diff --git a/codec2talkie/build.gradle b/codec2talkie/build.gradle
index 3c08299..fe1bab7 100644
--- a/codec2talkie/build.gradle
+++ b/codec2talkie/build.gradle
@@ -10,8 +10,8 @@ android {
         applicationId "com.radio.codec2talkie"
         minSdkVersion 21
         targetSdkVersion 30
-        versionCode 132
-        versionName "1.32"
+        versionCode 133
+        versionName "1.33"
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/MainActivity.java b/codec2talkie/src/main/java/com/radio/codec2talkie/MainActivity.java
index 19bc5ff..46ce723 100644
--- a/codec2talkie/src/main/java/com/radio/codec2talkie/MainActivity.java
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/MainActivity.java
@@ -110,6 +110,7 @@ public class MainActivity extends AppCompatActivity implements ServiceConnection
     private boolean _isConnecting = false;
     private boolean _isAppExit = false;
     private boolean _isAppRestart = false;
+    private boolean _isRigCtlUsbConnected = false;
 
     private long _backPressedTimestamp;
 
@@ -262,7 +263,11 @@ public class MainActivity extends AppCompatActivity implements ServiceConnection
                     break;
                 case "sound_modem":
                     _textConnInfo.setText(R.string.main_status_sound_modem);
-                    startAppService(TransportFactory.TransportType.SOUND_MODEM);
+                    String rig = _sharedPreferences.getString(PreferenceKeys.PORTS_SOUND_MODEM_RIG, "Disabled");
+                    if (rig.equals("Disabled"))
+                        startAppService(TransportFactory.TransportType.SOUND_MODEM);
+                    else
+                        startUsbConnectActivity();
                     break;
                 case "tcp_ip":
                     startTcpIpConnectActivity();
@@ -284,7 +289,11 @@ public class MainActivity extends AppCompatActivity implements ServiceConnection
             Intent data = result.getData();
             assert data != null;
             int resultCode = result.getResultCode();
-            if (resultCode == RESULT_CANCELED) {
+            String transportType = _sharedPreferences.getString(PreferenceKeys.PORTS_TYPE, "loopback");
+            if (transportType.equals("sound_modem")) {
+                _isRigCtlUsbConnected = resultCode == RESULT_OK;
+                startAppService(TransportFactory.TransportType.SOUND_MODEM);
+            } else if (resultCode == RESULT_CANCELED) {
                 _textConnInfo.setText(R.string.main_status_loopback_test);
                 startAppService(TransportFactory.TransportType.LOOPBACK);
             } else if (resultCode == RESULT_OK) {
@@ -296,6 +305,7 @@ public class MainActivity extends AppCompatActivity implements ServiceConnection
 
     protected void startUsbConnectActivity() {
         _isConnecting = true;
+        _isRigCtlUsbConnected = false;
         _usbActivityLauncher.launch(new Intent(this, UsbConnectActivity.class));
     }
 
@@ -456,6 +466,12 @@ public class MainActivity extends AppCompatActivity implements ServiceConnection
             status += getString(R.string.kiss_scrambler_label);
         }
 
+        // rig CAT control
+        String rigName = _sharedPreferences.getString(PreferenceKeys.PORTS_SOUND_MODEM_RIG, "Disabled");
+        if (!rigName.equals("Disabled") && _isRigCtlUsbConnected) {
+            status += getString(R.string.ports_sound_modem_rig_label);
+        }
+
         // aprs
         boolean aprsEnabled = _sharedPreferences.getBoolean(PreferenceKeys.APRS_ENABLED, false);
         if (aprsEnabled) {
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/connect/UsbConnectActivity.java b/codec2talkie/src/main/java/com/radio/codec2talkie/connect/UsbConnectActivity.java
index 5d86560..ccc06a4 100644
--- a/codec2talkie/src/main/java/com/radio/codec2talkie/connect/UsbConnectActivity.java
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/connect/UsbConnectActivity.java
@@ -92,7 +92,7 @@ public class UsbConnectActivity extends AppCompatActivity {
         customTable.addProduct(0x1b4f, 0x9204, CdcAcmSerialDriver.class);
         // Arduino Due
         customTable.addProduct(0x2341, 0x003d, CdcAcmSerialDriver.class);
-        // STM
+        // STM, MCHF
         customTable.addProduct(0x0483, 0x5732, CdcAcmSerialDriver.class);
         return new UsbSerialProber(customTable);
     }
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/protocol/Hdlc.java b/codec2talkie/src/main/java/com/radio/codec2talkie/protocol/Hdlc.java
index a7742bf..91f66e3 100644
--- a/codec2talkie/src/main/java/com/radio/codec2talkie/protocol/Hdlc.java
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/protocol/Hdlc.java
@@ -15,6 +15,7 @@ import com.radio.codec2talkie.transport.SoundModem;
 import com.radio.codec2talkie.transport.Transport;
 
