Cell phone repeater for my home.

I'm looking into getting a cell repeater for my home. I live in a rural area with not a lot of service inside my house, but four bars outside. The repeater I'm looking at uses an omni directional antenna that draws in signal from multiple towers for multiple carriers. My question is, since this system uses an omni antenna, wouldn't any antenna do? Such as a CB antenna? The way I look at it the antenna draws in all types of signal but its left up to the inside receiver what type of signal to use? Am I wrong on this?