From: Chris Wilson <dead.fets@gmail.com>
Date: Tue, 16 May 2017 16:45:56 +0100
Message-ID: <17610511749.20170516164556@gmail.com>
To: Andy Talbot <rsgb_lf_group@blacksheep.org>
In-Reply-To: <CAA8k23QYh36uzqQ21Zp2hD2J4xB0MmaesMZWz1etfCXrwp1dyw@mail.gmail.com>
References: <1147474554.20170513112552@gmail.com> <207D3508CBD84798B5755E41E731F4C4@Clemens0811> <3410649648.20170515115915@gmail.com> <CAA8k23QYh36uzqQ21Zp2hD2J4xB0MmaesMZWz1etfCXrwp1dyw@mail.gmail.com>
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Subject: Re: LF: RE: Combining LF amps revisited
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Hello Andy,

Thanks,  I seem to have had some success using 3 X the number of turns
and  changing  from  77 compound to 79 compound. I think I follow your
formulae,  as  I  say, maths is my very weakest point, so what appears
simple to some is often a struggle here :(


> For transformers the core is not terribly critical provided you use
> a grade of ferrite designed for the frequency of interest.  And at LF that means SMPSU cores


> If I see a certain size core being used in a 500W SMPSU then
> there's a pretty good chance a core of the same size is going to
> work OK in an LF Tx of the similar rating.   No data sheets or
> trying to work out temperature rises.   


> I just use whatever feels right and apply the V < 4.44F.N.A.B 
> absolutely rigorously, keeping B to less than 0.1 usually


> As for impedances:  well they're  just Z1/Z2 = SQRT(N1/N2)
> Use V = 4.44.F.N.A.B to give you turns min, then calculate N1 and N2 while meeting that criteria


> Andy  G4JNT


-- 
Best regards,
 Chris                            mailto:dead_fets@gmail.com