And so, now I am not my fourth aftermarket HU, and third aftermarket antenna, and on neither of them the radio reception was even remotely comparable to my stock headunit. I was messing with my antenna wires today, and here's what I discovered: the antenna connector basically consistins of an metal pin and outer shell, and I put some electrical tape around the outer shell, so that only the pin would have contack with the desk, and that solved my problem. The radio reception now is as good as it was when my car was fully stock, if not better. And I have a regular non powered antenna (not stock). I will experiment a little more with it tomorrow, see if it works with the stock antenna.

I don't know how to explain the result, but it works. If you guys going to try it, let me know how it works for you.