diff --git a/librfm69.c b/librfm69.c
index 71f816b..a030dac 100644
--- a/librfm69.c
+++ b/librfm69.c
@@ -116,8 +116,8 @@
     // completely removes susceptibility to temperature changes
     regWrite(RFM_RX_BW, 0x54);
 
-    // RX_BW during AFC (default 0x8b)
-    regWrite(RFM_AFC_BW, 0x54);
+    // RX_BW during AFC 41.7 kHz (AFC not used)
+    regWrite(RFM_AFC_BW, 0x83);
 
     // AFC auto on
     // regWrite(AFC_FEI, 0x04);
@@ -125,9 +125,9 @@
     // RSSI threshold (default, POR 0xff)
     regWrite(RFM_RSSI_THRESH, 0xe4);
 
-    // Preamble size
+    // Preamble size 5 bytes
     regWrite(RFM_PREAMB_MSB, 0x00);
-    regWrite(RFM_PREAMB_LSB, 0x03);
+    regWrite(RFM_PREAMB_LSB, 0x05);
 
     // turn off CLKOUT (not used)
     regWrite(RFM_DIO_MAP2, 0x07);
diff --git a/librfm69.h b/librfm69.h
index f43fa1a..c79332f 100644
--- a/librfm69.h
+++ b/librfm69.h
@@ -26,8 +26,8 @@
 #define RFM_PA_LEVEL    0x11
 #define RFM_LNA         0x18
 #define RFM_RX_BW       0x19
+#define RFM_AFC_BW      0x1a
 #define RFM_AFC_FEI     0x1e
-#define RFM_AFC_BW      0x20
 #define RFM_RSSI_CONFIG 0x23
 #define RFM_RSSI_VALUE  0x24
 #define RFM_DIO_MAP1    0x25