diff --git a/firmware.bin b/firmware.bin
index 2aa820a..50c397e 100644
Binary files a/firmware.bin and b/firmware.bin differ
diff --git a/firmware.packed.bin b/firmware.packed.bin
index 5f3bb55..39d82ae 100644
Binary files a/firmware.packed.bin and b/firmware.packed.bin differ
diff --git a/panadapter.c b/panadapter.c
index dd17fe0..292bf38 100644
--- a/panadapter.c
+++ b/panadapter.c
@@ -35,8 +35,10 @@ bool PAN_scanning(void)
 void PAN_set_freq(void)
 {	// set the frequency
 
-	const uint32_t step_size = g_tx_vfo->step_freq;
-	uint32_t       freq      = g_tx_vfo->p_rx->frequency;
+	uint32_t freq = g_tx_vfo->p_rx->frequency;
+
+	uint32_t step_size = g_tx_vfo->step_freq;
+	step_size = (step_size < PANADAPTER_MIN_STEP) ? PANADAPTER_MIN_STEP : (step_size > PANADAPTER_MAX_STEP) ? PANADAPTER_MAX_STEP : step_size;
 
 	if (g_panadapter_enabled && g_panadapter_vfo_mode <= 0)
 	{	// panadapter mode .. add the bin offset
@@ -163,15 +165,22 @@ void PAN_process_10ms(void)
 
 		#ifdef ENABLE_PANADAPTER_PEAK_FREQ
 		{	// find the peak freq
-			const int32_t step_size   = g_tx_vfo->step_freq;
 			const int32_t center_freq = g_tx_vfo->p_rx->frequency;
+			int32_t step_size = g_tx_vfo->step_freq;
+
 			uint8_t peak_rssi = 0;
 			uint8_t threshold_rssi;
+
 			uint8_t span_rssi = g_panadapter_max_rssi - g_panadapter_min_rssi;
 			if (span_rssi < 80)
 				span_rssi = 80;
+
+			step_size = (step_size < PANADAPTER_MIN_STEP) ? PANADAPTER_MIN_STEP : (step_size > PANADAPTER_MAX_STEP) ? PANADAPTER_MAX_STEP : step_size;
+
 			threshold_rssi = g_panadapter_min_rssi + (span_rssi / 4);
+
 			g_panadapter_peak_freq = 0;
+
 			for (i = 0; i < (int)ARRAY_SIZE(g_panadapter_rssi); i++)
 			{
 				const uint8_t rssi = g_panadapter_rssi[i];
diff --git a/panadapter.h b/panadapter.h
index 2f263dc..ee25d1b 100644
--- a/panadapter.h
+++ b/panadapter.h
@@ -25,6 +25,9 @@
 // number of bins either side of the VFO RX frequency
 #define PANADAPTER_BINS   ((LCD_WIDTH / 2) - 1)
 
+#define PANADAPTER_MAX_STEP    2500
+#define PANADAPTER_MIN_STEP    625
+
 extern bool     g_panadapter_enabled;
 extern uint32_t g_panadapter_peak_freq;
 extern int      g_panadapter_vfo_mode;
diff --git a/ui/main.c b/ui/main.c
index f37993b..558e1a2 100644
--- a/ui/main.c
+++ b/ui/main.c
@@ -424,14 +424,11 @@ void big_freq(const uint32_t frequency, const unsigned int x, const unsigned int
 		     g_current_function == FUNCTION_TRANSMIT   ||
 		     g_current_function == FUNCTION_POWER_SAVE ||
 		     g_monitor_enabled)
-		{
+		{	// don't draw the panadapter
 			return;
 		}
 
-//		if (g_squelch_open)
-//			return;
-
-		// auto scale
+		// auto vertical scale
 		max_rssi  = g_panadapter_max_rssi;
 		min_rssi  = g_panadapter_min_rssi;
 		span_rssi = max_rssi - min_rssi;
@@ -450,7 +447,7 @@ void big_freq(const uint32_t frequency, const unsigned int x, const unsigned int
 
 		#ifdef ENABLE_PANADAPTER_PEAK_FREQ
 			if (g_panadapter_peak_freq > 0)
-			{
+			{	// print the peak frequency
 				char str[16];
 				sprintf(str, "%u.%05u", g_panadapter_peak_freq / 100000, g_panadapter_peak_freq % 100000);
 				NUMBER_trim_trailing_zeros(str);
@@ -458,10 +455,10 @@ void big_freq(const uint32_t frequency, const unsigned int x, const unsigned int
 			}
 		#endif
 
-		// center marker (the VFO frequency)
-		base_line[PANADAPTER_BINS - (LCD_WIDTH * 2)] = 0x07;
+		// draw top center vertical marker (the VFO frequency)
+		base_line[PANADAPTER_BINS - (LCD_WIDTH * 2)] = 0x0F;
 
-		// top horizontal line
+		// draw top horizontal dotted line
 		for (i = 0; i < PANADAPTER_BINS; i += 4)
 		{
 			const unsigned int k = PANADAPTER_BINS - (LCD_WIDTH * 2);
@@ -469,25 +466,25 @@ void big_freq(const uint32_t frequency, const unsigned int x, const unsigned int
 			base_line[k + i] |= 1u;
 		}
 
-		// draw the vertical bins
+		// draw the panadapter vertical bins
 		for (i = 0; i < ARRAY_SIZE(g_panadapter_rssi); i++)
 		{
-			uint8_t  rssi = g_panadapter_rssi[i];
 			uint32_t pixels;
+			uint8_t  rssi = g_panadapter_rssi[i];
 
 			#if 0
 				rssi = (rssi < ((-129 + 160) * 2)) ? 0 : rssi - ((-129 + 160) * 2);  // min of -129dBm (S3)
 				rssi = rssi >> 2;
 			#else
-				rssi = ((rssi - min_rssi) * 20) / span_rssi;  // 0 ~ 20
+				rssi = ((uint16_t)(rssi - min_rssi) * 20) / span_rssi;  // 0 ~ 20
 			#endif
 
-			rssi += 2;
-			if (rssi > 21)
-				rssi = 21;
+			rssi += 2;                  // offset from the bottom
+			if (rssi > 22)
+				rssi = 22;              // limit peak value
 
-			pixels = (1u << rssi) - 1;
-			pixels &= 0xfffffffe;
+			pixels = (1u << rssi) - 1;  // set the line pixels
+			pixels &= 0xfffffffe;       // clear the bottom line
 
 			base_line[i - (LCD_WIDTH * 2)] |= bit_reverse_8(pixels >> 16);
 			base_line[i - (LCD_WIDTH * 1)] |= bit_reverse_8(pixels >>  8);