HI and thank you for your post, having spoken to one of our engineers this is what he had to say
"Thanks for your suggestion. Frequency response analysis (or indeed impedance analysis) would certainly be an interesting application for one of our oscilloscopes with a built-in sweepable signal generator, such as the PicoScope 3206 or the new PicoScope 5204.
Taking a look at the Ridley Engineering website, their product does have hardware features which make it particularly suited to this application, and which the PicoScope (being a more general-purpose instrument) lacks.
For example, the low output impedance and high power drive capability of the AP300 would mean that you might need to use an external RF amplifier with a PicoScope in order to achieve the same power output.
Your suggestion of plotting the relative gain and phase of two oscilloscope channels across a frequency sweep of the signal generator is something we'll bear in mind when looking at future software features. However, we do also supply DLLs and programming examples with most of our products (check the product information for the particular scope you are interested in) so you could consider writing your own application to analyse the oscilloscope data and display the frequency response."
Hope this helps.