I have the same cb. Ch 20, Go to cal, key mic, adjust knob to the cal (one short of full). Stop keying, push button on left to swr, key mic. Do same for 40 and 1. The meter is very poor and inaccurate though. I used a friends swr meter and he tuned my antenna for me. I also always get an antenna warning, called cobra and they said it is very common and sent me a pdf to adjust it but said i dont have to and it wont hurt anything.