Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
I found a bug with de-emphasis, the coefficients in de denominator should change their sign in gnuradio One question. I have tried your simple_fm_rcv and a similar version that I made on my own. In both cases I have found that there is a phase shift in the pilot tone. In the image the red curve is the L-R modulated signal and the green line is the recovered 38Khz carried recovered after squaring the pilot tone. It looks like the zero crossings are pi/2 rad shifted so the demodulated signal is almost zero. http://gnuradio.4.n7.nabble.com/file/n42875/Screen_Shot_2013-08-01_at_6.04.35_PM.png By delaying the pilot by one sample (which is almos pi/2) the problem solves, but I do not see any reason for doing this :-( Of course, I have been careful and all the filters to split the mux signal have the same delay and have linear phase Any idea? -- View this message in context: http://gnuradio.4.n7.nabble.com/Sample-audio-from-my-FM-stereo-receiver-tp1897p42875.html Sent from the GnuRadio mailing list archive at Nabble.com. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
Thanks for posting this - it appears to work just fine with an Ultra-cheap RTL2832U-based USB dongle. Sounds pretty good too. Eric On 03/12/2012 11:53 AM, mle...@ripnet.com wrote: Rafael: I added methods for resetting the state machines on the demodulator and the decoder, but apart from that, no. My code relies on those updates so I pushed the updates up to CGRAN for radio_data_system -Marcus On Mon, 12 Mar 2012 06:09:11 -0700, Rafael Diniz wrote: Marcus, Have you done any improvements to the good old RDS code in cgran? Best regards, Rafael Diniz On 03/11/2012 08:40 PM, Andrew Davis wrote: Wow, sounds good, I've got a bunch of 50KW stations about 2 miles away and I cannot get any to sound good at all. What receiver code are you using? The code that I put on on CGRAN yesterday: ** https://www.cgran.org/svn/projects/simple_fm_rcv And the supporting RDS code: ** https://www.cgran.org/svn/projects/radio_data_system I'm using a TVRX2 on a B100, and this was with 8-bit baseband samples at 320Ksps input rate to the FM demod. Your problem might actually be that you have a *bunch* of 50KW stations close by. Although with 70+ dB of dynamic range even at 12-bit ADC sampling, with the gain set right, you shouldn't have too many problems. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org mailto:Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
Marcus, Have you done any improvements to the good old RDS code in cgran? Best regards, Rafael Diniz On 03/11/2012 08:40 PM, Andrew Davis wrote: Wow, sounds good, I've got a bunch of 50KW stations about 2 miles away and I cannot get any to sound good at all. What receiver code are you using? The code that I put on on CGRAN yesterday: ** https://www.cgran.org/svn/projects/simple_fm_rcv And the supporting RDS code: ** https://www.cgran.org/svn/projects/radio_data_system I'm using a TVRX2 on a B100, and this was with 8-bit baseband samples at 320Ksps input rate to the FM demod. Your problem might actually be that you have a *bunch* of 50KW stations close by. Although with 70+ dB of dynamic range even at 12-bit ADC sampling, with the gain set right, you shouldn't have too many problems. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
Rafael: I added methods for resetting the state machines on the demodulator and the decoder, but apart from that, no. My code relies on those updates so I pushed the updates up to CGRAN for radio_data_system -Marcus On Mon, 12 Mar 2012 06:09:11 -0700, Rafael Diniz wrote: Marcus, Have you done any improvements to the good old RDS code in cgran? Best regards, Rafael Diniz On 03/11/2012 08:40 PM, Andrew Davis wrote: Wow, sounds good, I've got a bunch of 50KW stations about 2 miles away and I cannot get any to sound good at all. What receiver code are you using? The code that I put on on CGRAN yesterday: ** https://www.cgran.org/svn/projects/simple_fm_rcv [1] And the supporting RDS code: ** https://www.cgran.org/svn/projects/radio_data_system [2] I'm using a TVRX2 on a B100, and this was with 8-bit baseband samples at 320Ksps input rate to the FM demod. Your problem might actually be that you have a *bunch* of 50KW stations close by. Although with 70+ dB of dynamic range even at 12-bit ADC sampling, with the gain set right, you shouldn't have too many problems. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org [3] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [4] Links: -- [1] https://www.cgran.org/svn/projects/simple_fm_rcv [2] https://www.cgran.org/svn/projects/radio_data_system [3] mailto:Discuss-gnuradio@gnu.org [4] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
