diff --git a/op25/gr-op25_repeater/include/op25_repeater/ambe_encoder_sb.h b/op25/gr-op25_repeater/include/op25_repeater/ambe_encoder_sb.h
index 1bfe061..22bdf87 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/ambe_encoder_sb.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/ambe_encoder_sb.h
@@ -47,7 +47,7 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(int versbose_flag);
-      virtual void set_gain_adjust(float gain_adjust) {}
+      virtual void set_gain_adjust(float gain_adjust) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/dstar_tx_sb.h b/op25/gr-op25_repeater/include/op25_repeater/dstar_tx_sb.h
index 8564feb..be652d3 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/dstar_tx_sb.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/dstar_tx_sb.h
@@ -48,7 +48,7 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(int versbose_flag, const char * conf_file);
-      virtual void set_gain_adjust(float gain_adjust) {}
+      virtual void set_gain_adjust(float gain_adjust) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h b/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h
index f53a066..cb86b00 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/frame_assembler.h
@@ -48,11 +48,11 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(const char* options, int debug, gr::msg_queue::sptr queue, int msgq_id);
-      virtual void set_xormask(const char*p) {}
-      virtual void set_nac(int nac) {}
-      virtual void set_slotid(int slotid) {}
-      virtual void insert_whitelist(int grpaddr) {}
-      virtual void insert_blacklist(int grpaddr) {}
+      virtual void set_xormask(const char*p) = 0;
+      virtual void set_nac(int nac) = 0;
+      virtual void set_slotid(int slotid) = 0;
+      virtual void insert_whitelist(int grpaddr) = 0;
+      virtual void insert_blacklist(int grpaddr) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/nxdn_tx_sb.h b/op25/gr-op25_repeater/include/op25_repeater/nxdn_tx_sb.h
index c3cdd38..8c29fb4 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/nxdn_tx_sb.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/nxdn_tx_sb.h
@@ -48,7 +48,7 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(int versbose_flag, const char * conf_file, bool nxdn96_mode);
-      virtual void set_gain_adjust(float gain_adjust) {}
+      virtual void set_gain_adjust(float gain_adjust) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/p25_frame_assembler.h b/op25/gr-op25_repeater/include/op25_repeater/p25_frame_assembler.h
index ff366c7..9851b8e 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/p25_frame_assembler.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/p25_frame_assembler.h
@@ -48,9 +48,9 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(const char* udp_host, int port, int debug, bool do_imbe, bool do_output, bool do_msgq, gr::msg_queue::sptr queue, bool do_audio_output, bool do_phase2_tdma, int msgq_id);
-      virtual void set_xormask(const char*p) {}
-      virtual void set_nac(int nac) {}
-      virtual void set_slotid(int slotid) {}
+      virtual void set_xormask(const char*p) = 0;
+      virtual void set_nac(int nac) = 0;
+      virtual void set_slotid(int slotid) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/vocoder.h b/op25/gr-op25_repeater/include/op25_repeater/vocoder.h
index ce271e4..e1ec414 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/vocoder.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/vocoder.h
@@ -47,7 +47,7 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(bool encode_flag, bool verbose_flag, int stretch_amt, char* udp_host, int udp_port, bool raw_vectors_flag);
-      virtual void set_gain_adjust(float gain_adjust) {}
+      virtual void set_gain_adjust(float gain_adjust) = 0;
     };
 
   } // namespace op25_repeater
diff --git a/op25/gr-op25_repeater/include/op25_repeater/ysf_tx_sb.h b/op25/gr-op25_repeater/include/op25_repeater/ysf_tx_sb.h
index 570fbc3..06d6a64 100644
--- a/op25/gr-op25_repeater/include/op25_repeater/ysf_tx_sb.h
+++ b/op25/gr-op25_repeater/include/op25_repeater/ysf_tx_sb.h
@@ -48,7 +48,7 @@ namespace gr {
        * creating new instances.
        */
       static sptr make(int versbose_flag, const char * conf_file, bool fullrate_mode);
-      virtual void set_gain_adjust(float gain_adjust) {}
+      virtual void set_gain_adjust(float gain_adjust) = 0;
     };
 
   } // namespace op25_repeater