This device seems quite similar to what I made, a 10MHz reference feeds a PLL synthesizer chip to generate the signal at IF of the analyzer, which is then mixed up or down with the LO signal from the SA to produce the output. To switch bands you have to switch the RF and IF ports on the mixer, which is why they have an external jumper connection on the front panel.
It will probably have a lot of spurious outputs, not very flat, and not very good SWR. I'm sure it works, not sure it's worth 700$