diff --git a/Makefile b/Makefile
index 52f4113..3be841a 100644
--- a/Makefile
+++ b/Makefile
@@ -200,6 +200,7 @@ endif
 
 # May cause unhelpful build failures
 #CFLAGS += -Wpadded
+CFLAGS += -Wextra
 
 CFLAGS += -DPRINTF_INCLUDE_CONFIG_H
 CFLAGS += -DGIT_HASH=\"$(GIT_HASH)\"
diff --git a/am_fix.c b/am_fix.c
index 51c11ae..09d67e9 100644
--- a/am_fix.c
+++ b/am_fix.c
@@ -475,7 +475,7 @@
 
 		void AM_fix_print_data(const int vfo, char *s)
 		{
-			if (s != NULL && vfo >= 0 && vfo < ARRAY_SIZE(gain_table_index))
+			if (s != NULL && vfo >= 0 && vfo < (int)ARRAY_SIZE(gain_table_index))
 			{
 				const unsigned int index = gain_table_index[vfo];
 //				sprintf(s, "%2u.%u %4ddB %3u", index, ARRAY_SIZE(gain_table) - 1, gain_table[index].gain_dB, prev_rssi[vfo]);
diff --git a/app/app.c b/app/app.c
index 025544d..b4786e4 100644
--- a/app/app.c
+++ b/app/app.c
@@ -647,6 +647,9 @@ static void MR_NextChannel(void)
 
 	if (enabled)
 	{
+		#pragma GCC diagnostic push
+		#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 		switch (gCurrentScanList)
 		{
 			case SCAN_NEXT_CHAN_SCANLIST1:
@@ -680,7 +683,7 @@ static void MR_NextChannel(void)
 //				{
 //					chan = (gEeprom.RX_VFO + 1) & 1u;
 //					chan = gEeprom.ScreenChannel[chan];
-//					if (IS_MR_CHANNEL(chan))
+//					if (chan <= MR_CHANNEL_LAST)
 //					{
 //						gCurrentScanList = SCAN_NEXT_CHAN_DUAL_WATCH;
 //						gNextMrChannel   = chan;
@@ -695,6 +698,8 @@ static void MR_NextChannel(void)
 				chan             = 0xff;
 				break;
 		}
+
+		#pragma GCC diagnostic pop
 	}
 
 	if (!enabled || chan == 0xff)
@@ -2042,7 +2047,7 @@ void CHANNEL_Next(bool bFlag, int8_t Direction)
 	gCurrentScanList = SCAN_NEXT_CHAN_SCANLIST1;
 	gScanState       = Direction;
 
-	if (IS_MR_CHANNEL(gNextMrChannel))
+	if (gNextMrChannel <= MR_CHANNEL_LAST)
 	{
 		if (bFlag)
 			gRestoreMrChannel = gNextMrChannel;
diff --git a/app/dtmf.c b/app/dtmf.c
index ffb9241..0f96941 100644
--- a/app/dtmf.c
+++ b/app/dtmf.c
@@ -331,6 +331,9 @@ void DTMF_HandleRequest(void)
 
 			gUpdateDisplay = true;
 
+			#pragma GCC diagnostic push
+			#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 			switch (gEeprom.DTMF_DECODE_RESPONSE)
 			{
 				case DTMF_DEC_RESPONSE_BOTH:
@@ -348,6 +351,8 @@ void DTMF_HandleRequest(void)
 					break;
 			}
 
+			#pragma GCC diagnostic pop
+
 			if (gDTMF_IsGroupCall)
 				gDTMF_ReplyState = DTMF_REPLY_NONE;
 		}
diff --git a/app/menu.c b/app/menu.c
index 45ec8a5..018795b 100644
--- a/app/menu.c
+++ b/app/menu.c
@@ -408,6 +408,9 @@ void MENU_AcceptSetting(void)
 			gRequestSaveChannel = 1;
 			return;
 
