diff --git a/src/channelinfomodel.cpp b/src/channelinfomodel.cpp
--- a/src/channelinfomodel.cpp
+++ b/src/channelinfomodel.cpp
@@ -146,6 +146,16 @@ void ChannelInfoModel::setNumOfChannels(
 {
     if (number == _numOfChannels) return;
 
+    bool isInserting = number > _numOfChannels;
+    if (isInserting)
+    {
+        beginInsertRows(QModelIndex(), _numOfChannels, number-1);
+    }
+    else
+    {
+        beginRemoveRows(QModelIndex(), number, _numOfChannels-1);
+    }
+
     // we create channel info but never remove channel info to
     // remember user entered info
     if ((int) number > infos.length())
@@ -168,4 +178,13 @@ void ChannelInfoModel::setNumOfChannels(
     }
 
     _numOfChannels = number;
+
+    if (isInserting)
+    {
+        endInsertRows();
+    }
+    else
+    {
+        endRemoveRows();
+    }
 }
diff --git a/src/main.cpp b/src/main.cpp
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -55,12 +55,16 @@ int main(int argc, char *argv[])
     w.show();
 
     // test code
-    ChannelInfoModel cim(5, &a);
+    ChannelInfoModel cim(10, &a);
     QTableView tv;
 
     tv.setModel(&cim);
 
     tv.show();
 
+    // cim.setNumOfChannels(3);
+    // cim.setNumOfChannels(10);
+    // cim.setNumOfChannels(7);
+
     return a.exec();
 }