diff --git a/examples/SX126x/SX126x_FSK_Modem/SX126x_FSK_Modem.ino b/examples/SX126x/SX126x_FSK_Modem/SX126x_FSK_Modem.ino
index 65373380..f961f5a6 100644
--- a/examples/SX126x/SX126x_FSK_Modem/SX126x_FSK_Modem.ino
+++ b/examples/SX126x/SX126x_FSK_Modem/SX126x_FSK_Modem.ino
@@ -24,7 +24,7 @@ void setup() {
   // carrier frequency:           434.0 MHz
   // bit rate:                    48.0 kbps
   // frequency deviation:         50.0 kHz
-  // Rx bandwidth:                117.3 kHz
+  // Rx bandwidth:                156.2 kHz
   // output power:                14 dBm
   // current limit:               60.0 mA
   // preamble length:             16 bits
diff --git a/keywords.txt b/keywords.txt
index 7f96ac03..aa731e66 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -222,3 +222,7 @@ ERR_INVALID_NUM_BROAD_ADDRS	LITERAL1
 ERR_INVALID_CRC_CONFIGURATION	LITERAL1
 LORA_DETECTED	LITERAL1
 ERR_INVALID_TCXO_VOLTAGE	LITERAL1
+ERR_INVALID_MODULATION_PARAMETERS	LITERAL1
+ERR_SPI_CMD_TIMEOUT	LITERAL1
+ERR_SPI_CMD_INVALID	LITERAL1
+ERR_SPI_CMD_FAILED	LITERAL1
diff --git a/src/TypeDef.h b/src/TypeDef.h
index 8fadb264..9362018f 100644
--- a/src/TypeDef.h
+++ b/src/TypeDef.h
@@ -112,5 +112,9 @@
 #define ERR_INVALID_CRC_CONFIGURATION         -701
 #define LORA_DETECTED                         -702
 #define ERR_INVALID_TCXO_VOLTAGE              -703
+#define ERR_INVALID_MODULATION_PARAMETERS     -704
+#define ERR_SPI_CMD_TIMEOUT                   -705
+#define ERR_SPI_CMD_INVALID                   -706
+#define ERR_SPI_CMD_FAILED                    -707
 
 #endif
diff --git a/src/modules/SX1262.h b/src/modules/SX1262.h
index a80f92d1..ee668095 100644
--- a/src/modules/SX1262.h
+++ b/src/modules/SX1262.h
@@ -16,7 +16,7 @@ class SX1262: public SX126x {
 
     // basic methods
     int16_t begin(float freq = 434.0, float bw = 125.0, uint8_t sf = 9, uint8_t cr = 7, uint16_t syncWord = SX126X_SYNC_WORD_PRIVATE, int8_t power = 14, float currentLimit = 60.0, uint16_t preambleLength = 8);
-    int16_t beginFSK(float freq = 434.0, float br = 48.0, float freqDev = 50.0, float rxBw = 117.3, int8_t power = 14, float currentLimit = 60.0, uint16_t preambleLength = 16, float dataShaping = 0.5);
+    int16_t beginFSK(float freq = 434.0, float br = 48.0, float freqDev = 50.0, float rxBw = 156.2, int8_t power = 14, float currentLimit = 60.0, uint16_t preambleLength = 16, float dataShaping = 0.5);
 
