diff --git a/DMRTX.cpp b/DMRTX.cpp
old mode 100644
new mode 100755
index 9824f9c..81437ec
--- a/DMRTX.cpp
+++ b/DMRTX.cpp
@@ -54,6 +54,7 @@ const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02
 #define READ_BIT1(p,i)    (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
 
 const uint32_t STARTUP_COUNT = 20U;
+const uint32_t ABORT_COUNT = 6U;
 
 CDMRTX::CDMRTX() :
 m_fifo(),
@@ -69,6 +70,7 @@ m_poBuffer(),
 m_poLen(0U),
 m_poPtr(0U),
 m_frameCount(0U),
+m_abortCount(),
 m_abort()
 {
   ::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
@@ -83,6 +85,9 @@ m_abort()
 
   m_abort[0U] = false;
   m_abort[1U] = false;
+
+  m_abortCount[0U] = 0U;
+  m_abortCount[1U] = 0U;
 }
 
 void CDMRTX::process()
@@ -210,10 +215,12 @@ uint8_t CDMRTX::writeAbort(const uint8_t* data, uint8_t length)
 
   switch (data[0U]) {
     case 1U:
+      m_abortCount[0U] = 0U;
       m_abort[0U] = true;
       return 0U;
 
     case 2U:
+      m_abortCount[1U] = 0U;
       m_abort[1U] = true;
       return 0U;
 
@@ -227,6 +234,8 @@ void CDMRTX::setStart(bool start)
   m_state = start ? DMRTXSTATE_SLOT1 : DMRTXSTATE_IDLE;
 
   m_frameCount = 0U;
+  m_abortCount[0U] = 0U;
+  m_abortCount[1U] = 0U;
 
   m_abort[0U] = false;
   m_abort[1U] = false;
@@ -282,7 +291,7 @@ uint8_t CDMRTX::getSpace2() const
 
 void CDMRTX::createData(uint8_t slotIndex)
 {
-  if (m_fifo[slotIndex].getData() > 0U && m_frameCount >= STARTUP_COUNT) {
+  if (m_fifo[slotIndex].getData() >= DMR_FRAME_LENGTH_BYTES && m_frameCount >= STARTUP_COUNT && m_abortCount[slotIndex] >= ABORT_COUNT) {
     for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++) {
       m_poBuffer[i]   = m_fifo[slotIndex].get();
       m_markBuffer[i] = MARK_NONE;
@@ -335,6 +344,8 @@ void CDMRTX::createCal()
 void CDMRTX::createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex)
 {
   m_frameCount++;
+  m_abortCount[0U]++;
+  m_abortCount[1U]++;
 
   if (m_cachPtr >= 12U)
     m_cachPtr = 0U;
diff --git a/DMRTX.h b/DMRTX.h
old mode 100644
new mode 100755
index 00977d5..1e2f617
--- a/DMRTX.h
+++ b/DMRTX.h
@@ -72,6 +72,7 @@ private:
   uint16_t                         m_poLen;
   uint16_t                         m_poPtr;
   uint32_t                         m_frameCount;
+  uint32_t                         m_abortCount[2U];
   bool                             m_abort[2U];
 
   void createData(uint8_t slotIndex);
diff --git a/P25TX.cpp b/P25TX.cpp
index 2901a74..57a8db0 100644
--- a/P25TX.cpp
+++ b/P25TX.cpp
@@ -30,12 +30,10 @@ static q15_t RC_0_2_FILTER[] = {-897, -1636, -1840, -1278, 0, 1613, 2936, 3310,
                                -3011, 0, 2315, 3310, 2936, 1613, 0, -1278, -1840, -1636, -897, 0}; // numTaps = 40, L = 5
 const uint16_t RC_0_2_FILTER_PHASE_LEN = 8U; // phaseLength = numTaps/L
 
-// Generated in MATLAB using the following commands, and then normalised for unity gain
-// shape2 = 'Inverse-sinc Lowpass';
-// d2 = fdesign.interpolator(1, shape2);  
-// h2 = design(d2, 'SystemObject', true);
-static q15_t LOWPASS_FILTER[] = {1294, -2251, 4312, -8402, 20999, 20999, -8402, 4312, -2251, 1294};
-const uint16_t LOWPASS_FILTER_LEN = 10U;
+static q15_t LOWPASS_FILTER[] = {124, -188, -682, 1262, 556, -621, -1912, -911, 2058, 3855, 1234, -4592, -7692, -2799,
+                                8556, 18133, 18133, 8556, -2799, -7692, -4592, 1234, 3855, 2058, -911, -1912, -621,
+                                556, 1262, -682, -188, 124};
+const uint16_t LOWPASS_FILTER_LEN = 32U;
 
 const q15_t P25_LEVELA =  1260;
 const q15_t P25_LEVELB =   420;
@@ -56,7 +54,7 @@ m_poPtr(0U),
 m_txDelay(240U)       // 200ms
 {
   ::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
-  ::memset(m_lpState,  0x00U, 70U * sizeof(q15_t));
+  ::memset(m_lpState,  0x00U, 60U * sizeof(q15_t));
 
   m_modFilter.L           = P25_RADIO_SYMBOL_LENGTH;
   m_modFilter.phaseLength = RC_0_2_FILTER_PHASE_LEN;
diff --git a/P25TX.h b/P25TX.h
index 61f6a87..1d542f9 100644
--- a/P25TX.h
+++ b/P25TX.h
@@ -40,7 +40,7 @@ private:
   arm_fir_interpolate_instance_q15 m_modFilter;
   arm_fir_instance_q15             m_lpFilter;
   q15_t                            m_modState[16U];    // blockSize + phaseLength - 1, 4 + 9 - 1 plus some spare
-  q15_t                            m_lpState[70U];     // NoTaps + BlockSize - 1, 44 + 20 - 1 plus some spare
+  q15_t                            m_lpState[60U];     // NoTaps + BlockSize - 1, 32 + 20 - 1 plus some spare
   uint8_t                          m_poBuffer[1200U];
   uint16_t                         m_poLen;
   uint16_t                         m_poPtr;