src/ria_toolkit_oss/orchestration/tx_executor.py

@@ -70,6 +70,12 @@ _MOD_TABLE: dict[str, tuple[int, str]] = {
 
 _SPECIAL_MODS = {"FSK", "OOK", "GMSK", "OQPSK"}
 
+# usrp-uhd-client's tx_recording() streams 2 000-sample chunks and loops the
+# source buffer for the full tx_time, so only this many samples ever need to
+# be in RAM regardless of step duration or sample rate.
+# 50 000 complex64 samples ≈ 400 kB — enough spectral diversity for looping.
+_SYNTH_BLOCK_SAMPLES = 50_000
+
 
 class TxExecutor:
     """Synthesise and transmit a signal campaign via a local SDR.
@@ -145,7 +151,12 @@ class TxExecutor:
         )
 
         num_samples = int(duration * sample_rate)
-        signal = self._synthesise(modulation, sps, num_samples, filter_type, rolloff)
+
+        # Synthesise a short representative block. tx_recording() loops this
+        # buffer for the full tx_time using a 2 000-sample streaming callback,
+        # so peak memory is O(_SYNTH_BLOCK_SAMPLES) regardless of duration.
+        block_size = min(num_samples, _SYNTH_BLOCK_SAMPLES)
+        signal = self._synthesise(modulation, sps, block_size, filter_type, rolloff)
 
         if self._sdr is not None:
             try: