diff --git a/src/libam/am.c b/src/libam/am.c
index 7194b49..e09f7f2 100644
--- a/src/libam/am.c
+++ b/src/libam/am.c
@@ -127,7 +127,7 @@ void am_modulate_complex(am_mod_t *mod, sample_t *amplitude, uint8_t *power, int
 	mod->phase = phase;
 }
 
-/* init AM demodulator */
+/* init AM demodulator, the bandwidth is the demodulated bandwidth (bandwidth of one side band) */
 int am_demod_init(am_demod_t *demod, double samplerate, double offset, double bandwidth, double gain)
 {
 	memset(demod, 0, sizeof(*demod));
diff --git a/src/libfm/fm.c b/src/libfm/fm.c
index 079491c..cd13ea1 100644
--- a/src/libfm/fm.c
+++ b/src/libfm/fm.c
@@ -244,7 +244,7 @@ again:
 	mod->ramp = ramp;
 }
 
-/* init FM demodulator */
+/* init FM demodulator, bandwidth is the 2 * (deviation + modulation) */
 int fm_demod_init(fm_demod_t *demod, double samplerate, double offset, double bandwidth)
 {
 	if (!has_init) {
diff --git a/src/libsdr/sdr.c b/src/libsdr/sdr.c
index 537fd9b..e322b5e 100644
--- a/src/libsdr/sdr.c
+++ b/src/libsdr/sdr.c
@@ -482,9 +482,9 @@ void *sdr_open(int __attribute__((__unused__)) direction, const char __attribute
 			LOGP(DSDR, LOGL_DEBUG, "Frequency #%d: RX offset: %.6f MHz\n", c, rx_offset / 1e6);
 			sdr->chan[c].am = am[c];
 			if (am[c])
-				rc = am_demod_init(&sdr->chan[c].am_demod, samplerate, rx_offset, bandwidth, 1.0 / modulation_index);
+				rc = am_demod_init(&sdr->chan[c].am_demod, samplerate, rx_offset, bandwidth / 2.0, 1.0 / modulation_index); /* bandwidth is only one side band */
 			else
-				rc = fm_demod_init(&sdr->chan[c].fm_demod, samplerate, rx_offset, bandwidth / 2.0);
+				rc = fm_demod_init(&sdr->chan[c].fm_demod, samplerate, rx_offset, bandwidth); /* bandwidth are deviation and both side bands */
 			if (rc < 0)
 				goto error;
 		}