The magnetic field 2 meters from a loading coil handling=20= 500 watts might be near or slightly above accepted limits for= human exposure at low frequencies, but not greatly in excess.

However, as you surmise, you are not just being exposed to LF alone.&nb= sp;

The two middle items on your list are, far and away, the most likely so= urces. In addition to the normal high-frequency components o= f the switching waveform, it is possible for there to be surprising amounts=20= of UHF energy from parasitic oscillations during the on/off transitions of t= he FETs. This depends a lot on circuit layout.

Your symptoms sound very much like a story I heard in my younger days o= f an amateur radio operator whose unshielded high-power HF rig was emit= ting parasitic oscillations in the high UHF range. He, too, experience= d a rash and other allergy or flu-like symptoms, and eventually developed ey= e problems. I would very much encourage you shield the rig adequately=20= before further operation!

John

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