Return-Path: Received: from mtain-db12.r1000.mx.aol.com (mtain-db12.r1000.mx.aol.com [172.29.64.96]) by air-di02.mail.aol.com (v129.4) with ESMTP id MAILINDI021-eaba4c8b3c1efb; Sat, 11 Sep 2010 04:21:50 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db12.r1000.mx.aol.com (Internet Inbound) with ESMTP id 61FC438000122; Sat, 11 Sep 2010 04:21:48 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OuLJk-0002V6-Jw for rs_out_1@blacksheep.org; Sat, 11 Sep 2010 09:20:12 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OuLJa-0002Ut-5k for rsgb_lf_group@blacksheep.org; Sat, 11 Sep 2010 09:20:02 +0100 Received: from mtaout01-winn.ispmail.ntl.com ([81.103.221.47]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OuLJZ-0002L3-47 for rsgb_lf_group@blacksheep.org; Sat, 11 Sep 2010 09:20:02 +0100 Received: from know-smtpout-4.server.virginmedia.net ([62.254.123.2]) by mtaout01-winn.ispmail.ntl.com (InterMail vM.7.08.04.00 201-2186-134-20080326) with ESMTP id <20100911081955.VAMM3266.mtaout01-winn.ispmail.ntl.com@know-smtpout-4.server.virginmedia.net> for ; Sat, 11 Sep 2010 09:19:55 +0100 Received: from [86.29.39.189] (helo=desktop) by know-smtpout-4.server.virginmedia.net with esmtpa (Exim 4.63) (envelope-from ) id 1OuLJS-00041b-RO for rsgb_lf_group@blacksheep.org; Sat, 11 Sep 2010 09:19:55 +0100 From: "James Cowburn" To: References: <4C86CD6A.7030507@iup.uni-heidelberg.de> <4C8A0E6C.7080704@iup.uni-heidelberg.de> <16658606A1034120BA2D6ECE4CC79E58@JimPC> <002a01cb5102$6315f940$0401a8c0@xphd97xgq27nyf> <1078A0BF0C83451780876BF06785686B@JimPC> Date: Sat, 11 Sep 2010 09:19:30 +0100 Message-ID: <046b01cb518a$0ef70ec0$0217aac0@desktop> MIME-Version: 1.0 X-Mailer: Microsoft Office Outlook 11 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3664 thread-index: ActRLjKhBGBe5xbKTdiUsMfImBxI1AAWvr4g In-Reply-To: <1078A0BF0C83451780876BF06785686B@JimPC> X-Cloudmark-Analysis: v=1.1 cv=DhNl2YeytwJssBBGe49HJX82LNDFEEVkpVB34RXKaPo= c=1 sm=0 a=kj9zAlcOel0A:10 a=8RloEfZUAAAA:8 a=F3M5lZpKAAAA:8 a=JIVTwUX_GXDv2kSdMdUA:9 a=6FqN73HWwCh7h8KG6r0A:7 a=L88s7a9MsuCs8BI46dfCcpvuyy0A:4 a=CjuIK1q_8ugA:10 a=O58u2wXj750A:10 a=wk6s2zzMB60A:10 a=DKQasMv2A9qMxa8Q:21 a=cdNd0zdBJNJ-5RdP:21 a=HpAAvcLHHh0Zw7uRqdWCyQ==:117 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: LF: RE: Re: UK NoVs Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.2 required=5.0 tests=EXCUSE_16 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-sid: 3039ac1d40604c8b3c1c7d45 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Hi Jim Thanks for this very useful analysis. My expectations are currently a lot more modest and if I can get a 9khz signal to yourself, Roger (XBM), Chris (XIZ) and possibly with luck and a following wind out to 100km+ I will be more than pleased with what will almost certainly be a standard G7NKS compromise lash up. The chances of my wife authorizing a 150ft mast are zero, plus my new job over in NI during the week will eat into my time. For me the challenge is in "just doing it", I doubt I'll ever be a QRO T/A station like Mal but a nice 60km contact would do me just fine Thanks again for the analysis and fingers crossed that the Met Office are kind to us With best regards Jim G7NKS Dr. James Cowburn E james.cowburn@virgin.net The information transmitted is intended only for the person to whom it is addressed and may contain confidential and/or privileged material. If you are not the intended recipient, you are hereby notified that you must not read this message. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. Consequently, this email is not intended to be contractually binding. If you received this in error, please contact the sender, return the message as well as its attachments and delete the whole from any computer. -----Original Message----- From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of James Moritz Sent: 10 September 2010 22:19 To: rsgb_lf_group@blacksheep.org Subject: LF: Re: UK NoVs Dear Jim, Mal, LF Group G3KEV wrote... > Jim > Do you expect to reach me with this sort of erp? I am QRV when you are > ready. I expect you to hear me with a few hundred watts ...As a feasibility study, one can make order-of-magnitude estimates of required ERP fairly easily. The noise level at 9kHz in quiet winter-time conditions at a reasonably quiet QTH during DK7FC's previous tests was roughly 8uV/m per sqrt(Hz) by my estimate. The distance between G3KEV and G7NKS is roughly 200km. If we assume G7NKS actually achieves 5uW ERP, field strength at G3KEV will be E = 7*sqrt(Perp) / d, around 80nV/m, assuming ground wave losses are neglegible. This is 40dB below the noise floor in 1Hz bandwidth, so the RX bandwidth would have to be reduced to 100 microhertz to get 0dB SNR, or say 50 uHz to get a few dB positive SNR. I think this would be feasible to do; it would require frequency stability of the order of parts in 10^9 at both TX and RX, so both Mal and Jim would have to make some improvements! So can Mal really expect to be "heard with a few hundred watts"? Mal is always a bit vague about his antenna, but often mentions 3 x 150m wires supported by a 100ft mast, and unless he has a whole collection of other 100ft masts to support the other ends, one would assume this means sloping wires and an effective height in the region of 15m. Capacitive reactance at 9kHz would be roughly 6 kilohms, allowing 3A or so of antenna current with a reasonable voltage of 20kV. With a relatively big antenna like this, one would hope for a fairly low loss resistance, provided a very low-loss loading coil can be made. Let's optimistically assume 50ohms total loss resistance - to get 3A Iant, 450W TX power would be needed, which is stretching the "few hundred watts" a bit, but never mind. Radiation resistance at 9kHz would be 320 micro-ohms, and with Iant = 3A, ERP works out to about 5mW. This is comparable with the ERP from DK7FC's VLF experiments. 200km away at G7NKS, field strength would be about 2.5uV/m. I reckon if you actually want an audible CW signal, it has to be above 0dB SNR in a normal CW filter bandwidth, say 250Hz. The band noise in 250Hz would be about 130uV/m, so 2.5uV/m is 34dB below an audible signal level. So even though G3KEV might have an ERP 1000 times greater as an optimistic estimate, it would still be far too weak to be actually heard at G7NKS. QRSS30 should be quite easy, though. So, the verdict is that it is probably feasible for G7NKS to produce a detectable 9kHz signal over a distance of a few hundred km, but extreme narrow bandwidths, integrating periods of several hours and high frequency stability would be needed to do it. It should be possible for Mal to produce a 9kHz signal that can be detected at a similar range using techniques familiar from LF amateur radio, but it certainly won't be audible at that distance. Cheers, Jim Moritz 73 de M0BMU