Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 40F85380000B7; Sat, 30 Mar 2013 20:08:46 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1UM5ob-0005aj-1h for rs_out_1@blacksheep.org; Sun, 31 Mar 2013 00:08:05 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1UM5oa-0005aa-DS for rsgb_lf_group@blacksheep.org; Sun, 31 Mar 2013 00:08:04 +0000 Received: from imr-ma01.mx.aol.com ([64.12.206.39]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1UM5oX-0001CY-TJ for rsgb_lf_group@blacksheep.org; Sun, 31 Mar 2013 00:08:03 +0000 Received: from mtaout-mb04.r1000.mx.aol.com (mtaout-mb04.r1000.mx.aol.com [172.29.41.68]) by imr-ma01.mx.aol.com (Outbound Mail Relay) with ESMTP id D73713800009E for ; Sat, 30 Mar 2013 20:07:39 -0400 (EDT) Received: from Black (188-195-246-26-dynip.superkabel.de [188.195.246.26]) by mtaout-mb04.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 04311E00008D for ; Sat, 30 Mar 2013 20:07:38 -0400 (EDT) Message-ID: <6A619EDB5EC748B8B3B7AE3787290027@Black> From: "Markus Vester" To: References: <000501ce2d39$07bdd430$6401a8c0@JAYDELL> <0BE8C4F802314145B0A4A752B6DBDFA5@Black> <001901ce2d7c$eb8cc930$6401a8c0@JAYDELL> In-Reply-To: <001901ce2d7c$eb8cc930$6401a8c0@JAYDELL> Date: Sun, 31 Mar 2013 01:07:03 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1364688459; bh=SjA3XvTU/FvfVz7/w6b3S3JvhMrPZiZ5OhQpxOQmtzU=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=AKJ/EoyEEfJ6RYUm98A4dThUmwadPcZRxX/D+6q+XQsJ6VmUFyDcA1UCuJ5gFeMy0 pPebAJS1axV08aSmiOLRBg03De/ixz46dYMliQ9mbhc9KhwdEP1LkwPvqs8DcRIV7g acP7m8CUdBt0PxaJkNu5gYhBrU4Lw410GpC+PG/8= X-AOL-SCOLL-SCORE: 0:2:344566432:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-Spam-Score: -1.3 (-) 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: Fortunately it was not half as bad as it looks. During the transmission I heard the fan speed up as the current from the power supply dropped, opened the roof window where the coil is sitting, noticed the little flames eating the white plastic bag, and blew them out just like a birthday candle. The fire had probably started in the greenish foam insulation where the wire from the bottom of the outer coil runs back up to the top of the inner coil. Afterwards the whole coil was still intact DC-wise (4 ohms) but showed slightly lower inductance and very high RF loss resistance (about 53 ohms), apparently a short circuit between adjacent turns. After separating the injured turns with my fingernails, the RF resistance went back down to the normal 7 ohms, so I'm confident that this coil can be repaired. http://df6nm.bplaced.net/LF/pictures/topload_doubled/burnt_litz_detail_31.jpg [...] Content analysis details: (-1.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [64.12.206.39 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 SPF_PASS SPF: sender matches SPF record -1.3 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 91e1efbff209cbddb14bc9e018c2cfe8 Subject: LF: Re: Re: Re: Re: DF6NM DK7FC in CT Content-Type: multipart/alternative; boundary="----=_NextPart_000_000D_01CE2DAC.0DDD39F0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_NAME 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-AUTHENTICATION: mtain-db02.r1000.mx.aol.com ; domain : mx.aol.com DKIM : fail X-AOL-OVERRIDE-PIK-REASON: Y x-aol-sid: 3039ac1d405651577e8e470b X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_000D_01CE2DAC.0DDD39F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Fortunately it was not half as bad as it looks. During the transmission = I heard the fan speed up as the current from the power supply dropped, = opened the roof window where the coil is sitting, noticed the little = flames eating the white plastic bag, and blew them out just like a = birthday candle. The fire had probably started in the greenish foam = insulation where the wire from the bottom of the outer coil runs back up = to the top of the inner coil. Afterwards the whole coil was still intact = DC-wise (4 ohms) but showed slightly lower inductance and very high RF = loss resistance (about 53 ohms), apparently a short circuit between = adjacent turns. After separating the injured turns with my fingernails, = the RF resistance went back down to the normal 7 ohms, so I'm confident = that this coil can be repaired. http://df6nm.bplaced.net/LF/pictures/topload_doubled/burnt_litz_detail_31= .jpg But I decided that I want to build a more substantial coil using Decca = RF litzwire, the "secret weapon" which serves so well in Stefan's = beautiful large glass coil. However as this insulated litz is much = thicker than the old one (4.5 mm od instead of 1.5 mm), the only way to = get a compact 5 mH coil is winding in multiple layers. Here's my first = attempt http://df6nm.bplaced.net/LF/pictures/topload_doubled/decca_fourlayer_coil= _29.jpg , using 180 turns in a staggered four-layer winding, about 28 cm = diameter and 19 cm long in five segments. The inductance was then = adjusted by removing 18 turns from the bottom end. DC resistance is only = 1 ohm, but at 137 kHz the loss is a disappointing 6.5 ohms, hardly = better than the thin litz wire used before! This is clearly due to = proximity effect, ie eddy currents induced within each inner filament by = the magnetic field created by the outer layers. For a given strand = diameter, there must be an optimal total thickness of the layers, and = using more copper than that reduces the Q factor again. Guess I will try = to rewind this coil on a larger former in three or two layers, which = will require a longer wire but probably reduce AC losses. Antenna pulled in to low position now, watching LF but no transmissions = from here tonight. Best 73, Markus (DF6NM) ----- Original Message -----=20 From: jrusgrove@comcast.net=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Saturday, March 30, 2013 8:29 PM Subject: LF: Re: Re: Re: DF6NM DK7FC in CT Markus Sorry to hear of the mishap ... pix of the damage are always = appreciated! Wonder if your neighbors got to see the 'show'?=20 If you haven't started a fire while transmitting LF you're not running = enough power ;~) . Jay W1VD WD2XNS WE2XGR/2 ----- Original Message -----=20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Saturday, March 30, 2013 10:12 AM Subject: LF: Re: Re: DF6NM DK7FC in CT Here's the result of 13 minutes at 1W ERP = http://www.df6nm.bplaced.net/LF/pictures/topload_doubled/loading_coil_fir= e_28.jpg ...more work to do :-( Best 73, Markus ----- Original Message -----=20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Saturday, March 30, 2013 1:56 PM Subject: LF: Re: DF6NM DK7FC in CT ... At the end of a 15 minute transmission, the temperature at the inside = of the litzwire loading coil had gone up to 80=B0C, so I seem to be = limited by current rather than voltage now.=20 ... ------=_NextPart_000_000D_01CE2DAC.0DDD39F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Fortunately it was not half as bad as = it looks.=20 During the transmission I heard the fan speed up as the current from the = power=20 supply dropped, opened the roof window where the coil is sitting,=20 noticed the little flames eating the white plastic bag, and blew = them out=20 just like a birthday candle. The fire had probably = started in the=20 greenish foam insulation where the wire from the bottom of the outer = coil runs=20 back up to the top of the inner coil. Afterwards the whole coil was = still=20 intact DC-wise (4 ohms) but showed slightly lower inductance = and very=20 high RF loss resistance (about 53 ohms), apparently a short circuit = between=20 adjacent turns. After separating the injured = turns with=20 my fingernails, the RF resistance went back down to the normal 7 ohms, = so I'm=20 confident that this coil can be repaired.
http://df6nm.bplaced.net/LF/pictures/topload_doubled/burnt_= litz_detail_31.jpg
 
