Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-df05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 9BC6D380000FE; Sun, 2 Dec 2012 18:27:33 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1TfIvX-0005PM-4B for rs_out_1@blacksheep.org; Sun, 02 Dec 2012 23:26:23 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1TfIvW-0005PD-14 for rsgb_lf_group@blacksheep.org; Sun, 02 Dec 2012 23:26:22 +0000 Received: from relay2.uni-heidelberg.de ([129.206.210.211]) by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.77) (envelope-from ) id 1TfIvS-0006MA-Rr for rsgb_lf_group@blacksheep.org; Sun, 02 Dec 2012 23:26:20 +0000 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 qB2NQGae000639 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 3 Dec 2012 00:26:17 +0100 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 qB2NQFbV011127 for ; Mon, 3 Dec 2012 00:26:16 +0100 Message-ID: <50BBE391.7090302@iup.uni-heidelberg.de> Date: Mon, 03 Dec 2012 00:26:09 +0100 From: =?ISO-8859-2?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: <003f01cdd0cd$7ba8de30$6600a8c0@dupaod6d2sep9z> <1EB8E61D15EF47F696AC3097C512A95D@White> In-Reply-To: <1EB8E61D15EF47F696AC3097C512A95D@White> X-Spam-Score: -2.3 (--) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Marcin, Further suggestions: -If you have found the resonance with the existing setup, then i would do initial high power tests with it. You will have some first with this configuration. It will be no super DX but e.g. SQ5BPF will receive you! -I would forget about the variable duty cycle. Use a fixed 50% duty cycle. If you want to vary the duty cycle anyway there is a solution by using a stereo pot and 2 capacitors and a CD4093 for example. But there may be some transient voltage problems, as Markus mentioned. -For initial tests, you don't need a perfect stable transmit frequency. The typical stability on an xtal of the PC soundcard is fine as long as you keep temperature variations small. SpecLab does it perfectly, also in QRSS or DFCW! -Markus is right about the poor efficiency in the current configuration. So, _for later tests_ i would tend to rise L and to lower C, the parallel C. -It would be a first step to use a much bigger body for the coil. You should use at least 80cm diameter. If you use the same wire on a big water barrel, then you will get much higher L values and so you can reduce the parallel C. [...] 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 [129.206.210.211 listed in list.dnswl.org] -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 571129b349252c35b2bc09d7a1c6d0f3 Subject: Re: LF: Problem with generator to VLF transmitter - correction Content-Type: multipart/alternative; boundary="------------000700030705080104070908" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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-sid: 3039ac1d40d950bbe3e45bd3 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. --------------000700030705080104070908 Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit Hi Marcin, Further suggestions: -If you have found the resonance with the existing setup, then i would do initial high power tests with it. You will have some first with this configuration. It will be no super DX but e.g. SQ5BPF will receive you! -I would forget about the variable duty cycle. Use a fixed 50% duty cycle. If you want to vary the duty cycle anyway there is a solution by using a stereo pot and 2 capacitors and a CD4093 for example. But there may be some transient voltage problems, as Markus mentioned. -For initial tests, you don't need a perfect stable transmit frequency. The typical stability on an xtal of the PC soundcard is fine as long as you keep temperature variations small. SpecLab does it perfectly, also in QRSS or DFCW! -Markus is right about the poor efficiency in the current configuration. So, _for later tests_ i would tend to rise L and to lower C, the parallel C. -It would be a first step to use a much bigger body for the coil. You should use at least 80cm diameter. If you use the same wire on a big water barrel, then you will get much higher L values and so you can reduce the parallel C. It looks like the height above ground is remarkable. And 60V*50A sounds good as well. However you will have some problems to generate 3 kW with the circuit shown in the image. Anyway, have a good start! Aah, a last suggestion: Build an amperemeter for the antenna current! This is most interesting to see and to check for improvements. 73, Stefan/DK7FC Am 02.12.2012 23:27, schrieb Markus Vester: > sorry "(Cant+Cp)/8" is a typo, should be "(Cant+Cp)/Cant". 73, Markus > > *From:* Markus Vester > *Sent:* Sunday, December 02, 2012 11:21 PM > *To:* rsgb_lf_group@blacksheep.org > *Subject:* Re: LF: Problem with generator to VLF transmitter > > Marcin, > happy to read about upcoming Dreamers band activity! Just a few comments: > - 70 mH inductance seems too small for the antenna capacitance. Using > capacitors (4 nF) in parallel to the antenna is unfortunately very > inefficient, as only a small part of the coil current will go to the > antenna. This would decrease the effective coil Q by a large > factor (Cant+Cp)/8, ie about 8. It would be better to use more turns > of thinner wire to bring the inductance up. > - according to the photo, the IGBT module seems to be wired as a > half-bridge, with the transistors internally connected in series at > C2E1. You would have to break up that connection to use them > in grounded emitter push-pull configuration. > - do you want to change the duty cycle to modulate the output power? > With both transistors off, the current will have to go through > the freewheeling diodes, which will probably have unwanted effects on > the voltage waveforms. > - SpecLab with samplerate correction is probably the easiest choice > for an 8.97 kHz sinusoidal signal generator. But with some PC's > there can be problems with sampling gaps or glitches on the output. In > my opinion, an optimal hardware solution is a programmable Rubidium > synthesizer, followed by a fixed divider eg /1024. Chinese second-hand > FE5680-A modules are available around 80 Euro on eBay. > - Stefan mentioned linear AM by outphasing. For this you would need > two half bridges with two independent drivers, which can be driven by > two channels from a stereo soundcard. > Wishing the best of luck, > 73, Markus (DF6NM) > > *From:* Marcin > *Sent:* Sunday, December 02, 2012 9:42 PM > *To:* rsgb_lf_group@blacksheep.org > *Subject:* LF: Problem with generator to VLF transmitter > > Hi All! > We're building an 8,970kHz VLF transmitter at SP2KDS club. > We almost have everything in place: > > * transmitter (on IGBT transistors -- diagram attached) > * antenna coil 76mH > http://www.sp2kds.pl/136khz/303-klubowa-cewka-vlf-na-897khz > * 4 capacitors 4nF/30kV > * 100m long, 20m high antenna > * supply 60V 50 A > > What we still need is a generator to feed the transmitter. Required > parameters are the following: > > * 8,970kHz frequency > * regulating range +-0.05Hz > * adjusting duty cycle of 5 to 45%, at 5% for two signals at the > same time > * two signals shifted by 180 degrees > > A friend of mine has promised to build it but it's been over a year > now and nothing has happened. > Is there a software which would use a soundcard with the > aforementioned parameters? > 73! Marcin SQ2BXI --------------000700030705080104070908 Content-Type: text/html; charset=ISO-8859-2 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by relay2.uni-heidelberg.de id qB2NQGae000639 Hi Marcin,

