diff --git a/Boards.h b/Boards.h
index eaee2d5..ef2b8c5 100644
--- a/Boards.h
+++ b/Boards.h
@@ -417,6 +417,8 @@
       const int pin_tcxo_enable = -1;
       #define HAS_BUSY true
       #define DIO2_AS_RF_SWITCH true
+      #define LNA_GD_THRSHLD (-109)
+      #define LNA_GD_LIMIT   (-89)
 
       #define LORA_LNA_GAIN  17
       #define LORA_LNA_GVT   12
diff --git a/Config.h b/Config.h
index 2ada4a7..dec0063 100644
--- a/Config.h
+++ b/Config.h
@@ -151,7 +151,7 @@
 	uint8_t model     = 0x00;
 	uint8_t hwrev     = 0x00;
 
-	#define NOISE_FLOOR_SAMPLES 64
+	#define NOISE_FLOOR_SAMPLES 128
 	int     noise_floor     = -292;
     int     current_rssi    = -292;
 	int		last_rssi		= -292;
diff --git a/Display.h b/Display.h
index 59c5133..7d903b9 100644
--- a/Display.h
+++ b/Display.h
@@ -152,6 +152,7 @@ bool device_firmware_ok();
 
 #define WATERFALL_SIZE 46
 int waterfall[WATERFALL_SIZE];
+int waterfall_meta[WATERFALL_SIZE];
 int waterfall_head = 0;
 
 int p_ad_x = 0;
@@ -722,6 +723,9 @@ void draw_signal_bars(int px, int py) {
 #define WF_RSSI_MIN -135
 #define WF_RSSI_SPAN (WF_RSSI_MAX-WF_RSSI_MIN)
 #define WF_PIXEL_WIDTH 10
+#define WF_M_RX   0x00
+#define WF_M_TX   0x01
+#define WF_M_NTFR 0x02
 void draw_waterfall(int px, int py) {
   int rssi_val = current_rssi;
   if (rssi_val < WF_RSSI_MIN) rssi_val = WF_RSSI_MIN;
@@ -729,11 +733,14 @@ void draw_waterfall(int px, int py) {
   int rssi_normalised = ((rssi_val - WF_RSSI_MIN)*(1.0/WF_RSSI_SPAN))*WF_PIXEL_WIDTH;
   if (display_tx) {
     for (uint8_t i = 0; i < WF_TX_SIZE; i++) {
+      waterfall_meta[waterfall_head] = WF_M_TX;
       waterfall[waterfall_head++] = -1;
       if (waterfall_head >= WATERFALL_SIZE) waterfall_head = 0;
     }
     display_tx = false;
   } else {
+    if (interference_detected) { waterfall_meta[waterfall_head] = WF_M_NTFR; }
+    else                       { waterfall_meta[waterfall_head] = WF_M_RX; }
     waterfall[waterfall_head++] = rssi_normalised;
     if (waterfall_head >= WATERFALL_SIZE) waterfall_head = 0;
   }
@@ -742,8 +749,13 @@ void draw_waterfall(int px, int py) {
   for (int i = 0; i < WATERFALL_SIZE; i++){
     int wi = (waterfall_head+i)%WATERFALL_SIZE;
     int ws = waterfall[wi];
+    int wm = waterfall_meta[wi];
     if (ws > 0) {
-      stat_area.drawLine(px, py+i, px+ws-1, py+i, SSD1306_WHITE);
+      if      (wm == WF_M_RX)   { stat_area.drawLine(px, py+i, px+ws-1, py+i, SSD1306_WHITE); }
+      else if (wm == WF_M_NTFR) {
+        uint8_t o = 0;
+        for (uint8_t ti = 0; ti < WF_PIXEL_WIDTH/2; ti++) { stat_area.drawPixel(px+ti*2+o, py+i, SSD1306_WHITE); }
+      }
     } else if (ws == -1) {
       uint8_t o = i%2;
       for (uint8_t ti = 0; ti < WF_PIXEL_WIDTH/2; ti++) {
diff --git a/RNode_Firmware.ino b/RNode_Firmware.ino
index 5d2eb6a..5649206 100644
--- a/RNode_Firmware.ino
+++ b/RNode_Firmware.ino
@@ -1358,20 +1358,26 @@ int  noise_floor_buffer[NOISE_FLOOR_SAMPLES] = {0};
 void update_noise_floor() {
   #if MCU_VARIANT == MCU_ESP32 || MCU_VARIANT == MCU_NRF52
     if (!dcd) {
+      #if BOARD_MODEL != BOARD_HELTEC32_V4
       if (!noise_floor_sampled || current_rssi < noise_floor + CSMA_INFR_THRESHOLD_DB) {
+      #else
+      if ((!noise_floor_sampled || current_rssi < noise_floor + CSMA_INFR_THRESHOLD_DB) || (noise_floor_sampled && (noise_floor < LNA_GD_THRSHLD && current_rssi <= LNA_GD_LIMIT))) {
+      #endif
         #if HAS_LORA_LNA
           // Discard invalid samples due to gain variance
           // during LoRa LNA re-calibration
           if (current_rssi < noise_floor-LORA_LNA_GVT) { return; }
         #endif
+        bool sum_noise_floor = false;
         noise_floor_buffer[noise_floor_sample] = current_rssi;
         noise_floor_sample = noise_floor_sample+1;
         if (noise_floor_sample >= NOISE_FLOOR_SAMPLES) {
           noise_floor_sample %= NOISE_FLOOR_SAMPLES;
           noise_floor_sampled = true;
+          sum_noise_floor = true;
         }
 
-        if (noise_floor_sampled) {
+        if (noise_floor_sampled && sum_noise_floor) {
           noise_floor = 0;
           for (int ni = 0; ni < NOISE_FLOOR_SAMPLES; ni++) { noise_floor += noise_floor_buffer[ni]; }
           noise_floor /= NOISE_FLOOR_SAMPLES;
@@ -1402,7 +1408,13 @@ void update_modem_status() {
     portEXIT_CRITICAL();
   #endif
 
-  interference_detected = !carrier_detected && (current_rssi > (noise_floor+CSMA_INFR_THRESHOLD_DB));
+  #if BOARD_MODEL == BOARD_HELTEC32_V4
+    if (noise_floor > LNA_GD_THRSHLD)  { interference_detected = !carrier_detected && (current_rssi > (noise_floor+CSMA_INFR_THRESHOLD_DB)); }
+    else                               { interference_detected = !carrier_detected && (current_rssi > LNA_GD_LIMIT); }
+  #else
+    interference_detected = !carrier_detected && (current_rssi > (noise_floor+CSMA_INFR_THRESHOLD_DB));
+  #endif
+
   if (interference_detected) { if (led_id_filter < LED_ID_TRIG) { led_id_filter += 1; } }
   else                       { if (led_id_filter > 0) {led_id_filter -= 1; } }
 
@@ -1410,14 +1422,11 @@ void update_modem_status() {
   // LNA recalibration, antenna swap, moving into new RF
   // environment or similar.
   if (interference_detected && current_rssi < CSMA_RFENV_RECAL_LIMIT_DB) {
-    if (!interference_persists) {
-      interference_persists = true; interference_start = millis();
-    } else {
+    if (!interference_persists) { interference_persists = true; interference_start = millis(); }
+    else {
       if (millis()-interference_start >= CSMA_RFENV_RECAL_MS) { noise_floor_sampled = false; interference_persists = false; }
     }
-  } else {
-    interference_persists = false;
-  }
+  } else { interference_persists = false; }
 
   if (carrier_detected) { dcd = true; } else { dcd = false; }