An apparatus for generating pressure variances in a fluid flowing in a downhole tool having a longitudinal axis includes a flow section having an outer wall, a flow control member selectively blocking flow in the flow section, and an actuator moving the flow control member between a first position wherein the flow control member at least partially blocks flow in the flow section and a second position wherein the flow control member reduces the at least partial blockage of the flow in the flow section. The actuator may be disposed outside the outer wall of the flow section.