Hi, On 20.10.2018 02:20, Francesco Gugliuzza wrote: Hm, I haven't seen this on Linux so far. Would be interesting to see if only the time measurement goes wrong (could be caused by CPU frequency scaling etc.), or if something is actually going wrong with the device or transfers. fl2k_test outputs a rectangle signal, do you have an oscilloscope or an SDR you could use to check if the signal disappears when the measured sample rate starts to get strange? Regards, Steve

I have to start with an errata corrige: my laptop has Windows 8.1 and not 7, which is installed on another computer. Anyway, I've done some tests with a RTL-SDR, and I can definitely say that something goes wrong. When I start the rtl-test sometimes a peak appears at the correct frequency (e.g. if i set sampling at 100 MHz i find a peak at 3*100 - 50 = 250 MHz) and then disappears less than a second after; most times it doesn't even appear at all. I've also tried running fl2k_test on Linux with a live DVD of Ubuntu 18.10 and everything seems to go well: it runs correctly even at high sample rates (150 MS/s), spewing out just an error on zero-copy buffers. Here is a log: ubuntu@ubuntu:~/osmo-fl2k$ fl2k_test -s 150e6 Allocating 6 zero-copy buffers libusb: error [op_dev_mem_alloc] alloc dev mem failed errno 12 Failed to allocate zero-copy buffer for transfer 4 Falling back to buffers in userspace Reporting PPM error measurement every 10 seconds... Press ^C after a few minutes. real sample rate: 149990146 current PPM: -66 cumulative PPM: -66 real sample rate: 150001491 current PPM: 10 cumulative PPM: -28 real sample rate: 150009752 current PPM: 65 cumulative PPM: 3 real sample rate: 149996142 current PPM: -26 cumulative PPM: -4 real sample rate: 150012666 current PPM: 84 cumulative PPM: 14 real sample rate: 150001814 current PPM: 12 cumulative PPM: 14 real sample rate: 150003433 current PPM: 23 cumulative PPM: 15 real sample rate: 149999114 current PPM: -6 cumulative PPM: 12 real sample rate: 149999349 current PPM: -4 cumulative PPM: 10 real sample rate: 150014477 current PPM: 97 cumulative PPM: 19 real sample rate: 149995547 current PPM: -30 cumulative PPM: 15 real sample rate: 150008611 current PPM: 57 cumulative PPM: 18 real sample rate: 149994234 current PPM: -38 cumulative PPM: 14 real sample rate: 150004040 current PPM: 27 cumulative PPM: 15 real sample rate: 150011047 current PPM: 74 cumulative PPM: 19 real sample rate: 149990169 current PPM: -66 cumulative PPM: 13 real sample rate: 150008286 current PPM: 55 cumulative PPM: 16 real sample rate: 149999384 current PPM: -4 cumulative PPM: 15 Using my RTL-SDR I find the peak at 3*150 - 75 = 375 MHz, as expected. I will run some other tests on my other computer, the one with Windows 7. Have a nice evening, Francesco -- Francesco Gugliuzza