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 <3410649648.20170515115915@gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
Date: Mon, 15 May 2017 13:42:36 +0100
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE: Combining LF amps revisited
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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 =3D SQRT(N1/N2)
Use V =3D 4.44.F.N.A.B to give you turns min, then calculate N1 and N2 whil=
e
meeting that criteria

Andy  G4JNT

On 15 May 2017 at 11:59, Chris Wilson <dead.fets@gmail.com> wrote:

> Hello Clemens,
>
>
> Thanks  for  the  reply, the 3 stacked cores will rise to 70 degrees C
> plus  even with a small computer processor fan blowing through them. I
> am  investigating  ways  of  reducing  this, the cores are shown as 77
> material  in  jay's  schematic,  but  he  and I are using the newer 78
> material  for the PA output transformer cores. I may try using this 76
> material  in  the  combiner transformer. Someone else suggested making
> the   PA   output   transformers   work   at  100  ohms  and  using  a
> transformer less  zero  degree  hybrid  coupler.  I'd  try  Andy's twin
> primary,  one  secondary  transformer instead of the coupler if i knew
> what winding ratio and what core to start off with. Thanks again.
>
> > Hi Chris,
>
> > I have a tool by DJ5IL here which predicts around 60=C2=B0C for the cor=
es
> > (excluding heat caused by the winding)
> > and ca. 480 Gauss flux density.
>
> > 73
> > Clemens
> > DL4RAJ
>
>
>
> --
> Best regards,
>  Chris                            mailto:dead_fets@gmail.com
>
>
>

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<div dir=3D"ltr"><div>For transformers the core is not terribly critical pr=
ovided you use a grade of ferrite designed for the frequency of interest.=
=C2=A0 And at LF that means SMPSU cores</div><div><br></div><div>If I see a=
 certain size core being used in a 500W SMPSU then there&#39;s a pretty goo=
d chance a core of the same size is going to work OK in an LF Tx of the sim=
ilar rating.=C2=A0=C2=A0 No data sheets or trying to work out temperature r=
ises.=C2=A0=C2=A0 </div><div><br></div><div>I just use whatever feels right=
 and apply the V &lt; 4.44F.N.A.B=C2=A0 absolutely rigorously, keeping B to=
 less than 0.1 usually</div><div><br></div><div>As for impedances:=C2=A0 we=
ll they&#39;re =C2=A0just Z1/Z2 =3D SQRT(N1/N2)</div><div>Use V =3D 4.44.F.=
N.A.B to give you turns min, then calculate N1 and N2 while meeting that cr=
iteria</div><div><br></div><div>Andy=C2=A0 G4JNT</div></div><div class=3D"g=
mail_extra"><br><div class=3D"gmail_quote">On 15 May 2017 at 11:59, Chris W=
ilson <span dir=3D"ltr">&lt;<a href=3D"mailto:dead.fets@gmail.com" target=
=3D"_blank">dead.fets@gmail.com</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">Hello Clemens,<br>
<br>
<br>
Thanks=C2=A0 for=C2=A0 the=C2=A0 reply, the 3 stacked cores will rise to 70=
 degrees C<br>
plus=C2=A0 even with a small computer processor fan blowing through them. I=
<br>
am=C2=A0 investigating=C2=A0 ways=C2=A0 of=C2=A0 reducing=C2=A0 this, the c=
ores are shown as 77<br>
material=C2=A0 in=C2=A0 jay&#39;s=C2=A0 schematic,=C2=A0 but=C2=A0 he=C2=A0=
 and I are using the newer 78<br>
material=C2=A0 for the PA output transformer cores. I may try using this 76=
<br>
material=C2=A0 in=C2=A0 the=C2=A0 combiner transformer. Someone else sugges=
ted making<br>
the=C2=A0 =C2=A0PA=C2=A0 =C2=A0output=C2=A0 =C2=A0transformers=C2=A0 =C2=A0=
work=C2=A0 =C2=A0at=C2=A0 100=C2=A0 ohms=C2=A0 and=C2=A0 using=C2=A0 a<br>
transformer less=C2=A0 zero=C2=A0 degree=C2=A0 hybrid=C2=A0 coupler.=C2=A0 =
I&#39;d=C2=A0 try=C2=A0 Andy&#39;s twin<br>
primary,=C2=A0 one=C2=A0 secondary=C2=A0 transformer instead of the coupler=
 if i knew<br>
what winding ratio and what core to start off with. Thanks again.<br>
<br>
&gt; Hi Chris,<br>
<br>
&gt; I have a tool by DJ5IL here which predicts around 60=C2=B0C for the co=
res<br>
&gt; (excluding heat caused by the winding)<br>
&gt; and ca. 480 Gauss flux density.<br>
<br>
&gt; 73<br>
&gt; Clemens<br>
&gt; DL4RAJ<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
<br>
<br>
--<br>
Best regards,<br>
=C2=A0Chris=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 mailto:<a href=3D"mailto:dead_fets@gmail=
.com">dead_fets@gmail.com</a><br>
<br>
<br>
</font></span></blockquote></div><br></div>

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