Spectrum Coordination Act This bill requires periodic updates to the memorandum of understanding (MOU) that guides federal efforts to coordinate the efficient management and use of the electromagnetic spectrum. It also requires documentation of interagency coordination during spectrum actions. Specifically, the Federal Communications Commission (FCC) and the National Telecommunications and Information Administration (NTIA) must update the current MOU within three years and then update subsequent MOUs at least every four years thereafter. Additionally, the NTIA and the FCC must document their efforts to coordinate the identification and resolution of technical, procedural, or policy concerns of federal entities that are affected by a spectrum action (i.e., a proposed action by the FCC to reallocate spectrum that is anticipated to result in an auction or licensing that could potentially impact the spectrum operations of a federal entity). In particular, the NTIA must file specified information in the public record during the period for submitting comments about the spectrum action. The information must include (1) the date on which the FCC notified the NTIA about the action, (2) a list of federal entities that may be affected by the action, (3) the date on which the NTIA notified those entities about the action, and (4) a summary of concerns with the action raised by affected entities. The bill also requires the FCC to include in any final rule for a spectrum action an interagency coordination summary that describes (1) the date the FCC notified the NTIA about the spectrum action, (2) whether federal entities raised concerns, and (3) how any concerns were resolved.