diff --git a/app/app.c b/app/app.c
index e398769..4422c9f 100644
--- a/app/app.c
+++ b/app/app.c
@@ -1562,7 +1562,7 @@ void APP_process_flash_light_10ms(void)
 						GPIO_SetBit(&GPIOC->DATA, GPIOC_PIN_FLASHLIGHT);
 						#ifdef ENABLE_FLASH_LIGHT_SOS_TONE
 							if (!g_squelch_open && !g_monitor_enabled && !GPIO_CheckBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER))
-								BK4819_StartTone1(880, 50, g_current_function == FUNCTION_TRANSMIT);
+								BK4819_StartTone1(880, 50, g_current_function == FUNCTION_TRANSMIT, true);
 						#endif
 					}
 				}
diff --git a/audio.c b/audio.c
index 9e01dd5..008dc79 100644
--- a/audio.c
+++ b/audio.c
@@ -173,8 +173,7 @@ void AUDIO_PlayBeep(beep_type_t Beep)
 			break;
 	}
 
-//	BK4819_PlayTone(ToneFrequency, true);
-	BK4819_StartTone1(ToneFrequency, 96, false);
+	BK4819_StartTone1(ToneFrequency, 96, false, false);
 
 	SYSTEM_DelayMs(2);
 	GPIO_SetBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
diff --git a/driver/bk4819.c b/driver/bk4819.c
index e69979c..0a8b389 100644
--- a/driver/bk4819.c
+++ b/driver/bk4819.c
@@ -814,7 +814,7 @@ void BK4819_EnableDTMF(void)
 		(15u       << BK4819_REG_24_SHIFT_MAX_SYMBOLS));     // 0 ~ 15
 }
 
-void BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const bool tx)
+void BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const bool tx, const bool tx_unmute)
 {
 	GPIO_ClearBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
 	SYSTEM_DelayMs(2);
@@ -825,7 +825,10 @@ void BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const
 
 	BK4819_EnterTxMute();
 
-	BK4819_write_reg(0x70, BK4819_REG_70_ENABLE_TONE1 | ((level & 0x7f) << BK4819_REG_70_SHIFT_TONE1_TUNING_GAIN));
+	if (level > 0)
+		BK4819_write_reg(0x70, BK4819_REG_70_ENABLE_TONE1 | ((level & 0x7f) << BK4819_REG_70_SHIFT_TONE1_TUNING_GAIN));
+	else
+		BK4819_write_reg(0x70, 0);
 
 	BK4819_write_reg(0x30, 0);
 
@@ -862,10 +865,12 @@ void BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const
 
 	BK4819_write_reg(0x71, scale_freq(frequency));
 
-	BK4819_ExitTxMute();
+	if (tx_unmute)
+		BK4819_ExitTxMute();
 
 	SYSTEM_DelayMs(2);
-	if (!tx)
+
+	if (!tx && level > 0)
 		GPIO_SetBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
 }
 
@@ -918,7 +923,7 @@ void BK4819_StopTones(const bool tx)
 void BK4819_PlayTone(const unsigned int tone_Hz, const unsigned int delay, const unsigned int level)
 {
 	const uint16_t prev_af = BK4819_read_reg(0x47);
-	BK4819_StartTone1(tone_Hz, level, g_current_function == FUNCTION_TRANSMIT);
+	BK4819_StartTone1(tone_Hz, level, g_current_function == FUNCTION_TRANSMIT, true);
 	SYSTEM_DelayMs(delay - 2);
 	BK4819_StopTones(g_current_function == FUNCTION_TRANSMIT);
 	BK4819_write_reg(0x47, prev_af);
@@ -936,9 +941,9 @@ void BK4819_PlayRoger(void)
 	#endif
 
 	const uint16_t prev_af = BK4819_read_reg(0x47);
-	BK4819_StartTone1(tone1_Hz, 96, true);
+	BK4819_StartTone1(tone1_Hz, 96, true, true);
 	SYSTEM_DelayMs(80 - 2);
-	BK4819_StartTone1(tone2_Hz, 96, true);
+	BK4819_StartTone1(tone2_Hz, 96, true, true);
 	SYSTEM_DelayMs(80);
 	BK4819_StopTones(true);
 	BK4819_write_reg(0x47, prev_af);
@@ -2128,7 +2133,7 @@ void BK4819_reset_fsk(void)
 		}
 	}
 
-	void BK4819_send_MDC1200(const uint8_t op, const uint8_t arg, const uint16_t id)
+	void BK4819_send_MDC1200(const uint8_t op, const uint8_t arg, const uint16_t id, const bool long_preamble)
 	{
 		uint16_t fsk_reg59;
 		uint8_t  packet[42];
@@ -2320,10 +2325,11 @@ void BK4819_reset_fsk(void)
 					(0u << 10) |   // 0/1     1 = invert data when RX
 					(0u <<  9) |   // 0/1     1 = invert data when TX
 					(0u <<  8) |   // 0/1     ???
-					(3u <<  4) |   // 0 ~ 15  preamble length .. bit toggling
+					(0u <<  4) |   // 0 ~ 15  preamble length .. bit toggling
 					(1u <<  3) |   // 0/1     sync length
 					(0u <<  0);    // 0 ~ 7   ???
-
+		fsk_reg59 |= long_preamble ? 15u << 4 : 3u << 4; 
+			
 		// Set packet length (not including pre-amble and sync bytes that we can't seem to disable)
 		BK4819_write_reg(0x5D, ((size - 1) << 8));
 
diff --git a/driver/bk4819.h b/driver/bk4819.h
index b09aa37..a8e2b15 100644
--- a/driver/bk4819.h
+++ b/driver/bk4819.h
@@ -106,7 +106,7 @@ void     BK4819_SetCompander(const unsigned int mode);
 void     BK4819_DisableVox(void);
 void     BK4819_DisableDTMF(void);
 void     BK4819_EnableDTMF(void);
-void     BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const bool tx);
+void     BK4819_StartTone1(const uint16_t frequency, const unsigned int level, const bool tx, const bool tx_unmute);
 void     BK4819_StopTones(const bool tx);
 void     BK4819_PlayTone(const unsigned int tone_Hz, const unsigned int delay, const unsigned int level);
 void     BK4819_EnterTxMute(void);
@@ -165,7 +165,7 @@ void     BK4819_PlayRoger(void);
 
