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, HTML_MESSAGE,RCVD_IN_DNSWL_MED,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; 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 uBUGXcPL005788 for ; Fri, 30 Dec 2016 17:33:40 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1cMzzR-0002Qn-MJ for rs_out_1@blacksheep.org; Fri, 30 Dec 2016 16:25:09 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1cMzzQ-0002Qe-Et for rsgb_lf_group@blacksheep.org; Fri, 30 Dec 2016 16:25:08 +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 1cMzzM-0006Mp-4G for rsgb_lf_group@blacksheep.org; Fri, 30 Dec 2016 16:25:07 +0000 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id F245D209EC for ; Fri, 30 Dec 2016 17:25:00 +0100 (CET) Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 3tqsJD2t8Vzytm for ; Fri, 30 Dec 2016 17:25:00 +0100 (CET) Message-ID: <58668A5B.1080206@posteo.de> Date: Fri, 30 Dec 2016 17:24:59 +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 References: <58625259.9060909@posteo.de> In-Reply-To: <58625259.9060909@posteo.de> X-Scan-Signature: ed9dcf4545ec97a65e50af1597e81212 Subject: Re: VLF: Back on 5.17 kHz / 58 km... Content-Type: multipart/alternative; boundary="------------000902080807070508020103" 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: 10014 This is a multi-part message in MIME format. --------------000902080807070508020103 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Hi VLF, I managed to resonate my antenna on 5170 Hz. It was necessary to increase the inductance from 1.2 H to 2 H. This was done by increasing the number of iron powder cores (T106-52) from 100 to 176! It is the coil out of 10 stacked yoghurt cups that i got from Markus (many thanks again!). An image from the stacked cores into the coil: https://dl.dropboxusercontent.com/u/19882028/VLF/20161229_194850.jpg Although the number of turns of this coil is constant and the stacking height is even higher (means a lower coupling of the coils and so they must have a lower L), the inductance is higher now. So this increase must come from the cores. I clearly saw that the Q is significantly higher now, so the cores are a good choice for any VLF band. Also i need less power now. It also means that the proximity effect must be lower now (due to the lower coupling), because the Q is higher and the antenna current and the R(DC) of the coils is the same as on 6470 Hz. Now i'm running 230 mA since 14:40 UTC. I intend to run it until 8 UTC, then a first EbNaut message follows. The antenna voltage increased from 11.3 kV to 14.2 kV @ 230 mA. So far the antenna current is not really stable but it becomes foggy outside and i did not yet add the transductor to the system. Maybe i'm trying to build an ALC into SpecLab. This should work well now with the new interpreter command for the bypass factor of the delay line :-) Ah there is even a short video (6 sec, 1.2 MB) where you can see and hear (!) the coil and its internal fan on the roof while running at 14 kV: http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/VLF_coil_at_230mA_14kV_5170Hz.mp4 (hopefully the link works). Lets be optimistic, i'm announcing the first EbNaut message for tomorrow: *f = 5170.000000 Hz Start time: 31.12.2016 09:00:00 UTC Symbol length: 60 s Characters: 2 CRC 16 Coding 8K19A Duration: 6h, 08m, 0s Antenna current: ~ 230 mA* 73, Stefan Am 27.12.2016 12:36, schrieb DK7FC: > 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 > > > --------------000902080807070508020103 Content-Type: text/html; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit Hi VLF,

I managed to resonate my antenna on 5170 Hz. It was necessary to increase the inductance from 1.2 H to 2 H. This was done by increasing the number of iron powder cores (T106-52) from 100 to 176! It is the coil out of 10 stacked yoghurt cups that i got from Markus (many thanks again!). An image from the stacked cores into the coil: https://dl.dropboxusercontent.com/u/19882028/VLF/20161229_194850.jpg
Although the number of turns of this coil is constant and the stacking height is even higher (means a lower coupling of the coils and so they must have a lower L), the inductance is higher now. So this increase must come from the cores. I clearly saw that the Q is significantly higher now, so the cores are a good choice for any VLF band. Also i need less power now. It also means that the proximity effect must be lower now (due to the lower coupling), because the Q is higher and the antenna current and the R(DC) of the coils is the same as on 6470 Hz.

Now i'm running 230 mA since 14:40 UTC. I intend to run it until 8 UTC, then a first EbNaut message follows.
The antenna voltage increased from 11.3 kV to 14.2 kV @ 230 mA. So far the antenna current is not really stable but it becomes foggy outside and i did not yet add the transductor to the system. Maybe i'm trying to build an ALC into SpecLab. This should work well now with the new interpreter command for the bypass factor of the delay line :-)
Ah there is even a short video (6 sec, 1.2 MB) where you can see and hear (!) the coil and its internal fan on the roof while running at 14 kV: http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/VLF_coil_at_230mA_14kV_5170Hz.mp4 (hopefully the link works).

Lets be optimistic, i'm announcing the first EbNaut message for tomorrow:

f = 5170.000000 Hz
Start time: 31.12.2016   09:00:00 UTC
Symbol length: 60 s
Characters: 2
CRC 16
Coding 8K19A
Duration: 6h, 08m, 0s
Antenna current: ~ 230 mA


73, Stefan



Am 27.12.2016 12:36, schrieb DK7FC:
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



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