Download must be adjusted as shown for the CLASS E PA. More power is

Universal FAT5 PA (40m version)
The waveform (taken at one of the DRAIN outputs) must be adjusted as shown for the CLASS E PA. More
power is (affectively) available when the waveform is wrongly adjusted (narrower or with humps in the
trailing edge (R/H side of waveform)) but it will not be running in CLASS E. The wrongly adjusted
waveform will be showing volts and current which is not what is wanted. This will cause the FETS to get
hot!
When correctly set up for 40m CLASS E 'COMMANDO', the T200-2 toroids will have three turns (bifilar)
on each. The variable capacitor is set to 630pF on my test set-up. The number of turns and the capacitor
value may very well differ on your project. The aim of the set up, as well as producing the correct waveform, is to have approximately 5 Ohms impedance at the FETs. This is achieved by the combination of
the total Drain voltage and the current drawn. With the test results shown below, the impedance is
11.33 Ohms (34/3) and needs to be optimized if 5 Ohms is to be realized. The impedance is for matching
the PUWMA filter if used with that modulator.
Using a PA supply of 34V at 3A it is producing 98W into a 50R load. This equates to 96%. The PA with
the FETS (IRF640) can run with up to 50VDC on the drains so a higher power output can be achieved
(current will increase as well as the voltage).
Using the twin ferrites PA tuning
The PA can be used with the ‘conventional’ PA tuning as per the original FAT5 PA circuit with the two
(type 43) ferrites, tuning capacitor and coil and the loading capacitor.
As with all good Ham practice, a second harmonic filter should be used on the PA output.