1. You will not harm the vfo. Remember, they were used during a war.

2. There is not enough output from the BC-221 to drive the 12BY7 directly,
and it is true that the harmonics are lively in it. So, you can build a
tuned class A amplifier to build up the voltage, provide selectivity and
also isolate the BC-221 from the rig to prevent frequency pulling.

I have used a number of BC-221/LM frequency meters into vfos, turned one
into a regen receiver and presently have a solid state LM meter as a vfo in
my Central Electronics 20A. It has a crystal controlled mixer for output on
the different bands.

Sorry if I offended the tube purists with the last paragraph. The
calibration book was lost and I got bored one night.

Colin K7FM