Pretty fair comment,
rf-loop---pretty much what you have to do with an analog unit.
I found some are considerably more 'fiddly" than others,so if I had to look at an AM waveform with a 'scope I knew to be the "fiddly" type,I usually went straight to the external trigger option.
We weren't strictly speaking supposed to check modulation looking at the envelope.
The preferred way was the "trapezoid pattern,with the modulating waveform on the "X" axis,but the envelope was always good for a quick check.
On one occasion,we received a Modulation Monitor back for service because it was "reading too high"
We sent off a replacement,but a "quick check" showed that the "faulty" meter & the"scope envelope closely agreed ,so the Boss sent us off on a "roadtrip".
It turned out that the local Phone techs had done a lineup on a +8dBm tone instead of a +16dBm one,so the transmitter was overmodulating wildly on programme material.
You should have seen what
that envelope looked like!------ eeek!