 import java.io.IOException;
+import java.nio.BufferOverflowException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 
@@ -121,7 +122,12 @@ public class Hdlc implements Protocol {
                     _readByte = 0;
                     _prevHdlc = 0;
                 } else {
-                    _currentFrameBuffer.put(bit);
+                    try {
+                        _currentFrameBuffer.put(bit);
+                    } catch (BufferOverflowException e) {
+                        e.printStackTrace();
+                        _currentFrameBuffer.clear();
+                    }
                     _prevHdlc++;
                 }
             }
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Disabled.java b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Disabled.java
new file mode 100644
index 0000000..e700b27
--- /dev/null
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Disabled.java
@@ -0,0 +1,21 @@
+package com.radio.codec2talkie.rigctl;
+
+import android.content.Context;
+
+import com.radio.codec2talkie.transport.Transport;
+
+import java.io.IOException;
+
+public class Disabled implements RigCtl{
+    @Override
+    public void initialize(Transport transport, Context context, RigCtlCallback protocolCallback) throws IOException {
+    }
+
+    @Override
+    public void pttOn() {
+    }
+
+    @Override
+    public void pttOff() {
+    }
+}
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Ft817.java b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Ft817.java
new file mode 100644
index 0000000..4e9ad0b
--- /dev/null
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/Ft817.java
@@ -0,0 +1,51 @@
+package com.radio.codec2talkie.rigctl;
+
+import android.content.Context;
+import android.util.Log;
+
+import com.radio.codec2talkie.transport.Transport;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+
+// http://www.ka7oei.com/ft817_meow.html
+public class Ft817 implements RigCtl {
+    private static final String TAG = Ft817.class.getSimpleName();
+
+    private Transport _transport;
+
+    @Override
+    public void initialize(Transport transport, Context context, RigCtlCallback protocolCallback) throws IOException {
+        _transport = transport;
+    }
+
+    @Override
+    public void pttOn() throws IOException {
+        // 0x00, 0x00, 0x00, 0x00, 0x08
+        // returns 0x00 (was un-keyed), 0xf0 (already keyed)
+        Log.i(TAG, "PTT ON");
+        ByteBuffer cmd = ByteBuffer.allocate(5);
+        cmd.put((byte)0x00).put((byte)0x00).put((byte)0x00).put((byte)0x00).put((byte)0x08);
+        _transport.write(cmd.array());
+        Log.i(TAG, "PTT ON done");
+
+        byte[] response = new byte[1];
+        int bytesRead = _transport.read(response);
+        Log.i(TAG, "PTT ON response: " + bytesRead + " " + response[0]);
+    }
+
+    @Override
+    public void pttOff() throws IOException {
+        // 0x00, 0x00, 0x00, 0x00, 0x88
+        // returns 0x00 (was keyed), 0xf0 (already un-keyed)
+        Log.i(TAG, "PTT OFF");
+        ByteBuffer cmd = ByteBuffer.allocate(5);
+        cmd.put((byte)0x00).put((byte)0x00).put((byte)0x00).put((byte)0x00).put((byte)0x88);
+        _transport.write(cmd.array());
+        Log.i(TAG, "PTT OFF done");
+
+        byte[] response = new byte[1];
+        int bytesRead = _transport.read(response);
+        Log.i(TAG, "PTT OFF response: " + bytesRead + " " + response[0]);
+    }
+}
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtl.java b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtl.java
new file mode 100644
index 0000000..31788f3
--- /dev/null
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtl.java
@@ -0,0 +1,15 @@
+package com.radio.codec2talkie.rigctl;
+
+import android.content.Context;
+
+import com.radio.codec2talkie.protocol.ProtocolCallback;
+import com.radio.codec2talkie.transport.Transport;
+
+import java.io.IOException;
+
+public interface RigCtl {
+    void initialize(Transport transport, Context context, RigCtlCallback protocolCallback) throws IOException;
+
+    void pttOn() throws IOException;
+    void pttOff() throws IOException;
+}
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlCallback.java b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlCallback.java
new file mode 100644
index 0000000..ecc7b06
--- /dev/null
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlCallback.java
@@ -0,0 +1,4 @@
+package com.radio.codec2talkie.rigctl;
+
+public interface RigCtlCallback {
+}
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlFactory.java b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlFactory.java
new file mode 100644
index 0000000..38af74e
--- /dev/null
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/rigctl/RigCtlFactory.java
@@ -0,0 +1,29 @@
+package com.radio.codec2talkie.rigctl;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.util.Log;
+
+import androidx.preference.PreferenceManager;
+
+import com.radio.codec2talkie.connect.UsbPortHandler;
+import com.radio.codec2talkie.settings.PreferenceKeys;
+
+public class RigCtlFactory {
+    private static final String TAG = RigCtlFactory.class.getSimpleName();
+
+    public static RigCtl create(Context context) {
+        if (UsbPortHandler.getPort() == null)
+            return new Disabled();
+        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
+        String rigName = sharedPreferences.getString(PreferenceKeys.PORTS_SOUND_MODEM_RIG, "Disabled");
+        try {
+            Class<?> loadClass = Class.forName(String.format("com.radio.codec2talkie.rigctl.%s", rigName));
+            Log.i(TAG, "Using rig " + rigName);
+            return (RigCtl)loadClass.newInstance();
+        } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
+            e.printStackTrace();
+            return new Disabled();
+        }
+    }
+}
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/settings/PreferenceKeys.java b/codec2talkie/src/main/java/com/radio/codec2talkie/settings/PreferenceKeys.java
index 596a0e5..90cf9b5 100644
--- a/codec2talkie/src/main/java/com/radio/codec2talkie/settings/PreferenceKeys.java
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/settings/PreferenceKeys.java
@@ -20,6 +20,8 @@ public final class PreferenceKeys {
     public static String PORTS_SOUND_MODEM_TYPE = "ports_sound_modem_type";
     public static String PORTS_SOUND_MODEM_PREAMBLE = "ports_sound_modem_preamble";
     public static String PORTS_SOUND_MODEM_DISABLE_RX = "ports_sound_modem_disable_rx";
+    public static String PORTS_SOUND_MODEM_RIG = "ports_sound_modem_rig";
+    public static String PORTS_SOUND_MODEM_GAIN ="ports_sound_modem_gain";
 
