[Hackrf-dev] transmitting with one HackRF and receiving with another -- advice needed

[Rachel Citchlow]

I had somewhat better luck today using the -w option with hackrf_transfer.
Does HackRF only play back .wav files and not just a file of I/Q samples?
I sent a CW signal with one  HackRF (hackrf_transfer -c ...) and captured
with the other using hackrf_transfer -w
I was then able to play back the resulting wav file and see the spike on
osmocom_fft -f 97000000 -a hackrf -v.
The same procedure except for playing back a file captured by
"hackrf_transfer -r" did not play back correctly, showed lots of extra
noise and no spike.
Thanks
Rachel



On Sat, Nov 8, 2014 at 7:14 PM, Rachel Citchlow <rachel at citchlow.com> wrote:

> Hello all,
> I am trying  a setup with two HackRFs with their antenna ports connected
> to one another with an RF cable with a 30dB attenuator in between. I would
> like to send something with one of them and receive with the other.
>
> My steps were as follows:
>
> 1. started with lesson1.grc receiver with center_freq of 97M, and channel
> freq of 96.3M. Added a file sink  in parallel with the osmocom source to
> save the I/Q samples as received by the HackRF. I thus obtained a data
> file, data.bin,  with a part of a song played on the local music channel
> 96.3.
>
> 2. In lesson1.grc, substituted the osmocom source by a file source
> pointing to data.bin. Played lesson1.grc and was able to hear the audio the
> same way as in step 1. This confirmed that data.bin contains good I/Q
> samples.
>
> 3. Connected the two HackRFs to each other and played a sample signal on
> one and received it with the other, saw a strong narrow spike on the
> receive FFT plot:
> rachel at radio1:~/Documents/playback$ hackrf_transfer -c 10 -f 96300000 -s
> 2000000 -a 1 -x 20
>
> 4. Transmitted data.bin on one HackFR and tried to receive with
> lesson1.grc on the other.
> rachel at radio1:~/Documents/playback$ hackrf_transfer -t data.bin -f
> 97000000 -s 2000000 -a 1 -x 20
> This did not work. On the receiving end, I saw the FFT plot get several
> narrow spikes and generally rise up, but it did not look like the FFT plot
> in step #1. A different noise pattern (different from when nothing was
> transmitted) and some clicking came out of the speaker.
>
> What am I missing? Advice appreciated.
> thanks
> Rachel
>
>
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