I have a 1980's IC-251A 2m multi-mode. I have tried to add sub-tones so I can use it all an all around base station & on repeaters. I have attempted to add an external tone box, but... when I adjust the tone pk-to-pk voltage /modulation to where it accesses the repeater, all anyone can hear is the distorted tone. If I adjust the tone down to where it's not a bother, I can't access the repeater. What's wrong?