I would like to connect my sattelite receiver, blu ray player etc... to my plasma t.v. via a tuner of some sort, so only one cable runs from it to the t.v.
does anybody know exactly what i am looking for?
You may be thinking of an RF modulator...basically you feed the video outputs from each to an RF modulator then take the coax out to the Tv and tune it on the analogue tuner but you'll get a terrible picture and no HD.
Not to be recommended.
Do they all use the same connection type? If, for example they all use HDMI, you would use an HDMI switch. If not, your best bet is to use an AV receiver with upconversion (video conversion) so that it outputs via HDMI to the TV. This is assuming of course, that is what you actually want to do. Obviously this option would be expensive and wasted if you didn't want surround sound as well. In the end, the primary role of an AV Receiver is to provide surround sound.
Please state makes/model numbers so that you can give people a better understanding of what you want to achieve.