 #ifdef ENABLE_MDC1200
 	void BK4819_enable_mdc1200_rx(const bool enable);
-	void BK4819_send_MDC1200(const uint8_t op, const uint8_t arg, const uint16_t id);
+	void BK4819_send_MDC1200(const uint8_t op, const uint8_t arg, const uint16_t id, const bool long_preamble);
 #endif
 
 void     BK4819_Enable_AfDac_DiscMode_TxDsp(void);
diff --git a/firmware.bin b/firmware.bin
index d4e133d..f0f0880 100644
Binary files a/firmware.bin and b/firmware.bin differ
diff --git a/firmware.packed.bin b/firmware.packed.bin
index 188b714..f9fa9ec 100644
Binary files a/firmware.packed.bin and b/firmware.packed.bin differ
diff --git a/functions.c b/functions.c
index 0ec5dfb..af0d45b 100644
--- a/functions.c
+++ b/functions.c
@@ -220,7 +220,7 @@ void FUNCTION_Select(function_type_t Function)
 					GPIO_ClearBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
 
 					SYSTEM_DelayMs(2);
-					BK4819_StartTone1(500, 28, g_current_function == FUNCTION_TRANSMIT);
+					BK4819_StartTone1(500, 28, g_current_function == FUNCTION_TRANSMIT, true);
 					SYSTEM_DelayMs(2);
 
 					GPIO_SetBit(&GPIOC->DATA, GPIOC_PIN_SPEAKER);
@@ -267,15 +267,16 @@ void FUNCTION_Select(function_type_t Function)
 				if (g_current_vfo->channel.mdc1200_mode == MDC1200_MODE_BOT || g_current_vfo->channel.mdc1200_mode == MDC1200_MODE_BOTH)
 				{
 					#ifdef ENABLE_MDC1200_SIDE_BEEP
-						BK4819_StartTone1(880, 20, false);
-						SYSTEM_DelayMs(120);
-						BK4819_StopTones(true);
+//						BK4819_StartTone1(880, 20, true, false);
+//						SYSTEM_DelayMs(120);
+//						BK4819_StopTones(true);
 					#endif
+					SYSTEM_DelayMs(30);
 
-					BK4819_send_MDC1200(MDC1200_OP_CODE_PTT_ID, 0x80, g_eeprom.config.setting.mdc1200_id);
+					BK4819_send_MDC1200(MDC1200_OP_CODE_PTT_ID, 0x80, g_eeprom.config.setting.mdc1200_id, true);
 
 					#ifdef ENABLE_MDC1200_SIDE_BEEP
-						BK4819_StartTone1(880, 20, false);
+						BK4819_StartTone1(880, 20, true, false);
 						SYSTEM_DelayMs(120);
 						BK4819_StopTones(true);
 					#endif
@@ -287,19 +288,7 @@ void FUNCTION_Select(function_type_t Function)
 					BK4819_PlayTone(APOLLO_TONE1_HZ, APOLLO_TONE_MS, 0);
 				}
 			}
-/*			
-			BK4819_write_reg(0x30,
-				(1u  << 15) |    // enable  VCO calibration
-				(1u  << 14) |    // enable  something or other
-				(0u  << 10) |    // diable  RX link
-				(1u  <<  9) |    // enable  AF DAC
-				(1u  <<  8) |    // enable  DISC mode, what's DISC mode ?
-				(15u <<  4) |    // enable  PLL/VCO
-				(1u  <<  3) |    // enable  PA gain
-				(1u  <<  2) |    // enable  MIC ADC
-				(1u  <<  1) |    // enable  TX DSP
-				(0u  <<  0));    // disable RX DSP
-*/
+
 			if (g_eeprom.config.setting.enable_scrambler)
 				BK4819_set_scrambler(g_current_vfo->channel.scrambler);
 			
diff --git a/radio.c b/radio.c
index 02ea570..04e7b3c 100644
--- a/radio.c
+++ b/radio.c
@@ -1212,16 +1212,10 @@ void RADIO_tx_eot(void)
 //	if (g_eeprom.config.setting.roger_mode == ROGER_MODE_MDC)
 	if (g_current_vfo->channel.mdc1200_mode == MDC1200_MODE_EOT || g_current_vfo->channel.mdc1200_mode == MDC1200_MODE_BOTH)
 	{
-		#ifdef ENABLE_MDC1200_SIDE_BEEP
-			//BK4819_StartTone1(880, 20, false);
-			//SYSTEM_DelayMs(120);
-			//BK4819_StopTones(true);
-		#endif
-
-		BK4819_send_MDC1200(MDC1200_OP_CODE_POST_ID, 0x00, g_eeprom.config.setting.mdc1200_id);
+		BK4819_send_MDC1200(MDC1200_OP_CODE_POST_ID, 0x00, g_eeprom.config.setting.mdc1200_id, false);
 
 		#ifdef ENABLE_MDC1200_SIDE_BEEP
-			BK4819_StartTone1(880, 20, false);
+			BK4819_StartTone1(880, 30, true, false);
 			SYSTEM_DelayMs(120);
 			BK4819_StopTones(true);
 		#endif