diff --git a/Network/NetworkMessage.hpp b/Network/NetworkMessage.hpp
index d01a3475e..8055e2a49 100644
--- a/Network/NetworkMessage.hpp
+++ b/Network/NetworkMessage.hpp
@@ -447,16 +447,20 @@
  *      The server  may send  this message at  any time.   The message
  *      specifies  the background  and foreground  color that  will be
  *      used  to  highlight  the  specified callsign  in  the  decoded
- *      messages  printed  in  the  Band Activity  panel.  The  WSJT-X
+ *      messages  printed  in the  Band  Activity  panel.  The  WSJT-X
  *      clients maintain a list of such instructions and apply them to
  *      all decoded  messages in the  band activity window.   To clear
- *      highlighting send an  invalid QColor value for  either or both
- *      of the background and foreground fields.
+ *      and  cancel  highlighting send  an  invalid  QColor value  for
+ *      either or both  of the background and  foreground fields. When
+ *      using  this mode  the  total number  of callsign  highlighting
+ *      requests should be limited otherwise the performance of WSJT-X
+ *      decoding may be  impacted. A rough rule of thumb  might be too
+ *      limit the  number of active  highlighting requests to  no more
+ *      than 100.
  *
  *      The "Highlight last"  field allows the sender  to request that
- *      the  last  instance  only  instead of  all  instances  of  the
- *      specified  call  be  highlighted  or  have  it's  highlighting
- *      cleared.
+ *      all instances of  "Callsign" in the last  period only, instead
+ *      of all instances in all periods, be highlighted.
  *
  *
  * SwitchConfiguration  In 14                     quint32
diff --git a/widgets/displaytext.cpp b/widgets/displaytext.cpp
index db00e2587..b3ccf8eb2 100644
--- a/widgets/displaytext.cpp
+++ b/widgets/displaytext.cpp
@@ -497,60 +497,92 @@ namespace
 {
   void update_selection (QTextCursor& cursor, QColor const& bg, QColor const& fg)
   {
-    if (!cursor.isNull ())
+    QTextCharFormat format {cursor.charFormat ()};
+    if (bg.isValid ())
       {
-        QTextCharFormat format {cursor.charFormat ()};
-        if (bg.isValid ())
-          {
-            format.setBackground (bg);
-          }
-        else
-          {
-            format.clearBackground ();
-          }
-        if (fg.isValid ())
-          {
-            format.setForeground (fg);
-          }
-        else
-          {
-            format.clearForeground ();
-          }
-        cursor.mergeCharFormat (format);
+        format.setBackground (bg);
       }
+    else
+      {
+        format.clearBackground ();
+      }
+    if (fg.isValid ())
+      {
+        format.setForeground (fg);
+      }
+    else
+      {
+        format.clearForeground ();
+      }
+    cursor.mergeCharFormat (format);
   }
 
   void reset_selection (QTextCursor& cursor)
   {
-    if (!cursor.isNull ())
+    // restore previous text format, we rely on the text
+    // char format at he start of the selection being the
+    // old one which should be the case
+    auto c2 = cursor;
+    c2.setPosition (c2.selectionStart ());
+    cursor.setCharFormat (c2.charFormat ());
+  }
+}
+
+namespace
+{
+  QString get_timestamp (QTextCursor& cursor)
+  {
+    QString timestamp;
+    if (cursor.movePosition (QTextCursor::PreviousCharacter)
+        && cursor.movePosition (QTextCursor::StartOfLine)
+        && cursor.movePosition (QTextCursor::EndOfWord, QTextCursor::KeepAnchor)
+        && cursor.hasSelection ())
       {
-        // restore previous text format, we rely on the text
-        // char format at he start of the selection being the
-        // old one which should be the case
-        auto c2 = cursor;
-        c2.setPosition (c2.selectionStart ());
-        cursor.setCharFormat (c2.charFormat ());
+        timestamp = cursor.selectedText ();
+        cursor.movePosition (QTextCursor::StartOfLine);
       }
+    return timestamp;
   }
 }
 
