AM radio stations stand to gain relief from a potential permanent shift to daylight saving time after Sen. Tom Cotton (R-AR) restated his plan to filibuster the Sunshine Protection Act.
The legislation, which the House has already passed, would lock the United States into year-round daylight saving time. Cotton has pledged to block it when Congress returns from recess, preventing the measure from advancing in the Senate.
Permanent daylight saving time would delay winter sunrises, often pushing them past 8 or 9 a.m. in many parts of the country. That change would disrupt morning drive-time listening for daytime-only AM stations and those required to operate at reduced power or with directional antenna patterns after local sunset—problems broadcasters have flagged for years as a threat to their operations and audiences.
Operational Restrictions in Practice
- Day/night mode changes: Many stations switch at local sunset from a higher-power, often non-directional (or less directional) daytime mode to a lower-power and/or highly directional nighttime mode (DA-N or DA-2 patterns). Some use completely different antenna systems or sites.
- Daytimers: These Class D stations must sign off at sunset or operate at very low nighttime power (often a few watts to under 250 W). Their signals would otherwise interfere with distant clear-channel or regional stations via skywave.
- Directional antennas: Required for many Class A and B stations at night (and sometimes by day) to null radiation toward protected stations while concentrating energy toward desired service areas.
- Critical hours and transitional authority: The periods immediately around sunrise and sunset involve transitional ionospheric conditions. Eligible stations (especially daytimers) can apply for Pre-Sunrise Authorization (PSRA) and Post-Sunset Authorization (PSSA). These allow limited power (capped at 500 W or the station’s daytime power, whichever is lower) in the two hours before local sunrise and after local sunset. Permissible levels are calculated in 15-minute increments based on interference protection and are recalculated periodically (most recently updated by the FCC in 2024 after a long gap.
Impacts and Relevance to Daylight Saving Time
These restrictions directly affect coverage, especially during morning and evening drive times—the most valuable advertising periods. Daytimers and reduced-power stations lose audience when they must cut power or sign off while people are still commuting. Because switch times are tied to local solar sunrise and sunset (not clock time), permanent daylight saving time would push winter clock-time sunrises later (often after 8–9 a.m. in many areas). Stations would remain on nighttime (low-power or off) parameters deeper into the morning commute, shrinking coverage precisely when listenership peaks. This is the core concern raised by AM broadcasters regarding the Sunshine Protection Act.