     public static String CODEC2_MODE = "codec2_mode";
     public static String CODEC2_RECORDING_ENABLED = "codec2_recording_enabled";
diff --git a/codec2talkie/src/main/java/com/radio/codec2talkie/transport/SoundModem.java b/codec2talkie/src/main/java/com/radio/codec2talkie/transport/SoundModem.java
index 12032c8..705efe4 100644
--- a/codec2talkie/src/main/java/com/radio/codec2talkie/transport/SoundModem.java
+++ b/codec2talkie/src/main/java/com/radio/codec2talkie/transport/SoundModem.java
@@ -12,6 +12,8 @@ import android.util.Log;
 
 import androidx.preference.PreferenceManager;
 
+import com.radio.codec2talkie.rigctl.RigCtl;
+import com.radio.codec2talkie.rigctl.RigCtlFactory;
 import com.radio.codec2talkie.settings.PreferenceKeys;
 import com.radio.codec2talkie.tools.AudioTools;
 import com.radio.codec2talkie.tools.BitTools;
@@ -22,13 +24,18 @@ import java.io.IOException;
 import java.nio.BufferOverflowException;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
+import java.util.Timer;
+import java.util.TimerTask;
 
 public class SoundModem implements Transport, Runnable {
 
     private static final String TAG = SoundModem.class.getSimpleName();
 
+    private static final int PTT_OFF_DELAY_MS = 1000;
+
     // NOTE, codec2 library requires that sample_rate % bit_rate == 0
     public static final int SAMPLE_RATE = 19200;
+    //public static final int SAMPLE_RATE = 48000;
 
     private final String _name;
 
