GNURadio AM Receiver

[@user-bt3of9qp5l]

Hi John, What an awesome tutorial. I just purchased a "Hackrf one" and "Ham it Up!" and was immediate overwhelmed by how much I don't know. Any how, I followed this tutorial, and it all began to make complete sense. Until I hit generate and execute. It didn't seem to do much, so I removed the up-converter and tried your FM Broadcast receiver. That worked perfectly. So mack to the AM Receiver I get strings of UaUa... no matter where I set the Multiply Constant's value. When I turn it up passed 1, I hear an Putt-Putt-Putt sound, but no received audio. I've tried it at 1450KHz, 10,000KHz, and 20,000KHz. No difference at all. I also tried setting the Audio Sink to 32KHz and lowering the Interpolation value in the Rational Resample to 32. I also found your website and followed thru that version of the example. Still no love. Got any suggestions? 73 Mike

[@yasiribm]

Hi John it is very clear, I 'm expecting to get my RTL-SDR very soon and will start doing some exercises.

[@amaralkalbani7383]

Thanks for sharing this with us, I am using SDRPlay instead of RTL-SDR, so I don’t need the convert and the RF gain. But the issue is that I can’t listen to anything and I couldn’t know why is that, even tho that I have the same thing as you for the rest of the flowchart. Can you please help me? Thanks a lot.

[@ancapjack1837]

Hi John. First I want to say thank you for sharing this with us signal junkies. I'm having issues getting this one working with a hackrf, and I was just wondering what might be influenced by removing the convert aspect from this model (as I don't have a converter) after looking some things up I'm going to mess around with the amplitude a bit, but thought I'd reach out to see if you had any insight. Thanks!

[@VE6EY]

I used the "convert" variable because I had an HF upconverter to 125 MHz (to adjust for lack of lower frequency coverage with RTL-SDR). If you are actually tuning your receiver to the "real frequency", this stuff is not needed.

[@user-wu7nu5kj7d]

Hi John, Thanks a lot for explaining this in such a simpler manner. I am trying to implement this but at a different frequency band. But the problem being, there are so many spikes occurring in the spectrum and audio is sounding more like an on-off sound ~ something like a periodic bell. Could you please help me out with this. Thank you

[@VE6EY]

Perhaps you are listening to Morse Code or some sort of digital signal. This is an AM receiver so it will not demodulate continuous wave.

[@emanianjana1781]

Actually I have used the same parameters as yours. But it's just that I am transmitting the signal at a different frequency because of the USRP limit. I am using USRP B210

[@awesomedee5421]

the rtl-sdr is listed as 500kHz and up to 24MHz. so that covers the AM band, so I wasn't sure why the conversion had to happen. Could someone better explain this

[@flapjack9495]

I'm surprised nobody's answered this in 11 months. That's the RTL-SDR in direct-sampling mode, which is a kind of hack to get coverage below 24 MHz. Its usual range is 24 - 1700 MHz or so.

[@yougaming5866]

Hi, great video!! I would be happy if you could explain how you came to the cutoff frequency in the filter because it is very low in relation to your center frequency and how you got to the transition width that is also indicated in the filter?

[@VE6EY]

Hi Gaming. The lowpass filter width and sampling rate are two entirely different things. The RTL was sampling at 2M, then decimated to 200k. At this sampling rate I could do LPF anywhere up to 100k without aliasing. But 6k is the bandwidth that I wanted for AM reception. The transition width was the default value selected, i.e. how fast the LPF slope declines after cutoff frequency. Hope that helps!

[@Awsnap96]

how would you add a PIE demodulator into the receiver, which blocks would be used?

[@VE6EY]

Sorry, not my area of knowledge, sadly. You should find lots of articles on the web on decoding RFID with GNURadio, though.

[@cristinatavarez1275]

Hello oes anyone know how to make an AM stereo in GNU ? please

[@dk_dhanu]

If I want to add AGC block how to add it. My aim is to find the modulation index of received AM signal

[@VE6EY]

GNR has a couple of AGC components. Here is an example of use: wiki.gnuradio.org/index.php/AGC . I think you would just place in the signal chain before demodulation.

[@dk_dhanu]

Thank you, will update after checking.

[@rogerpettersen7062]

Hi John, thank you for the video I`m New to SDR and my HW is hack RF one. I copy Your design(except the Source) but I run in to trouble after the AM demod and in to the rational resampler. I see that the in and output after the AM demod is RED in Your design, but in my the rational resampler have blue in and output. Can you show me the details inside the "rational resampler " Best regard Roger (LB2OE)

[@VE6EY]

Hi Roger. You need to set the Data Type in the Rational Resampler Properties. Blue means complex data, and orange means float data. In my diagram, the Rational Resampler is working with float data for both in and out.

[@adiaz8892]

Using the flow graph from this video and also the flow graph from your other amplitude modulation video(the one where you transmit a classical music wav file using virtual sinks and sources) I was able to set up to SDR's to transmit and receive a tone at 100MHz. However when I attempt to transmit my own music wav file I am not able to hear anything. In other words, I am able to transmit only tones such like DTMF tones made in audacity but not music files that are also made in audacity. Do you have a suggestion to this issue?

[@VE6EY]

Hi Alan. Should work. Just check your # of channels, bit size and sample rate are set up correctly. Also, I could not get 24 bit to work, so go with 16 bit. Probably a simple thing like that. Cheers...