I understand now. The problem is that you have two controls that affect the sound - the BFO and the main tuning. The BFO is there to replace the suppressed carrier but you should not be able to hear it. To set the BFO to the correct frequency, tune in an AM BC station as exact as you can, turn the BFO on and tune the BFO pitch control for zero beat - leave the BFO alone from now on (but check it occasionally as it may drift). Now go back to your SSB station and carefully tune through it, it may be Lower or Upper sideband. At one point the transmission should come perfectly clear - reduce the RF gain and increase the AF to finally clean up the signal. Amateurs are not good at being all on the same frequency unfortunately so you may have to carefully tweak the main tuning at every 'over'.