Antenna plug question.

What you're referring to is called a splitter. It splits the antenna coax signal into 4 outputs. There is no noticeable difference in pic quality. Cheers Mate.

There is no noticeable difference in pic quality.

That may be your experience, but I would still be wary. If the signal quality is borderline then you'll find that a splitter makes things noticeably worse.

http://www.tvantenna.com.au/Antenna_Installation_Guide.htm