Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w6VIM0e8022525 for ; Tue, 31 Jul 2018 20:22:03 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fkZB0-0003wg-FK for rs_out_1@blacksheep.org; Tue, 31 Jul 2018 19:15:18 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fkZAw-0003wX-I7 for rsgb_lf_group@blacksheep.org; Tue, 31 Jul 2018 19:15:14 +0100 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1fkZAu-0006JK-FI for rsgb_lf_group@blacksheep.org; Tue, 31 Jul 2018 19:15:13 +0100 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id 2AF4B20F32 for ; Tue, 31 Jul 2018 20:15:08 +0200 (CEST) X-DKIM-Result: Domain=posteo.de Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.de; s=2017; t=1533060909; bh=wh0kmMkwkTHXkLzu1X5rl2GClXDUilKcv9nCs1Z25TA=; h=Date:From:To:Subject:From; b=CZy3iuNGjL+c0aaV0UzeMLgpqwlH32XPHLKokoXx1JFy9t3NstzO2FzqJ0YCeqoLV VjDJb+1Kbl0cQNs4Y2OtzqpELFoM5eQqeK5yCwZKBO6h+ahFgy4QM+ykB8PFRlw6kB LWnMKO6dOWsdAWf6GYkhaspr0BGEH/K5DomxxxyPaeRdTwz1wG52/3CSZo7j6MLH7c wrTXgmeOlRksHm10psUlQD4Gt98aYcOLInueVYvUrK2qbVcdljg8JsJqCPT+dkSXIg UwOwl28BEYoZZdaiZGu71LqFtv5quiW8H49ZbTdQsnQ4D6HJOwWaTh8ybd56eFrb1u uLOr0qh9f+aoQ== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 41g4NX4Gj1z9rxD for ; Tue, 31 Jul 2018 20:15:08 +0200 (CEST) Message-ID: <5B60A72B.90103@posteo.de> Date: Tue, 31 Jul 2018 20:15:07 +0200 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 References: <5B54CCCB.6060903@posteo.de> <5B59E687.5030805@posteo.de> <5B5C3ABF.3030809@posteo.de> <5B5C4A63.3040504@posteo.de> <5B5C5446.30105@posteo.de> <14080281532786049@iva8-6be7d23653d9.qloud-c.yandex.net> <5B5CD03F.40602@posteo.de> <14811811532865577@myt4-415a3339794b.qloud-c.yandex.net> <5B5DC8BC.9030601@posteo.de> <5B5E2D7D.6050908@posteo.de> <5B5F678B.7000506@posteo.de> <6dc15e3e-a325-4be2-55e3-44413e814f8a@web.de> <5B6050DA.60905@posteo.de> In-Reply-To: <5B6050DA.60905@posteo.de> X-Spam-Score: -2.3 (--) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Hi all, Now i had a closer look to the scope traces i photographed last weekend. For the 900m long wire the phase is 42 deg at 8270 Hz. That would mean that the ground loop has an L of 3 mH if the resistive component is R = 175 Ohm. So i would need 123 nF to series resonate the loop. The speaker cable should arrive in 2 days so i can do a next test next weekend, this time with much lower losses. 1 A antenna current is the goal! Ah and i like to try 2.47 kHz and 1.67 kHz and 1.57 kHz and 0.97 kHz!!! [...] Content analysis details: (-2.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [185.67.36.66 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: d63ea50e288c5ecb9bd7a86eeabe94f2 Subject: Re: VLF: Earth antenna transmissions on a guide rail | calculations Content-Type: text/plain; charset=UTF-8; format=flowed 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=0.0 required=5.0 tests=none 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 Hi all, Now i had a closer look to the scope traces i photographed last weekend. For the 900m long wire the phase is 42 deg at 8270 Hz. That would mean that the ground loop has an L of 3 mH if the resistive component is R = 175 Ohm. So i would need 123 nF to series resonate the loop. The speaker cable should arrive in 2 days so i can do a next test next weekend, this time with much lower losses. 1 A antenna current is the goal! Ah and i like to try 2.47 kHz and 1.67 kHz and 1.57 kHz and 0.97 kHz!!! I even modified our expensive Rohde & Schwarz scope. It's internal power supply has an output voltage of (guess!) 12.0 V. So i spent a series diode and now i can run it on batteries, just a normal '12 V' 7 Ah lead gel accu. It consumes 2.85 A during operation, quite much. With the scope i can accurately measure the phase and capture the screen. So this will be another improvement. Well, 3 mH at 8270 Hz. If this is true, then the loop size can be estimated. Assuming a simple model of a normal single turn loop with a rectangular cross section area, where one side is known to be 900m, the depth of the current into the soil can be calculated. I found the formula from ON7YDs website http://www.strobbe.eu/on7yd/136ant/#TransmitLoop and build an Excel table where i can tune the parameters until they appear reasonable. The results show something like a loop size of 108000 m^2 and the current flows back in a depth of 120 m. I'mnot sure whether this is the right order of magnitude at all :-) The excel sheet also calculates the radiation resistance (210 uOhm) and efficiency of the antenna (-59 dB) but this appears to be quite optimistic... 