diff --git a/plugins/channeltx/udpsink/udpsink.cpp b/plugins/channeltx/udpsink/udpsink.cpp
index 93e7769c3..0acb9b186 100644
--- a/plugins/channeltx/udpsink/udpsink.cpp
+++ b/plugins/channeltx/udpsink/udpsink.cpp
@@ -175,7 +175,7 @@ void UDPSink::modulateSample()
     }
     else if (m_settings.m_sampleFormat == UDPSinkSettings::FormatNFM)
     {
-        FixReal t;
+        qint16 t;
         readMonoSample(t);
 
         m_inMovingAverage.feed((t*t)/1073741824.0);
@@ -198,7 +198,7 @@ void UDPSink::modulateSample()
     }
     else if (m_settings.m_sampleFormat == UDPSinkSettings::FormatAM)
     {
-        FixReal t;
+        qint16 t;
         readMonoSample(t);
         m_inMovingAverage.feed((t*t)/(SDR_TX_SCALED*SDR_TX_SCALED));
         m_inMagsq = m_inMovingAverage.average();
@@ -219,7 +219,7 @@ void UDPSink::modulateSample()
     }
     else if ((m_settings.m_sampleFormat == UDPSinkSettings::FormatLSB) || (m_settings.m_sampleFormat == UDPSinkSettings::FormatUSB))
     {
-        FixReal t;
+        qint16 t;
         Complex c, ci;
         fftfilt::cmplx *filtered;
         int n_out = 0;
diff --git a/plugins/channeltx/udpsink/udpsink.h b/plugins/channeltx/udpsink/udpsink.h
index e9166156b..f2b4bd741 100644
--- a/plugins/channeltx/udpsink/udpsink.h
+++ b/plugins/channeltx/udpsink/udpsink.h
@@ -300,14 +300,14 @@ private:
         }
     }
 
-    inline void readMonoSample(FixReal& t)
+    inline void readMonoSample(qint16& t)
     {
-        Sample s;
 
         if (m_settings.m_stereoInput)
         {
-            m_udpHandler.readSample(s);
-            t = ((s.m_real + s.m_imag) * m_settings.m_gainIn) / 2;
+            AudioSample a;
+            m_udpHandler.readSample(a);
+            t = ((a.l + a.r) * m_settings.m_gainIn) / 2;
         }
         else
         {
diff --git a/plugins/channeltx/udpsink/udpsinkudphandler.cpp b/plugins/channeltx/udpsink/udpsinkudphandler.cpp
index b37134d10..da3f647a4 100644
--- a/plugins/channeltx/udpsink/udpsinkudphandler.cpp
+++ b/plugins/channeltx/udpsink/udpsinkudphandler.cpp
@@ -33,7 +33,7 @@ UDPSinkUDPHandler::UDPSinkUDPHandler() :
     m_udpDumpIndex(0),
     m_nbUDPFrames(m_minNbUDPFrames),
     m_nbAllocatedUDPFrames(m_minNbUDPFrames),
-    m_writeIndex(0),
+    m_writeFrameIndex(0),
     m_readFrameIndex(m_minNbUDPFrames/2),
     m_readIndex(0),
     m_rwDelta(m_minNbUDPFrames/2),
@@ -129,31 +129,45 @@ void UDPSinkUDPHandler::dataReadyRead()
 
 void UDPSinkUDPHandler::moveData(char *blk)
 {
-    memcpy(m_udpBuf[m_writeIndex], blk, m_udpBlockSize);
+    memcpy(m_udpBuf[m_writeFrameIndex], blk, m_udpBlockSize);
 
-    if (m_writeIndex < m_nbUDPFrames - 1) {
-        m_writeIndex++;
+    if (m_writeFrameIndex < m_nbUDPFrames - 1) {
+        m_writeFrameIndex++;
     } else {
-        m_writeIndex = 0;
+        m_writeFrameIndex = 0;
     }
 }
 