@@ -52,20 +59,25 @@ public class SoundModem implements Transport, Runnable {
 
     private final long _fskModem;
 
+    private final RigCtl _rigCtl;
+    private Timer _pttOffTimer;
+    private boolean _isPttOn = false;
+
     public SoundModem(Context context) {
         _context = context;
         _sharedPreferences = PreferenceManager.getDefaultSharedPreferences(_context);
 
         boolean disableRx = _sharedPreferences.getBoolean(PreferenceKeys.PORTS_SOUND_MODEM_DISABLE_RX, false);
         int bitRate = Integer.parseInt(_sharedPreferences.getString(PreferenceKeys.PORTS_SOUND_MODEM_TYPE, "1200"));
+        int gain = Integer.parseInt(_sharedPreferences.getString(PreferenceKeys.PORTS_SOUND_MODEM_GAIN, "10000"));
         _name = "SoundModem" + bitRate;
         if (bitRate == 300) {
             // <230 spacing for 300 bps does not work with codec2 fsk for receive
-            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 300, 1600, 200);
+            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 300, 1600, 200, gain);
         } else if (bitRate == 1200) {
-            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 1200, 1200, 1000);
+            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 1200, 1200, 1000, gain);
         } else {
-            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 2400, 2165, 1805);
+            _fskModem = Codec2.fskCreate(SAMPLE_RATE, 2400, 2165, 1805, gain);
         }
 
         _recordAudioBuffer = new short[Codec2.fskDemodSamplesBufSize(_fskModem)];
@@ -82,6 +94,15 @@ public class SoundModem implements Transport, Runnable {
         else
             _sampleBuffer = ByteBuffer.allocate(0);
 
+        _rigCtl = RigCtlFactory.create(context);
+        try {
+            _rigCtl.initialize(TransportFactory.create(TransportFactory.TransportType.USB, context), context, null);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        _isPttOn = false;
+
         if (!disableRx)
             new Thread(this).start();
     }
@@ -147,6 +168,8 @@ public class SoundModem implements Transport, Runnable {
 
     @Override
     public int write(byte[] srcDataBytesAsBits) throws IOException {
+        pttOn();
+
         //Log.v(TAG, "write     " + DebugTools.byteBitsToFlatString(srcDataBytesAsBits));
         byte[] dataBytesAsBits = BitTools.convertToNRZI(srcDataBytesAsBits);
         //Log.v(TAG, "write NRZ " + DebugTools.byteBitsToFlatString(dataBytesAsBits));
@@ -184,6 +207,7 @@ public class SoundModem implements Transport, Runnable {
         } else {
             _systemAudioPlayer.write(_playbackAudioBuffer, 0, bitBufferTail.length * _samplesPerSymbol);
         }
+        pttOff();
         return 0;
     }
 
