diff --git a/AX25Demodulator.cpp b/AX25Demodulator.cpp
index 276a8e6..eb0022d 100644
--- a/AX25Demodulator.cpp
+++ b/AX25Demodulator.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25Demodulator.h"
 #include "AX25Defines.h"
@@ -312,3 +315,5 @@ float32_t CAX25Demodulator::iir(float32_t input)
   return result;
 }
 
+#endif
+
diff --git a/AX25Demodulator.h b/AX25Demodulator.h
index d1baff8..dacd5ab 100644
--- a/AX25Demodulator.h
+++ b/AX25Demodulator.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_AX25)
+
 #if !defined(AX25Demodulator_H)
 #define  AX25Demodulator_H
 
-#include "Config.h"
-
 #include "AX25Frame.h"
 #include "AX25Twist.h"
 
@@ -71,3 +73,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/AX25Frame.cpp b/AX25Frame.cpp
index d666f33..1f54571 100644
--- a/AX25Frame.cpp
+++ b/AX25Frame.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25Frame.h"
 
@@ -120,3 +123,5 @@ void CAX25Frame::addCRC()
   m_data[m_length++] = crc8[1U];
 }
 
+#endif
+
diff --git a/AX25Frame.h b/AX25Frame.h
index 7f79c28..c83bffa 100644
--- a/AX25Frame.h
+++ b/AX25Frame.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_AX25)
+
 #if !defined(AX25Frame_H)
 #define  AX25Frame_H
 
-#include "Config.h"
-
 const uint16_t AX25_MAX_PACKET_LEN = 300U;
 
 class CAX25Frame {
@@ -41,3 +43,5 @@ public:
 
 #endif
 
+#endif
+
diff --git a/AX25RX.cpp b/AX25RX.cpp
index 093316b..eddac27 100644
--- a/AX25RX.cpp
+++ b/AX25RX.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25RX.h"
 
@@ -203,3 +206,6 @@ uint8_t CAX25RX::rand()
 
   return uint8_t(m_c);             //low order bits of other variables
 }
+
+#endif
+
diff --git a/AX25RX.h b/AX25RX.h
index cbafe91..61e50fd 100644
--- a/AX25RX.h
+++ b/AX25RX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_AX25)
+
 #if !defined(AX25RX_H)
 #define  AX25RX_H
 
-#include "Config.h"
-
 #include "AX25Demodulator.h"
 
 class CAX25RX {
@@ -57,3 +59,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/AX25TX.cpp b/AX25TX.cpp
index a5b6c95..a844c25 100644
--- a/AX25TX.cpp
+++ b/AX25TX.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25TX.h"
 
@@ -184,3 +187,5 @@ bool CAX25TX::NRZI(bool b)
     return m_nrzi;
 }
 
+#endif
+
diff --git a/AX25TX.h b/AX25TX.h
index 0a41757..f2e02f8 100644
--- a/AX25TX.h
+++ b/AX25TX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_AX25)
+
 #if !defined(AX25TX_H)
 #define  AX25TX_H
 
-#include "Config.h"
-
 class CAX25TX {
 public:
   CAX25TX();
@@ -47,3 +49,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/AX25Twist.cpp b/AX25Twist.cpp
index bf0c534..988a07d 100644
--- a/AX25Twist.cpp
+++ b/AX25Twist.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25Twist.h"
 
@@ -309,3 +312,5 @@ void CAX25Twist::setTwist(int8_t n)
   m_filter.pCoeffs = coeffs[twist];
 }
 
+#endif
+
diff --git a/AX25Twist.h b/AX25Twist.h
index ea1c6de..e127e7a 100644
--- a/AX25Twist.h
+++ b/AX25Twist.h
@@ -16,11 +16,12 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
-#if !defined(AX25Twist_H)
-#define  AX25Twist_H
-
 #include "Config.h"
 
+#if defined(MODE_AX25)
+
+#if !defined(AX25Twist_H)
+#define  AX25Twist_H
 
 class CAX25Twist {
 public:
@@ -37,3 +38,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/CalDMR.cpp b/CalDMR.cpp
index 949a8e9..3b2e884 100644
--- a/CalDMR.cpp
+++ b/CalDMR.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "CalDMR.h"
 
@@ -221,3 +224,5 @@ uint8_t CCalDMR::write(const uint8_t* data, uint16_t length)
   return 0U;
 }
 
+#endif
+
diff --git a/CalDMR.h b/CalDMR.h
index 9ba5f2c..3424db7 100644
--- a/CalDMR.h
+++ b/CalDMR.h
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(CALDMR_H)
 #define  CALDMR_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 enum DMRCAL1K {
@@ -53,3 +56,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/CalFM.cpp b/CalFM.cpp
index 22c3044..54c4b81 100644
--- a/CalFM.cpp
+++ b/CalFM.cpp
@@ -19,6 +19,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "CalFM.h"
 
@@ -125,3 +128,6 @@ uint8_t CCalFM::write(const uint8_t* data, uint16_t length)
 
   return 0U;
 }
+
+#endif
+
diff --git a/CalFM.h b/CalFM.h
index 9665bcc..a810e58 100644
--- a/CalFM.h
+++ b/CalFM.h
@@ -18,11 +18,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(CALFM_H)
 #define  CALFM_H
 
-#include "Config.h"
-
 class CCalFM {
 public:
   CCalFM();
@@ -49,3 +51,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/CalNXDN.cpp b/CalNXDN.cpp
index 3e46f3e..5722954 100644
--- a/CalNXDN.cpp
+++ b/CalNXDN.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #include "Globals.h"
 #include "CalNXDN.h"
 
@@ -93,3 +96,5 @@ uint8_t CCalNXDN::write(const uint8_t* data, uint16_t length)
   return 0U;
 }
 
+#endif
+
diff --git a/CalNXDN.h b/CalNXDN.h
index cad88a4..08ea55b 100644
--- a/CalNXDN.h
+++ b/CalNXDN.h
@@ -17,11 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #if !defined(CALNXDN_H)
 #define  CALNXDN_H
 
-#include "Config.h"
-
 enum NXDNCAL1K {
   NXDNCAL1K_IDLE,
   NXDNCAL1K_TX
@@ -43,3 +45,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/CalP25.cpp b/CalP25.cpp
index 6f3d4c0..354339e 100644
--- a/CalP25.cpp
+++ b/CalP25.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_P25)
+
 #include "Globals.h"
 #include "CalP25.h"
 
@@ -96,3 +99,5 @@ uint8_t CCalP25::write(const uint8_t* data, uint16_t length)
   return 0U;
 }
 
+#endif
+
diff --git a/CalP25.h b/CalP25.h
index 75bfe0d..00ff925 100644
--- a/CalP25.h
+++ b/CalP25.h
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_P25)
+
 #if !defined(CALP25_H)
 #define  CALP25_H
 
