You are using an FM repeater configured for 5 kHz deviation, but your transmitter is set to 2.5 kHz deviation. What is the consequence?

In Frequency Modulation (FM), the amplitude (loudness) of the recovered audio at the receiving end is directly determined by the amount of frequency deviation in the transmitted signal. A wider deviation produces louder audio, while a narrower deviation produces quieter audio. If a repeater is configured to expect a standard 5 kHz deviation, transmitting with only 2.5 kHz (often called "narrow FM") means your signal is only swinging half as wide as expected. Consequently, your recovered voice audio will sound very quiet or "low" to anyone listening on the output of the repeater. It will not cause distortion, which typically happens when deviation is too high and exceeds the receiver's filter bandwidth. It also does not affect the RF range or prevent the repeater from keying up, as the carrier power remains the same.