Force AM markers

plot.c

@@ -2113,12 +2113,16 @@ static void cell_draw_marker_info(int x0, int y0)
         setting.unit = old_unit;
         int depth = (int)( level * 2.0 * 80.0) + 20;
 #else
-        float level =  actual_t[markers[0].index] - (actual_t[markers[1].index] + actual_t[markers[2].index])/2.0;
-        int depth =(int) (pow((float)10.0, 2.0 + (-level + 6.0) / 31.0));
+        float delta = actual_t[markers[1].index] - actual_t[markers[2].index];
+        if (delta < -5 || delta > 5)
+          break;
+        float level = (actual_t[markers[1].index] + actual_t[markers[2].index])/2.0 -  actual_t[markers[0].index];
+        if (level < -40 || level > 0)
+          break;
+        int depth =(int) (pow((float)10.0, 2.0 + (level + 6.02) /20.0));
 #endif
         plot_printf(buf, sizeof buf, "DEPTH: %3d%%", depth);
         goto show_computed;
-        break;
       }
     }
     if (i >= 2 && setting.measurement == M_THD) {

sa_core.c

@@ -2311,6 +2311,27 @@ sweep_again:                                // stay in sweep loop when output mo
         if (markers[m].enabled && markers[m].mtype & M_TRACKING) {   // Available marker found
           markers[m].index = max_index[i];
           markers[m].frequency = frequencies[markers[m].index];
+#if 0
+          float v = actual_t[markers[m].index] - 10.0;              // -10dB points
+          int index = markers[m].index;
+          uint32_t f = markers[m].frequency;
+          uint32_t s = actual_rbw_x10 * 200;                        // twice the selected RBW
+          int left = index, right = index;
+          while (t > 0 && actual_t[t+1] > v && markers[t].frequency > f - s)                                        // Find left point
+            t--;
+          if (t > 0) {
+            left = t;
+          }
+          t = setting._sweep_points-1;;
+          while (t > setting._sweep_points-1 && actual_t[t+1] > v)                // find right -3dB point
+            t++;
+          if (t > index) {
+            right = t;
+            markers[2].frequency = frequencies[t];
+          }
+
+#endif
+
 #if 1                                                        // Hyperbolic interpolation, can be removed to save memory
           const int idx          = markers[m].index;
           if (idx > 0 && idx < sweep_points-1)

ui_sa.c

@@ -854,20 +854,31 @@ static UI_FUNCTION_ADV_CALLBACK(menu_measure_acb)
     case M_LINEARITY:
       set_measurement(M_LINEARITY);
       break;
-    case M_AM:                                     // OIP3
+    case M_AM:                                     // AM
       reset_settings(setting.mode);
       for (int i = 0; i< 3; i++) {
         markers[i].enabled = M_ENABLED;
-        markers[i].mtype = M_DELTA | M_TRACKING;
+        markers[i].mtype = M_DELTA;// | M_TRACKING;
       }
-      markers[0].mtype = M_REFERENCE | M_TRACKING;
+      uint32_t center, span;
+      markers[0].mtype = M_REFERENCE;// | M_TRACKING;
       kp_help_text = "Frequency of signal";
       ui_mode_keypad(KM_CENTER);
       ui_process_keypad();
+      center = uistat.value;
+      kp_help_text = "Modulation frequency, 2 .. 10 kHz";
+      ui_mode_keypad(KM_SPAN);
+      ui_process_keypad();
+      if (uistat.value < 2000)
+        break;
+      span = uistat.value + 1500;   // Enlarge span for RBW width
       set_sweep_frequency(ST_SPAN, 100000);     // 100kHz
       set_measurement(M_AM);
+      set_marker_frequency(0, center);
+      set_marker_frequency(1, center-span);
+      set_marker_frequency(2, center+span);
       break;
-    case M_FM:                                     // OIP3
+    case M_FM:                                     // FM
       reset_settings(setting.mode);
       for (int i = 0; i< 3; i++) {
         markers[i].enabled = M_ENABLED;