diff --git a/src/dialogs/fl_digi.cxx b/src/dialogs/fl_digi.cxx
index ea6d9b74..f954a3f6 100644
--- a/src/dialogs/fl_digi.cxx
+++ b/src/dialogs/fl_digi.cxx
@@ -585,17 +585,12 @@ void init_modem(trx_mode mode)
 
 void init_modem_sync(trx_mode m)
 {
-	if (trx_state != STATE_RX)
-		return;
+	ENSURE_THREAD(FLMAIN_TID);
 
-#ifndef NDEBUG
-        if (GET_THREAD_ID() == TRX_TID)
-                LOG_ERROR("trx thread called init_modem_sync!");
-#endif
+	if (trx_state != STATE_RX)
+		TRX_WAIT(STATE_RX, abort_tx());
 
-        wait_modem_ready_prep();
-        init_modem(m);
-        wait_modem_ready_cmpl();
+	TRX_WAIT(STATE_RX, init_modem(m));
 	REQ_FLUSH(TRX_TID);
 }
 
diff --git a/src/globals/globals.cxx b/src/globals/globals.cxx
index d7782596..a9641272 100644
--- a/src/globals/globals.cxx
+++ b/src/globals/globals.cxx
@@ -34,15 +34,6 @@
 
 using namespace std;
 
-const char *state_names[] = {
-	"PAUSED",
-	"RECEIVE",
-	"TRANSMIT",
-	"TUNING",
-	"ABORTED",
-	"FLUSHING"
-};
-
 // Elements are in enum trx_mode order. Mode name video-id uses the
 // first string (sname), so its length should be a multiple of 2.
 const struct mode_info_t mode_info[NUM_MODES] = {
diff --git a/src/include/globals.h b/src/include/globals.h
index 1846675d..2684c828 100644
--- a/src/include/globals.h
+++ b/src/include/globals.h
@@ -44,7 +44,6 @@ enum state_t {
 	STATE_IDLE,
 	STATE_NEW_MODEM
 };
-extern const char *state_names[];
 
 enum {
 	MODE_PREV = -2,
diff --git a/src/include/threads.h b/src/include/threads.h
index f71cae9f..fa5b68a5 100644
--- a/src/include/threads.h
+++ b/src/include/threads.h
@@ -15,7 +15,7 @@ int sem_timedwait_rel(sem_t* sem, double rel_timeout);
 int pthread_cond_timedwait_rel(pthread_cond_t* cond, pthread_mutex_t* mutex, double rel_timeout);
 
 // 3 threads use qrunner
-enum { UNKNOWN_TID = -1, TRX_TID, QRZ_TID, RIGCTL_TID,
+enum { INVALID_TID = -1, TRX_TID, QRZ_TID, RIGCTL_TID,
 #if USE_XMLRPC
        XMLRPC_TID,
 #endif
@@ -25,16 +25,39 @@ enum { UNKNOWN_TID = -1, TRX_TID, QRZ_TID, RIGCTL_TID,
 
 #if USE_TLS
 #       define THREAD_ID_TYPE __thread int
-#	define CREATE_THREAD_ID() thread_id_ = UNKNOWN_TID
+#	define CREATE_THREAD_ID() thread_id_ = INVALID_TID
 #	define SET_THREAD_ID(x)   thread_id_ = (x)
 #	define GET_THREAD_ID()    thread_id_
 #else
 #       define THREAD_ID_TYPE pthread_key_t
-#	define CREATE_THREAD_ID() pthread_key_create(&thread_id_, 0);
+#	define CREATE_THREAD_ID() pthread_key_create(&thread_id_, 0)
 #	define SET_THREAD_ID(x)   pthread_setspecific(thread_id_, (void *)(x))
 #	define GET_THREAD_ID()    (int)pthread_getspecific(thread_id_)
 #endif // USE_TLS
 
+
+#ifndef NDEBUG
+#  include "debug.h"
+bool thread_in_list(int id, const int* list);
+#  define ENSURE_THREAD(...)						\
+	do {								\
+		int id_ = GET_THREAD_ID();				\
+		int t_[] = { __VA_ARGS__, INVALID_TID };		\
+		if (!thread_in_list(id_, t_))				\
+			LOG_ERROR("bad thread context: %d", id_);	\
+	} while (0)
+#  define ENSURE_NOT_THREAD(...)					\
+	do {								\
+		int id_ = GET_THREAD_ID();				\
+		int t_[] = { __VA_ARGS__, INVALID_TID };		\
+		if (thread_in_list(id_, t_))				\
+			LOG_ERROR("bad thread context: %d", id_);	\
+	} while (0)
+#else
+#  define ENSURE_THREAD(...) ((void)0)
+#  define ENSURE_NOT_THREAD(...) ((void)0)
+#endif // ! NDEBUG
+
 extern THREAD_ID_TYPE thread_id_;
 
 #include "fl_lock.h"
diff --git a/src/include/trx.h b/src/include/trx.h
index 7dd00f1b..b5bd8e8b 100644
--- a/src/include/trx.h
+++ b/src/include/trx.h
@@ -48,9 +48,9 @@ extern	void	trx_receive();
 extern	void	trx_reset(void);
 extern	void	trx_start_macro_timer();
 
