My buddy bought a new magnum 257hp a short while ago, the blue lights with the built in RFX75. If he turns the RF power up more than 8 o'clock ( 7 being lo and 5 being high) there is a real bad squeal in in his transmit. So bad it covers up his audio. He has tried a different mic, same. It will do it at home on a regulated power supply OR in the mobile running on a 10 amp line. I am not familiar with this radio, any one got any ideas or should it go to be repaired?