-#include "Config.h"
 #include "P25Defines.h"
 
 enum P25CAL1K {
@@ -44,3 +47,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/Config.h b/Config.h
index 8bf2f35..29cb477 100644
--- a/Config.h
+++ b/Config.h
@@ -24,14 +24,14 @@
 
 // Enable D-Star support, the D-Star correlator improves the sensitivity of D-Star enormously but uses quite a lot
 // of processing power.
-// #define MODE_DSTAR
+#define MODE_DSTAR
 #define USE_DSTAR_CORRELATOR
 
 // Enable DMR support
 #define MODE_DMR
 
 // Enable System Fusion support
-// #define MODE_YSF
+#define MODE_YSF
 
 // Enable P25 phase 1 support, the boxcar filter sometimes improves the performance of P25 receive on some systems.
 #define MODE_P25
@@ -41,15 +41,15 @@
 #define MODE_NXDN
 
 // Enable M17 support
-// #define MODE_M17
+#define MODE_M17
 
 // Enable POCSAG support
-// #define MODE_POCSAG
+#define MODE_POCSAG
 
 // Enable FM support
 #define MODE_FM
 
-// Enable AX.25 support
+// Enable AX.25 support, this is only enabled if MODE_FM is also defined.
 #define MODE_AX25
 
 // Allow for the use of high quality external clock oscillators
diff --git a/DMRDMORX.cpp b/DMRDMORX.cpp
index 2c3bdef..60de367 100644
--- a/DMRDMORX.cpp
+++ b/DMRDMORX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRDMORX.h"
 #include "DMRSlotType.h"
@@ -423,3 +426,6 @@ void CDMRDMORX::writeRSSIData(uint8_t* frame)
   serial.writeDMRData(true, frame, DMR_FRAME_LENGTH_BYTES + 1U);
 #endif
 }
+
+#endif
+
diff --git a/DMRDMORX.h b/DMRDMORX.h
index 6952fd4..2a2fe3d 100644
--- a/DMRDMORX.h
+++ b/DMRDMORX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,10 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRDMORX_H)
 #define  DMRDMORX_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 const uint16_t DMO_BUFFER_LENGTH_SAMPLES = 1440U;   // 60ms at 24 kHz
@@ -67,3 +70,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/DMRDMOTX.cpp b/DMRDMOTX.cpp
index 4932aaf..1a560fb 100644
--- a/DMRDMOTX.cpp
+++ b/DMRDMOTX.cpp
@@ -19,6 +19,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRSlotType.h"
 
@@ -161,3 +164,5 @@ void CDMRDMOTX::setTXDelay(uint8_t delay)
     m_txDelay = 1200U;
 }
 
+#endif
+
diff --git a/DMRDMOTX.h b/DMRDMOTX.h
index 3ef53eb..1cccafb 100644
--- a/DMRDMOTX.h
+++ b/DMRDMOTX.h
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRDMOTX_H)
 #define  DMRDMOTX_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 #include "RingBuffer.h"
@@ -51,3 +54,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/DMRIdleRX.cpp b/DMRIdleRX.cpp
index 3d2b5f5..66fd752 100644
--- a/DMRIdleRX.cpp
+++ b/DMRIdleRX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRIdleRX.h"
 #include "DMRSlotType.h"
@@ -209,3 +212,6 @@ void CDMRIdleRX::setColorCode(uint8_t colorCode)
 {
   m_colorCode = colorCode;
 }
+
+#endif
+
diff --git a/DMRIdleRX.h b/DMRIdleRX.h
index 922ea85..e081006 100644
--- a/DMRIdleRX.h
+++ b/DMRIdleRX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,10 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRIDLERX_H)
 #define  DMRIDLERX_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 class CDMRIdleRX {
@@ -49,3 +52,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/DMRRX.cpp b/DMRRX.cpp
index 64320e8..a42ab0c 100644
--- a/DMRRX.cpp
+++ b/DMRRX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRRX.h"
 
@@ -68,3 +71,5 @@ void CDMRRX::reset()
   m_slot2RX.reset();
 }
 
+#endif
+
diff --git a/DMRRX.h b/DMRRX.h
index 6c99cd0..1d2c612 100644
--- a/DMRRX.h
+++ b/DMRRX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,10 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRRX_H)
 #define  DMRRX_H
 
-#include "Config.h"
 #include "DMRSlotRX.h"
 
 class CDMRRX {
@@ -40,3 +43,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/DMRSlotRX.cpp b/DMRSlotRX.cpp
index 0d34560..1ecae07 100644
--- a/DMRSlotRX.cpp
+++ b/DMRSlotRX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRSlotRX.h"
 #include "DMRSlotType.h"
@@ -400,3 +403,6 @@ void CDMRSlotRX::writeRSSIData(uint8_t* frame)
   serial.writeDMRData(m_slot, frame, DMR_FRAME_LENGTH_BYTES + 1U);
 #endif
 }
+
+#endif
+
diff --git a/DMRSlotRX.h b/DMRSlotRX.h
index a47cc73..dade4d7 100644
--- a/DMRSlotRX.h
+++ b/DMRSlotRX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,10 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRSLOTRX_H)
 #define  DMRSLOTRX_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 enum DMRRX_STATE {
@@ -70,3 +73,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/DMRSlotType.cpp b/DMRSlotType.cpp
index 2d89a74..70edb3d 100644
--- a/DMRSlotType.cpp
+++ b/DMRSlotType.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRSlotType.h"
 
@@ -285,3 +288,5 @@ void CDMRSlotType::encode(uint8_t colorCode, uint8_t dataType, uint8_t* frame) c
   frame[20U] = (frame[20U] & 0x03U) | ((slotType[1U] << 6) & 0xC0U) | ((slotType[2U] >> 2) & 0x3CU);
 }
 
+#endif
+
diff --git a/DMRSlotType.h b/DMRSlotType.h
index 0052467..ea27df4 100644
--- a/DMRSlotType.h
+++ b/DMRSlotType.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,6 +16,10 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRSLOTTYPE_H)
 #define  DMRSLOTTYPE_H
 
@@ -35,3 +39,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/DMRTX.cpp b/DMRTX.cpp
index 3342639..594ccff 100644
--- a/DMRTX.cpp
+++ b/DMRTX.cpp
@@ -19,6 +19,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DMR)
+
 #include "Globals.h"
 #include "DMRSlotType.h"
 
@@ -414,3 +417,6 @@ uint32_t CDMRTX::getFrameCount()
 {
   return m_frameCount;
 }
+
+#endif
+
diff --git a/DMRTX.h b/DMRTX.h
index 292b01b..8555f13 100644
--- a/DMRTX.h
+++ b/DMRTX.h
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_DMR)
+
 #if !defined(DMRTX_H)
 #define  DMRTX_H
 
