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From: Andy Talbot <andy.g4jnt@gmail.com>
Date: Wed, 19 Apr 2017 07:59:06 +0100
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: A transductor for power regulation?
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Stefan
your idea of saturating the transformer is, I think, flawed.    If you
reduce mu-r of the core by saturating with DC, the primary winding will
have vastly reduced inductance and appear as a near short circuit to the
transmitter - not what you want

The idea of saturable reactors applies to resonant inductors, where you use
the DC to change the inductance.    So it could be applied to a class D
transmitter with a tank arrangement, to retune the tank circuit to adjust
for match, or control amplitude.

Andy  G4JNT

On 18 April 2017 at 17:18, DK7FC <selberdenken@posteo.de> wrote:

> Hi all,
>
> I'm just thinking about transductors and find them them quite fascinating
> again. I read a bit Wikipedia and thought about the use as a steerable
> transformer.
> Imagine you have a hard switching class D PA, H bridge or so. The output
> is a constant voltage source and it is no problem to connect no load, as
> long as a proper type of low pass filter is used.
> Then imagine a simple 1:1 ferrite transformer, 50 Ohm to 50 Ohm. The
> transformer has a 3rd winding for a DC current (to compensate the AC
> component transformed from the RF windings, 2 cores must be used, which a=
re
> in parallel for the RF and anti-serial for DC).
> Then i can saturate the transformer with the DC so the =E7=9A=B4 falls do=
wn to 1.
> With this arrangement i could build a linear PA out of a switch mode PA,
> even a fast one, which avoids key-clicks, at least in QRSS-3 (you remembe=
r
> the mode) or OP32 or even EbNaut on LF?
> Sounds like an interesting experiment at least. The question is how warm
> the transformer would become when the RF output current is permanently
> reduced to 50%.
> Has someone ever tried that on LF/MF?
>
> 73, Stefan
>
>

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<div dir=3D"ltr">Stefan=C2=A0<div>your idea of saturating the transformer i=
s, I think, flawed. =C2=A0 =C2=A0If you reduce mu-r of the core by saturati=
ng with DC, the primary winding will have vastly reduced inductance and app=
ear as a near short circuit to the transmitter - not what you want</div><di=
v><br></div><div>The idea of saturable reactors applies to resonant inducto=
rs, where you use the DC to change the inductance. =C2=A0 =C2=A0So it could=
 be applied to a class D transmitter with a tank arrangement, to retune the=
 tank circuit to adjust for match, or control amplitude.</div><div><br></di=
v><div>Andy =C2=A0G4JNT</div></div><div class=3D"gmail_extra"><br><div clas=
s=3D"gmail_quote">On 18 April 2017 at 17:18, DK7FC <span dir=3D"ltr">&lt;<a=
 href=3D"mailto:selberdenken@posteo.de" target=3D"_blank">selberdenken@post=
eo.de</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi all,<br>
<br>
I&#39;m just thinking about transductors and find them them quite fascinati=
ng again. I read a bit Wikipedia and thought about the use as a steerable t=
ransformer.<br>
Imagine you have a hard switching class D PA, H bridge or so. The output is=
 a constant voltage source and it is no problem to connect no load, as long=
 as a proper type of low pass filter is used.<br>
Then imagine a simple 1:1 ferrite transformer, 50 Ohm to 50 Ohm. The transf=
ormer has a 3rd winding for a DC current (to compensate the AC component tr=
ansformed from the RF windings, 2 cores must be used, which are in parallel=
 for the RF and anti-serial for DC).<br>
Then i can saturate the transformer with the DC so the =E7=9A=B4 falls down=
 to 1.<br>
With this arrangement i could build a linear PA out of a switch mode PA, ev=
en a fast one, which avoids key-clicks, at least in QRSS-3 (you remember th=
e mode) or OP32 or even EbNaut on LF?<br>
Sounds like an interesting experiment at least. The question is how warm th=
e transformer would become when the RF output current is permanently reduce=
d to 50%.<br>
Has someone ever tried that on LF/MF?<br>
<br>
73, Stefan<br>
<br>
</blockquote></div><br></div>

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