However, I crossed article that states AirSpy passive antenna is designed for Hi-Z receiver input but AirSpy HF+ specifications show 50 ohms input...
My intention is to compare apples with apples.
Ok, but I think, the RSP1A you mentioned in your starting post also has 50 Ohm input impedance like the Airspy HF+ Discovery.?
So: comparing apples? ;-)
Dirk