-#include "Config.h"
 #include "DMRDefines.h"
 
 #include "RingBuffer.h"
@@ -83,3 +86,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/FM.cpp b/FM.cpp
index 787206b..6b35dd4 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FM.h"
 
@@ -1054,3 +1057,6 @@ void CFM::insertSilence(uint16_t ms)
   for (uint32_t i = 0U; i < nSamples; i++)
     m_outputRFRB.put(0);
 }
+
+#endif
+
diff --git a/FM.h b/FM.h
index 2ead4a3..4c25b6b 100644
--- a/FM.h
+++ b/FM.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FM_H)
 #define  FM_H
 
-#include "Config.h"
-
 #include "FMBlanking.h"
 #include "FMCTCSSRX.h"
 #include "FMCTCSSTX.h"
@@ -143,3 +145,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMBlanking.cpp b/FMBlanking.cpp
index 4d8af80..bf28bc3 100644
--- a/FMBlanking.cpp
+++ b/FMBlanking.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMBlanking.h"
 
@@ -80,3 +83,6 @@ q15_t CFMBlanking::process(q15_t sample)
 
   return sample;
 }
+
+#endif
+
diff --git a/FMBlanking.h b/FMBlanking.h
index 2aacd4c..f0a8522 100644
--- a/FMBlanking.h
+++ b/FMBlanking.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMBlanking_H)
 #define  FMBlanking_H
 
-#include "Config.h"
-
 class CFMBlanking {
 public:
   CFMBlanking();
@@ -39,3 +41,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMCTCSSRX.cpp b/FMCTCSSRX.cpp
index b2ecb43..cf31270 100644
--- a/FMCTCSSRX.cpp
+++ b/FMCTCSSRX.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMCTCSSRX.h"
 
@@ -173,3 +176,6 @@ void CFMCTCSSRX::reset()
   m_state = false;
   m_count = 0U;
 }
+
+#endif
+
diff --git a/FMCTCSSRX.h b/FMCTCSSRX.h
index 0980c4c..f9b1c04 100644
--- a/FMCTCSSRX.h
+++ b/FMCTCSSRX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMCTCSSRX_H)
 #define  FMCTCSSRX_H
 
-#include "Config.h"
-
 class CFMCTCSSRX {
 public:
   CFMCTCSSRX();
@@ -42,3 +44,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMCTCSSTX.cpp b/FMCTCSSTX.cpp
index a2253a6..7061fb7 100644
--- a/FMCTCSSTX.cpp
+++ b/FMCTCSSTX.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMCTCSSTX.h"
 
@@ -126,3 +129,6 @@ q15_t CFMCTCSSTX::getAudio(bool reverse)
   else
     return sample;
 }
+
+#endif
+
diff --git a/FMCTCSSTX.h b/FMCTCSSTX.h
index b6f9b12..8225f00 100644
--- a/FMCTCSSTX.h
+++ b/FMCTCSSTX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMCTCSSTX_H)
 #define  FMCTCSSTX_H
 
-#include "Config.h"
-
 class CFMCTCSSTX {
 public:
   CFMCTCSSTX();
@@ -36,3 +38,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMDirectForm1.h b/FMDirectForm1.h
index b3dccb7..912f719 100644
--- a/FMDirectForm1.h
+++ b/FMDirectForm1.h
@@ -29,6 +29,10 @@ THE SOFTWARE.
 
 // based on https://raw.githubusercontent.com/berndporr/iir_fixed_point/master/DirectFormI.h
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #include <cstdint>
 
 #ifndef DIRECTFORMI_H_
@@ -108,4 +112,7 @@ private:
 	q31_t c_a1,c_a2; // IIR
 };
 
-#endif /* DIRECTFORMI_H */
\ No newline at end of file
+#endif /* DIRECTFORMI_H */
+
+#endif
+
diff --git a/FMDownSampler.cpp b/FMDownSampler.cpp
index 8ed95bc..47fb120 100644
--- a/FMDownSampler.cpp
+++ b/FMDownSampler.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "FMDownSampler.h"
 
 CFMDownSampler::CFMDownSampler(uint16_t length) :
@@ -72,3 +75,6 @@ void CFMDownSampler::reset()
 {
   m_sampleIndex = 0U;
 }
+
+#endif
+
diff --git a/FMDownSampler.h b/FMDownSampler.h
index 9f26acf..fd255b6 100644
--- a/FMDownSampler.h
+++ b/FMDownSampler.h
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMDOWNSAMPLER_H)
 #define FMDOWNSAMPLER_H
 
-#include "Config.h"
 #include "RingBuffer.h"
 #include "FMSamplePairPack.h"
 
@@ -45,3 +48,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/FMKeyer.cpp b/FMKeyer.cpp
index 851441e..8ea4794 100644
--- a/FMKeyer.cpp
+++ b/FMKeyer.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMKeyer.h"
 
@@ -214,3 +217,6 @@ bool CFMKeyer::isRunning() const
 {
   return m_poPos > 0U || m_dotPos > 0U || m_audioPos > 0U;
 }
+
+#endif
+
diff --git a/FMKeyer.h b/FMKeyer.h
index 5b7bef5..546552a 100644
--- a/FMKeyer.h
+++ b/FMKeyer.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMKeyer_H)
 #define  FMKeyer_H
 
-#include "Config.h"
-
 class CFMKeyer {
 public:
   CFMKeyer();
@@ -52,3 +54,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMNoiseSquelch.cpp b/FMNoiseSquelch.cpp
index 6becf99..bd01fe9 100644
--- a/FMNoiseSquelch.cpp
+++ b/FMNoiseSquelch.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMNoiseSquelch.h"
 
@@ -125,3 +128,6 @@ void CFMNoiseSquelch::reset()
   m_state = false;
   m_count = 0U;
 }
+
+#endif
+
diff --git a/FMNoiseSquelch.h b/FMNoiseSquelch.h
index c4f5a62..52cce41 100644
--- a/FMNoiseSquelch.h
+++ b/FMNoiseSquelch.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMNOISESQUELCH_H)
 #define  FMNOISESQUELCH_H
 
-#include "Config.h"
-
 class CFMNoiseSquelch {
 public:
   CFMNoiseSquelch();
@@ -43,3 +45,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMSamplePairPack.h b/FMSamplePairPack.h
index 1301173..d9cf302 100644
--- a/FMSamplePairPack.h
+++ b/FMSamplePairPack.h
@@ -17,6 +17,10 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(TSAMPLEPACK_H)
 #define TSAMPLEPACK_H
 
