That page isn't really responsive to my comment. I'm not sure what point you're trying to make! Of course if you point a directional radio transmitter at an ob

That page isn't really responsive to my comment. I'm not sure what point you're trying to make! Of course if you point a directional radio transmitter at an observer, you are not being stealthy, to that observer. Of course if you power up a 100 gigawatt incandescent rocket motor, you're loudly advertising your presence. (No different than a stealth aircraft using afterburners—they don't). Stealth spacecraft would necessarily avoid doing that. Stealth spacecraft could, to highlight one option from a large decision space, consider cryogenic, cold-gas thrusters with invisible output plumes and zero infrared emissions.