Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 05245380000A6; Fri, 6 Apr 2012 20:17:02 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1SGJK3-0006nR-AO for rs_out_1@blacksheep.org; Sat, 07 Apr 2012 01:16:07 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1SGJK2-0006nI-IL for rsgb_lf_group@blacksheep.org; Sat, 07 Apr 2012 01:16:06 +0100 Received: from relay2.uni-heidelberg.de ([129.206.210.211]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1SGJK0-0005M6-MR for rsgb_lf_group@blacksheep.org; Sat, 07 Apr 2012 01:16:06 +0100 Received: from freitag.iup.uni-heidelberg.de (freitag.iup.uni-heidelberg.de [129.206.29.204]) by relay2.uni-heidelberg.de (8.13.8/8.13.8) with ESMTP id q370G3Gc022794 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sat, 7 Apr 2012 02:16:03 +0200 Received: from [129.206.22.206] (pc206.iup.uni-heidelberg.de [129.206.22.206]) by freitag.iup.uni-heidelberg.de (8.12.11.20060308/8.11.2) with ESMTP id q370G3MW021769 for ; Sat, 7 Apr 2012 02:16:03 +0200 Message-ID: <4F7F8721.50006@iup.uni-heidelberg.de> Date: Sat, 07 Apr 2012 02:15:29 +0200 From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= 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: <4F78CCE0.5050906@iup.uni-heidelberg.de> <4F7F03A4.8080000@iup.uni-heidelberg.de> In-Reply-To: <4F7F03A4.8080000@iup.uni-heidelberg.de> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: LOPTs Content-Type: multipart/alternative; boundary="------------000405080106050601080901" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=HTML_FONTCOLOR_UNSAFE, HTML_MESSAGE 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-SCOLL-SCORE: 0:2:456289024:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d41194f7f877e1310 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------000405080106050601080901 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay2.uni-heidelberg.de id q370G3Gc022794 VLF, In the evening i got the idea to make a comparison of the signal level=20 when using the LOPT and another reference signal. The levels were=20 measured and compared in SpecLab. I used an E field probe some 10m=20 distant, well shielded to prevent overloading of the input stage. No=20 noise reduction tools were used (connected to L1). As the reference signal is used my netbook and again SpecLab to generate=20 a 8970 Hz sine wave (which looks perfect on the scope). To get a higher=20 voltage i took 2 of the described audio transformers (1:10 types) and=20 switched them in parallel on the primary side and serial on the=20 secondary side. With a portable scope i measured 25 Vp. This produced a=20 signal level of -49 dB. When using the LOPT i can measure -15 dB. So my measurement and assumption to have 2 kV rms on the antenna is=20 wrong. It is just *900 V* *rms *:-(( After the DFCW-600 test in the afternoon, the LOPT was warm, but just=20 the ferrite, not the windings. So there must already be some saturation=20 of the material. I was just running 15 Watts or so. Now i did some=20 changes on the drive circuit and brought the LOPT outside on the roof=20 again. Since it was cold first, the current consumption was just half=20 the value as i stopped the transmission. However the current was rising=20 continuously. My new conclusion is that this kind of transformer is not really the=20 best choice, even for local tests. What i like to have is a compact=20 loading coil that can be covered and protected from rain, for permanent=20 tests. Anyway it was an interesting test and i will further investigate. BTW i=20 received my DFCW-600 signal in 3.0 km distance when using the E probe in=20 the forest. S/N was 15 dB in 3.8 mHz. Should be better anyway 73, Stefan/DK7FC Am 06.04.2012 16:54, schrieb Stefan Sch=E4fer: > VLF, > > The LOPT still works, seems to be no problem. Just a FET was sk.=20 > Somehow all the previous problems are gone now and i am getting about=20 > 2 kV rms from the transformer. So i stopped my LF beacon on 137 and=20 > QSYed to 8.97000 kHz. I also found the problem why my last=20 > transmission had so many phase glitches. Now the PC is locked to GPS=20 > again. The PA takes about 15 W input power, no not much DX is to be=20 > expected, just a local test. I do some tests with the VLF active E=20 > probe now, receiving my own signal in some distance and compare the=20 > S/N from the forest and a flat field. > I think Paul can't receive my weak signal but we've often been wrong=20 > with such assumptions :-) > > BTW i'm transmitting DFCW-600 centered at 8970.00000 Hz, so i should=20 > be outside eventual other VLF tests by DF6NM. > > 73, Stefan/DK7FC > > PS: If all works well with the transformer over a longer period, i=20 > intend to run a stable carrier over several days or transmit ma full=20 > call in DFCW-60000 or so :-) But the signal is 20 dB stronger with the=20 > big coil and another 20 dB stronger with the 300m kite... > > > Am 01.04.2012 23:47, schrieb Stefan Sch=E4fer: >> Hi Roger, >> >> Well, they are not as suitable as i expected. Just a few kV can be=20 >> generated and applied to the wire. But that's fine for local tests. I=20 >> didn't measure the L but rather tried to find a resonance. I took two=20 >> 1 nF capacitors and a 50 Ohm resistor in series to make an equivalent=20 >> circuit of my antenna for tests in the shack. I built a class D PA=20 >> out of the transformer, running at low input voltage and tried to=20 >> find the resonance. But there was no clear resonance. The output=20 >> waveform looks very different to a sine wave :-) Probably this is due=20 >> to internal winding capacitances, no idea. At least i spend a lot of=20 >> time and do not want to spend even more time on the LOPT project. >> A few weeks ago i tried some local tests with WOLF10 and got a decode=20 >> in 950m distance, which is close in the near field, so not really=20 >> exciting. I just want to go on a bit with these tests but i won't go=20 >> on much longer with the tests. The standard QRSS or DFCW or MFSK=20 >> analog modes, readout by a human is just the best in my opinion. >> >> 73, Stefan >> >> >> >> Am 01.04.2012 22:35, schrieb Roger Lapthorn: >>> Stefan et al, >>> >>> Not being too familiar with LOPTs what inductance are the windings?=20 >>> Are there particular non-encapsulated types that would be more=20 >>> suitable for compact loading coils for lower powered 8.97kHz E-field=20 >>> TX antennas? >>> >>> 73s >>> Roger G3XBM >>> >>> --=20 >>> http://qss2.blogspot.com/ >>> http://g3xbm-qrp.blogspot.com/ >>> http://www.g3xbm.co.uk >>> https://sites.google.com/site/sub9khz/ >>> >>> --------------000405080106050601080901 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit VLF,

