Return-Path: Received: from mtain-df02.r1000.mx.aol.com (mtain-df02.r1000.mx.aol.com [172.29.64.214]) by air-md05.mail.aol.com (v129.4) with ESMTP id MAILINMD054-8b874d836cdc6d; Fri, 18 Mar 2011 10:31:56 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-df02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3E81A380000AD; Fri, 18 Mar 2011 10:31:54 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q0ahc-0002Iy-Mj for rs_out_1@blacksheep.org; Fri, 18 Mar 2011 14:30:56 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q0ahc-0002Ip-7d for rsgb_lf_group@blacksheep.org; Fri, 18 Mar 2011 14:30:56 +0000 Received: from mail-iy0-f171.google.com ([209.85.210.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q0ahZ-0008Ki-Cd for rsgb_lf_group@blacksheep.org; Fri, 18 Mar 2011 14:30:56 +0000 Received: by iyf40 with SMTP id 40so5370742iyf.16 for ; Fri, 18 Mar 2011 07:30:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=efpgFXvS5NT2+YTYmVwdFDtiQ65zObAMn6bkX/x5eYI=; b=PKJybUaeFIiP+q6/Bx6y87fYaDQ4njlO23Gr9ofBbk+Aj6m7iTC95/T4zE12oaOZjW r5NPd89Vpcx9IxiINGg1Nq+gNTxIT8TEv0oa/8WpoxURiRF15ctVBY5Ir4i2GB5vJMhz p25KgEx2PVPKo9BHz2V90mdptdaC/edP5MsUg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=h3Oq/Eeqo7J+EPUv0WVepXNpUES3xAzyJDdm20bLvt6Hz7rqSQI2uUqCv+f3PwYs4w svngu9ICAsHPG6W27V6RbNjl/dZ3qA/zyD0XcDYLiRGrZ+kfzMhaWXPHFBlZPdeAjRAX 0f9MobNcaEioed4bl75X8orDuF1VtbP4cU5Zo= MIME-Version: 1.0 Received: by 10.43.49.69 with SMTP id uz5mr1740412icb.133.1300458296232; Fri, 18 Mar 2011 07:24:56 -0700 (PDT) Received: by 10.231.199.197 with HTTP; Fri, 18 Mar 2011 07:24:56 -0700 (PDT) In-Reply-To: References: Date: Fri, 18 Mar 2011 14:24:56 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Loop TX antennas at VLF? Content-Type: multipart/alternative; boundary=bcaec5299bf3cacc0f049ec28a09 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE 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 x-aol-global-disposition: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m018.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40d64d836cda3348 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --bcaec5299bf3cacc0f049ec28a09 Content-Type: text/plain; charset=ISO-8859-1 Here's an Excel S/S I did in the 73kHz days. Other people have updated versions now, but it serves to get you into a region to design from - or know when to not bother http://www.g4jnt.com/DownLoad/MAGLOOP.XLS Andy www.g4jnt.com On 18 March 2011 14:09, Roger Lapthorn wrote: > Just wondering if anyone has done the maths to work out what sort of ERP > could be expected at 8.97kHz with, say, 100W to a smallish loop antenna in > the garden? > > It would certainly avoid the need for very very large matching coils and > may be easier to engineer than a Marconi. Even an efficiency of -80dB would > allow 1uW ERP and, judging by results from G3XIZ with around 2uW, this could > be useful with long stable carrier transmissions of several hours. Most of > us could run a loop with an area of 100sq m. with thickish wire in our > gardens. A loop might also be more practical for portable operations perhaps > with a triangle with one high support. > > Certainly my own results with WSPR at 136 and 500kHz with just a few watts > and quite thin wire and around 80sq m loop area were encouraging. Mind you, > 9kHz is very much lower than 136kHz, so the radiation resistance would be > tiny I assume. > > 73s > Roger G3XBM > > -- > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > http://www.youtube.com/user/g3xbm > https://sites.google.com/site/sub9khz/ > G3XBM GQRP 1678 ISWL G11088 > --bcaec5299bf3cacc0f049ec28a09 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Here's an Excel S/S=A0I did in the 73kHz days.=A0=A0 Other people= =A0have updated versions now, but it serves to get you into a region to de= sign from - or know when to not bother
=A0
Andy

=A0
On 18 March 2011 14:09, Roger Lapthorn <rogerlapthorn@gma= il.com> wrote:
Just wondering if anyone has= done the maths to work out what sort of ERP could be expected at 8.97kHz= with, say, 100W to a smallish loop antenna in the garden?

It would certainly avoid the need for very very large matching coils= and may be easier to engineer than a Marconi. Even an efficiency of -80dB= would allow 1uW ERP and, judging by results from G3XIZ with around 2uW,= this could be useful with long stable carrier transmissions of several ho= urs. Most of us could run a loop with an area of 100sq m. with thickish wi= re in our gardens. A loop might also be more practical for portable operat= ions perhaps with a triangle with one high support.

Certainly my own results with WSPR at 136 and 500kHz with just a few= watts and quite thin wire and around 80sq m loop area were encouraging.= Mind you, 9kHz is very much lower than 136kHz, so the radiation resistanc= e would be tiny I assume.

73s
Roger G3XBM

-- http://g3xbm= -qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www= .youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
G3XBM=A0=A0 GQRP 1678= =A0=A0=A0 ISWL G11088

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