Return-Path: X-Spam-DCC: paranoid 1290; 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=-2.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_30_40,HTML_MESSAGE 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 u0D9tV7S010623 for ; Wed, 13 Jan 2016 10:55:31 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aJI4J-00028u-Oc for rs_out_1@blacksheep.org; Wed, 13 Jan 2016 09:50:19 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aJI4J-00028l-6j for rsgb_lf_group@blacksheep.org; Wed, 13 Jan 2016 09:50:19 +0000 Received: from mail-wm0-f42.google.com ([74.125.82.42]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1aJI3O-0006am-9W for rsgb_lf_group@blacksheep.org; Wed, 13 Jan 2016 09:50:18 +0000 Received: by mail-wm0-f42.google.com with SMTP id f206so286452632wmf.0 for ; Wed, 13 Jan 2016 01:49:09 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=znVkaBPJkst6I831n/Ybtx6FJ19fKZmSTsyHFNTK2x0=; b=iVxU9UOHJHgDQq0fr9nWEHrlEE3NpzVMeTwgZq6r+f3nMbx5VaYglmkJZh5EzRMD1k 2TGWC7W8p4GZMx3lEaziz14v7OMiTFeG1nAWN0pdgGLUkSSS9gtBHiEV1lIu7PaYCFwW 8BvfHaDOHtQtAJrdrO8QVwSi9zYXlLk+DT5AsxZjhZLwb8K66GbovLj4NmYFkL/hTVYi SIJwRm6L4ww7+PFO1F/r6NMTHNSdG9zoqVx5OfAPFpfzMNzOkLjHsImQlSn13ye8Q3fm 9+1wsMhWcY6ldpxYawXgRu4hRMJvx0rqhUxDvtCvPvJiVJF2g6KP8Kgb+9HCvi882N+k 68kg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=znVkaBPJkst6I831n/Ybtx6FJ19fKZmSTsyHFNTK2x0=; b=EdqdwhaylxcXETQRy8UzPm9Gul9HwHGmQ4SeiLNKdEhcyW4b/qaG9nNR+3CgFjO35I RT4vz7gwo1MMDW653j/NVx0zxHohOjGuOZBx3zEnYxIYck7Y9ZDu021d/p8WzUYEz0pJ Shf7HFFDy1p8p81SPn4tbVraPN/0U2jXPNxOqypXMlwi1vLsj1lYU72eiqZdCX3AwT1I giwroEJa/948XvLrGBjupd+33pXUxASF7PiJTj3MZ/YppjQX/EcM4uAlMLCp0OxZPQo6 0L4ZDB2E4Z/Qnu4tYXmx5BG5gsYMD/t6SCPvYM3TQPhrR4hO1CdGNRWVsSd3aGcR/QHn mfYA== X-Gm-Message-State: ALoCoQmisR1tmGNi1f/muoQujhCyWATEA6qz9UcnWO0fFH2OVMaXN+A03sSmPYl7L1v4PEZdUx+nFlWEzquhssafs12avloTgg== MIME-Version: 1.0 X-Received: by 10.194.103.164 with SMTP id fx4mr126394974wjb.56.1452678543765; Wed, 13 Jan 2016 01:49:03 -0800 (PST) Received: by 10.28.150.6 with HTTP; Wed, 13 Jan 2016 01:49:03 -0800 (PST) In-Reply-To: <15225b51bc6-5919-604e@webprd-m58.mail.aol.com> References: <15225b51bc6-5919-604e@webprd-m58.mail.aol.com> Date: Wed, 13 Jan 2016 09:49:03 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: 671be81035fb274514daa81d2095bf05 Subject: Re: LF: Decca 5501 Content-Type: multipart/alternative; boundary=047d7bf198e493032f052934141d 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 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 6295 --047d7bf198e493032f052934141d Content-Type: text/plain; charset=UTF-8 Bit late now, but I found the circuit of the Deca transmitter on G3XDV's website. http://homepage.ntlworld.com/mike.dennison/index/lf/decca/transmitter.htm. (Look at Fig 4, 'right' ) The driver circuit is just a single IFR520 FET switching into the transformer, so there is a net DC component - and of course it has to be a gapped core. In fact I'm a bit surprised at that circuitry, considering it has to switch the FETs alternately on each half of the output waveform, a single ended, flyback drive like that cannot possibly be symmetrical. Especially as the only reverse clamp appears to be a 68V zener.. But no doubt it is '*good enough'* In my 137kHz Tx design - very loosely based on the Decca output stage, I used a ferrite transformer (ungapped) and AC coupling from the driver IC into that. Andy G4JNT On 9 January 2016 at 09:26, wrote: > Thanks for the reply the transformer failed because of a small cut in the > rubber sleeving where it entered the ferrite. As the ferrite is earthed the > insulation on the litz was not good enough. I have a diagram and used that > to help rewind the new transformer. There does not appear to be any DC > component flowing in any winding according to the diagram. This unit has > possibly been exposed to damp conditions as two of the input transformers > were also OC primary and were rebuilt. One set of gate windings are running > at the OP from the bridge and this is the one that failed. I am thinking of > rebuilding the whole drive board to improve the isolation. I have already > added voltage regulators to supply the ICs, this makes the 27v current a > lot lower! > 73 Dave > > > > -----Original Message----- > From: Andy Talbot > To: rsgb_lf_group > Sent: Fri, 8 Jan 2016 18:53 > Subject: Re: LF: Decca 5501 > > The fact it is a GAPPED core is of more significance than that of the type > of ferrite. In a transformer application - as that appears to do - it is > surprising that a gapped one is used. I do not have the circuit of the > Decca transmitter to hand, but can only assume the driver has DC passing > through the winding, hence the need to introduce an air gap to prevent > ferrite saturation. > > In which case, the fact your unit overheated suggests your gap was too > small and the Vt product (volt-seconds is what saturates ferrite, not > current). BUT if that was the was the original unit, you need to ask the > question why it should have failed before trying to replace it. Those > transmitter units were very reliable under rated things, so components > failing need investigating. > > Andy G4JNT > > On 8 January 2016 at 11:09, wrote: > >> >> >> >> Does anybody know what ferrite grade is used on the fet driver >> transformer. I have had one burn out and have rebuilt it but would like to >> redesign it with better isolation between windings. Have tried various >> cores but cannot get the same clean waveform. The original is a gapped core >> of unknown material ferrite. Does anybody have a scrap amp unit that I can >> use for testing. The finished mods have given 1 kw at 53 volts, can be >> driven up to 75 volts but dummy load cannot take it!!! >> 73 Dave GW8GLO >> > > --047d7bf198e493032f052934141d Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Bit late now, but I found the circuit of the Deca tra= nsmitter on G3XDV's website. http://homepage.ntlworld.com/mi= ke.dennison/index/lf/decca/transmitter.htm.
(Look at Fig 4, &= #39;right' )

