so ive been licensed about 4 months now and when i get on HF i try to use alpha bravo charlie etc but sometimes i hear guys just saying random words for letters like they'll say something like "N for Nancy" or "T for Texas" and im not sure if thats actually allowed or just an old habit or what. my elmer told me to just stick with NATO but i dont want to come across as the phonetics police either. is there like an actual rule about this or is it just convention

no hard rule in the FCC regs about which phonetics you use, its just convention really. the NATO/ITU phonetics exist because they were designed to be understood across language barriers and in bad conditions, like the words were literally chosen because they sound distinct even when a signal is weak or distorted. "november" vs "nancy" -- november is going to punch through noise better in most cases because its less common and the syllables land differently.

that said plenty of old timers use whatever they grew up with and it works fine on a clear 20m contact. where it starts to matter is when you're in a pileup or the band is rough and you really need the other op to get your callsign right. ive had guys give me a "lima" when i said my call and the other station came back with something completely wrong because they used a weird phonetic that sounded like another letter on a bad band. just stick with NATO, youll be glad you did when conditions get ugly

honestly i was confused about this same thing when i started. i just use the standard ones now and it feels natural after a while. took me maybe a couple weeks of actually getting on air before i stopped having to think about it. the weird thing is sometimes i forget a word mid-callsign and just blank on what november or uniform is supposed to sound like lol. so yeah there's that too