@@ -226,8 +250,10 @@ public class SoundModem implements Transport, Runnable {
                 }
             } else {
                 int readCnt = _systemAudioRecorder.read(_recordAudioBuffer, 0, nin);
+                // TODO, read tail
                 if (readCnt != nin) {
-                    Log.e(TAG, "" + readCnt + " != " + nin);
+                    Log.w(TAG, "" + readCnt + " != " + nin);
+                    continue;
                 }
                 //Log.v(TAG, "read samples: " + DebugTools.shortsToHex(_recordAudioBuffer));
             }
@@ -248,4 +274,36 @@ public class SoundModem implements Transport, Runnable {
             }
         }
     }
+
+    private void pttOn() {
+        if (_isPttOn) return;
+
+        try {
+            _rigCtl.pttOn();
+            _isPttOn = true;
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    private void pttOff() {
+        if (!_isPttOn) return;
+        if (_pttOffTimer != null) {
+            _pttOffTimer.cancel();
+            _pttOffTimer.purge();
+            _pttOffTimer = null;
+        }
+        _pttOffTimer = new Timer();
+        _pttOffTimer.schedule(new TimerTask() {
+            @Override
+            public void run() {
+                try {
+                    _rigCtl.pttOff();
+                    _isPttOn = false;
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }
+        }, PTT_OFF_DELAY_MS);
+    }
 }
diff --git a/codec2talkie/src/main/res/values/arrays.xml b/codec2talkie/src/main/res/values/arrays.xml
index 7f31538..569fda1 100644
--- a/codec2talkie/src/main/res/values/arrays.xml
+++ b/codec2talkie/src/main/res/values/arrays.xml
@@ -352,4 +352,46 @@
         <item>usb</item>
         <item>sound_modem</item>
     </string-array>
+
+    <string-array name="ports_sound_modem_rig_entries">
+        <item>Do not use rig control</item>
+        <item>FT-817/818/MCHF</item>
+    </string-array>
+
+    <string-array name="ports_sound_modem_rig_values">
+        <item>Disabled</item>
+        <item>Ft817</item>
+    </string-array>
+
+    <string-array name="ports_sound_modem_gain_entries">
+        <item>+0 db</item>
+        <item>+1 db</item>
+        <item>+2 db</item>
+        <item>+3 db</item>
+        <item>+4 db</item>
+        <item>+5 db</item>
+        <item>+6 db</item>
+        <item>+7 db</item>
+        <item>+8 db</item>
+        <item>+9 db</item>
+        <item>+10 db</item>
+        <item>+11 db</item>
+        <item>+12 db</item>
+    </string-array>
+
+    <string-array name="ports_sound_modem_gain_values">
+        <item>1000</item>
+        <item>1258</item>
+        <item>1584</item>
+        <item>1995</item>
+        <item>2511</item>
+        <item>3162</item>
+        <item>3981</item>
+        <item>5011</item>
+        <item>6309</item>
+        <item>7943</item>
+        <item>10000</item>
+        <item>12589</item>
+        <item>15848</item>
+    </string-array>
 </resources>
\ No newline at end of file
diff --git a/codec2talkie/src/main/res/values/strings.xml b/codec2talkie/src/main/res/values/strings.xml
index d6a2332..bd09f34 100644
--- a/codec2talkie/src/main/res/values/strings.xml
+++ b/codec2talkie/src/main/res/values/strings.xml
@@ -302,4 +302,7 @@
     <string name="ports_type_title">TNC transport type</string>
     <string name="ports_sound_modem_disable_rx_title">Disable receive</string>
     <string name="ports_sound_modem_disable_rx_summary">Run modem in transmit only mode, receive is disabled to save CPU cycles</string>
+    <string name="ports_sound_modem_rig_title">Select RIG model for CAT PTT control</string>
+    <string name="ports_sound_modem_gain_title">Set modem audio gain</string>
+    <string name="ports_sound_modem_rig_label">&#127899;</string>
 </resources>
\ No newline at end of file
diff --git a/codec2talkie/src/main/res/xml/preferences_sound_modem.xml b/codec2talkie/src/main/res/xml/preferences_sound_modem.xml
index ffe11a0..1716424 100644
--- a/codec2talkie/src/main/res/xml/preferences_sound_modem.xml
+++ b/codec2talkie/src/main/res/xml/preferences_sound_modem.xml
@@ -29,5 +29,23 @@
             app:defaultValue="false">
         </SwitchPreference>
 
+        <ListPreference
+            app:key="ports_sound_modem_rig"
+            app:title="@string/ports_sound_modem_rig_title"
+            app:entries="@array/ports_sound_modem_rig_entries"
+            app:entryValues="@array/ports_sound_modem_rig_values"
+            app:defaultValue="Disabled"
+            app:summary="%s">
+        </ListPreference>
+
+        <ListPreference
+            app:key="ports_sound_modem_gain"
+            app:title="@string/ports_sound_modem_gain_title"
+            app:entries="@array/ports_sound_modem_gain_entries"
+            app:entryValues="@array/ports_sound_modem_gain_values"
+            app:defaultValue="10000"
+            app:summary="%s">
+        </ListPreference>
+
     </PreferenceCategory>
 </PreferenceScreen>
\ No newline at end of file
diff --git a/libcodec2-android/src/main/cpp/Codec2JNI.cpp b/libcodec2-android/src/main/cpp/Codec2JNI.cpp
index 698a3f3..fe1df4b 100644
--- a/libcodec2-android/src/main/cpp/Codec2JNI.cpp
+++ b/libcodec2-android/src/main/cpp/Codec2JNI.cpp
@@ -25,6 +25,7 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         int Nbits;
         int N;
         int Ts;
+        int gain;
     };
 
     static Context *getContext(jlong jp) {
@@ -56,7 +57,7 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         return pv;
     }
 
