[Hackrf-dev] RX data loss with hackrf_transfer

[OSQZSS]

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
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