No. Jamming is evident to the radar operator.
Have you ever had a physics lab where sound was made completely inaudible by the application of more sound waves? If not it is quite impressive. Now is the original noise silent? Yes and No, the sound waves are still there, but unlike just making a loud racket (jamming), they are completely undetectable to the receiver. The ear drum goes in and just stays there. You can still hear, just not the noise that is being canceled.
<<<<No. Jamming is evident to the radar operator.
Not always. It can be indistinguishable from natural phenomena. Or it can be subtle. I’ve seen radar operators looking at a completely black suppressed scope thinking everything was fine when the ‘aggressor’ aircraft flew overhead. All jamming does not necessarily look like the 40 year old black and white pictures I was trained on.
In order to have a chance anti-aircraft systems have to be new and up-to-date, functioning normally within their designed capabilities, be configured correctly and manned by alert, expert users. That is hard to accomplish.