Why does my reciever have static, everytime I turn a knob?

I will assume that the receiver is old enough to have a real volume control as opposed to a “digital” one. That being said, older systems have open controls that can get dirty. Using a switch cleaner spray that contains a lubricant as well should resolve this. In detail: volume controls have a fixed resistance coil between 2 of the three tabs on the unit. The third is connected to a “wiper” that makes contact with that resistance coil (or flat surface) and varies the resistance for the circuit which is seen as a change in the volume. If there is dirt, dust,debris present, the contact may be briefly interrupted which will result in the noise that you hear. Using the spray will not only remove any debris from the unit, it will also provide a protective layer that should prevent the problem from recurring for quite a while. This is a common failure that is easily remedied.

Dan