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All of the following circuit cbanges are found to noticeably degrade output power as well as PA efficiency:

1. Omitting the 10 turn FT37-43 choke completely (L502);

2. Decoupling T501 center tap with a capacitor to ground or +12V;

3. Putting a 1N4148 diode across the 10 turn FT37-43 choke (L502);

4. Feeding DC to the two drains separately, each side having its own FT37-43 choke;

Note that reducing the number of turns on the FT37-43 reduces the energy in the dI/dt key-up spike; but if you keep reducing it further and further you approach the no-choke case (point 1 above), approaching the same loss in power output and efficiency; reduction in this inductance value has more impact the lower the operating frequency as you'd expect.?

All the above are experimental observations by actual measurement.