+		#pragma GCC diagnostic push
+		#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 		case MENU_T_CTCS:
 			pConfig = &gTxVfo->freq_config_TX;
 		case MENU_R_CTCS:
@@ -436,6 +439,8 @@ void MENU_AcceptSetting(void)
 			gRequestSaveChannel = 1;
 			return;
 
+		#pragma GCC diagnostic pop
+
 		case MENU_SFT_D:
 			gTxVfo->TX_OFFSET_FREQUENCY_DIRECTION = gSubMenuSelection;
 			gRequestSaveChannel                   = 1;
@@ -1170,7 +1175,7 @@ static void MENU_Key_0_to_9(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
 
 		if (edit_index < 10)
 		{
-			if (Key >= KEY_0 && Key <= KEY_9)
+			if (/* Key >= KEY_0 && */ Key <= KEY_9)
 			{
 				edit[edit_index] = '0' + Key - KEY_0;
 
@@ -1193,6 +1198,9 @@ static void MENU_Key_0_to_9(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
 
 	if (!gIsInSubMenu)
 	{
+		#pragma GCC diagnostic push
+		#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 		switch (gInputBoxIndex)
 		{
 			case 2:
@@ -1224,6 +1232,8 @@ static void MENU_Key_0_to_9(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
 				break;
 		}
 
+		#pragma GCC diagnostic pop
+
 		gInputBoxIndex = 0;
 
 		gBeepToPlay = BEEP_500HZ_60MS_DOUBLE_BEEP_OPTIONAL;
@@ -1269,7 +1279,7 @@ static void MENU_Key_0_to_9(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
 
 		Value = ((gInputBox[0] * 100) + (gInputBox[1] * 10) + gInputBox[2]) - 1;
 
-		if (IS_MR_CHANNEL(Value))
+		if (Value <= MR_CHANNEL_LAST)
 		{
 			#ifdef ENABLE_VOICE
 				gAnotherVoiceID = (VOICE_ID_t)Key;
@@ -1661,6 +1671,9 @@ static void MENU_Key_UP_DOWN(bool bKeyPressed, bool bKeyHeld, int8_t Direction)
 
 	VFO = 0;
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (gMenuCursor)
 	{
 		case MENU_DEL_CH:
@@ -1681,6 +1694,8 @@ static void MENU_Key_UP_DOWN(bool bKeyPressed, bool bKeyHeld, int8_t Direction)
 			return;
 	}
 
+	#pragma GCC diagnostic pop
+
 	Channel = RADIO_FindNextChannel(gSubMenuSelection + Direction, Direction, bCheckScanList, VFO);
 	if (Channel != 0xFF)
 		gSubMenuSelection = Channel;
diff --git a/app/scanner.c b/app/scanner.c
index b203ad4..b74fc27 100644
--- a/app/scanner.c
+++ b/app/scanner.c
@@ -67,7 +67,7 @@ static void SCANNER_Key_DIGITS(KEY_Code_t Key, bool bKeyPressed, bool bKeyHeld)
 			gInputBoxIndex = 0;
 			Channel        = ((gInputBox[0] * 100) + (gInputBox[1] * 10) + gInputBox[2]) - 1;
 
-			if (IS_MR_CHANNEL(Channel))
+			if (Channel <= MR_CHANNEL_LAST)
 			{
 				#ifdef ENABLE_VOICE
 					gAnotherVoiceID = (VOICE_ID_t)Key;
@@ -193,7 +193,7 @@ static void SCANNER_Key_MENU(bool bKeyPressed, bool bKeyHeld)
 				}
 			}
 
-			if (IS_MR_CHANNEL(gTxVfo->CHANNEL_SAVE))
+			if (gTxVfo->CHANNEL_SAVE <= MR_CHANNEL_LAST)
 			{
 				gScannerEditState = 1;
 				gScanChannel      = gTxVfo->CHANNEL_SAVE;
@@ -247,7 +247,7 @@ static void SCANNER_Key_MENU(bool bKeyPressed, bool bKeyHeld)
 				gTxVfo->freq_config_TX.Code     = gScanCssResultCode;
 			}
 