-void UDPSinkUDPHandler::readSample(FixReal &t)
+void UDPSinkUDPHandler::readSample(qint16 &t)
 {
-    if (m_readFrameIndex == m_writeIndex) // block until more writes
+    if (m_readFrameIndex == m_writeFrameIndex) // block until more writes
     {
         t = 0;
     }
     else
     {
-        memcpy(&t, &m_udpBuf[m_readFrameIndex][m_readIndex], sizeof(FixReal));
-        advanceReadPointer((int) sizeof(FixReal));
+        memcpy(&t, &m_udpBuf[m_readFrameIndex][m_readIndex], sizeof(qint16));
+        advanceReadPointer((int) sizeof(qint16));
+    }
+}
+
+void UDPSinkUDPHandler::readSample(AudioSample &a)
+{
+    if (m_readFrameIndex == m_writeFrameIndex) // block until more writes
+    {
+        a.l = 0;
+        a.r = 0;
+    }
+    else
+    {
+        memcpy(&a, &m_udpBuf[m_readFrameIndex][m_readIndex], sizeof(AudioSample));
+        advanceReadPointer((int) sizeof(AudioSample));
     }
 }
 
 void UDPSinkUDPHandler::readSample(Sample &s)
 {
-    if (m_readFrameIndex == m_writeIndex) // block until more writes
+    if (m_readFrameIndex == m_writeFrameIndex) // block until more writes
     {
         s.m_real = 0;
         s.m_imag = 0;
@@ -181,7 +195,7 @@ void UDPSinkUDPHandler::advanceReadPointer(int nbBytes)
         }
         else
         {
-            m_rwDelta = m_writeIndex; // raw R/W delta estimate
+            m_rwDelta = m_writeFrameIndex; // raw R/W delta estimate
             int nbUDPFrames2 = m_nbUDPFrames/2;
             float d = (m_rwDelta - nbUDPFrames2)/(float) m_nbUDPFrames;
             //qDebug("UDPSinkUDPHandler::advanceReadPointer: w: %02d d: %f", m_writeIndex, d);
@@ -233,7 +247,7 @@ void UDPSinkUDPHandler::applyUDPLink(const QString& address, quint16 port)
 
 void UDPSinkUDPHandler::resetReadIndex()
 {
-    m_readFrameIndex = (m_writeIndex + (m_nbUDPFrames/2)) % m_nbUDPFrames;
+    m_readFrameIndex = (m_writeFrameIndex + (m_nbUDPFrames/2)) % m_nbUDPFrames;
     m_rwDelta = m_nbUDPFrames/2;
     m_readIndex = 0;
     m_d = 0.0f;
@@ -252,7 +266,7 @@ void UDPSinkUDPHandler::resizeBuffer(float sampleRate)
     }
 
     m_nbUDPFrames = 2*halfNbFrames;
-    m_writeIndex = 0;
+    m_writeFrameIndex = 0;
 
     resetReadIndex();
 }
diff --git a/plugins/channeltx/udpsink/udpsinkudphandler.h b/plugins/channeltx/udpsink/udpsinkudphandler.h
index 52de91143..e75cca5b3 100644
--- a/plugins/channeltx/udpsink/udpsinkudphandler.h
+++ b/plugins/channeltx/udpsink/udpsinkudphandler.h
@@ -40,8 +40,9 @@ public:
     void resetReadIndex();
     void resizeBuffer(float sampleRate);
 
-    void readSample(FixReal &t);
-    void readSample(Sample &s);
+    void readSample(qint16 &t);      //!< audio mono
+    void readSample(AudioSample &a); //!< audio stereo
+    void readSample(Sample &s);      //!< I/Q stream
 
