Pre-sunrise and post-sunset authorization

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In USA AM broadcasting, presunrise authorization (PSRA) and postsunset authorization (PSSA) are permission from the Federal Communications Commission to broadcast in AM on mediumwave using a power level higher than what would normally be permitted prior to sunrise/after sunset, or in the latter case, provide Class D stations with service into the evening where they would otherwise be required to sign off. Sunrise and sunset times are provided on the licensee's basic instrument of authorization.

AM broadcasting radio broadcasting using amplitude modulation

AM broadcasting is a radio broadcasting technology, which employs amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave transmissions, but also on the longwave and shortwave radio bands.

Federal Communications Commission independent agency of the United States government

The Federal Communications Commission (FCC) is an independent agency of the United States government created by statute to regulate interstate communications by radio, television, wire, satellite, and cable. The FCC serves the public in the areas of broadband access, fair competition, radio frequency use, media responsibility, public safety, and homeland security.

Sunrise instant at which the upper edge of the Sun appears over the eastern horizon in the morning

Sunrise is the moment when the upper limb of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects.

Contents

The power level for both PSRA and PSSA service cannot exceed 500 watts. Power calculations are based on co-channel stations.

The watt is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In dimensional analysis, power is described by .

Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel. Co-channel interference can be caused by many factors from weather conditions to administrative and design issues. Co-channel interference may be controlled by various radio resource management schemes.

PSRA

At 6:00am local time, stations may power up using the station's daytime antenna (if applicable).

Daylight saving

Provided the locale participates in daylight saving time, special provisions must be made since the PSRA time is based on local time. The exact wording of the rule states:

Daylight saving time Practice of advancing clocks so that evenings have more daylight and mornings have less

Daylight saving time (DST), also daylight savings time or daylight time and summer time, is the practice of advancing clocks during summer months so that evening daylight lasts longer, while sacrificing normal sunrise times. Typically, regions that use daylight saving time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time. In effect, DST causes a lost hour of sleep in the spring and an extra hour of sleep in the fall.

Between the first Sunday in April and the end of the month of April, Class D stations will be permitted to conduct pre-sunrise operation beginning at 6 a.m. local time with a maximum power of 500 watts (not to exceed the station's regular daytime or critical hours power)...

For example, if the instrument of authorization states sunrise as being at 5:30am local standard time in April, the station does not require PSRA operation since sunrise time is prior to the 6:00am rule. When the clocks advance, this becomes 6:30am local time. PSRA will permit the station to power up at 5:00am standard time, since that would be 6:00am advanced time and local time would reflect the advanced time.

As of 2007 (when the new US daylight saving times went into effect), the FCC instructed licensees to use the April advanced times when DST goes into effect in March.

PSSA

At sunset, Class D stations must sign off if they do not possess a nighttime license. PSSA operation allows the station to remain on the air an additional two hours at reduced power level determined by several factors:

A clear-channel station is an AM radio station in North America that has the highest protection from interference from other stations, particularly concerning night-time skywave propagation. The system exists to ensure the viability of cross-country or cross-continent radio service, and is enforced through a series of treaties and statutory laws. Now known as Class A stations since 1982, they are occasionally still referred to by their former classifications of Class I-A, Class I-B, or Class I-N. The term "clear-channel" is used most often in the context of North America and the Caribbean, where the concept originated.

Daylight saving

There are no specific provisions related to daylight saving time within PSSA operation.

Exceptions

PSSA operation must cease at local sunset time for the closest co-channel Class A located west of the Class D station.

Class D stations west of a co-channel Class A do not qualify.

History

The first presunrise authorizations came from a proposed rulemaking in 1967 (Operation by Standard Broadcast Stations, 8 FCC 2d 698 (1967)). There were major concerns of skywave interference to clear channel stations, so only a handful of stations were permitted to apply.

Skywave an electrically charged layer of the upper atmosphere

In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere. Since it is not limited by the curvature of the Earth, skywave propagation can be used to communicate beyond the horizon, at intercontinental distances. It is mostly used in the shortwave frequency bands.

On February 25, 1981, the FCC determined that there were no detrimental effects to clear-channel stations in remote areas, therefore, they permitted even more stations to apply for authorization.

Current authorization

Applications for PSRA and PSSA operation are no longer required. The licensee must merely notify the FCC.

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