"I hear you 5 by 2, Please say all words twice."
I've heard that msg before, both as a ham radio operator and a military radio operator on HF air-to-ground frequencies.
In ham radio it's RST - R = readability, S = signal strength (up to 9 on a Q-meter), and T = tone (when using Morse code).
In the military, it's sort of the opposite. 5 x 5 would be loud and clear, but a 3 x 3 would be weak and barely readable. Been there, done that.