 void DisplayText::highlight_callsign (QString const& callsign, QColor const& bg,
-                                      QColor const& fg, bool last_only)
+                                      QColor const& fg, bool last_period_only)
 {
+  // qDebug () << "DisplayText::highlight_callsign: callsign:" << callsign << "last period:" << last_period_only;
+  if (!callsign.size ())
+    {
+      return;
+    }
+  QRegularExpression target {QString {"<?"} + callsign + QString {">?"}, QRegularExpression::DontCaptureOption};
   QTextCharFormat old_format {currentCharFormat ()};
   QTextCursor cursor {document ()};
-  if (last_only)
+  if (last_period_only)
     {
+      // highlight each instance of the given callsign (word) in the
+      // current period
       cursor.movePosition (QTextCursor::End);
-      cursor = document ()->find (callsign, cursor
-                                  , QTextDocument::FindBackward | QTextDocument::FindWholeWords);
-      if (bg.isValid () || fg.isValid ())
+      QTextCursor period_start {cursor};
+      QTextCursor prior {cursor};
+      auto period_timestamp = get_timestamp (period_start);
+      while (period_timestamp.size () && period_timestamp == get_timestamp (prior))
         {
-          update_selection (cursor, bg, fg);
+          period_start = prior;
         }
-      else
+      while (!cursor.isNull () && cursor > period_start)
         {
-          reset_selection (cursor);
+          cursor = document ()->find (target, cursor
+                                      , QTextDocument::FindBackward | QTextDocument::FindWholeWords);
+          if (!cursor.isNull () && cursor.hasSelection ())
+            {
+              if (bg.isValid () || fg.isValid ())
+                {
+                  update_selection (cursor, bg, fg);
+                }
+              else
+                {
+                  reset_selection (cursor);
+                }
+            }
         }
     }
   else
@@ -569,8 +601,11 @@ void DisplayText::highlight_callsign (QString const& callsign, QColor const& bg,
             }
           while (!cursor.isNull ())
             {
-              cursor = document ()->find (callsign, cursor, QTextDocument::FindWholeWords);
-              update_selection (cursor, bg, fg);
+              cursor = document ()->find (target, cursor, QTextDocument::FindWholeWords);
+              if (!cursor.isNull () && cursor.hasSelection ())
+                {
+                  update_selection (cursor, bg, fg);
+                }
             }
         }
       else if (pos != highlighted_calls_.end ())
@@ -579,8 +614,11 @@ void DisplayText::highlight_callsign (QString const& callsign, QColor const& bg,
           QTextCursor cursor {document ()};
           while (!cursor.isNull ())
             {
-              cursor = document ()->find (callsign, cursor, QTextDocument::FindWholeWords);
-              reset_selection (cursor);
+              cursor = document ()->find (target, cursor, QTextDocument::FindWholeWords);
+              if (!cursor.isNull () && cursor.hasSelection ())
+                {
+                  reset_selection (cursor);
+                }
             }
         }
     }
diff --git a/widgets/displaytext.h b/widgets/displaytext.h
index 5aa8c7103..fb8bb6134 100644
--- a/widgets/displaytext.h
+++ b/widgets/displaytext.h
@@ -43,7 +43,7 @@ public:
   Q_SLOT void appendText (QString const& text, QColor bg = QColor {}, QColor fg = QColor {}
                           , QString const& call1 = QString {}, QString const& call2 = QString {});
   Q_SLOT void erase ();
-  Q_SLOT void highlight_callsign (QString const& callsign, QColor const& bg, QColor const& fg, bool last_only);
+  Q_SLOT void highlight_callsign (QString const& callsign, QColor const& bg, QColor const& fg, bool last_period_only);
 
 private:
   void mouseDoubleClickEvent (QMouseEvent *) override;