@@ -26,4 +30,7 @@ struct TSamplePairPack {
   uint8_t byte2;
 };
 
-#endif
\ No newline at end of file
+#endif
+
+#endif
+
diff --git a/FMTimeout.cpp b/FMTimeout.cpp
index 771e840..04a7dbd 100644
--- a/FMTimeout.cpp
+++ b/FMTimeout.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMTimeout.h"
 
@@ -72,3 +75,6 @@ void CFMTimeout::stop()
 {
   m_running = false;
 }
+
+#endif
+
diff --git a/FMTimeout.h b/FMTimeout.h
index b2f747c..c8a4293 100644
--- a/FMTimeout.h
+++ b/FMTimeout.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMTimeout_H)
 #define  FMTimeout_H
 
-#include "Config.h"
-
 class CFMTimeout {
 public:
   CFMTimeout();
@@ -40,3 +42,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMTimer.cpp b/FMTimer.cpp
index 826bc13..1757d16 100644
--- a/FMTimer.cpp
+++ b/FMTimer.cpp
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "Globals.h"
 #include "FMTimer.h"
 
@@ -68,3 +71,6 @@ bool CFMTimer::hasExpired() const
 
   return false;
 }
+
+#endif
+
diff --git a/FMTimer.h b/FMTimer.h
index 00dc343..a8a3356 100644
--- a/FMTimer.h
+++ b/FMTimer.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMTimer_H)
 #define  FMTimer_H
 
-#include "Config.h"
-
 class CFMTimer {
 public:
   CFMTimer();
@@ -45,3 +47,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/FMUpSampler.cpp b/FMUpSampler.cpp
index 80cba37..d177f59 100644
--- a/FMUpSampler.cpp
+++ b/FMUpSampler.cpp
@@ -17,6 +17,10 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #include "FMUpSampler.h"
 
 const uint32_t FM_UPSAMPLE_MASK = 0x00000FFFU;
@@ -94,4 +98,7 @@ uint16_t CFMUpSampler::getSpace() const
 {
   //return available space in bytes
   return m_samples.getSpace() * sizeof(TSamplePairPack);
-}
\ No newline at end of file
+}
+
+#endif
+
diff --git a/FMUpSampler.h b/FMUpSampler.h
index b76982f..d5867a9 100644
--- a/FMUpSampler.h
+++ b/FMUpSampler.h
@@ -18,10 +18,13 @@
  */
 
 
+#include "Config.h"
+
+#if defined(MODE_FM)
+
 #if !defined(FMUPSAMPLER_H)
 #define FMUPSAMPLER_H
 
-#include "Config.h"
 #include "RingBuffer.h"
 #include "FMSamplePairPack.h"
 
@@ -45,4 +48,7 @@ private:
   bool m_running;
 };
 
-#endif
\ No newline at end of file
+#endif
+
+#endif
+
diff --git a/IO.cpp b/IO.cpp
index 70dc72b..6e7fd7f 100644
--- a/IO.cpp
+++ b/IO.cpp
@@ -22,9 +22,11 @@
 #include "Globals.h"
 #include "IO.h"
 
+#if defined(USE_DCBLOCKER)
 // Generated using [b, a] = butter(1, 0.001) in MATLAB
 static q31_t   DC_FILTER[] = {3367972, 0, 3367972, 0, 2140747704, 0}; // {b0, 0, b1, b2, -a1, -a2}
 const uint32_t DC_FILTER_STAGES = 1U; // One Biquad stage
+#endif
 
 #if defined(MODE_DMR) || defined(MODE_YSF)
 // Generated using rcosdesign(0.2, 8, 5, 'sqrt') in MATLAB
@@ -42,6 +44,7 @@ static q15_t RRC_0_5_FILTER[] = {-147, -88, 72, 220, 223, 46, -197, -285, -79, 3
 const uint16_t RRC_0_5_FILTER_LEN = 42U;
 #endif
 
+#if defined(MODE_NXDN)
 // Generated using rcosdesign(0.2, 8, 10, 'sqrt') in MATLAB
 static q15_t NXDN_0_2_FILTER[] = {284, 198, 73, -78, -240, -393, -517, -590, -599, -533, -391, -181, 79, 364, 643, 880, 1041, 1097, 1026, 819,
                                   483, 39, -477, -1016, -1516, -1915, -2150, -2164, -1914, -1375, -545, 557, 1886, 3376, 4946, 6502, 7946, 9184,
@@ -53,6 +56,7 @@ const uint16_t NXDN_0_2_FILTER_LEN = 82U;
 static q15_t NXDN_ISINC_FILTER[] = {790, -1085, -1073, -553, 747, 2341, 3156, 2152, -893, -4915, -7834, -7536, -3102, 4441, 12354, 17394, 17394,
                                    12354, 4441, -3102, -7536, -7834, -4915, -893, 2152, 3156, 2341, 747, -553, -1073, -1085, 790};
 const uint16_t NXDN_ISINC_FILTER_LEN = 32U;
+#endif
 
 #if defined(MODE_DSTAR)
 // Generated using gaussfir(0.5, 4, 5) in MATLAB
@@ -60,9 +64,11 @@ static q15_t   GAUSSIAN_0_5_FILTER[] = {8, 104, 760, 3158, 7421, 9866, 7421, 315
 const uint16_t GAUSSIAN_0_5_FILTER_LEN = 12U;
 #endif
 
+#if defined(MODE_P25)
 // One symbol boxcar filter
 static q15_t   BOXCAR_FILTER[] = {12000, 12000, 12000, 12000, 12000, 0};
 const uint16_t BOXCAR_FILTER_LEN = 6U;
+#endif
 
 const uint16_t DC_OFFSET = 2048U;
 
