: Requires an RF signal generator. You feed a precise microvolt signal (e.g., -73 dBm for an S9 reading) into the antenna jack and adjust the service menu value until the on-screen S-Meter aligns with the S9 mark. Best Practices for a Successful Tune-Up
: Always let the AT-5555N II run for at least 15 to 20 minutes before entering the service menu. Internal components expand with heat, causing natural frequency drift. Calibrating a cold radio will result in an off-frequency radio once it warms up during a long transmission. anytone at5555n ii service menu work