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Record IQ data on Raspberry Pi #airspyhfplus #raspberrypi

Tudor Vedeanu
 

Let's say I have an Airspy HF+ and a headless Raspberry Pi. Can I record IQ data with them? If so, what's the best/most efficient way to do that? I don't need anything else, no demodulation, no waterfall display, nothing, just a dump of IQ in a WAV file.

Ideally I imagine this as a command line utility accepting config parameters from a file (center frequency, bandwidth, rec start time, rec end time). But any software which can record data AND keep the resource usage at minimum would be good.

Is it doable?

Thanks, Tudor

Randall Wayth
 

Hi Tudor,
Doesn't the command-line tool airspy_rx do most of what you need? If you want to record at a specific time then a simple script wrapper around airspy_rx will do the job.

On my pi model 2, it airspy_rx cannot handle the full 10 Msamp/sec when receiving in 16-bit I/Q mode, but can easily handle the full rate when receiving in real-value mode. Otherwise you can always back down to 2.5 Msamp/sec with the command-line tool if you don't need the full bandwidth. (use -a 1 option from memory)

Cheers,
Randall

Tudor Vedeanu
 

On Wed, Jan 24, 2018 at 03:24 pm, Randall Wayth wrote:

Doesn't the command-line tool airspy_rx do most of what you need?

Hi Randall,

I'm not familiar with the airspy_rx tool. Does it work with the Airspy HF+ too?

Tudor

Bjarne Mjelde
 

In principle it should be doable. A similar solution was developed several years ago for the Perseus SDR, it's called Mestor, which later developed into a full-fledged program. Mestor is extremely light on resources, so the question is if recording of the 660 kHz sample rate to a HDD is doable on a Raspberry Pi. And "someone" has to develop it.
--
Bjarne Mjelde
World's Northernmost DX-er
arcticdx.blogspot.com
Arctic web-rx:  kongsdr.proxy.kiwisdr.com:8073

Tudor Vedeanu
 

On Thu, Jan 25, 2018 at 02:08 am, Bjarne Mjelde wrote:

the question is if recording of the 660 kHz sample rate to a HDD is doable on a Raspberry Pi.

I've just tried recording a 1 minute I/Q file with Gqrx on my Raspberry Pi and it worked. With the "Demodulator off" option enabled and the FFT display disabled, the CPU usage was under 20%. (This is important to me because I plan to use the Raspberry Pi on batteries so it has to consume as little power as possible.)

--

Tudor

Leif Asbrink
 

Hi Bjarne Mjelde,

Recording 1.6 MHz with Linrad on a Raspberry Pi2 is
demonstrated here:
https://www.youtube.com/watch?v=YWg6bqp-RyQ

The Pi2 will easily record the data from two HF+ units
at 2*768 kHz (=1.536 MHz) sampling rate. Linrad makes
recordings in an 18 bit integer format. More bits does
not provide any improvement. Saves disk space....

The Raspberry Pi3 is much faster:-)

73

Leif

In principle it should be doable. A similar solution was developed several years ago for the Perseus SDR, it's called Mestor, which later developed into a full-fledged program. Mestor is extremely light on resources, so the question is if recording of the 660 kHz sample rate to a HDD is doable on a Raspberry Pi. And "someone" has to develop it.
--
Bjarne Mjelde
World's Northernmost DX-er
arcticdx.blogspot.com
Arctic web-rx:  kongsdr.proxy.kiwisdr.com:8073

Bjarne Mjelde
 

Leif,
totally agree that more bits is a waste of space and money. Now, if the 32-bit fans at Winradio would realize that...
--
Bjarne Mjelde
World's Northernmost DX-er
arcticdx.blogspot.com
Arctic web-rx:  kongsdr.proxy.kiwisdr.com:8073