using sdr devices with higher sample rate

[jamesshao8]

Do you know how to use this code with higher end sdr devices?
Because rtlsdr has a limited bandwidth, some signal cannot be viewed inside 2.4MHz.
I wanted to try your program with LimeSDR. But the reshape part seems to causing problem.

LimeSDR can only be set with a sample_rate above 2.5MHz, I am currently using it with 4.8MHz.

[jamesshao8]

I solved this problem by carefully producing the length of iq_samples before reshape, I kept the same as in predict_scan for rtlsdr. In order to do that, I used several stages of signal.decimate.

But now the dc offset of LimeSDR is still causing problem, which rtlsdr doesnt have. Now every time it scans, it would label the LO frequency as WFM signal.

[randaller]

Don't you have tried to read from LimeSDR using shifted DC offset tuning?

def read_samples(freq):
    f_offset = 250000  # shifted tune to avoid DC
    sdr.center_freq = freq - f_offset
    time.sleep(0.06)
    iq_samples = sdr.read_samples(sample_rate * 0.25)  # sample 1/4 sec
    fc1 = np.exp(-1.0j * 2.0 * np.pi * f_offset / sample_rate * np.arange(len(iq_samples)))  # shift down 250kHz
    iq_samples = iq_samples * fc1
    return iq_samples

[jamesshao8]

Thank you! I will try that. And get back to you with my results.

[FFY00]

@jamesshao8 can you share your patch?

[jamesshao8]

@jamesshao8 can you share your patch?

Hi, you mean you need my modification of cnn-rtlsdr with the support of limesdr?

[FFY00]

Yes 😁

[jamesshao8]

@FFY00 Sorry for late response. I uploaded my code now. you can have a try. https://github.com/jamesshao8/cnn-limesdr

[szy96]

Yes 😁

Hi Here I use tensorflow 2.1.0
Last step is to copy 2 files from x64!!! osmocom rtl-sdr drivers: https://osmocom.org/attachments/download/2242/RelWithDebInfo.zip
Copy these [rtl-sdr-release/x64/]: rtlsdr.dll & libusb-1.0.dll into C:\Windows folder.
Reboot your system.
Now open your anaconda prompt again, change folder to C:\rtlsdr and run:
python predict_scan.py

error ModuleNotFoundError: No module named 'rtlsdr' .
Do you know how can I fix it?

[jamesshao8]

I dont know. I am not a windows user.