Texas Star 667V help

Input levels are very low and adjustments to the radio should only be made with an oscilloscope to see the output of the amplifier. Unless of course you have a variable attenuator between the radio and the amplifier in which case you could play with it. I would recommend starting out with a different radio though since somebody already hacked up the one that you currently have. Anything beyond a 4:1 Peak to carrier ratio is over modulated which is going to blow your amplifier up and cause interference on adjacent channels. If it was just a single stage it would be easy to predict but because there are two stages in that particular amplifier it's hard to predict what the output would be from the second stage based on the input level going into the first stage so it's best done on a proper test bench.