Your RV may have a TV antenna amplifies in line with the cable that you hook to the pedestal. Look around your RV for a TV amplifier box. It should have a switch on it. Throw that switch and try tuning the TV again.
Another possibility, check the RV wire ends. Make sure they have a bare wire in the center of it. If not, the connector will need to be re-worked. Remove the connector end from the RV wire. Cut the insulation at and the end of the RV wire about 1/2 inch. Then re connect the connector to the RV wire, making sure the outer wire shield connects to the metal of the connector, and not touching the center wire inside the connector. Then reconnect the cable to the pedestal. Then try your TV search again.