Jamming is not a method of stealth. It is not used to evade detection. It is properly termed electronic attack and should be considered as such (that is, an offensive action).
Indeed, jamming someone tells them that you are 100% in the area and have hostile intent. What it DOES do is (hopefully) mess with their targeting systems enough that they can't pinpoint your location. You know how when you get a microphone near a speaker you get a really, really, painfully loud high pitched squeal? Yeah that's basically what jamming is (at least with radar, also there's multiple types of it and they get even more complicated but you get the picture).
Like, it has a specific purpose and all. Foul up a seeker system on a missile or make the other guy's radar think there's a million planes where there might only be a handful and so on and so forth. In the '91 Gulf War jamming was used extremely successfully to suppress Iraqi Air Defenses and allow US strike packages to hit targets almost without fear. The Iraqi's knew they were coming and fired missiles left and right, but the passive-radar seeker system on the SA-2 and SA-6 systems was basically useless, so they were firing blind. In other words it's a calculated risk, because it necessarily gives away your position, or at least the fact that you're there.
The only feasible method of stealth in the real world is to use passive sensors only and generate as little electromagnetic noise as possible (read: none). That still doesn't protect you from visual sighting, of course, but for a modern ship or aircraft if they're close enough for visual you're already karking wrong. Star Wars, of course, has methods around that particular issue (and handwavium tech to get around most of the other issues of stealth in space, which is otherwise impossible).
Does this technically matter with regard to Star Wars? Not really, since I sincerely doubt they're using radar or any system limited by the speed of light for sensors and detection and really who cares it's not sci-fi it's science fantasy, but I see it used in this manner enough to feel it merits getting pointed out. Props to those who already understand this and use it correctly. Everyone else, carry on anyway, this is just a rant why would you let some stranger on the internet tell you how to write FICTION?
The final line is not sarcastic. You do you, whether you do jamming properly simply it doesn't matter int the end.