-			if (IS_MR_CHANNEL(gTxVfo->CHANNEL_SAVE))
+			if (gTxVfo->CHANNEL_SAVE <= MR_CHANNEL_LAST)
 			{
 				Channel                               = gScanChannel;
 				gEeprom.MrChannel[gEeprom.TX_VFO] = Channel;
@@ -428,7 +428,7 @@ void SCANNER_Stop(void)
 
 	if (!bScanKeepFrequency)
 	{
-		if (IS_MR_CHANNEL(gNextMrChannel))
+		if (gNextMrChannel <= MR_CHANNEL_LAST)
 		{
 			gEeprom.MrChannel[gEeprom.RX_VFO]     = gRestoreMrChannel;
 			gEeprom.ScreenChannel[gEeprom.RX_VFO] = Previous;
@@ -446,7 +446,7 @@ void SCANNER_Stop(void)
 		return;
 	}
 
-	if (!IS_MR_CHANNEL(gRxVfo->CHANNEL_SAVE))
+	if (gRxVfo->CHANNEL_SAVE > MR_CHANNEL_LAST)
 	{
 		RADIO_ApplyOffset(gRxVfo);
 		RADIO_ConfigureSquelchAndOutputPower(gRxVfo);
diff --git a/app/uart.c b/app/uart.c
index c109419..f54e722 100644
--- a/app/uart.c
+++ b/app/uart.c
@@ -450,7 +450,7 @@ bool UART_IsCommandAvailable(void)
 	Index = DMA_INDEX(gUART_WriteIndex, 2);
 	Size  = (UART_DMA_Buffer[DMA_INDEX(Index, 1)] << 8) | UART_DMA_Buffer[Index];
 
-	if ((Size + 8) > sizeof(UART_DMA_Buffer))
+	if ((Size + 8u) > sizeof(UART_DMA_Buffer))
 	{
 		gUART_WriteIndex = DmaLength;
 		return false;
diff --git a/audio.c b/audio.c
index 671d386..b46fd44 100644
--- a/audio.c
+++ b/audio.c
@@ -142,6 +142,9 @@ void AUDIO_PlayBeep(BEEP_Type_t Beep)
 
 	SYSTEM_DelayMs(60);
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (Beep)
 	{
 		case BEEP_880HZ_60MS_TRIPLE_BEEP:
@@ -181,6 +184,8 @@ void AUDIO_PlayBeep(BEEP_Type_t Beep)
 			break;
 	}
 
+	#pragma GCC diagnostic pop
+
 	SYSTEM_DelayMs(Duration);
 	BK4819_EnterTxMute();
 	SYSTEM_DelayMs(20);
diff --git a/driver/adc.c b/driver/adc.c
index 6f0214b..bde01f0 100644
--- a/driver/adc.c
+++ b/driver/adc.c
@@ -134,9 +134,9 @@ void ADC_Configure(ADC_Config_t *pAdc)
 		;
 
 	if (SARADC_IE == 0) {
-		NVIC_DisableIRQ(DP32_SARADC_IRQn);
+		NVIC_DisableIRQ((IRQn_Type)DP32_SARADC_IRQn);
 	} else {
-		NVIC_EnableIRQ(DP32_SARADC_IRQn);
+		NVIC_EnableIRQ((IRQn_Type)DP32_SARADC_IRQn);
 	}
 }
 
diff --git a/driver/aes.c b/driver/aes.c
index 17a3990..6a8b5c0 100644
--- a/driver/aes.c
+++ b/driver/aes.c
@@ -24,6 +24,8 @@ static void AES_Setup_ENC_CBC(bool IsDecrypt, const void *pKey, const void *pIv)
 	const uint32_t *pK = (const uint32_t *)pKey;
 	const uint32_t *pI = (const uint32_t *)pIv;
 
