Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_40_50,HTML_MESSAGE,RATWARE_GECKO_BUILD,SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u1RLf1Ze001680 for ; Sat, 27 Feb 2016 22:41:01 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aZmY5-0003KG-LW for rs_out_1@blacksheep.org; Sat, 27 Feb 2016 21:37:13 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aZmY5-0003K5-AZ for rsgb_lf_group@blacksheep.org; Sat, 27 Feb 2016 21:37:13 +0000 Received: from mout01.posteo.de ([185.67.36.65]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.86) (envelope-from ) id 1aZmWF-00048d-5u for rsgb_lf_group@blacksheep.org; Sat, 27 Feb 2016 21:37:12 +0000 Received: from dovecot03.posteo.de (dovecot03.posteo.de [172.16.0.13]) by mout01.posteo.de (Postfix) with ESMTPS id 642A320A06 for ; Sat, 27 Feb 2016 22:34:51 +0100 (CET) Received: from mail.posteo.de (localhost [127.0.0.1]) by dovecot03.posteo.de (Postfix) with ESMTPSA id 3qCLjR2KwDz5vNB for ; Sat, 27 Feb 2016 22:34:51 +0100 (CET) Message-ID: <56D2167A.9040403@posteo.de> Date: Sat, 27 Feb 2016 22:34:50 +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: <56D08BEF.7070708@abelian.org> <8D33ED4DA8562EE-14E0-601004@webmail-vm018.sysops.aol.com> <56D0934B.1040700@abelian.org> <56D098D3.80501@abelian.org> <56D0B22B.2020107@abelian.org> <56D0B58A.80908@tiscali.co.uk> <56D0C373.1090004@abelian.org> <56D0CC55.1060400@tele2.se> <56D0D587.7080309@abelian.org> <56D1DEAF.10202@abelian.org> In-Reply-To: X-Scan-Signature: 3547ef0bd9aa4f6a2596c8a6b1b20265 Subject: Re: LF: MF: EbNaut Content-Type: multipart/alternative; boundary="------------030503080105080207070902" 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 2.56 on 10.1.3.11 Status: O X-Status: X-Keywords: X-UID: 7059 This is a multi-part message in MIME format. --------------030503080105080207070902 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Paul, Your core is a good choice and it will handle 500W without a problem on MF. I'm also using the blue EPCOS cores for nearly any transformer on LF and MF. https://dl.dropboxusercontent.com/u/19882028/MF/20150822_162812.jpg I prefer the B64290L699X830 (https://www.buerklin.com/default.asp?search=B64290L699X830%2C+R+63%2C+10800+nH&event=ShowSE%28%29&l=d&ch=97476&suggestion=) :-) 73, Stefan Am 27.02.2016 21:03, schrieb Andy Talbot: > Why not just twist together some multi-filar turns and use all the > sirface area you can for cooiling? > > I use standard ETD54 type SMPSU cores for 400 Watts at 475kHz and > 700 Watts on 137kHz and they barely get warm. I think the ferrite > type is EC90, but the cores are quite old, and may be EC85. Those > are just standard transformer winding used for isolation and impedance > changing. > > Andy G4JNT > > On 27 February 2016 at 17:36, Paul Nicholson > wrote: > > On again. > > Freq: 477690.00000 Hz > Chars: 15 > Symbols: 0.5 seconds > Code: 8K19A > Duration: 496 seconds, 00:08:16 > Repeat: XX:00 XX:20 XX:40 > > I rewound the transformer, the primary windings are the braid > of coax and the secondary is the series connected coax cores. > FETs running a lot cooler now and the only thing getting > warm is the coax. DC in 27V at 3.8A and getting the same > antenna volts as yesterday with 150W in so that's a lot better. > The cause of last night's high unloaded current was a shorted > secondary turn - the insulation had melted. > > I'm a bit worried about using coax like this, the inner will be > at the temperature of the braid plus its own temperature rise. > I expect a short from primary to secondary when the dielectric > of the tightly wound coax coil softens. I'd like to find some > flat braid with high temperature insulation. > > The toroid I'm using is this one > > http://uk.rs-online.com/web/p/ferrite-rings/2120803/ > > which I picked because I found a MF PA design on the web which > used it. It's the wire that's producing the heat, not the core. > > -- > Paul Nicholson > -- > > --------------030503080105080207070902 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Paul,

Your core is a good choice and it will handle 500W without a problem on MF.
I'm also using the blue EPCOS cores for nearly any transformer on LF and MF.
https://dl.dropboxusercontent.com/u/19882028/MF/20150822_162812.jpg
I prefer the B64290L699X830 (https://www.buerklin.com/default.asp?search=B64290L699X830%2C+R+63%2C+10800+nH&event=ShowSE%28%29&l=d&ch=97476&suggestion=)
:-)

73, Stefan

Am 27.02.2016 21:03, schrieb Andy Talbot:
Why not just twist together some multi-filar turns and use all the sirface area you can for cooiling?

I  use standard ETD54  type  SMPSU cores for 400 Watts at 475kHz and 700 Watts on 137kHz and they barely get warm.  I think the ferrite type is EC90, but the cores are quite old, and may be EC85.    Those are just standard transformer winding used for isolation and impedance changing.   

Andy  G4JNT

On 27 February 2016 at 17:36, Paul Nicholson <vlf0403@abelian.org> wrote:
On again.

 Freq: 477690.00000 Hz
 Chars: 15
 Symbols: 0.5 seconds
 Code: 8K19A
 Duration: 496 seconds, 00:08:16
 Repeat: XX:00 XX:20 XX:40

I rewound the transformer, the primary windings are the braid
of coax and the secondary is the series connected coax cores.
FETs running a lot cooler now and the only thing getting
warm is the coax.   DC in 27V at 3.8A and getting the same
antenna volts as yesterday with 150W in so that's a lot better.
The cause of last night's high unloaded current was a shorted
secondary turn - the insulation had melted.

I'm a bit worried about using coax like this, the inner will be
at the temperature of the braid plus its own temperature rise.
I expect a short from primary to secondary when the dielectric
of the tightly wound coax coil softens.   I'd like to find some
flat braid with high temperature insulation.

The toroid I'm using is this one

 http://uk.rs-online.com/web/p/ferrite-rings/2120803/

which I picked because I found a MF PA design on the web which
used it.  It's the wire that's producing the heat, not the core.

--
Paul Nicholson
--


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