@@ -71,26 +77,32 @@ m_started(false),
 m_rxBuffer(RX_RINGBUFFER_SIZE),
 m_txBuffer(TX_RINGBUFFER_SIZE),
 m_rssiBuffer(RX_RINGBUFFER_SIZE),
+#if defined(USE_DCBLOCKER)
 m_dcFilter(),
 m_dcState(),
+#endif
 #if defined(MODE_DSTAR)
 m_gaussianFilter(),
 m_gaussianState(),
 #endif
-m_boxcarFilter(),
-m_nxdnFilter(),
-m_nxdnISincFilter(),
 #if defined(MODE_DMR) || defined(MODE_YSF)
 m_rrc02Filter(),
 m_rrc02State(),
 #endif
+#if defined(MODE_P25)
+m_boxcarFilter(),
+m_boxcarState(),
+#endif
+#if defined(MODE_NXDN)
+m_nxdnFilter(),
+m_nxdnISincFilter(),
+m_nxdnState(),
+m_nxdnISincState(),
+#endif
 #if defined(MODE_M17)
 m_rrc05Filter(),
 m_rrc05State(),
 #endif
-m_boxcarState(),
-m_nxdnState(),
-m_nxdnISincState(),
 m_pttInvert(false),
 m_rxLevel(128 * 128),
 m_cwIdTXLevel(128 * 128),
@@ -114,6 +126,14 @@ m_dacOverflow(0U),
 m_watchdog(0U),
 m_lockout(false)
 {
+#if defined(USE_DCBLOCKER)
+  ::memset(m_dcState,       0x00U,   4U * sizeof(q31_t));
+  m_dcFilter.numStages = DC_FILTER_STAGES;
+  m_dcFilter.pState    = m_dcState;
+  m_dcFilter.pCoeffs   = DC_FILTER;
+  m_dcFilter.postShift = 0;
+#endif
+
 #if defined(MODE_DSTAR)
   ::memset(m_gaussianState, 0x00U, 40U * sizeof(q15_t));
   m_gaussianFilter.numTaps = GAUSSIAN_0_5_FILTER_LEN;
@@ -121,16 +141,6 @@ m_lockout(false)
   m_gaussianFilter.pCoeffs = GAUSSIAN_0_5_FILTER;
 #endif
 
-  ::memset(m_boxcarState,   0x00U,  30U * sizeof(q15_t));
-  ::memset(m_nxdnState,     0x00U, 110U * sizeof(q15_t));
-  ::memset(m_nxdnISincState, 0x00U, 60U * sizeof(q15_t));
-  ::memset(m_dcState,       0x00U,   4U * sizeof(q31_t));
-
-  m_dcFilter.numStages = DC_FILTER_STAGES;
-  m_dcFilter.pState    = m_dcState;
-  m_dcFilter.pCoeffs   = DC_FILTER;
-  m_dcFilter.postShift = 0;
-
 #if defined(MODE_DMR) || defined(MODE_YSF)
   ::memset(m_rrc02State, 0x00U, 70U * sizeof(q15_t));
   m_rrc02Filter.numTaps = RRC_0_2_FILTER_LEN;
@@ -138,17 +148,17 @@ m_lockout(false)
   m_rrc02Filter.pCoeffs = RRC_0_2_FILTER;
 #endif
 
-#if defined(MODE_M17)
-  ::memset(m_rrc05State, 0x00U, 70U * sizeof(q15_t));
-  m_rrc05Filter.numTaps = RRC_0_5_FILTER_LEN;
-  m_rrc05Filter.pState  = m_rrc05State;
-  m_rrc05Filter.pCoeffs = RRC_0_5_FILTER;
-#endif
-
+#if defined(MODE_P25)
+  ::memset(m_boxcarState, 0x00U, 30U * sizeof(q15_t));
   m_boxcarFilter.numTaps = BOXCAR_FILTER_LEN;
   m_boxcarFilter.pState  = m_boxcarState;
   m_boxcarFilter.pCoeffs = BOXCAR_FILTER;
-  
+#endif
+
+#if defined(MODE_NXDN)  
+  ::memset(m_nxdnState,      0x00U, 110U * sizeof(q15_t));
+  ::memset(m_nxdnISincState, 0x00U, 60U * sizeof(q15_t));
+
   m_nxdnFilter.numTaps = NXDN_0_2_FILTER_LEN;
   m_nxdnFilter.pState  = m_nxdnState;
   m_nxdnFilter.pCoeffs = NXDN_0_2_FILTER;
@@ -156,6 +166,14 @@ m_lockout(false)
   m_nxdnISincFilter.numTaps = NXDN_ISINC_FILTER_LEN;
   m_nxdnISincFilter.pState  = m_nxdnISincState;
   m_nxdnISincFilter.pCoeffs = NXDN_ISINC_FILTER;
+#endif
+
+#if defined(MODE_M17)
+  ::memset(m_rrc05State, 0x00U, 70U * sizeof(q15_t));
+  m_rrc05Filter.numTaps = RRC_0_5_FILTER_LEN;
+  m_rrc05Filter.pState  = m_rrc05State;
+  m_rrc05Filter.pCoeffs = RRC_0_5_FILTER;
+#endif
 
   initInt();
   
@@ -292,8 +310,10 @@ void CIO::process()
     // Two seconds timeout
     if (m_watchdog >= 48000U) {
       if (m_modemState == STATE_DSTAR || m_modemState == STATE_DMR || m_modemState == STATE_YSF || m_modemState == STATE_P25 || m_modemState == STATE_NXDN || m_modemState == STATE_M17 || m_modemState == STATE_POCSAG) {
+#if defined(MODE_DMR)
         if (m_modemState == STATE_DMR && m_tx)
           dmrTX.setStart(false);
+#endif
         setMode(STATE_IDLE);
       }
 
@@ -383,6 +403,7 @@ void CIO::process()
       }
 #endif
 
+#if defined(MODE_P25)
       if (m_p25Enable) {
         q15_t P25Vals[RX_BLOCK_SIZE];
 #if defined(USE_DCBLOCKER)
@@ -392,7 +413,9 @@ void CIO::process()
 #endif
         p25RX.samples(P25Vals, rssi, RX_BLOCK_SIZE);
       }
+#endif
 
+#if defined(MODE_NXDN)
       if (m_nxdnEnable) {
         q15_t NXDNValsTmp[RX_BLOCK_SIZE];
 #if defined(USE_DCBLOCKER)
@@ -405,7 +428,9 @@ void CIO::process()
 
         nxdnRX.samples(NXDNVals, rssi, RX_BLOCK_SIZE);
       }
+#endif
 
+#if defined(MODE_DMR)
       if (m_dmrEnable) {
         q15_t DMRVals[RX_BLOCK_SIZE];
         ::arm_fir_fast_q15(&m_rrc02Filter, samples, DMRVals, RX_BLOCK_SIZE);
@@ -415,6 +440,7 @@ void CIO::process()
         else
           dmrDMORX.samples(DMRVals, rssi, RX_BLOCK_SIZE);
       }
+#endif
 
 #if defined(MODE_YSF)
       if (m_ysfEnable) {
@@ -440,6 +466,7 @@ void CIO::process()
       }
 #endif
 
+#if defined(MODE_FM)
       if (m_fmEnable) {
         bool cos = getCOSInt();
 #if defined(USE_DCBLOCKER)
@@ -448,7 +475,9 @@ void CIO::process()
         fm.samples(cos, samples, RX_BLOCK_SIZE);
 #endif
       }
+#endif
 
+#if defined(MODE_FM) && defined(MODE_AX25)
       if (m_ax25Enable) {
 #if defined(USE_DCBLOCKER)
         ax25RX.samples(dcSamples, RX_BLOCK_SIZE);
@@ -456,6 +485,7 @@ void CIO::process()
         ax25RX.samples(samples, RX_BLOCK_SIZE);
 #endif
       }
+#endif
     }
 