+	(void)IsDecrypt;	// unused
+	
 	AES_CR = (AES_CR & ~AES_CR_EN_MASK) | AES_CR_EN_BITS_DISABLE;
 	AES_CR = AES_CR_CHMOD_BITS_CBC;
 	AES_KEYR3 = pK[0];
diff --git a/driver/keyboard.c b/driver/keyboard.c
index e490a13..91285df 100644
--- a/driver/keyboard.c
+++ b/driver/keyboard.c
@@ -103,7 +103,7 @@ KEY_Code_t KEYBOARD_Poll(void)
 	
 
 	// *****************
-        for (int j = 0; j < ARRAY_SIZE(keyboard); j++)
+        for (unsigned int j = 0; j < ARRAY_SIZE(keyboard); j++)
 		{
             //Set all high
             GPIOA->DATA |=  1u << GPIOA_PIN_KEYBOARD_4 |
@@ -118,7 +118,7 @@ KEY_Code_t KEYBOARD_Poll(void)
 
             // Read all 4 GPIO pins at once
             uint16_t reg = GPIOA->DATA;
-            for (int i = 0; i < ARRAY_SIZE(keyboard[j].pins); i++)
+            for (unsigned int i = 0; i < ARRAY_SIZE(keyboard[j].pins); i++)
             {
                 uint16_t mask = 1u << keyboard[j].pins[i].pin;
                 if (!(reg & mask))
diff --git a/driver/spi.c b/driver/spi.c
index 9fb5e02..4a1a279 100644
--- a/driver/spi.c
+++ b/driver/spi.c
@@ -93,9 +93,9 @@ void SPI_Configure(volatile SPI_Port_t *pPort, SPI_Config_t *pConfig)
 
 	if (pPort->IE) {
 		if (pPort == SPI0) {
-			NVIC_EnableIRQ(DP32_SPI0_IRQn);
+			NVIC_EnableIRQ((IRQn_Type)DP32_SPI0_IRQn);
 		} else if (pPort == SPI1) {
-			NVIC_EnableIRQ(DP32_SPI1_IRQn);
+			NVIC_EnableIRQ((IRQn_Type)DP32_SPI1_IRQn);
 		}
 	}
 }
diff --git a/firmware.bin b/firmware.bin
index 1c41ed7..021cb5e 100644
Binary files a/firmware.bin and b/firmware.bin differ
diff --git a/firmware.packed.bin b/firmware.packed.bin
index 09cbff6..7f88a7a 100644
Binary files a/firmware.packed.bin and b/firmware.packed.bin differ
diff --git a/misc.h b/misc.h
index d19c28e..7de519d 100644
--- a/misc.h
+++ b/misc.h
@@ -24,26 +24,22 @@
 	#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
 #endif
 
-#define IS_MR_CHANNEL(x)           ((x) >= MR_CHANNEL_FIRST   && (x) <= MR_CHANNEL_LAST)
-#define IS_FREQ_CHANNEL(x)         ((x) >= FREQ_CHANNEL_FIRST && (x) <= FREQ_CHANNEL_LAST)
-#define IS_VALID_CHANNEL(x)        ((x) < LAST_CHANNEL)
+#define IS_MR_CHANNEL(x)       ((x) >= MR_CHANNEL_FIRST   && (x) <= MR_CHANNEL_LAST)
+#define IS_FREQ_CHANNEL(x)     ((x) >= FREQ_CHANNEL_FIRST && (x) <= FREQ_CHANNEL_LAST)
+#define IS_VALID_CHANNEL(x)    ((x) < LAST_CHANNEL)
 
-#ifdef ENABLE_NOAA
-	#define IS_NOAA_CHANNEL(x)     ((x) >= NOAA_CHANNEL_FIRST && (x) <= NOAA_CHANNEL_LAST)
-	#define IS_NOT_NOAA_CHANNEL(x) ((x) >= MR_CHANNEL_FIRST   && (x) <= FREQ_CHANNEL_LAST)
-#endif
+#define IS_NOAA_CHANNEL(x)     ((x) >= NOAA_CHANNEL_FIRST && (x) <= NOAA_CHANNEL_LAST)
+#define IS_NOT_NOAA_CHANNEL(x) ((x) >= MR_CHANNEL_FIRST   && (x) <= FREQ_CHANNEL_LAST)
 
