diff --git a/SerialArduino.cpp b/SerialArduino.cpp
index 65f05c6..021bfbc 100644
--- a/SerialArduino.cpp
+++ b/SerialArduino.cpp
@@ -112,25 +112,5 @@ void CSerialPort::writeInt(uint8_t n, const uint8_t* data, uint16_t length, bool
   }
 }
 
-int CSerialPort::availableForWriteInt(uint8_t n)
-{
-  switch (n) {
-    case 1U:
-    #if defined(STM32_USART1_HOST) && defined(__STM32F1__)
-      return Serial1.availableForWrite();
-    #else
-      return Serial.availableForWrite();
-    #endif
-    case 3U:
-    #if defined(SERIAL_REPEATER) && defined(__STM32F1__)
-      return Serial2.availableForWrite();
-    #elif defined(SERIAL_REPEATER) && (defined(__MK20DX256__) || defined(__MK64FX512__) || defined(__MK66FX1M0__))
-      return Serial1.availableForWrite();
-    #endif
-    default:
-      return false;
-  }
-}
-
 #endif
 
diff --git a/SerialPort.cpp b/SerialPort.cpp
index 891aafa..9acfc52 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2013,2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2013,2015,2016 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2016, 2017 by Andy Uribe CA6JAU
  *
@@ -90,8 +90,7 @@ CSerialPort::CSerialPort() :
 m_buffer(),
 m_ptr(0U),
 m_len(0U),
-m_debug(false),
-m_repeat()
+m_debug(false)
 {
 }
 
@@ -537,11 +536,12 @@ void CSerialPort::process()
             }
             break;
 
+#if defined(SERIAL_REPEATER)
           case MMDVM_SERIAL:
-            for (uint8_t i = 3U; i < m_len; i++)
-              m_repeat.put(m_buffer[i]);
+            writeInt(3U, m_buffer + 3U, m_len - 3U);
             break;
-            
+#endif
+
           default:
             // Handle this, send a NAK back
             sendNAK(1U);
@@ -555,20 +555,7 @@ void CSerialPort::process()
   }
 
 #if defined(SERIAL_REPEATER)
-  // Write any outgoing serial data
-  uint16_t space = m_repeat.getData();
-  if (space > 0U) {
-    int avail = availableForWriteInt(3U);
-    if (avail < space)
-      space = avail;
-
-    for (uint16_t i = 0U; i < space; i++) {
-      uint8_t c = m_repeat.get();
-      writeInt(3U, &c, 1U);
-    }
-  }
-
-  // Read any incoming serial data
+  // Drain any incoming serial data
   while (availableInt(3U))
     readInt(3U);
 #endif
diff --git a/SerialPort.h b/SerialPort.h
index 7cf3300..920b220 100644
--- a/SerialPort.h
+++ b/SerialPort.h
@@ -20,7 +20,6 @@
 #define  SERIALPORT_H
 
 #include "Globals.h"
-#include "SerialRB.h"
 
 class CSerialPort {
 public:
@@ -56,7 +55,6 @@ private:
   uint8_t m_ptr;
   uint8_t m_len;
   bool    m_debug;
-  CSerialRB m_repeat;
 
   void    sendACK();
   void    sendNAK(uint8_t err);
@@ -70,7 +68,6 @@ private:
   // Hardware versions
   void    beginInt(uint8_t n, int speed);
   int     availableInt(uint8_t n);
-  int     availableForWriteInt(uint8_t n);
   uint8_t readInt(uint8_t n);
   void    writeInt(uint8_t n, const uint8_t* data, uint16_t length, bool flush = false);
 };
diff --git a/SerialSTM.cpp b/SerialSTM.cpp
index 7e1f639..d8dd0d7 100644
--- a/SerialSTM.cpp
+++ b/SerialSTM.cpp
@@ -41,8 +41,8 @@ USART2 - TXD PA2  - RXD PA3
 
 */
 
-#define TX_SERIAL_FIFO_SIZE 256U
-#define RX_SERIAL_FIFO_SIZE 256U
+#define TX_SERIAL_FIFO_SIZE 512U
+#define RX_SERIAL_FIFO_SIZE 512U
 
 #if defined(STM32_USART1_HOST)
 
@@ -208,7 +208,7 @@ void InitUSART1(int speed)
   RXSerialfifoinit1();
 }
 
-uint8_t AvailUSART1()
+uint8_t AvailUSART1(void)
 {
   if (RXSerialfifolevel1() > 0U)
     return 1U;
@@ -216,12 +216,7 @@ uint8_t AvailUSART1()
     return 0U;
 }
 
-int AvailForWriteUSART1()
-{
-  return TX_SERIAL_FIFO_SIZE - TXSerialfifolevel1();
-}
-
-uint8_t ReadUSART1()
+uint8_t ReadUSART1(void)
 {
   uint8_t data_c = RXSerialfifo1[RXSerialfifotail1];
 
@@ -408,7 +403,7 @@ void InitUSART2(int speed)
   RXSerialfifoinit2();
 }
 
-uint8_t AvailUSART2()
+uint8_t AvailUSART2(void)
 {
   if (RXSerialfifolevel2() > 0U)
     return 1U;
@@ -416,12 +411,7 @@ uint8_t AvailUSART2()
     return 0U;
 }
 
-int AvailForWriteUSART2()
-{
-  return TX_SERIAL_FIFO_SIZE - TXSerialfifolevel2();
-}
-
-uint8_t ReadUSART2()
+uint8_t ReadUSART2(void)
 {
   uint8_t data_c = RXSerialfifo2[RXSerialfifotail2];
 
@@ -478,23 +468,7 @@ int CSerialPort::availableInt(uint8_t n)
       return AvailUSART2();
     #endif
     default:
-      return 0;
-  }
-}
-
-int CSerialPort::availableForWriteInt(uint8_t n)
-{
-  switch (n) {
-    case 1U:
-    #if defined(STM32_USART1_HOST)
-      return AvailForWriteUSART1();
-    #endif
-    #if defined(SERIAL_REPEATER)
-    case 3U:
-      return AvailForWriteUSART2();
-    #endif
-    default:
-      return 0;
+      return false;
   }
 }