 #if defined(MODE_DSTAR)
@@ -472,6 +502,7 @@ void CIO::process()
     }
 #endif
 
+#if defined(MODE_DMR)
     else if (m_modemState == STATE_DMR) {
       if (m_dmrEnable) {
         q15_t DMRVals[RX_BLOCK_SIZE];
@@ -488,6 +519,7 @@ void CIO::process()
         }
       }
     }
+#endif
 
 #if defined(MODE_YSF)
     else if (m_modemState == STATE_YSF) {
@@ -503,6 +535,7 @@ void CIO::process()
     }
 #endif
 
+#if defined(MODE_P25)
     else if (m_modemState == STATE_P25) {
       if (m_p25Enable) {
         q15_t P25Vals[RX_BLOCK_SIZE];
@@ -513,7 +546,11 @@ void CIO::process()
 #endif
         p25RX.samples(P25Vals, rssi, RX_BLOCK_SIZE);
       }
-    } else if (m_modemState == STATE_NXDN) {
+    }
+#endif
+
+#if defined(MODE_NXDN)
+    else if (m_modemState == STATE_NXDN) {
       if (m_nxdnEnable) {
         q15_t NXDNValsTmp[RX_BLOCK_SIZE];
 #if defined(USE_DCBLOCKER)
@@ -527,6 +564,7 @@ void CIO::process()
         nxdnRX.samples(NXDNVals, rssi, RX_BLOCK_SIZE);
       }
     }
+#endif
 
 #if defined(MODE_M17)
     else if (m_modemState == STATE_M17) {
@@ -542,18 +580,26 @@ void CIO::process()
     }
 #endif
 
+#if defined(MODE_FM)
     else if (m_modemState == STATE_FM) {
       bool cos = getCOSInt();
 #if defined(USE_DCBLOCKER)
       fm.samples(cos, dcSamples, RX_BLOCK_SIZE);
+
+#if defined(MODE_AX25)
       if (m_ax25Enable)
         ax25RX.samples(dcSamples, RX_BLOCK_SIZE);
+#endif
 #else
       fm.samples(cos, samples, RX_BLOCK_SIZE);
+
+#if defined(MODE_AX25)
       if (m_ax25Enable)
         ax25RX.samples(samples, RX_BLOCK_SIZE);
+#endif
 #endif
     }
+#endif
 
 #if defined(MODE_DSTAR)
     else if (m_modemState == STATE_DSTARCAL) {
diff --git a/IO.h b/IO.h
index 8361b93..09987ef 100644
--- a/IO.h
+++ b/IO.h
@@ -67,32 +67,38 @@ private:
   CRingBuffer<TSample>  m_txBuffer;
   CRingBuffer<uint16_t> m_rssiBuffer;
 
+#if defined(USE_DCBLOCKER)
   arm_biquad_casd_df1_inst_q31 m_dcFilter;
   q31_t                        m_dcState[4];
+#endif
 
 #if defined(MODE_DSTAR)
   arm_fir_instance_q15 m_gaussianFilter;
   q15_t                m_gaussianState[40U];      // NoTaps + BlockSize - 1, 12 + 20 - 1 plus some spare
 #endif
 
-  arm_fir_instance_q15 m_boxcarFilter;
-  arm_fir_instance_q15 m_nxdnFilter;
-  arm_fir_instance_q15 m_nxdnISincFilter;
-
 #if defined(MODE_DMR) || defined(MODE_YSF)
   arm_fir_instance_q15 m_rrc02Filter;
   q15_t                m_rrc02State[70U];         // NoTaps + BlockSize - 1, 42 + 20 - 1 plus some spare
 #endif
 
+#if defined(MODE_P25)
+  arm_fir_instance_q15 m_boxcarFilter;
+  q15_t                m_boxcarState[30U];        // NoTaps + BlockSize - 1,  6 + 20 - 1 plus some spare
+#endif
+
+#if defined(MODE_NXDN)
+  arm_fir_instance_q15 m_nxdnFilter;
+  arm_fir_instance_q15 m_nxdnISincFilter;
+  q15_t                m_nxdnState[110U];         // NoTaps + BlockSize - 1, 82 + 20 - 1 plus some spare
+  q15_t                m_nxdnISincState[60U];     // NoTaps + BlockSize - 1, 32 + 20 - 1 plus some spare
+#endif
+
 #if defined(MODE_M17)
   arm_fir_instance_q15 m_rrc05Filter;
   q15_t                m_rrc05State[70U];         // NoTaps + BlockSize - 1, 42 + 20 - 1 plus some spare
 #endif
 
-  q15_t                m_boxcarState[30U];        // NoTaps + BlockSize - 1,  6 + 20 - 1 plus some spare
-  q15_t                m_nxdnState[110U];         // NoTaps + BlockSize - 1, 82 + 20 - 1 plus some spare
-  q15_t                m_nxdnISincState[60U];     // NoTaps + BlockSize - 1, 32 + 20 - 1 plus some spare
-
   bool                 m_pttInvert;
   q15_t                m_rxLevel;
   q15_t                m_cwIdTXLevel;
diff --git a/NXDNRX.cpp b/NXDNRX.cpp
index e9bd41b..a607e25 100644
--- a/NXDNRX.cpp
+++ b/NXDNRX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2018,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #include "Globals.h"
 #include "NXDNRX.h"
 #include "Utils.h"
@@ -403,3 +406,5 @@ void CNXDNRX::writeRSSIData(uint8_t* data)
   m_rssiCount = 0U;
 }
 
+#endif
+
diff --git a/NXDNRX.h b/NXDNRX.h
index 1bff2ac..51d7df2 100644
--- a/NXDNRX.h
+++ b/NXDNRX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017,2018 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2018,2020 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -16,10 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #if !defined(NXDNRX_H)
 #define  NXDNRX_H
 
-#include "Config.h"
 #include "NXDNDefines.h"
 
 enum NXDNRX_STATE {
@@ -67,3 +70,5 @@ private:
 
 #endif
 
+#endif
+
diff --git a/NXDNTX.cpp b/NXDNTX.cpp
index 44c243e..c9cf1de 100644
--- a/NXDNTX.cpp
+++ b/NXDNTX.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #include "Globals.h"
 #include "NXDNTX.h"
 
@@ -200,3 +203,6 @@ void CNXDNTX::setParams(uint8_t txHang)
 {
   m_txHang = txHang * 600U;
 }
+
+#endif
+
diff --git a/NXDNTX.h b/NXDNTX.h
index 0efdf01..ae25db6 100644
--- a/NXDNTX.h
+++ b/NXDNTX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_NXDN)
+
 #if !defined(NXDNTX_H)
 #define  NXDNTX_H
 