-enum {
+typedef enum {
 	MR_CHANNEL_FIRST   = 0,
 	MR_CHANNEL_LAST    = 199u,
 	FREQ_CHANNEL_FIRST = 200u,
 	FREQ_CHANNEL_LAST  = 206u,
-	#ifdef ENABLE_NOAA
-		NOAA_CHANNEL_FIRST = 207u,
-		NOAA_CHANNEL_LAST  = 216u,
-	#endif
+	NOAA_CHANNEL_FIRST = 207u,
+	NOAA_CHANNEL_LAST  = 216u,
 	LAST_CHANNEL
-};
+} channel_num_t;
 
 enum {
 	FLASHLIGHT_OFF = 0,
diff --git a/radio.c b/radio.c
index f712f2d..bced7d7 100644
--- a/radio.c
+++ b/radio.c
@@ -51,7 +51,7 @@ bool RADIO_CheckValidChannel(uint16_t Channel, bool bCheckScanList, uint8_t VFO)
 	uint8_t PriorityCh1;
 	uint8_t PriorityCh2;
 
-	if (!IS_MR_CHANNEL(Channel))
+	if (Channel > MR_CHANNEL_LAST)
 		return false;
 
 	Attributes = gMR_ChannelAttributes[Channel];
@@ -176,7 +176,7 @@ void RADIO_ConfigureChannel(const unsigned int VFO, const unsigned int configure
 			}
 		#endif
 
-		if (IS_MR_CHANNEL(Channel))
+		if (Channel <= MR_CHANNEL_LAST)
 		{
 			Channel = RADIO_FindNextChannel(Channel, RADIO_CHANNEL_UP, false, VFO);
 			if (Channel == 0xFF)
@@ -200,7 +200,7 @@ void RADIO_ConfigureChannel(const unsigned int VFO, const unsigned int configure
 
 		uint8_t Index;
 
-		if (IS_MR_CHANNEL(Channel))
+		if (Channel <= MR_CHANNEL_LAST)
 		{
 			Channel                    = gEeprom.FreqChannel[VFO];
 			gEeprom.ScreenChannel[VFO] = gEeprom.FreqChannel[VFO];
@@ -218,7 +218,7 @@ void RADIO_ConfigureChannel(const unsigned int VFO, const unsigned int configure
 		Band = BAND6_400MHz;
 	}
 
-	if (IS_MR_CHANNEL(Channel))
+	if (Channel <= MR_CHANNEL_LAST)
 	{
 		gEeprom.VfoInfo[VFO].Band                    = Band;
 		gEeprom.VfoInfo[VFO].SCANLIST1_PARTICIPATION = !!(Attributes & MR_CH_SCANLIST1);
@@ -235,7 +235,7 @@ void RADIO_ConfigureChannel(const unsigned int VFO, const unsigned int configure
 	gEeprom.VfoInfo[VFO].SCANLIST2_PARTICIPATION = bParticipation2;
 	gEeprom.VfoInfo[VFO].CHANNEL_SAVE            = Channel;
 
-	if (IS_MR_CHANNEL(Channel))
+	if (Channel <= MR_CHANNEL_LAST)
 		Base = Channel * 16;
 	else
 		Base = 0x0C80 + ((Channel - FREQ_CHANNEL_FIRST) * 32) + (VFO * 16);
@@ -380,13 +380,13 @@ void RADIO_ConfigureChannel(const unsigned int VFO, const unsigned int configure
 	if (Frequency >= 10800000 && Frequency < 13600000)
 		gEeprom.VfoInfo[VFO].TX_OFFSET_FREQUENCY_DIRECTION = TX_OFFSET_FREQUENCY_DIRECTION_OFF;
 	else
-	if (!IS_MR_CHANNEL(Channel))
+	if (Channel > MR_CHANNEL_LAST)
 		gEeprom.VfoInfo[VFO].TX_OFFSET_FREQUENCY = FREQUENCY_FloorToStep(gEeprom.VfoInfo[VFO].TX_OFFSET_FREQUENCY, gEeprom.VfoInfo[VFO].StepFrequency, 0);
 
