For several years, Sea Tow operated an Automated Radio Check System, which was available on VHF Channels 24 to 28 for the benefit of mariners in over 130 locations. However, on October 2nd, 2020 that service was discontinued. The Coast Guard Inspections and Compliance Directorate has issued MSIB 20-20 to inform mariners of the proper procedure for performing a VHF radio check.
Read more at https://mariners.coastguard.blog/2020/10/19/performing-a-vhf-marine-radio-check/..