Return-Path: Received: from rly-dc09.mx.aol.com (rly-dc09.mail.aol.com [172.19.136.38]) by air-dc02.mail.aol.com (v123.4) with ESMTP id MAILINDC021-b3f4a1a6f24201; Mon, 25 May 2009 06:13:07 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dc09.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDC093-b3f4a1a6f24201; Mon, 25 May 2009 06:12:54 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M8X9v-0003uL-NP for rs_out_1@blacksheep.org; Mon, 25 May 2009 11:11:55 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M8X9v-0003uC-6q for rsgb_lf_group@blacksheep.org; Mon, 25 May 2009 11:11:55 +0100 Received: from mhost01h.leeds.ac.uk ([129.11.77.238]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M8X9t-0003UK-CB for rsgb_lf_group@blacksheep.org; Mon, 25 May 2009 11:11:55 +0100 Received: from APOLLO2.ds.leeds.ac.uk (apollo2.leeds.ac.uk [129.11.5.5]) by mhost01h.leeds.ac.uk (8.14.3/8.14.3) with ESMTP id n4PACvHR027721 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NOT) for ; Mon, 25 May 2009 11:12:57 +0100 (BST) Received: from HERMES8.ds.leeds.ac.uk ([fe80::39ce:23e:d0b5:7e24]) by APOLLO2.ds.leeds.ac.uk ([129.11.5.5]) with mapi; Mon, 25 May 2009 11:11:45 +0100 From: Chris Trayner To: "rsgb_lf_group@blacksheep.org" Date: Mon, 25 May 2009 11:11:44 +0100 Thread-Topic: Re: Modelling aerials Thread-Index: AcnczD8R1vgSpxTSRiOLxSCR2wAtZAAUlTWy Message-ID: <38F4A9873A5B474DB6FB337B1B69ABA11CEAA58819@HERMES8.ds.leeds.ac.uk> References: <4A199D1F.7070201@btconnect.com>,<007a01c9dccb$b3021620$0900a8c0@AM> In-Reply-To: <007a01c9dccb$b3021620$0900a8c0@AM> Accept-Language: en-US, en-GB Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, en-GB MIME-Version: 1.0 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: RE: Re: Modelling aerials Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=TO_ADDRESS_EQ_REAL 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-IP: 193.82.116.20 X-Mailer: Unknown (No Version) Hi Andy and Richard, > I can imagine that modelling ground strata of a rocky hill top will be almost impossible.=20 Our cave radio experience certainly supports that. The geological maps will=20= give you the underlying rock type, but overlaying it you often have an unkno= wn depth of soil.=20 The next problem is that you need the conductivities of these. For the rock,= the map will give the specific type of (e.g.) sandstone, but the reference=20= works on conductivity will probably just list "sandstone" and give conductiv= ities ranging over several orders of magnitude.* The final cause to reach for the bottle is when you realise that the conduct= ivities of the soil, and of the rock unless it's impermiable to water, will=20= depend on how saturated they are. This will depend on the recent rainfall hi= story. If you want to try modelling that I'll come back in a few years and r= ead your doctoral thesis (or put flowers on your grave) ... Some of us in the cave radio community have in fact speculated that it might= be more profitable to turn this round and make the sort of electrical measu= rements that Alan alluded to to find out the electrical properties of the ro= ck. * If anyone does know of reference works that give the conductivities for ma= ny specific rock types (e.g. Great Scar Limestone as against just limestone)= , I'd be very grateful to be told. 73, Chris G4OKW