That is “stealth”. It’s obvious because it is expensive and secret tech. But also because if you look at the ship you see a ship, whereas the radar shows an albatross or something small. Transitions are also notable for radar operators that are really paying attention. A ship that turns into a goose and then back into a ship, for example.
I think you may be mixing up active jamming (which works like shining a searchlight in someone's eyes--they can't see or track you, but it's very obvious that there's someone out there) and passive stealth (which tries to reduce the emissions that the vehicle emits or reflects).
Anyone can make a jammer, but it only helps if you can evade your pursuer before they get a look at you optically; it's not much use for a lumbering oil tanker.
As zentiggr says, you can get some degree of passive stealth just by turning off your own radio/radar, but anything more than that requires a custom-engineered (and strangely-shaped) hull, propulsion, etc. that takes military-level money to design and would be extremely obvious in any port. So, again, not practical for this kind of smuggler.
