Andrew,
The default drive strength is 2mA.
just curious:
under what conditions did you try the different drive levels?
Assumed (default) condition is a standard unmodified BITX40 board:
- VFO on the low side of the IF (so 5Mhz, not 19MHz)
- L4 removed
- caps C91 and C92 not removed
73, Allard PE1NWL