Frequency Management: Staying on and Leaving the Frequency
In practice, courtesy suggests you announce your departure when you leave the frequency. This is not required, but it is good airmanship. You might transmit: "Wels Radio, OE-CMV, airborne runway 27, leaving your frequency." The operator will acknowledge or simply note your departure.
If you intend to remain in the circuit (e.g., for multiple touch-and-go landings), you remain on the frequency throughout. You do not leave the frequency after each landing. You simply conduct your next approach and land again, announcing each circuit leg as before.