 	RADIO_ApplyOffset(pRadio);
 
 	memset(gEeprom.VfoInfo[VFO].Name, 0, sizeof(gEeprom.VfoInfo[VFO].Name));
-	if (IS_MR_CHANNEL(Channel))
+	if (Channel < MR_CHANNEL_LAST)
 	{	// 16 bytes allocated to the channel name but only 10 used, the rest are 0's
 		EEPROM_ReadBuffer(0x0F50 + (Channel * 16), gEeprom.VfoInfo[VFO].Name + 0, 8);
 		EEPROM_ReadBuffer(0x0F58 + (Channel * 16), gEeprom.VfoInfo[VFO].Name + 8, 2);
@@ -576,6 +576,9 @@ void RADIO_SetupRegisters(bool bSwitchToFunction0)
 
 	BK4819_ToggleGpioOut(BK4819_GPIO0_PIN28_GREEN, false);
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (Bandwidth)
 	{
 		default:
@@ -591,6 +594,8 @@ void RADIO_SetupRegisters(bool bSwitchToFunction0)
 			break;
 	}
 
+	#pragma GCC diagnostic pop
+
 	BK4819_ToggleGpioOut(BK4819_GPIO1_PIN29_RED, false);
 
 	BK4819_SetupPowerAmplifier(0, 0);
@@ -825,6 +830,9 @@ void RADIO_SetTxParameters(void)
 
 	BK4819_ToggleGpioOut(BK4819_GPIO6_PIN2, false);
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (Bandwidth)
 	{
 		default:
@@ -840,6 +848,8 @@ void RADIO_SetTxParameters(void)
 			break;
 	}
 
+	#pragma GCC diagnostic pop
+
 	BK4819_SetFrequency(gCurrentVfo->pTX->Frequency);
 
 	// TX compressor
diff --git a/settings.c b/settings.c
index 8bec24b..7755012 100644
--- a/settings.c
+++ b/settings.c
@@ -184,10 +184,6 @@ void SETTINGS_SaveSettings(void)
 	EEPROM_WriteBuffer(0x0F40, State);
 }
 
-void SETTINGS_LoadChannel(uint8_t Channel, uint8_t VFO, const VFO_Info_t *pVFO)
-{
-}
-
 void SETTINGS_SaveChannel(uint8_t Channel, uint8_t VFO, const VFO_Info_t *pVFO, uint8_t Mode)
 {
 	#ifdef ENABLE_NOAA
@@ -197,13 +193,13 @@ void SETTINGS_SaveChannel(uint8_t Channel, uint8_t VFO, const VFO_Info_t *pVFO,
 		const uint16_t OffsetMR  = Channel * 16;
 		      uint16_t OffsetVFO = OffsetMR;
 
-		if (!IS_MR_CHANNEL(Channel))
+		if (Channel > MR_CHANNEL_LAST)
 		{	// it's a VFO, not a channel
 			OffsetVFO  = (VFO == 0) ? 0x0C80 : 0x0C90;
 			OffsetVFO += (Channel - FREQ_CHANNEL_FIRST) * 32;
 		}
 
-		if (Mode >= 2 || !IS_MR_CHANNEL(Channel))
+		if (Mode >= 2 || Channel > MR_CHANNEL_LAST)
 		{	// copy VFO to a channel
 
 			uint8_t State[8];
@@ -228,8 +224,9 @@ void SETTINGS_SaveChannel(uint8_t Channel, uint8_t VFO, const VFO_Info_t *pVFO,
 
 			SETTINGS_UpdateChannel(Channel, pVFO, true);
 
