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Ralph Mowery[_3_]

In article , says...

Well, I've been using a coax T. On one end, there's the 50 ohm dummy
load, other side is input from the URM 25 signal generator, and the
final side goes into channel 1 of the scope. I wonder if I should use
some sort of a buffer here, on the side leading to the scope, like a
voltage divider, etc, rather than direct? Or, perhaps actually check
from the "open circuit" output on the generator as the URM has that too?
Yes, I'm now compensating for PP by converting to RMS after I see the
waveform. It may be closer than it was, but will know with more
certainty after the probes arrive today.

Instead of the RF generator have you tried a transformer that converts
the line voltage to something between 6 volts and 50 volts AC ? Then
you can do the conversion from the RMS to peak voltage to see if the
calibration is correct.

One other thing if it is a dual trace scope go to the X-Y mode and feed
both chanels the same signal and see what the trace looks like.

As someone else mentioned feed the same signal to both inputs and use
the invert function and see if they cancel each other out.

I am thinking that URM 25 has several matching networks that go on the
end of the cable. Do you have the correct one for what you are trying
to do ? Sometimes those networks get lost over the years.