The measureTxMode may be set to MEASURE_SILENT in order not
to send measurement packets even during an active frame and
established synchronization. There are even two setter
functions measure_set_tx_active() and
measure_set_tx_silent().

However, this possibility is used nowhere. In the current
implementation there is even a bug in the measurement
scheduler: The packet transmission is started without
checking the measureTXMode. This may lead to situations
where the scheduler tries to start the transmission of a
packet that never was prepared before (The frame
preparation respects the measureTxMode).