1. When you say I don't calibrate the probe, what do you mean the probe is what I'm trying to measure? I thought you're supposed to "calibrate out" the probe (and cable) so that it won't get in the way of the measurements whenever you use a VNA.
Are you sure? So if you had a filter instead of a probe, would you calibrate out the filter so its response would show up as flat?
What you calibrate is the source of the current vs the input port, so that this response is flat. Since this application of yours is for less than 100MHz forget about the cable. But the response of the probe is what it is and don't let the VNA meddle with it.
2. When you say calibrate the "source" of the instrument: You mean the injecting port?
Yes, the port that generates energy
3. "terminating it with an external 50Ohm load, and connect it to the receiving port terminated in 1MOhms." - could you elaborate on this? I don't understand
You want to measure current right? So how do you generate a current? By loading the source with a 50Ohm load (external load). Then you need to measure this current (the voltage at the output loaded node) at the input in the same conditions that you would if you had the probe attached, that is with a 1MOhm input.
4. "After that you can add the current probe tied to the source, again with the source terminated in 50Ohms, and the measuring port to 1Mohm if you are using the p6021 termination" - When you say source terminated in 50 ohms.. This is a setting on the VNA, correct? The input/output impedance of each port, right? If so, then I don't think the E5061 has a 1Mohm option. It only has 50Ohms...
The source is always 50Ohm but it needs additional and external 50Ohm termination (to generate a current). The source impedance is one thing, and the source termination is another thing.
The P6021 with termination box is to be used on 1MOhm terminated devices, you can't use it on a 50Ohm input device. Here you can do a few things if you VNA only has 50Ohm input port:
- Use a VNA that has 1MOhm input: HP 3589A, MS4630b
- Use a current probe that has 50Ohm output: AM503
- Use an amplifier between the P6021 and the VNA, that has 1MOhm input and 50Ohm output, this is easy to breadboard.