Hi, I have a TDMA flowgraph that defines packets using tx_time and tx_sob + tx_eob. Packets are sent to a B200mini every 10 ms (which is not important). Below I have the packet format from GRC followed by 3 oscilloscope captures that show the effect I’m seeing. The B200mini is connected to an Octoclock 1 PPS reference. The modulation is BPSK, 2x oversampled, RRC. Image 1 - the GRC waveform that is input to the USRP sink Image 2 - this time the transmitted signal looks pretty good. Note the leading zeros so that the transmit power rises to full before samples are applied. Image 3 - it appears that some form of slow modulation has been applied Image 4 - same again, but obviously at a different offset (oops, forgot to turn off stupid network config menu in scope caps) I am a bit stumped. A “theory” is that maybe I’m seeing a window of some kind being convolved with the signal. Steven Knudsen, Ph.D., P.Eng. www. techconficio.ca www.linkedin.com/in/knudstevenknudsen Der entscheidende Augenblick der menschlichen Entwicklung ist immerwährend. Darum sind die revolutionären geistigen Bewegungen, welche alles Frühere für nichtig erklären, im Recht, denn es ist noch nichts geschehen. - Franz Kafka