-#include "Config.h"
-
 #include "RingBuffer.h"
 
 class CNXDNTX {
@@ -55,3 +57,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/P25RX.cpp b/P25RX.cpp
index d322db0..b8d0d51 100644
--- a/P25RX.cpp
+++ b/P25RX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2018 by Bryan Biedenkapp <gatekeep@gmail.com>
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_P25)
+
 #include "Globals.h"
 #include "P25RX.h"
 #include "Utils.h"
@@ -535,3 +538,6 @@ void CP25RX::writeRSSILdu(uint8_t* ldu)
   m_rssiAccum = 0U;
   m_rssiCount = 0U;
 }
+
+#endif
+
diff --git a/P25RX.h b/P25RX.h
index 7cab1dd..238fd5d 100644
--- a/P25RX.h
+++ b/P25RX.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2018 by Bryan Biedenkapp <gatekeep@gmail.com>
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -17,10 +17,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_P25)
+
 #if !defined(P25RX_H)
 #define  P25RX_H
 
-#include "Config.h"
 #include "P25Defines.h"
 
 enum P25RX_STATE {
@@ -72,3 +75,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/P25TX.cpp b/P25TX.cpp
index 23aef3d..76aba0c 100644
--- a/P25TX.cpp
+++ b/P25TX.cpp
@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_P25)
+
 #include "Globals.h"
 #include "P25TX.h"
 
@@ -198,3 +201,6 @@ void CP25TX::setParams(uint8_t txHang)
 {
   m_txHang = txHang * 1200U;
 }
+
+#endif
+
diff --git a/P25TX.h b/P25TX.h
index d6ac3cc..a49d0f2 100644
--- a/P25TX.h
+++ b/P25TX.h
@@ -16,11 +16,13 @@
  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include "Config.h"
+
+#if defined(MODE_P25)
+
 #if !defined(P25TX_H)
 #define  P25TX_H
 
-#include "Config.h"
-
 #include "RingBuffer.h"
 
 class CP25TX {
@@ -55,3 +57,6 @@ private:
 };
 
 #endif
+
+#endif
+
diff --git a/SerialPort.cpp b/SerialPort.cpp
index 590de0d..72614ac 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -112,7 +112,7 @@ const uint8_t MMDVM_DEBUG5       = 0xF5U;
 #define	HW_TYPE	"MMDVM"
 #endif
 
-#define DESCRIPTION "20201106 (D-Star/DMR/System Fusion/P25/NXDN/M17/POCSAG/FM/AX.25)"
+#define DESCRIPTION "20201108 (D-Star/DMR/System Fusion/P25/NXDN/M17/POCSAG/FM/AX.25)"
 
 #if defined(GITVERSION)
 #define concat(h, a, b, c) h " " a " " b " GitID #" c ""
@@ -204,6 +204,7 @@ void CSerialPort::getStatus()
   reply[5U] = 0U;
 #endif
 
+#if defined(MODE_DMR)
   if (m_dmrEnable) {
     if (m_duplex) {
       reply[6U] = dmrTX.getSpace1();
@@ -216,6 +217,10 @@ void CSerialPort::getStatus()
     reply[6U] = 0U;
     reply[7U] = 0U;
   }
+#else
+  reply[6U] = 0U;
+  reply[7U] = 0U;
+#endif
 
 #if defined(MODE_YSF)
   if (m_ysfEnable)
@@ -226,15 +231,23 @@ void CSerialPort::getStatus()
   reply[8U] = 0U;
 #endif
 
+#if defined(MODE_P25)
   if (m_p25Enable)
     reply[9U] = p25TX.getSpace();
   else
     reply[9U] = 0U;
+#else
+  reply[9U] = 0U;
+#endif
 
+#if defined(MODE_NXDN)
   if (m_nxdnEnable)
     reply[10U] = nxdnTX.getSpace();
   else
     reply[10U] = 0U;
+#else
+  reply[10U] = 0U;
+#endif
 
 #if defined(MODE_M17)
   if (m_m17Enable)
@@ -254,15 +267,23 @@ void CSerialPort::getStatus()
   reply[12U] = 0U;
 #endif
 
+#if defined(MODE_FM)
   if (m_fmEnable)
     reply[13U] = fm.getSpace();
   else
     reply[13U] = 0U;
+#else
+  reply[13U] = 0U;
+#endif
 
+#if defined(MODE_AX25)
   if (m_ax25Enable)
     reply[14U] = ax25TX.getSpace();
   else
     reply[14U] = 0U;
+#else
+  reply[14U] = 0U;
+#endif
 
   writeInt(1U, reply, 15);
 }
@@ -390,32 +411,48 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
 #if defined(MODE_YSF)
   ysfTX.setTXDelay(txDelay);
 #endif
+#if defined(MODE_P25)
   p25TX.setTXDelay(txDelay);
+#endif
+#if defined(MODE_DMR)
   dmrDMOTX.setTXDelay(txDelay);
+#endif
+#if defined(MODE_NXDN)
   nxdnTX.setTXDelay(txDelay);
+#endif
 #if defined(MODE_M17)
   m17TX.setTXDelay(txDelay);
 #endif
 #if defined(MODE_POCSAG)
   pocsagTX.setTXDelay(txDelay);
 #endif
+#if defined(MODE_AX25)
   ax25TX.setTXDelay(ax25TXDelay);
+#endif
 
+#if defined(MODE_DMR)
   dmrTX.setColorCode(colorCode);
   dmrRX.setColorCode(colorCode);
   dmrRX.setDelay(dmrDelay);
   dmrDMORX.setColorCode(colorCode);
   dmrIdleRX.setColorCode(colorCode);
+#endif
 
 #if defined(MODE_YSF)
   ysfTX.setParams(ysfLoDev, ysfTXHang);
 #endif
+#if defined(MODE_P25)
   p25TX.setParams(p25TXHang);
+#endif
+#if defined(MODE_NXDN)
   nxdnTX.setParams(nxdnTXHang);
+#endif
 #if defined(MODE_M17)
   m17TX.setParams(m17TXHang);
 #endif
+#if defined(MODE_AX25)
   ax25RX.setParams(ax25RXTwist, ax25SlotTime, ax25PPersist);
+#endif
 
   io.setParameters(rxInvert, txInvert, pttInvert, rxLevel, cwIdTXLevel, dstarTXLevel, dmrTXLevel, ysfTXLevel, p25TXLevel, nxdnTXLevel, m17TXLevel, pocsagTXLevel, fmTXLevel, ax25TXLevel, txDCOffset, rxDCOffset, useCOSAsLockout);
 
