Question regarding using a cable modem with Bandwidth

Sorry if this question is being posted in the wrong section, BUT.....

I am running a cable modem and I had a question (probably dumb one)

Is there ANY way to get more bandwidth to come through using your cable modem than the normal bandwidth your service provider gives you?

I "heard" through the grape vine, that there are ways to double the speed you are taking in, by using an amp or tower on your roof, or mount antenna.

The deal is when I read up on amps and antennas, it seems the only thing they do is rather keep your signal steady. Not so much increasing the speed/bandwidth, while others have told me that is not always true, and that antennas seem to work best with wireless connection. Not cable connection.

So I ask the guru's out there reading this, if there truly is a way to boost your signal or bandwidth while using a cable modem?? If so, could you point me to the sites or products that would do this?

Ive looked at 3gstore.com and similar sites but they seem to have just plain amps and antennas that dont boost your signal but mainly used for wireless devices to help in keeping you from being dropped or loosing signal.

Any advise, suggestions or offers would be greatly appreciated.