-			if (IS_MR_CHANNEL(Channel))
-			{
+			if (Channel <= MR_CHANNEL_LAST)
+			{	// it's a memory channel
+		
 				#ifndef ENABLE_KEEP_MEM_NAME
 					// clear/reset the channel name
 					//memset(&State, 0xFF, sizeof(State));
@@ -262,7 +259,7 @@ void SETTINGS_UpdateChannel(uint8_t Channel, const VFO_Info_t *pVFO, bool keep)
 		uint8_t  Attributes = 0xFF;        // default attributes
 		uint16_t Offset = 0x0D60 + (Channel & ~7u);
 		
-		Attributes &= ~MR_CH_COMPAND;  // default to '0' = compander disabled
+		Attributes &= (uint8_t)(~MR_CH_COMPAND);  // default to '0' = compander disabled
 
 		EEPROM_ReadBuffer(Offset, State, sizeof(State));
 
@@ -280,8 +277,9 @@ void SETTINGS_UpdateChannel(uint8_t Channel, const VFO_Info_t *pVFO, bool keep)
 		gMR_ChannelAttributes[Channel] = Attributes;
 
 //		#ifndef ENABLE_KEEP_MEM_NAME
-			if (IS_MR_CHANNEL(Channel))
-			{
+			if (Channel <= MR_CHANNEL_LAST)
+			{	// it's a memory channel
+		
 				const uint16_t OffsetMR = Channel * 16;
 				if (!keep)
 				{	// clear/reset the channel name
diff --git a/ui/main.c b/ui/main.c
index 3f2c910..c829cf3 100644
--- a/ui/main.c
+++ b/ui/main.c
@@ -14,6 +14,10 @@
  *     limitations under the License.
  */
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+	#pragma GCC diagnostic pop
+
 #include <string.h>
 #include <stdlib.h>  // abs()
 
@@ -42,6 +46,9 @@ center_line_t center_line = CENTER_LINE_NONE;
 
 void UI_drawBars(uint8_t *p, const unsigned int level)
 {
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (level)
 	{
 		default:
@@ -54,6 +61,8 @@ void UI_drawBars(uint8_t *p, const unsigned int level)
 		case 1: memmove(p +  0, BITMAP_Antenna,       sizeof(BITMAP_Antenna));
 		case 0: break;
 	}
+
+	#pragma GCC diagnostic pop
 }
 
 #ifdef ENABLE_AUDIO_BAR
@@ -214,6 +223,8 @@ void UI_UpdateRSSI(const int16_t rssi, const int vfo)
 {
 	#ifdef ENABLE_RSSI_BAR
 
+		(void)vfo;  // unused
+		
 		// optional larger RSSI dBm, S-point and bar level
 
 		if (center_line != CENTER_LINE_RSSI)
@@ -333,13 +344,13 @@ void UI_DisplayMain(void)
 	for (vfo_num = 0; vfo_num < 2; vfo_num++)
 	{
 		const unsigned int line       = (vfo_num == 0) ? line0 : line1;
-		uint8_t            channel    = gEeprom.TX_VFO;
-//		uint8_t            tx_channel = (gEeprom.CROSS_BAND_RX_TX == CROSS_BAND_OFF) ? gEeprom.RX_VFO : gEeprom.TX_VFO;
+		unsigned int       channel    = gEeprom.TX_VFO;
+//		unsigned int       tx_channel = (gEeprom.CROSS_BAND_RX_TX == CROSS_BAND_OFF) ? gEeprom.RX_VFO : gEeprom.TX_VFO;
 		const bool         same_vfo   = (channel == vfo_num) ? true : false;
 		uint8_t           *p_line0    = gFrameBuffer[line + 0];
 		uint8_t           *p_line1    = gFrameBuffer[line + 1];
-		uint8_t            mode       = 0;
-		uint8_t            state;
+		unsigned int       mode       = 0;
+		unsigned int       state;
 
 		if (single_vfo)
 		{	// we're in single VFO mode - screen is dedicated to just one VFO
@@ -457,7 +468,7 @@ void UI_DisplayMain(void)
 			}
 		}
 