     void setAutoRWBalance(bool autoRWBalance) { m_autoRWBalance = autoRWBalance; }
     void setFeedbackMessageQueue(MessageQueue *messageQueue) { m_feedbackMessageQueue = messageQueue; }
@@ -104,7 +105,7 @@ private:
     int m_udpDumpIndex;
     int m_nbUDPFrames;
     int m_nbAllocatedUDPFrames;
-    int m_writeIndex;
+    int m_writeFrameIndex;
     int m_readFrameIndex;
     int m_readIndex;
     int m_rwDelta;
diff --git a/swagger/sdrangel/examples/tx_test.py b/swagger/sdrangel/examples/tx_test.py
index 4332402ee..e1720ade6 100644
--- a/swagger/sdrangel/examples/tx_test.py
+++ b/swagger/sdrangel/examples/tx_test.py
@@ -26,6 +26,7 @@ def getInputOptions():
     parser.add_option("-f", "--channel-freq", dest="channel_freq", help="channel center frequency (Hz)", metavar="FREQ", type="int")
     parser.add_option("-s", "--sample-rate", dest="sample_rate", help="host to device sample rate (S/s)", metavar="RATE", type="int")
     parser.add_option("-l", "--log2-interp", dest="log2_interp", help="log2 of interpolation factor", metavar="RATE", type="int")
+    parser.add_option("-L", "--log2-interp-hard", dest="log2_interp_hard", help="log2 of hardware interpolation factor", metavar="RATE", type="int")
     parser.add_option("-A", "--antenna-path", dest="antenna_path", help="antenna path number", metavar="NUMBER", type="int")
     parser.add_option("-c", "--create", dest="create", help="create a new device set", metavar="CREATE", action="store_true", default=False)
     parser.add_option("--ppm", dest="lo_ppm", help="LO correction in ppm", metavar="FILENAME", type="float", default=0)
@@ -55,6 +56,9 @@ def getInputOptions():
     if options.log2_interp == None:
         options.log2_interp = 4
 
+    if options.log2_interp_hard == None:
+        options.log2_interp = 4
+
     if options.antenna_path == None:
         options.antenna_path = 1
 
@@ -121,7 +125,7 @@ def setupDevice(options):
     elif options.device_hwid == "LimeSDR":
         settings["limeSdrOutputSettings"]["antennaPath"] = options.antenna_path
         settings["limeSdrOutputSettings"]["devSampleRate"] = options.sample_rate
-        settings["limeSdrOutputSettings"]["log2HardInterp"] = 4
+        settings["limeSdrOutputSettings"]["log2HardInterp"] = options.log2_interp_hard
         settings["limeSdrOutputSettings"]["log2SoftInterp"] = options.log2_interp
         settings["limeSdrOutputSettings"]["centerFrequency"] = options.device_freq*1000 + 500000
         settings["limeSdrOutputSettings"]["ncoEnable"] = 1
@@ -129,6 +133,7 @@ def setupDevice(options):
         settings["limeSdrOutputSettings"]["lpfBW"] = 4050000
         settings["limeSdrOutputSettings"]["lpfFIRBW"] = 100000
         settings["limeSdrOutputSettings"]["lpfFIREnable"] = 1
+        settings["limeSdrOutputSettings"]["gain"] = 17
     elif options.device_hwid == "HackRF":
         settings['hackRFOutputSettings']['LOppmTenths'] = round(options.lo_ppm*10)
         settings['hackRFOutputSettings']['centerFrequency'] = options.device_freq*1000
@@ -208,13 +213,15 @@ def setupChannel(options):
         settings["UDPSinkSettings"]["title"] = "Test UDP Sink"
         settings["UDPSinkSettings"]["inputFrequencyOffset"] = options.channel_freq
         settings["UDPSinkSettings"]["rfBandwidth"] = 12500
-        settings["UDPSinkSettings"]["fmDeviation"] = 5000
-        settings["UDPSinkSettings"]["autoRWBalance"] = 0
+        settings["UDPSinkSettings"]["fmDeviation"] = 6000
+        settings["UDPSinkSettings"]["autoRWBalance"] = 1
         settings["UDPSinkSettings"]["stereoInput"] = 0
         settings["UDPSinkSettings"]["udpAddress"] = "127.0.0.1"
         settings["UDPSinkSettings"]["udpPort"] = 9998
-        settings["UDPSinkSettings"]["inputSampleRate"] = 24000
+        settings["UDPSinkSettings"]["inputSampleRate"] = 48000
         settings["UDPSinkSettings"]["sampleFormat"] = 1 # FormatNFM
+        settings["UDPSinkSettings"]["gainIn"] = 2.5
+        settings["UDPSinkSettings"]["gainOut"] = 2.8
     elif options.channel_id == "WFMMod":
         settings["WFMModSettings"]["title"] = "Test WFM"
         settings["WFMModSettings"]["inputFrequencyOffset"] = options.channel_freq