Hello Eamon,
You should see something like this on your spectrum. I used QT Fosphor Sink (from gr-fosphor) instead of the QT GUI Frequency sink, because bursty packets are 'more visible' this way.
A few thing that you should do:
- Check whether you are looking at the correct channel (frequency). Maybe your router is transmitting on a different frequency.
- Check the configurations of your Osmocom source. For the gain settings, especially, see:
https://github.com/mossmann/hackrf/wiki/FAQ
- Try using different antennas.
Also, you can actually damage the RF frontend of your SDR transceiver by putting it too close to strong RF emitters. Although I think the chance is low (I think most WiFi routers won't kill your HackRF so easily), but always be careful when you are putting
them close together.
I think WiFi has null subcarriers on the DC frequency, so you probably do not have to correct the DC term, but maybe you want to double-check that. If your DC term is correctly removed, you won't see any peak at the center of your "QT Frequency Sink" plot.
Regards,
Kyeong Su Shin
Pic of the output from the QT GUI Frequency sink is shown below. I didn't see anything significantly different from this, even when I put the radio right up next to my home router.
I've been told that it would be a good idea to set a DC offset for my source, but I'm unsure how to calculate that, and it was working without an offset before.
On Mon, Aug 12, 2019 at 8:20 PM Müller, Marcus (CEL) <
address@hidden> wrote:
Ah OK, but then it's *barely* enough for wifi.
I meant that you attach a visual sink, for example the "Qt GUI
frequency sink" in GNU Radio directly to your HackRF-interfacing source
(probably the osmocom source?).
Best regards,
Marcus
On Mon, 2019-08-12 at 15:27 -0400, Eamon Heaney wrote:
> Do you mean with a spectrum analyzer? Forgive me if that's a dumb
> question, I'm a bit new to this.
>
> The max bandwidth of the HackRF One is 20MHz, so I should be able to
> receive data.
>
> On Mon, Aug 12, 2019 at 3:13 PM Müller, Marcus (CEL) <address@hidden
> > wrote:
> > I'd recommend looking at the spectrum you receive. Also, how does
> > receiving a 20 MHz wide channel with a HackRF work? Wasn't the
> > maximum
> > bandwidth of that lower?
> >
> > On Mon, 2019-08-12 at 15:10 -0400, Eamon Heaney wrote:
> > > Last week, I was able to capture wifi packets in the 2.4 GHz band
> > > (using a modified example from this repo), but now I am unable
> > to.
> > > I'm using the same .grc flowchart, with the sample rate and
> > bandwidth
> > > both set to 20 MHz, and the channel frequency of 2.412 GHz.
> > >
> > > Any idea why that might be? I was previously only able to receive
> > > signals with my phone right next to the HackRF antenna, but now
> > even
> > > that won't help. I tried putting it right next to my router, too,
> > but
> > > it still isn't getting anything.
> > >
> > > Thanks!
> > >
> > > _______________________________________________
> > > Discuss-gnuradio mailing list
> > > address@hidden
> > >
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
--
Eamon Heaney
Fleet Commander
President, Model UN at Virginia Tech