-    static jlong fskCreate(JNIEnv *env, jclass clazz, int sampleFrequency, int symbolRate, int toneFreq, int toneSpacing) {
+    static jlong fskCreate(JNIEnv *env, jclass clazz, int sampleFrequency, int symbolRate, int toneFreq, int toneSpacing, int gain) {
         struct ContextFsk *conFsk;
         conFsk = (struct ContextFsk *) malloc(sizeof(struct ContextFsk));
         struct FSK *fsk;
@@ -74,6 +75,8 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         conFsk->demodBits = (uint8_t*)malloc(sizeof(uint8_t) * fsk->Nbits);
         conFsk->demodBuf = (int16_t*)malloc(sizeof(short) * (fsk->N + 2 * fsk->Ts));
 
+        conFsk->gain = gain;
+
         fsk_set_freq_est_limits(fsk, 500, sampleFrequency / 4);
         fsk_set_freq_est_alg(fsk, 0);
 
@@ -168,7 +171,7 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         fsk_mod(conFsk->fsk, conFsk->modBuf, conFsk->modBits, inputBitsSize);
         jshort *jOutBuf = env->GetShortArrayElements(outputSamples, nullptr);
         for (int i = 0; i < conFsk->N; i++) {
-            jOutBuf[i] = (int16_t)(conFsk->modBuf[i] * FDMDV_SCALE);
+            jOutBuf[i] = (int16_t)(conFsk->modBuf[i] * conFsk->gain);
         }
         env->ReleaseShortArrayElements(outputSamples, jOutBuf, 0);
         return 0;
@@ -186,7 +189,7 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         ContextFsk *conFsk = getContextFsk(n);
         env->GetShortArrayRegion(inputSamples, 0, conFsk->N, reinterpret_cast<jshort*>(conFsk->demodBuf));
         for(int i = 0; i < fsk_nin(conFsk->fsk); i++){
-            conFsk->demodCBuf[i].real = ((float)conFsk->demodBuf[i]) / FDMDV_SCALE;
+            conFsk->demodCBuf[i].real = ((float)conFsk->demodBuf[i]) / conFsk->gain;
             conFsk->demodCBuf[i].imag = 0.0;
         }
         fsk_demod(conFsk->fsk, conFsk->demodBits, conFsk->demodCBuf);
@@ -201,7 +204,7 @@ namespace Java_com_ustadmobile_codec2_Codec2 {
         {"destroy",            "(J)I",     (void *) destroy},
         {"encode",             "(J[S[C)J", (void *) encode},
         {"decode",             "(J[S[B)J", (void *) decode},
-        {"fskCreate",          "(IIII)J",  (void *) fskCreate},
+        {"fskCreate",          "(IIIII)J", (void *) fskCreate},
         {"fskDestroy",         "(J)I",     (void *) fskDestroy},
         {"fskModulate",        "(J[S[B)J", (void *) fskModulate},
         {"fskDemodulate",      "(J[S[B)J", (void *) fskDemodulate},
diff --git a/libcodec2-android/src/main/java/com/ustadmobile/codec2/Codec2.java b/libcodec2-android/src/main/java/com/ustadmobile/codec2/Codec2.java
index 4c8a58d..5de0986 100644
--- a/libcodec2-android/src/main/java/com/ustadmobile/codec2/Codec2.java
+++ b/libcodec2-android/src/main/java/com/ustadmobile/codec2/Codec2.java
@@ -35,7 +35,7 @@ public class Codec2 {
     public native static long encode(long con, short[] inputSamples, char[] outputBits);
     public native static long decode(long con, short[] outputSamples, byte[] inputsBits);
 
-    public native static long fskCreate(int sampleFrequency, int symbolRate, int toneFreq, int toneSpacing);
+    public native static long fskCreate(int sampleFrequency, int symbolRate, int toneFreq, int toneSpacing, int gain);
     public native static int fskDestroy(long conFsk);
 
     public native static int fskDemodBitsBufSize(long conFsk);