"Phil Allison" wrote

** If you can't see them on the scope how do you even know when
they are
there ?

I measure with a voltmeter. Also, the scope's trace goes fuzzy.

If you don't know they are there then why would you use an
(RF)
voltmeter ??

To check they are not there :-)

This is in the context of audio valve amplifiers. When I check an
amp I put a 25MHz voltmeter across the load. If I get a significant
reading with no input signal, it is oscillating. If I need to know
the frequency of oscillation then I use a frequency counter. The
scope only gets connected when I know the amp is not oscillating.
Both these instruments are decent, ex-military units and fairly
recently calibrated. I can read them without using a ruler.

To check for ringing above 2MHz, I suppose I could sweep and use the
voltmeter, but I don't bother. Perhaps for guitar amps, or other
things with complicated voltage stages and crowded wiring?

Do you often discover anything worth finding above 2MHz? Maybe I
should save up for a new scope?

cheers, Ian