Re:5:5 , 5:5 is the best signal and best readability
Signal strength and readability report
A report format commonly referred to as five by five. The report format ostensibly consists of two digits, each ranging from 1 to 5, resulting in 25 possible combinations, with five by five being the best signal possible out of 25 combinations. As no reliable source has been found documenting this format, it may simply be Cold War-era slang, inappropriately mapping the radiotelegraph signal report numbers to radio-telephony signals.
https://en.m.wikipedia.org/wiki/Signal_strength_and_readability_report