replace USRP block with RTL SDR

[sajadmathe]

Hi
I am a new in gnuradio.
I replaced USRP block with RTL SDR block in lora_RX.grc.

when i run lora_RX.grc flowgraph in GNURadio i see this outpot:

I don't understand anything from this output. Can you guide me?

thanx

[tapparelj]

Hi @sajadmathe,
Based on the error, it seems that the SDR you are using doesn't support a sample rate of 125kHz. To know which rates it supports, try searching in its datasheets.
If it supports any multiple of 125kHz, you can simply add a Keep one in N block to decimate the signal. Else you might need to use a Fractional resampler or a Rational resampler.

In addition, I see some errors with the parameters you set in the block:

• The Sample rate should be set to the variable samp_rate (you can use variables in flowgraphs). The example uses an oversampling factor of 4 (that I would recommend to keep) to synchronize, hence being set to 500kHz for a LoRa bandwidth (bw) of 125kHz.
• The Frequency should be set to the variable center_freq. This variable of course needs to match the frequency used by your transmitter.

If you are new to gnuradio, try having a look at the tutorials here to get familiar with the main concepts of flowgraphs.

[tapparelj]

I'll close this issue as there has been no follow-up in the past two months, but feel free to reopen it if needed.