USB-SA44B – max VDC

Hello!
USB-SA44B analyzer works from 1 Hz and has 50 Ohm input impedance. Max input power is +20 dBm (100 mW) and max DC input is 0 VDC.
It’s difficult to realize passive high pass filter from 1 Hz on 50 Ohm load (about 20 mF capacitance). It means that filter can be only realized as active filter by using OpAmp. Why don’t you create low frequency analyzer with high impedance input and active internal DC block?
+20 dBm is about 2 V on 50 Ohm load. It means that I can apply to input square pulse with 2 V amplitude and 1 Hz frequency. But 1 Hz is very low frequency (quasiconstant signal), the device will be broken?
Best wishes,
Nikita