diff --git a/src/urh/controller/GeneratorTabController.py b/src/urh/controller/GeneratorTabController.py
index 0fec975c..a8f22d58 100644
--- a/src/urh/controller/GeneratorTabController.py
+++ b/src/urh/controller/GeneratorTabController.py
@@ -253,6 +253,8 @@ class GeneratorTabController(QWidget):
 
         self.has_default_modulation = False
 
+        return c
+
     @pyqtSlot()
     def on_table_selection_changed(self):
         min_row, max_row, start, end = self.ui.tableMessages.selection_range()
diff --git a/src/urh/ui/ui_modulation.py b/src/urh/ui/ui_modulation.py
index b1efb9e4..ac5c7e68 100644
--- a/src/urh/ui/ui_modulation.py
+++ b/src/urh/ui/ui_modulation.py
@@ -73,7 +73,7 @@ class Ui_DialogModulation(object):
         self.doubleSpinBoxCarrierFreq.setSuffix("")
         self.doubleSpinBoxCarrierFreq.setDecimals(3)
         self.doubleSpinBoxCarrierFreq.setMinimum(0.0)
-        self.doubleSpinBoxCarrierFreq.setMaximum(99999999.0)
+        self.doubleSpinBoxCarrierFreq.setMaximum(99999999999.0)
         self.doubleSpinBoxCarrierFreq.setObjectName("doubleSpinBoxCarrierFreq")
         self.gridLayout.addWidget(self.doubleSpinBoxCarrierFreq, 0, 1, 1, 1)
         self.label_2 = QtWidgets.QLabel(DialogModulation)
diff --git a/tests/test_modulator_gui.py b/tests/test_modulator_gui.py
new file mode 100644
index 00000000..921a4789
--- /dev/null
+++ b/tests/test_modulator_gui.py
@@ -0,0 +1,118 @@
+import unittest
+
+from PyQt5.QtCore import Qt
+from PyQt5.QtGui import QDropEvent
+from PyQt5.QtTest import QTest
+
+import tests.utils_testing
+from tests.utils_testing import get_path_for_data_file
+from urh.controller.MainController import MainController
+
+app = tests.utils_testing.app
+
+
+class TestModulatorGUI(unittest.TestCase):
+    def setUp(self):
+        self.form = MainController()
+        self.form.add_signalfile(get_path_for_data_file("esaver.complex"))
+        self.signal = self.form.signal_tab_controller.signal_frames[0].signal
+        self.gframe = self.form.generator_tab_controller
+        self.form.ui.tabWidget.setCurrentIndex(2)
+        self.dialog = self.gframe.show_modulation_dialog()
+
+    def test_add_remove_modulator(self):
+        self.assertEqual(len(self.dialog.modulators), 1)
+        self.dialog.ui.btnAddModulation.click()
+        self.assertEqual(len(self.dialog.modulators), 2)
+        self.dialog.ui.btnRemoveModulation.click()
+        self.assertEqual(len(self.dialog.modulators), 1)
+
+    def test_edit_carrier(self):
+        self.dialog.ui.doubleSpinBoxCarrierFreq.setValue(1e9)
+        self.dialog.ui.doubleSpinBoxCarrierFreq.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.carrier_freq_hz, 1e9)
+
+        self.dialog.ui.doubleSpinBoxCarrierPhase.setValue(100)
+        self.dialog.ui.doubleSpinBoxCarrierPhase.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.carrier_phase_deg, 100)
+
+    def test_edit_data(self):
+        bits = self.dialog.current_modulator.display_bits
+        self.dialog.ui.linEdDataBits.setText("10101010")
+        self.dialog.ui.linEdDataBits.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.display_bits, "10101010")
+
+        self.dialog.ui.btnRestoreBits.click()
+        self.dialog.ui.linEdDataBits.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.display_bits, bits)
+
+        self.dialog.ui.spinBoxBitLength.setValue(1337)
+        self.dialog.ui.spinBoxBitLength.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.samples_per_bit, 1337)
+
+        self.dialog.ui.spinBoxSampleRate.setValue(5e6)
+        self.dialog.ui.spinBoxSampleRate.editingFinished.emit()
+        self.assertEqual(self.dialog.current_modulator.sample_rate, 5e6)
+
+    def test_edit_modulation(self):
+        self.dialog.ui.comboBoxModulationType.setCurrentText("Amplitude Shift Keying (ASK)")
+        self.assertEqual(self.dialog.ui.lParameterfor0.text(), "Amplitude for 0:")
