[Hackrf-dev] RX data loss with hackrf_transfer

[Jiao Xianjun]

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 <osqzss at 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
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