This depends on the passband of the duplexer, if the new frequencies fall within the passband then no retuning is required. However, if the new frequencies fall outside the passband then the duplexer must be retuned. For example, a duplexer with a passband of ±3.5 MHz (7 MHz) is tuned to the following frequencies:
- High port: 1480 MHz
- Low port: 1420 MHz
The user wants to change the frequencies to:
- High port: 1482 MHz
- Low port: 1435 MHz
Since the high port new frequency is within the passband it does not require to be retuned. However, the low port must be retuned as the new frequency is outside the passband.