The other day with my friend open RX65 the HORN antennae consist of a cover secured by 4 screws. On the circuit board a potentionmeter for calibration using a miniature screwdriver turning clockwise or anti-clockwise. Pulled into a regular gas station and calibrate according to band ferquency. This is a trial & error maynot be accurate at least my RX65 does not display SERVICE REQUIRED. Still monitoring the sensivity and it does pick-up LASER and X & K band.