The driver circuit is just a sing= le IFR520 FET switching into the transformer, so there is a net DC componen= t - and of course it has to be a gapped core.=C2=A0 In fact I'm a bit s= urprised at that circuitry, considering it has to switch the FETs alternate= ly on each half of the output waveform, a single ended, flyback drive like = that cannot possibly be symmetrical.=C2=A0 Especially as the only reverse c= lamp appears to be a 68V zener..=C2=A0 But no doubt it is 'good eno= ugh'=C2=A0=C2=A0=C2=A0 In my 137kHz Tx design - very loosely based= on the Decca output stage, I used a ferrite transformer=C2=A0 (ungapped)= =C2=A0 and AC coupling from the driver IC into that.

Andy=C2=A0 G4JNT


On 9 January 2016 at 09:26, <<= a href=3D"mailto:gw8glo@aol.co.uk" target=3D"_blank">gw8glo@aol.co.uk&g= t; wrote:
Thanks for the reply the transformer failed beca= use of a small cut in the rubber sleeving where it entered the ferrite. As = the ferrite is earthed the insulation on the litz was not good enough. I ha= ve a diagram and used that to help rewind the new transformer. There does n= ot appear to be any DC component flowing in any winding according to the di= agram. This unit has possibly been exposed to damp conditions as two of the= input transformers were also OC primary and were rebuilt. One set of gate = windings are running at the OP from the bridge and this is the one that fai= led. I am thinking of rebuilding the whole drive board to improve the isola= tion. I have already added voltage regulators to supply the ICs, this makes= the 27v current a lot lower!
73 Dave



-----= Original Message-----
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Sent: Fri, 8 Jan 2016 18:53
Subject: Re: LF: Decca 5501

The fact it is a GAPPED core is of more significance than = that of the type of ferrite. =C2=A0 In a transformer application - as that = appears to do - it is surprising that a gapped one is used. =C2=A0 I do not= have the circuit of the Decca transmitter to hand, but can only assume the= driver has DC passing through the winding, hence the need to introduce an = air gap to prevent ferrite saturation.

In which case, the fact your unit overheated suggests your gap was too= small and the Vt product (volt-seconds is what saturates ferrite, not curr= ent). =C2=A0 BUT if that was the was the original unit, you need to ask the= question why it should have failed before trying to replace it. =C2=A0 =C2= =A0Those transmitter units were very reliable under rated things, so compon= ents failing need investigating.

Andy =C2=A0G4JNT

On 8 January 2016 at 11:09, &= lt;gw8glo@aol.co.uk> wrote:



Does anybody know what ferrite grade is used on the fet driver = transformer. I have had one burn out and have rebuilt it but would like to = redesign it with better isolation between windings. Have tried various core= s but cannot get the same clean waveform. The original is a gapped core of = unknown material ferrite. Does anybody have a scrap amp unit that I can use= for testing. The finished mods have given 1 kw at 53 volts, can be driven = up to 75 volts but dummy load cannot take it!!!
73 Dave GW8GLO


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