Why does Sam Quint smash the CB radio?

I suspect that it is due to one of the following:

1. He wants to focus those on board to the task at hand. If there's no hope of help then the only thing they can do is kill the shark.
2. It's basically a macho thing that says 'I don't need anyone's help'. After all Quint is a loner who basically doesn't ask for help and expects none.

Whichever way, the story would not have been so good if the whole town had turned out to help !

I think secretly he never really intended to return ashore if he failed, he felt guilty he survived Indianapolis whilst several if not all of his friends perished. For him, being taken by the shark is like an honourable discharge and he's going down to be reunited with his buddies from WW2.

I believe the reason Quint smashed the radio is because back in the 70's 10,000 dollars was a lot and he didn't want to get help from others so they could get the share and he wanted the money for himself. But I do also believe that he smashed it is because he believed it would be dishonourable to receive assistance because of his experience on the USS Indianapolis and he wanted to be brave to impress his friends who weren't there.