I bought a boosted car TV antenna on ebay, and as the output it has 4 3.5mm plugs...does anyone know if they all need to be used, or if they are for 4 devices?

thanks!

mine only has one out of the unit, does the calbe split into 4, or is it 4 out of the top of the aerial. i would say only one would be needed. others would be for other tv's

It's a "diversity" antenna. Which means it's actually several antennas in one package.
The 4 plugs connect the different antennas and the system chooses which has the best reception.

I guess you could connect just one, but it's not really going to perform.