I did a few RMS measurements on my 2701C this morning.
NOTE: The power switcher in my 2701C is not the original. I made a new one from scratch as the switcher was blown in my 2701C when I got it.
This is likely going to impact the switching noise generated, and thereby the RMS measurements.
I hope that other owners of a 2701C (with the original switcher) can make RMS measurements, so that we may compare.
Anyway, here are my numbers:
Between 2701C chassis and any of the four output terminals, 20 V range and 10 V setting, activate or standby:
About 215 mV measured with a Racal-Dana 9300B
About 217 mV measured with a Rohde & Schwarz URE (same reading in different BW settings => Must be dominated by LF noise)
Between the output terminals, 20 V range and 10 V setting
Operate:
Rohde & Schwarz URE, full BW: 1.054 mV (drops to 0.968 mV when connecting the chassis to the negative terminal)
Rohde & Schwarz URE, 100 kHz BW: 0.274 mV
HP 3400A: About 1.05 mV
Racal-Dana 9300B: About 1.29 mV
Standby:
Rohde & Schwarz URE, full BW: 1.048 mV (drops to 0.945 mV when connecting the chassis to the negative terminal)
Rohde & Schwarz URE, 100 kHz BW: 0.268 mV
HP 3400A: About 1.02 mV
Racal-Dana 9300B: About 1.28 mV
The larger reading by the Racal-Dana 9300B can be explained by its wider bandwidth (-3 dB @ 57 MHz) compared to the HP 3400A and the R&S URE.
The measurements are sensitive to the wiring of the setup. By merely touching the instruments I could make the values change. This could be an indication of switching noise being radiated from both the output terminals and the power line. During the measurements the 2701C and the RMS meters were connected to the same power outlet strip with ground, and all power cables used had ground.
On my web page
https://dabbledoo.weebly.com/valhalla-2701c.html there are a few more noise measurements.
Besides this, your measurements in 100 kHz bandwidth are not far from mine, but you seem to have more noise in a wide bandwidth. Maybe that is related to the some of the components I added to the power switcher. For instance, I have a 680 nF / 300 VAC noise suppressing capacitor connected across the mains power going to the switcher. If you try something similar make sure that the capacitor is a Class X safety capacitor.