The purpose of a repeater/frequency coordination entity is to try to keep interference between repeaters and their users to a minimum.

According to Wikipedia, repeater coordination is not required by the Federal Communications Commission (FCC), nor does the FCC regulate, certify, or otherwise regulate frequency coordination.

Amateur Radio Repeater Coordinators or coordination groups are all volunteers and have no legal authority to assume jurisdictional or regional control in any area where the Federal Communications Commission regulates the Amateur Radio Service. The United States Code of Federal Regulations Title 47 CFR, Part 97, which are the laws in which the Amateur Radio Service is regulated clearly states the definition of Frequency Coordinator.

The purpose of coordinating a repeater or frequency is to reduce harmful interference to other fixed operations. Coordinating a repeater or frequency with other fixed operations demonstrates good engineering and amateur practice.

• Alabama Repeater Council (N/A)

• Alaska Repeater Coordination

• Arizona Repeater Owners Frequency Coordination Committee (B)

• Arkasas Repeater Council (B)

• Northern: Northern Amateur Relay Council of California (NARCC) (C)
• Southern 10-m, 6-m, 70-cm and above only: Southern California Repeater and Remote Base Association
• Southern 2-meter only: Two Meter Area Spectrum Management Association
• Southern 1.25-meter only: 220 MHz Spectrum Management Association

• Colorado Council of Amateur Radio Clubs (B)

• Connecticut Spectrum Management Association

• The Mid Atlantic Repeater Council (T-MARC)

• Florida Amateur Spectrum Management Association

• Southeastern Repeater Association

• Hawaii State Repeater Advisory Council

Northern Idaho

• Inland Amateur Coordination Council

All other areas

• [https://www.idahoarrl.info/repeaters.html|Idaho ARRL]]

• Illinois Repeater Association

• Indiana Repeater Council

• Iowa Repeater Council, Inc.

• Kansas Amateur Repeater Council

• Southeastern Repeater Association

• Louisiana Council of Amateur Radio Clubs

• New England Spectrum Management Council

• The Mid-Atlantic Repeater Council (T-MARC

• New England Spectrum Management Council

Upper Peninsula

• Upper Peninsula Amateur Radio Repeater Association

Lower Peninsula

• Michigan Repeater Council

• Minnesota Repeater Council

• Southeastern Repeater Association

• Missouri Repeater Council

• Email Don Heide, W7MRI

http://www.nebraska-repeaters.us

• Email Shawn Kyker, KCØSWG

Southern

• Southern Nevada Repeater Council

Northern

• Combined Amateur Relay Council of Nevada

• New England Spectrum Management Council

Southern/Western

• Area Repeater Coordination Council

Northern

• Metropolitan Coordination Association

• New Mexico Frequency Coordination Committee (C)

Northern

• Saint Lawrence Valley Repeater Council

Eastern/Central

• Upper New York Repeater Council

Western

• Western New York and Southern Ontario Repeater Council

New York City and Long Island

• Metropolitan Coordination Association

• Southeastern Repeater Association

• Email Joseph M Ferrara, N7IV

• Ohio Area Repeater Council (D)

• Oklahoma Repeater Society (B)

• Oregon Region Relay Council (C)

Eastern

• Area Repeater Coordination Council

Western

• Western Pennsylvania Repeater Council

The accuracy seemed OK. Found a few bad call signs and about a dozen repeaters that are gone.

• Puerto Rico/Virgin Islands Volunteer Frequency Coordinators, Inc

• New England Spectrum Management Council

• Southeastern Repeater Association

• Southeastern Repeater Association

• Texas VHF/FM Society

• Utah VHF Society (B)

• Vermont Independent Repeater Coordination Committee

South of 38th Parallel and US Route 33

• Southeastern Repeater Association

North of 38th Parallel and US Route 33

• The Mid Atlantic Repeater Council (T-MARC)

Eastern Washington

• Inland Amateur Coordination Council

Western

• Western Washington Amateur Radio Relay Association (B)

Southwestern

• Oregon Region Relay Council (C)

Eastern Panhandle

• The Mid Atlantic Repeater Council (T-MARC)

All Other Areas

• Southeastern Repeater Association

• Wisconsin Association of Repeaters

• Wyoming Repeater Coordination Group

• AB North: VE6JY
• AB South: VE6AFO

• Critich Columbia Amateur Radio Coordination Council

• Uncoordinated

• Manitoba Amateur Repeater Coordination Council (MARCC)

• MARCAN Frequency Coordinator

• VOARA

• VE6AFO

• Southwest: Western New York Southern Ontario Repeater Council (WNYSORC)
• East and North: St Lawrence Valley Repeater Council (SLVRC)

• Radio Amateur du Quebec, Inc (RAQI)

• Saskatchewan Amateur Radio League (SARL)

• Yukon Amateur Radio Association

• Radio Society of Great Britain (RSGB)