A downlink system that includes at least one mud pump for pumping drilling fluid from a drilling fluid storage tank to a drilling system, a standpipe in fluid communication with the mud pump and in fluid communication with the drilling system, and a return line in fluid communication with the drilling system for returning the drilling fluid to the drilling fluid storage tank is provided. A drilling fluid modulator may be in fluid communication with at least one of the group consisting of the standpipe and the return line.