No one is going to be able to give you any helpful advise unless we know exactly where the scanner is located. For all we know, you're in central Westchester trying to pull the Putnam system in using the inefficient back of set telescoping antenna in the basement. Also keep in mind that those telescoping antennas require a bit of fiddling with to "tune" them to the optimal length for the primary band you're trying to receive, so fully extending it might not be the best idea for 769-775 MHz.
Manually tune the scanner to the control channel and see if you're receiving any signal at all. If not, then you're certainly not going to pick up any traffic.
