Five by Five ?

I’m new posting here… so be gentle with me. I have heard the phrase 5 by 5 several times recently in movies. I understand that the phrase means that everything is “ok” and ready to go but where does the term originate from? I have search high and low for an answer to this and can’t seem to find it. Any help would be greatly appreciated !

Here is a page that says it has to do with radio transmission.
You have to scroll down a bit.

Here is a link with a little more info:

Or at least it was back when I was taught radio procedures back in the mid-eighties.

If another operator was asking about his signal quality, and the signal indeed was clear and powerful, the correct reply would be the shorter “(station id), roger, out” (or the equivalent in Danish, this being the army in question) instead of “I hear you five-by-five”. You would only rate the signal on a one-to-five scale if there was signal degradation.

Keeping transmissions short can be relatively important if, for instance, a CO needs to check if he’s in touch with all units. 3 seconds saved per unit might add up, and keep the frequency available for other traffic - stuff like the whereabouts of the enemy, chemical attacks and polite requests to your own artillery if they’d please stop dropping HE on your current location.

S. Norman, once better known as “2 5 OSCAR”

As a former USMC 2531 (field radio operator) in Vietnam in the late 60’s, I can testify brief checks were encouraged and common. Typically it would go:

“how hear?”

“five by five, how me?”

“five by five”