Yes, another example of a frequency not published by the FAA. It is listed on the official sector charts issued by the Center. It shows 128.425 as Sector 86 (Zephyr Ultra High), extending from FL350 and above. Sector 86 covers basically the same area as 125.175, Sector 16 (Mayo High) which extends from FL270 to FL340. As MIAMIATC mentions they only turn on 128.425 when it's required due traffic volume, otherwise they will use 125.175 to cover both sectors. The RCAG for 128.425 is in Gainsville.
Speaking of ZJX, they were using their spare frequency 134.400 the other day in place of 128.625, Sector 85 (adjacent north to Sector 86). Anyone else hear 134.400 in use recently ?
JS