-extern	void	wait_modem_ready_prep(void);
-extern	void	wait_modem_ready_cmpl(void);
-extern	void	signal_modem_ready(void);
+extern void	wait_trx_state_prep(void);
+extern void	wait_trx_state_wait(void);
+extern void	wait_trx_state_cmpl(void);
 
 extern	void	macro_timer(void *);
 
@@ -62,4 +62,14 @@ extern	SoundBase 	*scard;
 
 extern  bool bHistory;
 
+#define TRX_WAIT(s_, code_)			\
+	do {					\
+		ENSURE_NOT_THREAD(TRX_TID);	\
+		wait_trx_state_prep();		\
+		code_;				\
+		while (trx_state != s_)		\
+			wait_trx_state_wait();	\
+		wait_trx_state_cmpl();		\
+	} while (0)
+
 #endif
diff --git a/src/misc/threads.cxx b/src/misc/threads.cxx
index ccb81371..7304532c 100644
--- a/src/misc/threads.cxx
+++ b/src/misc/threads.cxx
@@ -54,3 +54,13 @@ int pthread_cond_timedwait_rel(pthread_cond_t* cond, pthread_mutex_t* mutex, dou
 
 	return pthread_cond_timedwait(cond, mutex, &t);
 }
+
+#ifndef NDEBUG
+bool thread_in_list(int id, const int* list)
+{
+	while (*list != INVALID_TID)
+		if (id == *list++)
+			return true;
+	return false;
+}
+#endif
diff --git a/src/trx/trx.cxx b/src/trx/trx.cxx
index 1fc91447..4742b170 100644
--- a/src/trx/trx.cxx
+++ b/src/trx/trx.cxx
@@ -52,6 +52,7 @@ void	trx_start_modem_loop();
 void	trx_receive_loop();
 void	trx_transmit_loop();
 void	trx_tune_loop();
+static void signal_trx_state(void);
 
 //#define DEBUG
 
@@ -321,7 +322,13 @@ void *trx_loop(void *args)
 {
 	SET_THREAD_ID(TRX_TID);
 
+	state_t old_state = STATE_NOOP;
+
 	for (;;) {
+		if (unlikely(old_state != trx_state)) {
+			old_state = trx_state;
+			signal_trx_state();
+		}
 		switch (trx_state) {
 		case STATE_ABORT:
 			delete scard;
@@ -351,32 +358,21 @@ void *trx_loop(void *args)
 }
 
 //=============================================================================
-modem *trx_m;
+modem* new_modem;
 
 void trx_start_modem_loop()
 {
-	if (trx_m == active_modem) {
-		trx_state = STATE_RX;
+	if (new_modem == active_modem) {
 		active_modem->restart();
-		signal_modem_ready();
+		trx_state = STATE_RX;
 		return;
 	}
 
 	modem* old_modem = active_modem;
 
-	if (old_modem == trx_m) {
-		trx_state = STATE_RX;
-		signal_modem_ready();
-		return;
-	}
-
-	if (old_modem)
-		old_modem->shutdown();
-
-	active_modem = trx_m;
-	active_modem->init();
+	new_modem->init();
+	active_modem = new_modem;
 	trx_state = STATE_RX;
-	signal_modem_ready();
 	REQ(&waterfall::opmode, wf);
 
 	if (old_modem) {
@@ -388,7 +384,7 @@ void trx_start_modem_loop()
 //=============================================================================
 void trx_start_modem(modem *m)
 {
-	trx_m = m;
+	new_modem = m;
 	trx_state = STATE_NEW_MODEM;
 }
 
@@ -538,36 +534,24 @@ void trx_tune(void) { trx_state = STATE_TUNE; }
 void trx_receive(void) { trx_state = STATE_RX; }
 
 //=============================================================================
-void wait_modem_ready_prep(void)
-{
-#ifndef NDEBUG
-        if (GET_THREAD_ID() == TRX_TID)
-		LOG_ERROR("trx thread called wait_modem_ready_prep!");
-#endif
 
+void wait_trx_state_prep(void)
+{
         pthread_mutex_lock(&trx_cond_mutex);
 }
-
-void wait_modem_ready_cmpl(void)
+void wait_trx_state_wait(void)
 {
-#ifndef NDEBUG
-        if (GET_THREAD_ID() == TRX_TID)
-                LOG_ERROR("trx thread called wait_modem_ready_cmpl!");
-#endif
-
         pthread_cond_wait(&trx_cond, &trx_cond_mutex);
+}
+void wait_trx_state_cmpl(void)
+{
         pthread_mutex_unlock(&trx_cond_mutex);
 }
 
-void signal_modem_ready(void)
+static void signal_trx_state(void)
 {
-#ifndef NDEBUG
-        if (GET_THREAD_ID() != TRX_TID)
-		LOG_ERROR("thread %d called signal_modem_ready!", GET_THREAD_ID());
-#endif
-
+	ENSURE_THREAD(TRX_TID);
         pthread_mutex_lock(&trx_cond_mutex);
         pthread_cond_broadcast(&trx_cond);
         pthread_mutex_unlock(&trx_cond_mutex);
 }
-