Ed,
The answer is that the Ultra is useful for typical SSB 2-tone testing, but only just. The image below shows some promotional material taken at maximum (500 Hz) resolution and 1 kHz per division on the horizontal axis. The 2 tones, separated by about the usual and recommended spacing, are distinguishable and while a full test involving lower-level, higher-order, products would be possible, it's starting to stretch the imagination.
I'm a fan (and owner) of a number of items of low-cost test gear and they've more than paid for themselves in terms of project applications. However, it's also important to appreciate that the demands on test gear are also increasing: serious de-bugging of noise in e.g. digital mode transmitting systems demands 1 Hz or better RBW and simultaneous fast readout, while for many other modern radio applications a ~10 kHz phase noise of -100 dBc/Hz is barely adequate. Rigols, Siglents, etc. will get you to that level but dump you into a world of poor firmware and accessory software curation which, interestingly, can be worse in terms of bug fixes etc. than either the low-end open-source ("semi-random") or high-end (Keysight, R&S, ...) environments.
None of the above is meant to minimize the usefulness of the low-cost gear but, as always, serious application demands a good knowledge of the test equipment and its limitations - whatever your budget.
73, Peter.