73, Stefan >> >> Am 30.07.2018 um 21:31 schrieb DK7FC: >>> Hi VLF and ULF friends, >>> >>> In the attachment you can find 3 spectrograms from transmission of >>> the last weekend. For the 8270 Hz and 2970 Hz transmission i took >>> the data of the 900m ground loop, 5170 Hz is from the 450m ground loop. >>> The 8270 Hz signal was very strong even in 3.8 mHz ('DFCW-600'). >>> Some real QRSS-60 would have been possible! >>> The spectrograms also show that there was no trace on the frequency >>> of interest before and after the transmission (no traces from the >>> right channel ( 1 PPS) ). >>> >>> A few minutes ago i built the switchable network for resonating the >>> antenna properly. And i actually ordered 1000 m of that 0.75 mm^2 >>> loudspeaker cable. Thus, in the next experiment i think the Q of the >>> antenna will be much higher and it will be possible to tune it >>> accurately. Then, the tuning capacitance will tell us what the >>> ground loop inductance is! And then, we can calculate the depth >>> where the current is flowing backwards in the ground, asuming a >>> simple model in first steps. >>> Next, we can see whether the inductance or depth stays constant at >>> lower frequencies (hopefully it will increase!) by resonating the >>> antenna at 2.97 kHz for example. >>> >>> BTW i measured the DC resistance of the wire i used last weekend, it >>> is 116 Ohm, so it agrees well with the calculated 120 Ohm... >>> The new wire should have 21.4 Ohm only. >>> >>> The big advantage of this antenna is that no high voltage and large >>> coils are needed. Usually the voltage is the limiting factor for a >>> VLF or ULF TX antenna. But not here. Here it is the power of the PA. >>> The antenna could easily handle 2 kW, which means 5.16 A, no problem >>> for the wire. And it would be a 20 dB stronger signal than last >>> weekend... >>> >>> 73, Stefan >>> >>> >>> >>> Am 29.07.2018 23:11, schrieb DK7FC: >>>> As a next result from today's experiment, here is a spectrum peak >>>> of the 2970.005 Hz transmission. I reached 20 dB SNR in 180 uHz! >>>> This far more than expected, in July anyway. >>>> It is the first ULF transmission (by amateurs) from an earth >>>> electrode TX antenna, detected in the far field. >>>> Spectrograms will be produced soon... >>>> >>>> 73, Stefan >>>> >>>> >>>> Am 29.07.2018 16:01, schrieb DK7FC: >>>>> Hello Roman, VLF, >>>>> >>>>> I transmitted pure carriers each time. It was just a first test. >>>>> >>>>> Today i've done a second experiment, this time using a 900m long >>>>> wire! So the wire should have about 125 Ohm DC resistance. I >>>>> measured 220 mA DC at 38.4 V, so the overall loss is 175 Ohm. Very >>>>> interesting; the ground loss resistance stays at 50 Ohm although >>>>> the distance between the electrodes has doubled! >>>>> If i would use the 0.75 mm loudspeaker cable then i can reduce the >>>>> losses by 100 Ohm which is more than 50 %, so i will gain 3 dB at >>>>> the same output power! Then with a switch mode PA having nearly >>>>> 100% efficiency i may gain 2 dB more (mmy lonear mode PA was not >>>>> well matched today and quite warm). So maybe i can reach 1 A >>>>> antenna current with just 75 watts??!!! >>>>> Today i tuned to 550 mA antenna current again, at 8270 Hz. With >>>>> the scope, i measured the phas, it was more inductive than >>>>> yesterday. I actually found a 1 uF MKP-10 cap in my car and >>>>> switched it in series to the antenna. This improved the phase >>>>> slightly. Then i also found a low pass filter for 137 kHz, the >>>>> pypical pi configuration, i.e. it acts as 4*22 nF in parallel here >>>>> on this frequency. Switching this in series leads to a low >>>>> current, so the C is to small. So for the next experiment i'm >>>>> preraring a switchable C network (47n, 100n, 220n, 470n, 1u, 2.2u, >>>>> 4.7u). It will be even more necessary when i lower the wire >>>>> resistance (higher Q). >>>>> Well, today the QRN was much lower, especially for the 2970.005 Hz >>>>> transmission period. Yesterday this was totally buried in the >>>>> noise on my RX on the tree. But today! I transmitted another 90 >>>>> minutes with much lower QRN background. I already have a clear >>>>> spectrum peak but i like to try to improve it a bit more before >>>>> presenting it here. >>>>> Todays carrier transmissions: >>>>> 8270.000 Hz : 08:12...09:33 UTC >>>>> 2970.005 Hz : 09:42...11:15 UTC >>>>> >>>>> Sorry for the confusing email ;-) >>>>> >>>>> 73, Stefan >> >> >> >