+        self.assertEqual(self.dialog.ui.lParameterfor1.text(), "Amplitude for 1:")
+        self.assertFalse(self.dialog.ui.lGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.lGaussWidth.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussFilterWidth.isVisible())
+
+        self.dialog.ui.comboBoxModulationType.setCurrentText("Frequency Shift Keying (FSK)")
+        self.assertEqual(self.dialog.ui.lParameterfor0.text(), "Frequency for 0:")
+        self.assertEqual(self.dialog.ui.lParameterfor1.text(), "Frequency for 1:")
+        self.assertFalse(self.dialog.ui.lGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.lGaussWidth.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussFilterWidth.isVisible())
+
+        self.dialog.ui.comboBoxModulationType.setCurrentText("Gaussian Frequency Shift Keying (GFSK)")
+        self.assertEqual(self.dialog.ui.lParameterfor0.text(), "Frequency for 0:")
+        self.assertEqual(self.dialog.ui.lParameterfor1.text(), "Frequency for 1:")
+        self.assertTrue(self.dialog.ui.lGaussBT.isVisible())
+        self.assertTrue(self.dialog.ui.spinBoxGaussBT.isVisible())
+        self.assertTrue(self.dialog.ui.lGaussWidth.isVisible())
+        self.assertTrue(self.dialog.ui.spinBoxGaussFilterWidth.isVisible())
+
+        self.dialog.ui.comboBoxModulationType.setCurrentText("Phase Shift Keying (PSK)")
+        self.assertEqual(self.dialog.ui.lParameterfor0.text(), "Phase (degree) for 0:")
+        self.assertEqual(self.dialog.ui.lParameterfor1.text(), "Phase (degree) for 1:")
+        self.assertFalse(self.dialog.ui.lGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.lGaussWidth.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussFilterWidth.isVisible())
+
+        self.dialog.ui.comboBoxModulationType.setCurrentText("Amplitude Shift Keying (ASK)")
+        self.assertEqual(self.dialog.ui.lParameterfor0.text(), "Amplitude for 0:")
+        self.assertEqual(self.dialog.ui.lParameterfor1.text(), "Amplitude for 1:")
+        self.assertFalse(self.dialog.ui.lGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussBT.isVisible())
+        self.assertFalse(self.dialog.ui.lGaussWidth.isVisible())
+        self.assertFalse(self.dialog.ui.spinBoxGaussFilterWidth.isVisible())
+
+        self.assertEqual(int(self.dialog.ui.lSamplesInViewModulated.text()), int(self.dialog.ui.gVModulated.view_rect().width()))
+
+    def test_signal_view(self):
+        tree_view = self.dialog.ui.treeViewSignals
+        tree_model = tree_view.model()
+        item = tree_model.rootItem.children[0].children[0]
+        index = tree_model.createIndex(0, 0, item)
+        rect = tree_view.visualRect(index)
+        QTest.mousePress(tree_view.viewport(), Qt.LeftButton, pos=rect.center())
+        self.assertEqual(tree_view.selectedIndexes()[0], index)
+        mime_data = tree_model.mimeData(tree_view.selectedIndexes())
+        drag_drop = QDropEvent(rect.center(), Qt.CopyAction|Qt.MoveAction, mime_data, Qt.LeftButton, Qt.NoModifier)
+        drag_drop.acceptProposedAction()
+        self.dialog.ui.gVOriginalSignal.dropEvent(drag_drop)
+        self.assertEqual(self.dialog.ui.gVOriginalSignal.sceneRect().width(), self.signal.num_samples)
+
+        self.dialog.ui.cbShowDataBitsOnly.click()
+        self.dialog.ui.chkBoxLockSIV.click()
+
+        self.assertEqual(int(self.dialog.ui.gVOriginalSignal.view_rect().width()),
+                         int(self.dialog.ui.gVModulated.view_rect().width()))
diff --git a/ui/modulation.ui b/ui/modulation.ui
index 1ba5c0ea..22aeef61 100644
--- a/ui/modulation.ui
+++ b/ui/modulation.ui
@@ -137,7 +137,7 @@
           <double>0.000000000000000</double>
          </property>
          <property name="maximum">
-          <double>99999999.000000000000000</double>
+          <double>99999999999.000000000000000</double>
          </property>
         </widget>
        </item>