Hi folks,

The other day, I was trying to troubleshoot a 100MHz amaplifier in a
piece of equipment ( actually, a Cushman CE-3 Spectrum Monitor ). I
was using a 150MHz tektronix scope with a 10X probe.
I was getting different results with each measurement, it was driving
me crazy.

My friend Bob, the RF guru, said "Your trouble is that you're
using the HI-Z input to the scope. For VHF, Hi-Z is crap. It
just doesn't work. Especially if you have a pigtail for the
ground." Guilty as charged...

He then asked if the scope had a 50-ohm input ( which it does ).
"Then just make up a probe with a 450-ohm series resistor, and
some little ground clip. That's all you need. It will be stable, and
it will work up to about a gig. The impedances in
this RF stuff tend to be low anyway, so you don't really need Hi-Z."

Makes sense. Any way to buy a probe like this off he shelf?

- Jerry Kaidor ( )