Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_MED,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: EATSERVER: mailn 1166; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id uBRBeYjQ024103 for ; Tue, 27 Dec 2016 12:40:36 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1cLq3y-00052B-Tm for rs_out_1@blacksheep.org; Tue, 27 Dec 2016 11:37:02 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1cLq3y-000522-Dc for rsgb_lf_group@blacksheep.org; Tue, 27 Dec 2016 11:37:02 +0000 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.87) (envelope-from ) id 1cLq3u-0007aj-N1 for rsgb_lf_group@blacksheep.org; Tue, 27 Dec 2016 11:37:01 +0000 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id 3008020854 for ; Tue, 27 Dec 2016 12:36:58 +0100 (CET) Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 3tnv3F6Pgjz105r for ; Tue, 27 Dec 2016 12:36:57 +0100 (CET) Message-ID: <58625259.9060909@posteo.de> Date: Tue, 27 Dec 2016 12:36:57 +0100 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: "rsgb_lf_group@blacksheep.org" X-Scan-Signature: 739d4fb39bd02fc5a2de5437a39bb056 Subject: VLF: Back on 5.17 kHz / 58 km... Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit 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-Scanned-By: MIMEDefang 2.75 Status: O X-Status: X-Keywords: X-UID: 9969 Hi VLF, It's time to come back to 5.17 kHz where i have been in the last kite experiments 2010/2011. The best result was about 10 dB in 3.8 mHz in 904 km distance, detected by SQ5BPF. His website about this experiment is still on the web, http://www.lipkowski.org/~sq5bpf/dk7fc_20101023/index_en.html In these kite tests my ERP was about 3 mW on 5170 Hz. But this was with a 300m vertical antenna! With my fixed antenna i can never radiate such strong signals. The limiting factor is the coil which can handle 250 mA on that frequency. The radiation resistance is about 210 uOhm, so the ERP will be up to 23 uW. So this is 20 dB weaker (oh, actually i expected it is even more weaker). But on the fixed antenna it is no problem to transmit 100x longer!! We will see what is possible on that band with such a low power. Who wants to make a guess? :-) But i'm not yet sure if i can resonate the antenna down there at all. The plan is to use the small coil that was used for 6470 Hz. Inside the coil there are 100 iron powder cores, shown here https://dl.dropboxusercontent.com/u/19882028/VLF/20160415_155753.jpg and here https://dl.dropboxusercontent.com/u/19882028/VLF/20160415_163021.jpg I want to replace (a few) of them by ferrite cores, many ferrite cores "switched in parallel". I need to get the inductance down from 1.2 H to 2.0 H. So first the ferrite cores much provide a higher effective µr (ur) which is no problem i guess. Secondly the must not saturate (to much), which is the critical question here. We will see what happens... It's the right time in the year for such a work and i think i can do a first transmission on 58 km during this week... 73, Stefan