diff --git a/main.c b/main.c
index 51f3d08..24ef665 100644
--- a/main.c
+++ b/main.c
@@ -990,6 +990,7 @@ config_t config = {
   .cor_am = -14,
   .cor_wfm = -17,
   .cor_nfm = -17,
+  .ext_zero_level = 128,
 #endif
 #ifdef TINYSA4
   .vbat_offset = 220,
@@ -1010,6 +1011,7 @@ config_t config = {
   .cor_nfm = -55,
   .ultra = false,
   .high_out_adf4350 = true,
+  .ext_zero_level = 174,
 #endif
   .sweep_voltage = 3.3,
   .switch_offset = 0.0,
@@ -2377,6 +2379,7 @@ static const VNAShellCommand commands[] =
 //  {"gamma"       , cmd_gamma       , 0},
     {"scan"        , cmd_scan        , CMD_WAIT_MUTEX},
     {"scanraw"     , cmd_scanraw     , CMD_WAIT_MUTEX},
+    {"zero"        , cmd_zero        , CMD_WAIT_MUTEX},
     {"sweep"       , cmd_sweep       , 0},
     {"test"        , cmd_test        , 0},
     {"touchcal"    , cmd_touchcal    , CMD_WAIT_MUTEX},
diff --git a/nanovna.h b/nanovna.h
index 40105e5..a16c7e5 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -616,6 +616,7 @@ typedef struct config {
   uint8_t high_out_adf4350;
   float sweep_voltage;
   float switch_offset;
+  int16_t   ext_zero_level;
   uint32_t    dummy;
 //  uint8_t _reserved[22];
   freq_t checksum;
@@ -1240,12 +1241,7 @@ typedef uint8_t  deviceRSSI_t;
 typedef int16_t  pureRSSI_t;
 
 // RSSI values conversion macro
-// External programm zero level settings (need decrease on this value -)
-#ifdef TINYSA4
-#define EXT_ZERO_LEVEL            (174)
-#else
-#define EXT_ZERO_LEVEL            (128)
-#endif
+
 #define DEVICE_TO_PURE_RSSI(rssi) ((rssi)<<4)
 #define PURE_TO_DEVICE_RSSI(rssi) ((rssi)>>4)
 #define float_TO_PURE_RSSI(rssi)  ((rssi)*32)
diff --git a/plot.c b/plot.c
index 2e863f2..28c0bba 100644
--- a/plot.c
+++ b/plot.c
@@ -284,7 +284,6 @@ draw_on_strut(int v0, int d, int color)
 }
 #endif
 
-
 /*
  * calculate log10f(abs(gamma))
  */ 
@@ -940,11 +939,12 @@ draw_cell(int m, int n)
 #endif
 // Draw trigger line
   if (setting.trigger != T_AUTO) {
+	c = GET_PALTETTE_COLOR(LCD_TRIGGER_COLOR);
     int tp = get_trigger_level() - y0;
     if (tp>=0 && tp < h)
       for (x = 0; x < w; x++)
         if ((uint32_t)(x + x0 - CELLOFFSETX) <= WIDTH + CELLOFFSETX)
-          cell_buffer[tp * CELLWIDTH + x] = LCD_TRIGGER_COLOR;
+          cell_buffer[tp * CELLWIDTH + x] = c;
   }
 
 #if 1
diff --git a/sa_cmd.c b/sa_cmd.c
index b66d708..d4a1690 100644
--- a/sa_cmd.c
+++ b/sa_cmd.c
@@ -328,6 +328,17 @@ VNA_SHELL_FUNCTION(cmd_if)
   }
 }
 
+VNA_SHELL_FUNCTION(cmd_zero)
+{
+  if (argc != 1) {
+  usage:
+    shell_printf("usage: zero {level}\r\n%ddBm\r\n", config.ext_zero_level);
+    return;
+  } else {
+    config.ext_zero_level = my_atoi(argv[0]);
+  }
+}
+
 #ifdef TINYSA4
 VNA_SHELL_FUNCTION(cmd_ultra_start)
 {
@@ -676,7 +687,7 @@ void sweep_remote(void)
   for (i = 0; i <= step; i++, f+=delta) {
     if (operation_requested)
       break;
-    int val = perform(false, i, f, false) + float_TO_PURE_RSSI(EXT_ZERO_LEVEL);
+    int val = perform(false, i, f, false) + float_TO_PURE_RSSI(config.ext_zero_level);
     streamPut(shell_stream, 'x');
     streamPut(shell_stream, (uint8_t)(val & 0xFF));
     streamPut(shell_stream, (uint8_t)((val>>8) & 0xFF));
@@ -822,7 +833,7 @@ VNA_SHELL_FUNCTION(cmd_scanraw)
   dirty = true;
 
   for (uint32_t i = 0; i<points; i++) {
-    int val = perform(false, i, start +(freq_t)(f_step * i), false) + float_TO_PURE_RSSI(EXT_ZERO_LEVEL);
+    int val = perform(false, i, start +(freq_t)(f_step * i), false) + float_TO_PURE_RSSI(config.ext_zero_level);
     if (operation_requested && SDU1.config->usbp->state != USB_ACTIVE) // break on operation in perform
       break;
     streamPut(shell_stream, 'x');