In December 2007, Gary Mitchell, WB6YRU, President of the Northern California Packet Association (NCPA), filed a Petition with the FCC, asking for the Commission to clarify the definition of a repeater. According to Part 97, Section 3(a)(39), A repeater in the amateur service is "[a]n amateur station that simultaneously retransmits the transmission of another amateur station on a different channel or channels."

Mitchell sought clarification on the word "simultaneously," asking if it referred to the signal information being retransmitted, or to the fact that the receiver and transmitter must both be active at the same time while acting on the same signal information. On March 23, 2009, the Commission clarified that even if there is a slight delay between what is received and what it transmits (as in the case of D-STAR and other digital repeaters), it is considered simultaneous if the receiver and transmitter are both active at the same time.

Mitchell pointed out in his petition that while the Commission's Rules specify on which bands amateur repeaters may operate, "some amateur repeaters are operating on bands other than set forth in Section 97.205(b) with systems that are essentially voice repeater stations, but that digitize and retransmit the user's voice, on the theory that because there is a small delay in retransmitting the signal of another amateur station, the signal is not 'simultaneously' retransmitted and, therefore, the system is not a repeater."

In its reply, the Commission pointed out that prior to 1994, a repeater was defined as "[a]n amateur station that automatically retransmits the signals of other stations." This, the Commission told Mitchell, was revised to clarify "that certain accommodations for message forwarding systems do not apply to other operating activities such as repeaters and auxiliary stations." The Commission proposed to define a repeater as "[a]n amateur station that instantaneously retransmits the transmission of another amateur station on a different channel or channels," but ultimately replaced "instantaneously" with "simultaneously" because commenters noted that there is always a small propagation delay through a repeater. As one commenter explained, "The word 'simultaneously' in this case means that the repeater is receiving and transmitting concurrently, whereas each signal might be slightly displaced in time between receive and transmit."

To be able to repeat another station's transmission, the Commission said that a repeater "must be able to receive a transmission from another station and retransmit it. Because the word 'simultaneously' in the definition is used to modify 'retransmit,' we believe it refers to a repeater station's transmitter being active when retransmitting the signal received by the repeater station's receiver from another amateur station. We conclude, therefore, that 'simultaneously' as used in the definition of a repeater refers to the receiver and transmitter both being active at the same time."