Time to revisit this review. R&S has released new firmware and the biggest addition is a 'Boadie plot' function as R&S tends to call it in their video. Other manufacturers call it frequency response analysis (FRA). The firmware has been out for a while but until now I didn't had time to give it a spin.
Let's start with something simple: an amplifier swept from 10Hz to 25MHz (which is the maximum range):
The frequency range can be set at the top left side of the screen. The rest of the parameters (like amplitude and number of points per decade) can be set in the setup menu. An interesting feature is that it is possible to divide the frequency sweep in sections and set a difference amplitude for each section.
Another interesting test is a 7th order eliptic high-pass filter.
The attenuation in the stop band is too big for the oscilloscope to get any signal out of it (despite having 10 bit ADCs) so the phase is jumping allover the place. This test also showed that the RTM3004 is scaling the input attenuation to try and get the maximum resolution.
Last but not least I tried an 8MHz crystal (connected to a pi-network).
This is where things get a bit ugly. The setting for the sweep is limited to a number of points per decade and doesn't increase when a limited span is selected. This means that it is not possible to get a detailed analysis of circuits which have sharp peaks in their frequency responses. This is probably easy to fix though because it doesn't make sense to be able to set a narrow span but not getting an adequate number of measurement points. Another limitation is that is works for one channel at a time. It could be handy to analyse more input/output relations at the same time.