On 03/12/2012 09:09 AM, Rafael Diniz wrote: Marcus, Have you done any improvements to the good old RDS code in cgran? Just updated the simple_fm_rcv code to use 250e3 sample rate, since that's a common rate between B100/USRP1/E1XX and N2XX family, and all the math works out. That will more lightly load the cpu as well, compared to 320e3. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
On 03/12/2012 09:01 PM, Marcus D. Leech wrote: On 03/12/2012 09:09 AM, Rafael Diniz wrote: Marcus, Have you done any improvements to the good old RDS code in cgran? Just updated the simple_fm_rcv code to use 250e3 sample rate, since that's a common rate between B100/USRP1/E1XX and N2XX family, and all the math works out. That will more lightly load the cpu as well, compared to 320e3. And here's an audio sample using the new common sample rate: http://www.sbrac.org/files/fm_stereo_test2.ogg -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
Doesn't sound as good to me, maybe it's just a bad sample. I for some reason ( I know the math tells me otherwise ) I find it sounds better the faster I sample, like 500M. I feel like it has something to do with more exact following of the FM signal curve or something. So how exactly does the software FM Demod work ( crossing detection )? And why can my $5 toy FM radio sound so much cleaner? On Mon, Mar 12, 2012 at 9:09 PM, Marcus D. Leech mle...@ripnet.com wrote: On 03/12/2012 09:01 PM, Marcus D. Leech wrote: On 03/12/2012 09:09 AM, Rafael Diniz wrote: Marcus, Have you done any improvements to the good old RDS code in cgran? Just updated the simple_fm_rcv code to use 250e3 sample rate, since that's a common rate between B100/USRP1/E1XX and N2XX family, and all the math works out. That will more lightly load the cpu as well, compared to 320e3. And here's an audio sample using the new common sample rate: http://www.sbrac.org/files/fm_stereo_test2.ogg -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
On 12/03/12 10:08 PM, Andrew Davis wrote: Doesn't sound as good to me, maybe it's just a bad sample. I for some reason ( I know the math tells me otherwise ) I find it sounds better the faster I sample, like 500M. I feel like it has something to do with more exact following of the FM signal curve or something. I had the bass turned up, which matches my speakers well, but now that I'm listening to the Baba O'Reilly sample on my headphones, it's quite a bit too bassy. So how exactly does the software FM Demod work ( crossing detection )? And why can my $5 toy FM radio sound so much cleaner? It's a quadrature demodulator using ATAN2--not a simple crossing detector. It should be quite high fidelity. Some of these listening tests are notoriously subjective as well, and the source material varies wildly in quality. The other thing is this receiver doesn't do any deemphasis processing, choosing instead to have a 3-band equalizer with settable gains that allow you to tweak the audio spectrum of the output a bit. Some keener could make it more fine-grained to tune the resulting sound to suit personal preferences/room/etc. -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
Wow, sounds good, I've got a bunch of 50KW stations about 2 miles away and I cannot get any to sound good at all. What receiver code are you using? On Sun, Mar 11, 2012 at 7:46 PM, Marcus D. Leech mle...@ripnet.com wrote: http://www.sbrac.org/files/fm_stereo_test.ogg This is tuned to a station that's approximately 100km from my location. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Sample audio from my FM stereo receiver
On Sun, Mar 11, 2012 at 17:50, Marcus D. Leech mle...@ripnet.com wrote: ...with the gain set right... This is where I've run into a lot of issues. Too much gain, the lower end of the dynamic range is filled with IMD. Too little gain, the noise figure is too high. It's hard to get even 12 bits of ADC dynamic range in the presence of strong signals. Johnathan ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
