In answer to the question about how a radio signal near a star could be seen. Most stellar energy is in the light region, visible, ir, uV. It also tends to be radiated in all directions. A radio transmission is typically at a particular frequency - or a vary narrow bandwidth of frequencies and then it is fed to a highly directional antenna so virtually all of the transmitter energy is going in one direction. Also, stars tend to be rather quiet at radio frequency wavelengths. So a transmitter and antenna system like the aricebo radar and dish in puerto rico tremendously 'outshine' the sun at that particular transmitting frequency and in the direction that the dish antenna system is 'pointing'. Quite obviously if one tried to outshine the sun using a flashlight at visible light levels, it wouldn't work at all.