In the evening i got the idea to make a comparison of the signal level when using the LOPT and another reference signal. The levels were measured and compared in SpecLab. I used an E field probe some 10m distant, well shielded to prevent overloading of the input stage. No noise reduction tools were used (connected to L1).
As the reference signal is used my netbook and again SpecLab to generate a 8970 Hz sine wave (which looks perfect on the scope). To get a higher voltage i took 2 of the described audio transformers (1:10 types) and switched them in parallel on the primary side and serial on the secondary side. With a portable scope i measured 25 Vp. This produced a signal level of -49 dB. When using the LOPT i can measure -15 dB.
So my measurement and assumption to have 2 kV rms on the antenna is wrong. It is just 900 V rms :-((

After the DFCW-600 test in the afternoon, the LOPT was warm, but just the ferrite, not the windings. So there must already be some saturation of the material. I was just running 15 Watts or so. Now i did some changes on the drive circuit and brought the LOPT outside on the roof again. Since it was cold first, the current consumption was just half the value as i stopped the transmission. However the current was rising continuously.

My new conclusion is that this kind of transformer is not really the best choice, even for local tests. What i like to have is a compact loading coil that can be covered and protected from rain, for permanent tests.

Anyway it was an interesting test and i will further investigate. BTW i received my DFCW-600 signal in 3.0 km distance when using the E probe in the forest. S/N was 15 dB in 3.8 mHz. Should be better anyway

73, Stefan/DK7FC



Am 06.04.2012 16:54, schrieb Stefan Schäfer:
VLF,

The LOPT still works, seems to be no problem. Just a FET was sk. Somehow all the previous problems are gone now and i am getting about 2 kV rms from the transformer. So i stopped my LF beacon on 137 and QSYed to 8.97000 kHz. I also found the problem why my last transmission had so many phase glitches. Now the PC is locked to GPS again. The PA takes about 15 W input power, no not much DX is to be expected, just a local test. I do some tests with the VLF active E probe now, receiving my own signal in some distance and compare the S/N from the forest and a flat field.
I think Paul can't receive my weak signal but we've often been wrong with such assumptions :-)

BTW i'm transmitting DFCW-600 centered at 8970.00000 Hz, so i should be outside eventual other VLF tests by DF6NM.

73, Stefan/DK7FC

PS: If all works well with the transformer over a longer period, i intend to run a stable carrier over several days or transmit ma full call in DFCW-60000 or so :-) But the signal is 20 dB stronger with the big coil and another 20 dB stronger with the 300m kite...


Am 01.04.2012 23:47, schrieb Stefan Schäfer:
Hi Roger,

Well, they are not as suitable as i expected. Just a few kV can be generated and applied to the wire. But that's fine for local tests. I didn't measure the L but rather tried to find a resonance. I took two 1 nF capacitors and a 50 Ohm resistor in series to make an equivalent circuit of my antenna for tests in the shack. I built a class D PA out of the transformer, running at low input voltage and tried to find the resonance. But there was no clear resonance. The output waveform looks very different to a sine wave :-) Probably this is due to internal winding capacitances, no idea. At least i spend a lot of time and do not want to spend even more time on the LOPT project.
A few weeks ago i tried some local tests with WOLF10 and got a decode in 950m distance, which is close in the near field, so not really exciting. I just want to go on a bit with these tests but i won't go on much longer with the tests. The standard QRSS or DFCW or MFSK analog modes, readout by a human is just the best in my opinion.

73, Stefan



Am 01.04.2012 22:35, schrieb Roger Lapthorn:
Stefan et al,

Not being too familiar with LOPTs what inductance are the windings? Are there particular non-encapsulated types that would be more suitable for compact loading coils for lower powered 8.97kHz E-field TX antennas?

73s
Roger G3XBM

--
http://qss2.blogspot.com/
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
https://sites.google.com/site/sub9khz/


--------------000405080106050601080901--