Also, are you comparing the repeater range by activating the repeater or are you directly keying up the repeater's transmitter to do the test? If you're having any kind of receiver issue or desense issue then you're going to see that as either poor range or a fast keyup and an immediate drop of the input. Best way to make sure the TX side is good is to have someone physically key up the transmitter and verify its range independent of the repeat functionality. If that's good, start looking at the RX side for issues. If not, maybe you're slightly off-frequency and once you go out of the 500 yard range you're no longer picking up the transmitter anymore bleeding over onto the right frequency.