     // configuration methods
     int16_t setFrequency(float freq);
diff --git a/src/modules/SX126x.cpp b/src/modules/SX126x.cpp
index 4fe2c359..2d8bf23e 100644
--- a/src/modules/SX126x.cpp
+++ b/src/modules/SX126x.cpp
@@ -67,7 +67,8 @@ int16_t SX126x::beginFSK(float br, float freqDev, float rxBw, uint16_t preambleL
   // initialize configuration variables (will be overwritten during public settings configuration)
   _br = 21333;                                  // 48.0 kbps
   _freqDev = 52428;                             // 50.0 kHz
-  _rxBw = SX126X_GFSK_RX_BW_117_3;
+  _rxBw = SX126X_GFSK_RX_BW_156_2;
+  _rxBwKhz = 156.2;
   _pulseShape = SX126X_GFSK_FILTER_GAUSS_0_5;
   _crcTypeFSK = SX126X_GFSK_CRC_2_BYTE_INV;     // CCIT CRC configuration
   _preambleLengthFSK = preambleLength;
@@ -163,7 +164,10 @@ int16_t SX126x::transmit(uint8_t* data, size_t len, uint8_t addr) {
   DEBUG_PRINTLN(F(" us"));
 
   // start transmission
-  startTransmit(data, len, addr);
+  int16_t state = startTransmit(data, len, addr);
+  if(state != ERR_NONE) {
+    return(state);
+  }
 
   // wait for packet transmission or timeout
   uint32_t start = micros();
@@ -508,8 +512,13 @@ int16_t SX126x::setFrequencyDeviation(float freqDev) {
   }
 
   // calculate raw frequency deviation value
-  //_freqDev = (uint32_t)((freqDev * 1000.0) / ((SX126X_CRYSTAL_FREQ * 1000000.0) / (float)((uint32_t)(1) << 25)));
-  _freqDev = (uint32_t)(((freqDev * 1000.0) * (float)((uint32_t)(1) << 25)) / (SX126X_CRYSTAL_FREQ * 1000000.0));
+  uint32_t freqDevRaw = (uint32_t)(((freqDev * 1000.0) * (float)((uint32_t)(1) << 25)) / (SX126X_CRYSTAL_FREQ * 1000000.0));
+
+  // check modulation parameters
+  if(2 * freqDevRaw + _br > _rxBwKhz * 1000.0) {
+    return(ERR_INVALID_MODULATION_PARAMETERS);
+  }
+  _freqDev = freqDevRaw;
 
   // update modulation parameters
   setModulationParamsFSK(_br, _pulseShape, _rxBw, _freqDev);
@@ -529,7 +538,13 @@ int16_t SX126x::setBitRate(float br) {
   }
 
   // calculate raw bit rate value
-  _br = (uint32_t)((SX126X_CRYSTAL_FREQ * 1000000.0 * 32.0) / (br * 1000.0));
+  uint32_t brRaw = (uint32_t)((SX126X_CRYSTAL_FREQ * 1000000.0 * 32.0) / (br * 1000.0));
+
+  // check modulation parameters
+  if(2 * _freqDev + brRaw > _rxBwKhz * 1000.0) {
+    return(ERR_INVALID_MODULATION_PARAMETERS);
+  }
+  _br = brRaw;
 
   // update modulation parameters
   setModulationParamsFSK(_br, _pulseShape, _rxBw, _freqDev);
@@ -543,6 +558,12 @@ int16_t SX126x::setRxBandwidth(float rxBw) {
     return(ERR_WRONG_MODEM);
   }
 
+  // check modulation parameters
+  if(2 * _freqDev + _br > rxBw * 1000.0) {
+    return(ERR_INVALID_MODULATION_PARAMETERS);
+  }
+  _rxBwKhz = rxBw;
+
   // check alowed receiver bandwidth values
   if(abs(rxBw - 4.8) <= 0.001) {
     _rxBw = SX126X_GFSK_RX_BW_4_8;
diff --git a/src/modules/SX126x.h b/src/modules/SX126x.h
index d3da4c00..c2878e31 100644
--- a/src/modules/SX126x.h
+++ b/src/modules/SX126x.h
@@ -401,6 +401,7 @@ class SX126x: public PhysicalLayer {
     uint32_t _br, _freqDev;
     uint8_t _rxBw, _pulseShape, _crcTypeFSK, _syncWordLength, _addrComp;
     uint16_t _preambleLengthFSK;
+    float _rxBwKhz;
 
     float _dataRate;