Informal use of the most common Q-codes

QRG - Frequency

QRM - Interference from other stations

QRN - Interference from atmospheric noise or from nearby electrical apparatus

QRO - High-power

QRP - Low-power

QRT - Close(d) down

QRV - Ready

QRX - Stand by

QSB - Fading

QSL - Verification card; confirm contact

QSY - Change frequency

QTC - Message

QTH - Location

QTR - Time

Note also: QTHR means: Address is correct in the current RSGB yearbook