@@ -424,7 +461,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
   return 0U;
 }
 
-#if defined(MODE_AX25)
+#if defined(MODE_FM)
 uint8_t CSerialPort::setFMParams1(const uint8_t* data, uint16_t length)
 {
   if (length < 8U)
@@ -633,30 +670,38 @@ void CSerialPort::setMode(MMDVM_STATE modemState)
     dstarRX.reset();
 #endif
 
+#if defined(MODE_DMR)
   if (modemState != STATE_DMR) {
     dmrIdleRX.reset();
     dmrDMORX.reset();
     dmrRX.reset();
   }
+#endif
 
 #if defined(MODE_YSF)
   if (modemState != STATE_YSF)
     ysfRX.reset();
 #endif
 
+#if defined(MODE_P25)
   if (modemState != STATE_P25)
     p25RX.reset();
+#endif
 
+#if defined(MODE_NXDN)
   if (modemState != STATE_NXDN)
     nxdnRX.reset();
+#endif
 
 #if defined(MODE_M17)
   if (modemState != STATE_M17)
     m17RX.reset();
 #endif
 
+#if defined(MODE_FM)
   if (modemState != STATE_FM)
     fm.reset();
+#endif
 
   cwIdTX.reset();
 
@@ -822,14 +867,22 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
       if (m_modemState == STATE_DSTARCAL)
         err = calDStarTX.write(buffer, length);
 #endif
+#if defined(MODE_DMR)
       if (m_modemState == STATE_DMRCAL || m_modemState == STATE_LFCAL || m_modemState == STATE_DMRCAL1K || m_modemState == STATE_DMRDMO1K)
         err = calDMR.write(buffer, length);
+#endif
+#if defined(MODE_FM)
       if (m_modemState == STATE_FMCAL10K || m_modemState == STATE_FMCAL12K || m_modemState == STATE_FMCAL15K || m_modemState == STATE_FMCAL20K || m_modemState == STATE_FMCAL25K || m_modemState == STATE_FMCAL30K)
         err = calFM.write(buffer, length);
+#endif
+#if defined(MODE_P25)
       if (m_modemState == STATE_P25CAL1K)
         err = calP25.write(buffer, length);
+#endif
+#if defined(MODE_NXDN)
       if (m_modemState == STATE_NXDNCAL1K)
         err = calNXDN.write(buffer, length);
+#endif
 #if defined(MODE_POCSAG)
       if (m_modemState == STATE_POCSAGCAL)
         err = calPOCSAG.write(buffer, length);
@@ -896,6 +949,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
       break;
 #endif
 
+#if defined(MODE_DMR)
     case MMDVM_DMR_DATA1:
       if (m_dmrEnable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_DMR) {
@@ -968,6 +1022,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
         sendNAK(err);
       }
       break;
+#endif
 
 #if defined(MODE_YSF)
     case MMDVM_YSF_DATA:
@@ -985,6 +1040,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
       break;
 #endif
 
+#if defined(MODE_P25)
     case MMDVM_P25_HDR:
       if (m_p25Enable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_P25)
@@ -1012,7 +1068,9 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
         sendNAK(err);
       }
       break;
+#endif
 
+#if defined(MODE_NXDN)
     case MMDVM_NXDN_DATA:
       if (m_nxdnEnable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_NXDN)
@@ -1026,6 +1084,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
         sendNAK(err);
       }
       break;
+#endif
 
 #if defined(MODE_M17)
     case MMDVM_M17_DATA:
@@ -1059,6 +1118,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
       break;
 #endif
 
+#if defined(MODE_FM)
     case MMDVM_FM_DATA:
       if (m_fmEnable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_FM)
@@ -1072,7 +1132,9 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
         sendNAK(err);
       }
       break;
+#endif
 
+#if defined(MODE_AX25)
     case MMDVM_AX25_DATA:
       if (m_ax25Enable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_FM)
@@ -1083,6 +1145,7 @@ void CSerialPort::processMessage(const uint8_t* buffer, uint16_t length)
         sendNAK(err);
       }
       break;
+#endif
 
     case MMDVM_TRANSPARENT:
     case MMDVM_QSO_INFO:
@@ -1188,6 +1251,7 @@ void CSerialPort::writeDStarEOT()
 }
 #endif
 
+#if defined(MODE_DMR)
 void CSerialPort::writeDMRData(bool slot, const uint8_t* data, uint8_t length)
 {
   if (m_modemState != STATE_DMR && m_modemState != STATE_IDLE)
@@ -1227,6 +1291,7 @@ void CSerialPort::writeDMRLost(bool slot)
 
   writeInt(1U, reply, 3);
 }
+#endif
 
 #if defined(MODE_YSF)
 void CSerialPort::writeYSFData(const uint8_t* data, uint8_t length)
@@ -1270,6 +1335,7 @@ void CSerialPort::writeYSFLost()
 }
 #endif
 
+#if defined(MODE_P25)
 void CSerialPort::writeP25Hdr(const uint8_t* data, uint8_t length)
 {
   if (m_modemState != STATE_P25 && m_modemState != STATE_IDLE)
@@ -1332,7 +1398,9 @@ void CSerialPort::writeP25Lost()
 
   writeInt(1U, reply, 3);
 }
+#endif
 
+#if defined(MODE_NXDN)
 void CSerialPort::writeNXDNData(const uint8_t* data, uint8_t length)
 {
   if (m_modemState != STATE_NXDN && m_modemState != STATE_IDLE)
@@ -1372,6 +1440,7 @@ void CSerialPort::writeNXDNLost()
 
   writeInt(1U, reply, 3);
 }
+#endif
 
 #if defined(MODE_M17)
 void CSerialPort::writeM17Data(const uint8_t* data, uint8_t length)
@@ -1415,6 +1484,7 @@ void CSerialPort::writeM17Lost()
 }
 #endif
 
+#if defined(MODE_FM)
 void CSerialPort::writeFMData(const uint8_t* data, uint16_t length)
 {
   if (m_modemState != STATE_FM && m_modemState != STATE_IDLE)
@@ -1481,7 +1551,9 @@ void CSerialPort::writeFMEOT()
 
   writeInt(1U, reply, 3U);
 }
+#endif
 
+#if defined(MODE_AX25)
 void CSerialPort::writeAX25Data(const uint8_t* data, uint16_t length)
 {
   if (m_modemState != STATE_FM && m_modemState != STATE_IDLE)
@@ -1513,6 +1585,7 @@ void CSerialPort::writeAX25Data(const uint8_t* data, uint16_t length)
     writeInt(1U, reply, length + 3U);
   }
 }
+#endif
 
 void CSerialPort::writeCalData(const uint8_t* data, uint8_t length)
 {