But I decided that I want to = build a more=20 substantial coil using Decca RF litzwire, the "secret weapon" which = serves so=20 well in Stefan's beautiful large glass coil. However as = this insulated=20 litz is much thicker than the old one (4.5 mm od instead of 1.5 = mm), the=20 only way to get a compact 5 mH coil is winding in multiple = layers.=20 Here's my first = attempt
http://df6nm.bplaced.net/LF/pictures/topload_doubled/dec= ca_fourlayer_coil_29.jpg ,=20 using 180 turns in a staggered = four-layer=20 winding, about 28 cm diameter and 19 cm long in five=20 segments. The inductance was then adjusted by = removing 18 turns=20 from the bottom end. DC resistance is only 1 ohm, but at 137 = kHz the=20 loss is a disappointing 6.5 ohms, hardly better than the thin litz = wire=20 used before! This is clearly due to proximity effect, ie eddy currents = induced=20 within each inner filament by the magnetic field = created by=20 the outer layers. For a given strand diameter, there must be an = optimal=20 total thickness of the layers, and using more copper than that = reduces=20 the Q factor again. Guess I will try to rewind this coil on a = larger=20 former in three or two layers, which will require a longer wire=20 but probably reduce AC losses.
 
Antenna pulled in to low position now, = watching LF=20 but no transmissions from here tonight.
 
Best 73,
Markus (DF6NM)
 
 
----- Original Message -----=20
From: jrusgrove@comcast.net
Sent: Saturday, March 30, 2013 8:29 PM
Subject: LF: Re: Re: Re: DF6NM DK7FC in CT

Markus
 
Sorry to hear of the mishap ... pix of = the damage=20 are always appreciated! Wonder if your neighbors got to see the 'show'?=20
 
If you haven't started a fire = while=20 transmitting LF you're not running enough power ;~) .
 
Jay W1VD  WD2XNS  = WE2XGR/2
----- Original Message -----
From:=20 Markus=20 Vester
Sent: Saturday, March 30, 2013 = 10:12=20 AM
Subject: LF: Re: Re: DF6NM = DK7FC in=20 CT

Here's the result of 13 = minutes at 1W=20 ERP
http://www.df6nm.bplaced.net/LF/pictures/topload_double= d/loading_coil_fire_28.jpg
...more work to = do :-(
 
Best 73,
Markus
 
----- Original Message -----=20
From: Markus=20 Vester
Sent: Saturday, March 30, 2013 1:56 PM
Subject: LF: Re: DF6NM DK7FC in CT

...
At the end of a 15 minute = transmission, the=20 temperature at the inside of the litzwire loading coil had gone up to = 80=B0C, so=20 I seem to be limited by current rather than voltage now.
...
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