[600MRG] Tuning my transmitter

[John Langridge]

Steve -

First make sure you are using the most current revision to the circuit.
Here is a link to current revision:
http://www.gw3uep.ukfsn.org/100W_QTX/100WTX/PA_cmos.gif

Note that there is a 680 pF in parallel with C1.  That was missed in
earlier revisions.  It will have a major impact.

Note also that C2 has an additional 1200 pF in parallel for a total of
17000 pF.

I also find switching to ferrite rather than using the PVC coil forms is a
lot better.

Using a T106-2, L1 (12 uH): 30 turns, L2 (6.5 uH): 22 turns, L3 (16 uH): 34
turns.

You mention two FET's, Im guessing you duplicated the clipper
diode/resistor pair on the gate for each FET...

Candidly, I have built these in my sleep, hastily tacking down junk to a
copper board, and even being sloppy I can get better than 85% efficiency on
the first try so I am guessing maybe you have some component tolerances
that are not tight enough (2.5% can be important in the filter network) or
have left a few of the revised parts out as mentioned above.  This should
be a design that just works right out of the box.

73 and good luck!

John XIQ

On Fri, Oct 23, 2015 at 8:53 AM, Steve Flood <kk7uv at bresnan.net> wrote:

> I am using the GW3UEP 100w transmitter circuit.  I have two IRF540's in
> parallel.
>
> I am attempting to optimize my transmitter efficiency while learning
> something about FET operation and Class E behavior.
>
>
>
> In much of what I've been reading, tuning and optimization is done while
> monitoring drain voltage and drain current, with the idea that one of these
> must be zero when the other is non-zero or "on".  However, I do not have a
> current probe for my oscilloscope, nor do I intend to buy one for $1700
> (Rigol).   By only looking at drain voltage, I've only made minor
> adjustments to the tank circuit to make the waveform look as clean as
> possible.
>
>
>
> With my power input at 86 watts (24v @ 3.6A),  I get 64 watts out to a
> dummy
> load, or 74% efficiency.  GW3UEP specifies 80% and the general class E
> literature cite efficiencies in excess of 90% (such as Sokal's 2001 QEX
> article).
>
>
>
> Without a current probe to measure drain current, how are others
> tuning/optimizing such circuits?
>
>
>
> Thanks,
>
> Steve KK7UV/WH2XNV
>
>
>
>
>
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