Further suggestions:
-If you have found the resonance with the existing setup, then i would do initial high power tests with it. You will have some first with this configuration. It will be no super DX but e.g. SQ5BPF will receive you! -I would forget about the variable duty cycle. Use a fixed 50% duty cycle. If you want to vary the duty cycle anyway there is a solution by using a stereo pot and 2 capacitors and a CD4093 for example. But there may be some transient voltage problems, as Markus mentioned.
-For initial tests, you don't need a perfect stable transmit frequency. The typical stability on an xtal of the PC soundcard is fine as long as you keep temperature variations small. SpecLab does it perfectly, also in QRSS or DFCW!
-Markus is right about the poor efficiency in the current configuration. So, for later tests i would tend to rise L and to lower C, the parallel C.
-It would be a first step to use a much bigger body for the coil. You should use at least 80cm diameter. If you use the same wire on a big water barrel, then you will get much higher L values and so you can reduce the parallel C.

It looks like the height above ground is remarkable. And 60V*50A sounds good as well. However you will have some problems to generate 3 kW with the circuit shown in the image. Anyway, have a good start!

Aah, a last suggestion: Build an amperemeter for the antenna current! This is most interesting to see and to check for improvements.

73, Stefan/DK7FC

Am 02.12.2012 23:27, schrieb Markus Vester:
sorry "(Cant+Cp)/8" is a typo,=A0<= /font>should be=A0"(Cant+Cp)/Cant".=A0 73, Markus=A0

Sent: Sunday, December 02, 2012 11:21 PM
Subject: Re: LF: Problem with generator to VLF transmitter<= /div>

Marcin,
=A0
happy to read about upcoming Dreamers band activity! Just a few comments:
=A0
-=A070 mH inductance seems=A0too s= mall for the antenna capacitance. Using capacitors (4 nF) in parallel to the antenna=A0is unfortunately=A0very inefficient, as=A0only a small part of = the coil current will go to the antenna.=A0This would decrease the effective coil Q by a large factor=A0(Cant+Cp)/8, ie about 8.=A0It would be better = to use more turns of thinner wire to=A0bring the inductance up.
=A0
- according to the photo, the IGBT module seems to be wired as=A0a half-bridge, with the transistors internally=A0connected in series at C2E1.=A0You would have to=A0break up = that connection to use them in=A0grounded emitter push-pull configuration.
=A0
- do you want to change the duty cycle to modulate the output power? With both transistors off, the current will have to go through the=A0freewheeling diodes, which will=A0probably have unwanted effects on the voltage waveforms.
=A0
- SpecLab with samplerate correcti= on is probably the easiest choice for an 8.97 kHz sinusoidal signal generator. But=A0with some PC's there=A0can be=A0problems with sampling g= aps or glitches on the output. In my opinion, an optimal hardware solution=A0is a programmable Rubidium synthesizer, followed by a fixed divider eg /1024. Chinese second-hand FE5680-A modules are available=A0around 80 Euro on eBay.
=A0
- Stefan mentioned linear AM by outphasing. For this you would need two half bridges with two independent drivers, which can be driven by two channels from a stereo soundcard.
=A0
Wishing the best of luck,
=A0
73, Markus (DF6NM)
=A0
=A0
=A0

From: Marcin
Sent: Sunday, December 02, 2012 9:42 PM
Subject: LF: Problem with generator to VLF transmitter

Hi All!
We’re building an 8,970kHz VLF transmitter at SP2KDS club.
We almost have everything in place:
=A0
What we still need is a generator to feed the transmitter. Required parameters are the following:
  • 8,970kHz frequency
  • regulating range=A0+-0.05Hz
  • adjusting duty cycle of 5 to 45%, at 5% for two signals at the same time
  • two signals shifted by 180 degree= s
A friend of mine has promised to build it but it’s been over= a year now and nothing has happened.
Is there a software which would use a soundcard with the aforementioned parameters?
=A0
73! Marcin SQ2BXI
--------------000700030705080104070908--