Another issue is where the UUT is grossly faulty, e.g. has DC on the signal.
Indeed
. But most "professional" analyzers can / should tolerate relatively high levels of DC at the inputs - up to 50 VDC in the case of all our spec ans
Almost certainly needs a pad and DC block!
Yes, these are cheap insurance no matter what. I have a huge assortment of attenuators and if I were given a "mystery signal" to look at, I would probably start out with one of the larger pads
An external step attenuator might be another option.