-		if (IS_MR_CHANNEL(gEeprom.ScreenChannel[vfo_num]))
+		if (gEeprom.ScreenChannel[vfo_num] <= MR_CHANNEL_LAST)
 		{	// channel mode
 			const unsigned int x = 2;
 			const bool inputting = (gInputBoxIndex == 0 || gEeprom.TX_VFO != vfo_num) ? false : true;
@@ -508,7 +519,7 @@ void UI_DisplayMain(void)
 		if (state != VFO_STATE_NORMAL)
 		{
 			const char *state_list[] = {"", "BUSY", "BAT LOW", "TX DISABLE", "TIMEOUT", "ALARM", "VOLT HIGH"};
-			if (state >= 0 && state < ARRAY_SIZE(state_list))
+			if (state < ARRAY_SIZE(state_list))
 				UI_PrintString(state_list[state], 31, 0, line, 8);
 		}
 		else
@@ -528,8 +539,8 @@ void UI_DisplayMain(void)
 					frequency = gEeprom.VfoInfo[vfo_num].pTX->Frequency;
 			}
 
-			if (IS_MR_CHANNEL(gEeprom.ScreenChannel[vfo_num]))
-			{	// channel mode
+			if (gEeprom.ScreenChannel[vfo_num] <= MR_CHANNEL_LAST)
+			{	// it's a channel
 
 				// show the channel symbols
 				const uint8_t attributes = gMR_ChannelAttributes[gEeprom.ScreenChannel[vfo_num]];
@@ -546,6 +557,9 @@ void UI_DisplayMain(void)
 				
 				#endif
 
+				#pragma GCC diagnostic push
+				#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 				switch (gEeprom.CHANNEL_DISPLAY_MODE)
 				{
 					case MDF_FREQUENCY:	// show the channel frequency
@@ -595,6 +609,8 @@ void UI_DisplayMain(void)
 
 						break;
 				}
+				
+				#pragma GCC diagnostic pop
 			}
 			else
 			{	// frequency mode
@@ -660,7 +676,7 @@ void UI_DisplayMain(void)
 			const FREQ_Config_t *pConfig = (mode == 1) ? gEeprom.VfoInfo[vfo_num].pTX : gEeprom.VfoInfo[vfo_num].pRX;
 			const unsigned int code_type = pConfig->CodeType;
 			const char *code_list[] = {"", "CT", "DCS", "DCR"};
-			if (code_type >= 0 && code_type < ARRAY_SIZE(code_list))
+			if (code_type < ARRAY_SIZE(code_list))
 				strcpy(String, code_list[code_type]);
 		}
 		UI_PrintStringSmall(String, LCD_WIDTH + 24, 0, line + 1);
@@ -669,7 +685,7 @@ void UI_DisplayMain(void)
 		{	// show the TX power
 			const char pwr_list[] = "LMH";
 			const unsigned int i = gEeprom.VfoInfo[vfo_num].OUTPUT_POWER;
-			String[0] = (i >= 0 && i < ARRAY_SIZE(pwr_list)) ? pwr_list[i] : '\0';
+			String[0] = (i < ARRAY_SIZE(pwr_list)) ? pwr_list[i] : '\0';
 			String[1] = '\0';
 			UI_PrintStringSmall(String, LCD_WIDTH + 46, 0, line + 1);
 		}
diff --git a/ui/menu.c b/ui/menu.c
index 424e137..26b3cc0 100644
--- a/ui/menu.c
+++ b/ui/menu.c
@@ -436,6 +436,9 @@ void UI_DisplayMenu(void)
 
 	bool already_printed = false;
 
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wimplicit-fallthrough="
+
 	switch (gMenuCursor)
 	{
 		case MENU_SQL:
@@ -806,6 +809,8 @@ void UI_DisplayMenu(void)
 		}
 	}
 
+	#pragma GCC diagnostic pop
+
 	if (!already_printed)
 	{	// we now do multi-line text in a single string