"Patrick Turner" wrote in message
...


Occasionally, one does see RF oscillations at higher F than 20 MHz,
and a sixth sense is needed to detect them, or a meter.
A cascode preamp I recently built did oscillate at some high RF,
and just touching parts where the voltage was supposed to be fully
bypassed with a screw driver caused a loud click at the output speaker.


** A simple voltage regulator using a BD139 and 18 volt zener built for a
disco mixer proved effective at wiping channel 9 completely off the screen
of a TV set in the same room. No sign of trouble on a 10 MHz scope.

Power mosfets make nice HF and VHF oscillators as well - the Hitachi
2SJ /K ones - it pays to keep leads to them short with minimal inductance.



............... Phil