Re: LF: A transductor for power regulation?

[Andy Talbot <andy.g4jnt@gmail.com>]

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 are in parallel for the RF and anti-serial for DC).
Then i can saturate the transformer with the DC so the 皴 falls down 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 remember 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