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 u0DAlskl010734 for ; Wed, 13 Jan 2016 11:47:54 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aJItO-0002rF-4T for rs_out_1@blacksheep.org; Wed, 13 Jan 2016 10:43:06 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aJItN-0002r6-MC for rsgb_lf_group@blacksheep.org; Wed, 13 Jan 2016 10:43:05 +0000 Received: from mail-wm0-f54.google.com ([74.125.82.54]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1aJIsO-0006uK-9T for rsgb_lf_group@blacksheep.org; Wed, 13 Jan 2016 10:43:04 +0000 Received: by mail-wm0-f54.google.com with SMTP id f206so289820248wmf.0 for ; Wed, 13 Jan 2016 02:41:49 -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=Na47f5F0tdhFnqA7y+E5Q493/SgKhuI9T+9J9CtIbvo=; b=kDzT0eE4Vn7jTN8ouPykelxjrMthc2xly9WKLcK88jYhy6GZVvzTY6ow7YBbM/wpNE WYZ2fKS54lJTCUqjaHts4GQZa4A2MfazKhJ6eRe3p3soa3mTrMf1x8kcGlvWj9fR9FDB EcF2H99YLFHprExoz0spnA3zvdE69FqefZzXNd15/Xd8MtXurPX3pZOuuifCSDhErxlj FxRDd3Off2CqnrmDMeodNzC6BIYttK1SpYAmPY7zsO8UccXcZVvELEFD632aL2CqH+uY xhKkdPKNoa3mPQVtcTF/vh3DICnISq5jznOotXF/pOOO95bw9L6Ap5I1QylZ1T6fpHeN hfNA== 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=Na47f5F0tdhFnqA7y+E5Q493/SgKhuI9T+9J9CtIbvo=; b=HicT0DZJ9bVpZK5jp37CpYUO7HY4g1Rj2Qm7WQoFmCcS9YeEiwUKpJHr0uh+qXses1 FfrNMry6VSMyayP0/oKYwa/3X61dMn6wt3b4wPaz8NrneSjsQ/6JLy0p7NCwKbanKSGa XthbU7RsTUHarH6d0nmdpVpjalyqk9AAitXhXF6gJKs5485mWz982SxTl4P8WszsXo0L iv9XsWQO4DvqbQeS0mztlZEnb3wWwI3WuqAvVvtK4V+jjrY/rNfENmt9nt3IpFi8hcWe mr/b/qz0tNuiZ7SHNgoe4O2TCNHcik/xdm5d2rHrvCrExHm1Yk6rj7gFSNbhMl+omNuh H3Yw== X-Gm-Message-State: ALoCoQm4okHbIkLyopm0I2tZ+SsvngEkP27YZGv2OOOAnYTSucrxxFtkEB0SwONQS81O1mmzEwfvTBmE1U7EmFpQ7d8SGCY/Zw== MIME-Version: 1.0 X-Received: by 10.194.95.72 with SMTP id di8mr9265013wjb.144.1452681708827; Wed, 13 Jan 2016 02:41:48 -0800 (PST) Received: by 10.28.150.6 with HTTP; Wed, 13 Jan 2016 02:41:48 -0800 (PST) In-Reply-To: <1523a82f816-4f04-68c2@webprd-a32.mail.aol.com> References: <1523a82f816-4f04-68c2@webprd-a32.mail.aol.com> Date: Wed, 13 Jan 2016 10:41:48 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: 5ad12379ca48ff091cbac2f0e4edb6f5 Subject: Re: LF: Decca 5501 Content-Type: multipart/alternative; boundary=047d7beb90a639ffd7052934d149 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: 6299 --047d7beb90a639ffd7052934d149 Content-Type: text/plain; charset=UTF-8 I've just looked again, and there's more to to the drive circuitry than that. It is single ended drive for current into the inductor, as I stated, but there is another IRF520 used as an active clamp (the circuit diagram was drawn a bit ambiguously, so didn't spot the arrangement straightaway). So when these two FETs are driven alternately there will be a proper equal amplitude symmetrical drive waveform generated. It is definitely used as an energy storage inductor though, hence a gapped core is essential. 'jnt On 13 January 2016 at 10:23, wrote: > Andy thanks for that I am looking to find a scrap amplifier module to > play around with with a view to rebuild the PCB and drive circuits. Looking > on a scope the switching is very symmetrical but that may be only luck. I > have used pushpull fets to drive another amp I designed and it worked well > using a rewound driver transformer from a pc power supply. The complete > setup is now on the QRP labs website if you want to have a look, look under > GW8GLO. > 73 Dave > > > > -----Original Message----- > From: Andy Talbot > To: rsgb_lf_group > Sent: Wed, 13 Jan 2016 9:51 > Subject: Re: LF: Decca 5501 > > 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 >>> >> >> > --047d7beb90a639ffd7052934d149 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I've just looked again, and there's more to= =C2=A0to the drive circuitry than that.=C2=A0 It is single ended drive for = current into the inductor, as I stated, but there is another IRF520 used as= an active clamp=C2=A0(the circuit diagram was drawn a bit ambiguously, so = didn't spot the arrangement straightaway).=C2=A0=C2=A0So when these two= FETs are driven alternately there will be a proper equal amplitude symmetr= ical drive waveform generated.

It is definitely us= ed as an energy storage inductor though, hence a gapped core is essential.= =C2=A0

'jnt=C2=A0

On 13 January 2016 at 10:23, <gw8= glo@aol.co.uk> wrote:
Andy thanks for= that I am looking to find a scrap amplifier module to play around with wit= h a view to rebuild the PCB and drive circuits. Looking on a scope the swit= ching is very symmetrical but that may be only luck. I have used pushpull f= ets to drive another amp I designed and it worked well using a rewound driv= er transformer from a pc power supply. The complete setup is now on the QRP= labs website if you want to have a look, look under GW8GLO.
73 Dave



-----= Original Message-----
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Sent: Wed, 13 Jan 2016 9:51
Subject: Re: LF: Decca 5501

Bit late now, but I found the circuit of the Deca transmitter on G3XDV= 's website. http://homepage.ntlworld.com/m= ike.dennison/index/lf/decca/transmitter.htm.
(Look at Fig 4, 'right' )

The driver circuit is just a single IFR520 FET switching into the tran= sformer, so there is a net DC component - and of course it has to be a gapp= ed core.=C2=A0 In fact I'm a bit surprised at that circuitry, consideri= ng it has to switch the FETs alternately on each half of the output wavefor= m, a single ended, flyback drive like that cannot possibly be symmetrical.= =C2=A0 Especially as the only reverse clamp appears to be a 68V zener..=C2= =A0 But no doubt it is 'good enough'=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 drive= r IC into that.

Andy=C2=A0 G4JNT


On 9 January 2016 at 09:26, &= lt;gw8glo@aol.co.uk> wrote:
Thanks for the reply the transformer failed because of a small cut i= n the rubber sleeving where it entered the ferrite. As the ferrite is earth= ed the insulation on the litz was not good enough. I have a diagram and use= d 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 o= f 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 l= ot 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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