Updated my HackRF One to the latest firmware (2021.03.1) following Michael Ossmann's repository, but now having TX problems in GNU Radio 3.10. After firmware update, disconnect and reconnect the HackRF One to verify the update - that part worked fine. The issue is GNU Radio flowgraphs that worked perfectly before now throw buffer underrun errors during transmission. RX works flawlessly, it's only affecting TX mode. HackRF One covers 1MHz to 6 GHz frequency range, half-duplex, adequate for replay attacks where we capture and replay signals. Has anyone else seen similar behavior after the firmware update?

Check your sample rate settings - HackRF is half-duplex meaning it can only send or receive, not both simultaneously. Buffer underruns usually indicate the flowgraph can't keep up with the requested sample rate. Try reducing from 10MHz to 8MHz and see if that helps with TX stability.

I had similar issues after updating. The solution was to run volk_profile utility before running gqrx - this detects and enables processor-specific optimizations and gives significant performance boost. Same principle applies to GNU Radio - the VOLK kernels need optimization after major updates.

Are you running this on Linux? HackRF doesn't transmit in Windows, so that could be your issue if you switched OS. Also verify your USB connection isn't dropping power - HackRF TX draws more current than RX mode and can cause voltage drops on marginal USB ports.