diff --git a/NanoVNASaver.py b/NanoVNASaver.py
index acf6fec..66086ef 100644
--- a/NanoVNASaver.py
+++ b/NanoVNASaver.py
@@ -188,6 +188,11 @@ class NanoVNASaver(QtWidgets.QWidget):
         self.tdr_velocity_dropdown.addItem("Foam or Cellular PE (0.78)", 0.78)
         self.tdr_velocity_dropdown.addItem("Semi-solid PE (SSPE) (0.84)", 0.84)
         self.tdr_velocity_dropdown.addItem("Air (Helical spacers) (0.94)", 0.94)
+        self.tdr_velocity_dropdown.insertSeparator(7)
+        self.tdr_velocity_dropdown.addItem("RG174 (0.66)", 0.66)
+        self.tdr_velocity_dropdown.addItem("RG316 (0.69)", 0.69)
+        self.tdr_velocity_dropdown.addItem("RG402 (0.695)", 0.695)
+        self.tdr_velocity_dropdown.insertSeparator(11)
         self.tdr_velocity_dropdown.addItem("Custom", -1)
 
         self.tdr_velocity_dropdown.setCurrentIndex(1)  # Default to PE (0.66)
diff --git a/README.md b/README.md
index 73723f8..df89c83 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,18 @@ In order to run this app in Linux environment, you'll need the following package
 python3 nanovna-saver.py
 ```
 
+### Using the software
+
+Connect your NanoVNA to a serial port, and enter this serial port in the serial port box. Click "Open serial" to connect.
+
+The app can collect multiple sweeps to get more accurate measurements. Enter the number of sweeps to be done in the
+sweep count box. Each sweep is 101 data points, and takes about 1.5 seconds to complete.
+
+Marker frequencies are entered in Hz. Press enter after typing the frequency for it to take effect.
+
+To get accurate TDR measurements, calibrate the device, and attach the cable to be measured at the calibration plane -
+ie. at the same position where the calibration load would be attached.
+
 ### License
 This software is licensed under version 3 of the GNU General Public License. It comes with NO WARRANTY.