How can you avoid harmful interference on an apparently clear frequency before calling CQ on CW or phone?
Send “QRL?” on CW, followed by your call sign; or, if using phone, ask if the frequency is in use, followed by your call sign✓Respuesta correcta
Listen for 2 minutes before calling CQ
Send the letter “V” in Morse code several times and listen for a response, or say “test” several times and listen for a response
Send “QSY” on CW or if using phone, announce “the frequency is in use,” then give your call sign and listen for a response
Explicación
Asking whether the frequency is in use is the necessary check, because a station you cannot hear may still be working someone who can hear you. Adding your call sign identifies the transmission as the rules require, and simply listening for a set time will never reveal a station that is currently receiving.