Last week, the FCC granted a brief extension of time in which to file comments on the proposed increase in power for the HD Radio operations of FM stations.  We wrote about the request for comments here and here.  Comments will address the requests of those who want higher power for their digital operations in order to increase building penetration of the HD radio signals (which have proven difficult to receive in some brick and steel buildings) and otherwise fill in coverage areas, and will also include submissions of those who are concerned about the potential interference to adjacent channel stations. The later includes NPR Labs, which produced a set of maps, available here, computing the potential interference that higher power HD operations could cause to a number of stations.  Especially for stations which rely on coverage beyond their protected service areas, and which operate close to adjacent channel stations that run HD operations, the proposed increase could have a substantial impact.   With the proposal for shared time operations that has now been highlighted by the Ion Media applications about which we wrote here, the diversity that comes from such fringe stations will have to be balanced against the diversity that can come from multicast digital channels.  Comments are now due on December 5, with reply comments due January 12.