The Equipment Rules mandate that your VHF be of a minimum wattage (25W) and that the connection to your masthead antenna not lose more than a stated amount of that wattage due to cable loss, dirty connectors, or other factors.
From Malcolm's Article:
"The purpose of this section is to help you review the electrical system on board your vessel and make any necessary upgrades in order to meet the challenges of an extended offshore race.
The production of adequate electric power to perform your lighting and communications requirements, as well as any cooling, inside lighting, navigation and other modern conveniences you may require is important to a safe and comfortable passage. Electrical failure is a common, and preventable cause of boats turning back after the start.
Many skippers take their boats "off the grid" for a month or so before the race to reveal any weaknesses in their charging and battery systems.