Date: Tue, 28 Dec 2004 00:06:01 +0100
Message-Id: <259320497@web.de>
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From: "Hans-Albrecht Haffa" <dk8nd@web.de>
To: rsgb_lf_group@blacksheep.org
Organization: http://freemail.web.de/
Subject: Re: LF: Re: RE: M0BMU mods for G0MRF 300 W Tx is this a gap? from
 DK 8 ND
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Dear Mal, 
yes, it is better to have a gap, but it may be very small, so just an gap of a layer of insulating tape or a layer of varnish.  Just to keep low the remanent flux of the core.  Do not use carbonyle iron cores (powder cores) or gapped ferrites  with a gap of about 1 % of magnetic path length. Use a deflection transformer, the magnetic material is best for  136 k.  Its better than a 62 mm toroid without any gap.
55, Hans- Albrecht 
DK 8 ND


rsgb_lf_group@blacksheep.org schrieb am 27.12.04 16:00:07:
> 
> 
> ----- Original Message -----
> From: "Hans-Albrecht Haffa" <dk8nd@web.de>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Sunday, December 26, 2004 8:34 PM
> Subject: LF: RE: M0BMU mods for G0MRF 300 W Tx is this a gap?
> 
> 
> > Hello Lowfers,
> > yes it is a gap. A residuous gap of two core halves with lapped surfaces
> is still a gap. It will reduce relative permeability and remanent flux. It
> is better to use core halves with a bit greater gapmade of a layer of
> insulating tape  (0,05 mm thickness ) on both  sides of a core half.
> Lowering remanent flux from 180 mt (ungapped ring core) to about 30 mT
> gapped will rise magnetic swing in mMilli-Tesla. Thats what counts.  If You
> 
take out the spacers of a deflection transformer, You get agood core for a
> forward converter SMPS or a 136 kHz PA.
> 
> Hi Hans
> If I understand you correctly, it is better to have a gap for a 136 khz PA.
> 

de Mal/G3KEV
> 
> >
> > 55, Hans-Albrecht
> > DK 8 ND
> >
> >
> > rsgb_lf_group@blacksheep.org schrieb am 24.12.04 10:55:28:
> > >
> > >
> > > ----- Original Message -----
> > > From: "james moritz" <j.r.moritz@herts.ac.uk>
> > > To: <rsgb_lf_group@blacksheep.org>
> > > Sent: Thursday, December 23, 2004 11:31 AM
> > > Subject: LF: RE: M0BMU mods for G0MRF 300 W Tx
> > >
> > >
> > > Dear Gary, LF Group,
> > >
> > > You need one without an air gap - the air gap will drastically reduce
> the
> > > winding inductance, unfortunately.
> > >
> > > Hi All
> > > I have used these cores and noticed no difference between them and a
> > > continuous type core. I put the two core halves together tightly and
> used
> > > the same number of turns as used on the continuous core, maybe I was
> lucky.
> > > What does Jim call a gap? If they are tight together is that considered
> a
> > > gap? Must the core be totally continuous?
> > > de Mal/G3KEV
> > >
> >
> >
> >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> > ________________________________________________________________
> > Verschicken Sie romantische, coole und witzige Bilder per SMS!
> > Jetzt neu bei WEB.DE FreeMail: http://freemail.web.de/?mc=021193
> >
> >
> 
> 


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