#35 Updates AM & NBFM decoders to use Adaptive Squelch, a power squelch that includes an adaptive noise floor monitor. Implements vectorized magnitude operations for AM & FM decoders. Adds talkgroup assignment and squelch controls to AM channel configuration editor. Implements new AM gain control that attempts to normalize audio gain quickly at beginning of call/transmission and maintains that gain across lifecycle of the call and resets the gain for the next call. (#1540)

Notes on usage:
- When using either AM or FM squelch control use either the Heterodyne channelizer or if using the Polyphase channelizer, avoid using trunk tracking decoders like DMR or P25 or set the squelch threshold high enough to avoid changes in noise floor from polyphase channelizer where it can vary between using the one channel or the two-channel combined channel sources.

Co-authored-by: Dennis Sheirer <dsheirer@github.com>

src/main/java/io/github/dsheirer/source/SourceEvent.java

@@ -45,6 +45,7 @@ public class SourceEvent
         NOTIFICATION_RECORDING_FILE_LOADED,
         NOTIFICATION_SAMPLE_RATE_CHANGE,
         NOTIFICATION_SQUELCH_THRESHOLD,
+        NOTIFICATION_SQUELCH_AUTO_TRACK,
         NOTIFICATION_STOP_SAMPLE_STREAM,
         NOTIFICATION_TUNER_SHUTDOWN,
         NOTIFICATION_ERROR_STATE,
@@ -54,6 +55,8 @@ public class SourceEvent
         REQUEST_FREQUENCY_SELECTION,
         REQUEST_CHANGE_SQUELCH_THRESHOLD,
         REQUEST_CURRENT_SQUELCH_THRESHOLD,
+        REQUEST_CHANGE_SQUELCH_AUTO_TRACK,
+        REQUEST_CURRENT_SQUELCH_AUTO_TRACK,
         REQUEST_START_SAMPLE_STREAM,
         REQUEST_STOP_SAMPLE_STREAM;
 
@@ -428,12 +431,11 @@ public class SourceEvent
 
     /**
      * Requests the current squelch threshold value
-     * @param source optional
      * @return source event
      */
-    public static SourceEvent requestCurrentSquelchThreshold(Source source)
+    public static SourceEvent requestCurrentSquelchThreshold()
     {
-        return new SourceEvent(Event.REQUEST_CURRENT_SQUELCH_THRESHOLD, source, 0);
+        return new SourceEvent(Event.REQUEST_CURRENT_SQUELCH_THRESHOLD, null, 0);
     }
 
     /**
@@ -447,6 +449,35 @@ public class SourceEvent
         return new SourceEvent(Event.REQUEST_CHANGE_SQUELCH_THRESHOLD, source, thresholdDb);
     }
 
+    /**
+     * Creates a new request squelch auto track status source event.
+     * @return new source event
+     */
+    public static SourceEvent requestCurrentSquelchAutoTrack()
+    {
+        return new SourceEvent(Event.REQUEST_CURRENT_SQUELCH_AUTO_TRACK, null, 0);
+    }
+
+    /**
+     * Creates a new squelch auto-track notification
+     * @param autoTrack true or false.
+     * @return source event
+     */
+    public static SourceEvent squelchAutoTrack(boolean autoTrack)
+    {
+        return new SourceEvent(Event.NOTIFICATION_SQUELCH_AUTO_TRACK, null, autoTrack ? 1 : 0);
+    }
+
+    /**
+     * Creates a new squelch auto-track request
+     * @param autoTrack to enable (true) or disable auto-track.
+     * @return source event
+     */
+    public static SourceEvent requestSquelchAutoTrack(boolean autoTrack)
+    {
+        return new SourceEvent(Event.REQUEST_CHANGE_SQUELCH_AUTO_TRACK, null, autoTrack ? 1 : 0);
+    }
+
     @Override
     public String toString()
     {