Hi Johan
Tnx for your observations and info on class E.
>From what you say there is no real point in having two class E pa's
connected in series, just use a single ended pa and choose the components to
suit the power output required. The second harmonic and all other harmonics
can be suppressed with a LPF.
My single ended pa is very clean and symetrical sine wave without any LPF
although I have one in line, because I had already built it and use it.
I was surprised that there were no odd harmonics detectable on the output
rf signal considering all the sq wave in the pa driver etc. There has been
very little response from anyone else about class E amp experiences, I
expect they have never heard about this type of amplifier, or do not use
them.
I expect most are using class A,AB or C on 137 and 500 khz.
73 de Mal/G3KEV
----- Original Message -----
From: "Johan H. Bodin" <[email protected]>
To: <[email protected]>
Sent: Tuesday, November 20, 2007 3:56 PM
Subject: Re: LF: CLASS E
> Mal,
>
> for proper class E operation, the drain waveform must be allowed to be
> non-symmetrical so you cannot just use a center tapped output transformer.
In
> other words, there must be no "hard coupling" between the drains in a
class E
> push-pull amplifier. One way is to design two identical class E
amplifiers, each
> designed for an output power P into the load R. Note: Each amplifier must
have
> its own DC feeding choke - no center tapped stuff here! Then feed these
two
> amplifiers with push-pull drive (180 degrees phase shift) and connect the
> primary winding of an output transformer between the outputs of the two
> amplifiers. The output transformer should be designed so that 2*R will be
"seen"
> when "looking" into the primary. The total output power will be 2*P. With
> sufficient Q in the series tanks (C2, L), the output current will be
almost
> sinusoidal, as in the single ended case, so the two halves of the
amplifier will
> not "know" that they are actually operating in push-pull. Since the two
series
> resonant tanks of the two amplifiers and the output transformer primary
will all
> be connected in series, you can simplify the circuit by using a single
resonant
> tank with twice the L and half the C. This may look assymetrical but it
gives
> exactly the same result (a few pF stray C can be neglected at these low
> frequencies...). One can say that this is simply two class E amplifiers
> connected in series. However, the even harmonic cancelling property of
push-pull
> is still there because of circuit (and drive) symmetry.
>
> I have tried this configuration, for example on 160m QRP, and it seems to
work
> very well.
>
> 73
> Johan SM6LKM
>
>
> hamilton mal skrev:
> > Hi all
> > Is anyone else using a class E PA on 500 or 137. Mine is single ended,
maybe
> > someone has a push pull design.
> > 73 de Mal/G3KEV
> >
> >
> >
>
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