I think the first thing is DC offset. It is usual in hackrf. You may process it out by some simple strategy. Like estimate DC then subtract.
Sent from my iPhone > On Dec 2, 2014, at 11:09, OSQZSS <osq...@gmail.com> wrote: > > Hi, > > After reading the work of Jiao Xianjun, I was motivated to record and replay > GPS signals with hackrf_transfer. With careful selection of signal strength, > I can see the playback signals from HackRF One on my u-blox GPS receiver, > but there are a couple of issues I need to resolve. > > 1. GPS signals are weak and buried under the thermal noise. The recorded I/Q > samples should have Gaussian distribution, but there are eminent projections > around zero. I uploaded a histogram plot to the following site: > http://goo.gl/NzVulj > > 2. The received data transfer rate gets lower every once in a while, and some > samples are lost. It occurs in a constant time interval, every 30 seconds on > my Core i5 laptop, regardless sampling rates. > > $ hackrf_info > Found HackRF board. > Board ID Number: 2 (HackRF One) > Firmware Version: 2014.08.1 > Part ID Number: 0xa000cb3c 0x00604f39 > Serial Number: 0x00000000 0x00000000 0x457863c8 0x2f52161f > > $ hackrf_transfer -r gps.bin -f 1575420000 -s 2600000 -n 260000000 -g 30 -l > 40 -a 0 > call hackrf_sample_rate_set(2600000 Hz/2.600 MHz) > call hackrf_baseband_filter_bandwidth_set(2500000 Hz/2.500 MHz) > call hackrf_set_freq(1575420000 Hz/1575.420 MHz) > call hackrf_set_amp_enable(0) > samples_to_xfer 260000000/260Mio > Stop with Ctrl-C > 5.0 MiB / 1.000 sec = 5.0 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > ... > 5.2 MiB / 1.000 sec = 5.2 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > 2.6 MiB / 1.000 sec = 2.6 MiB/second > 2.4 MiB / 1.000 sec = 2.4 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > ... > 5.0 MiB / 1.000 sec = 5.0 MiB/second > 4.5 MiB / 1.000 sec = 4.5 MiB/second > 3.1 MiB / 1.000 sec = 3.1 MiB/second > 1.0 MiB / 1.000 sec = 1.0 MiB/second > 5.0 MiB / 1.000 sec = 5.0 MiB/second > 5.2 MiB / 1.000 sec = 5.2 MiB/second > > Does anyone have any idea of what I should do to solve these problems? > > OSQZSS > _______________________________________________ > HackRF-dev mailing list > HackRF-dev@greatscottgadgets.com > https://pairlist9.pair.net/mailman/listinfo/hackrf-dev
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