Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
Matt Ettus wrote: Martin Dvh wrote: Hi, I found a nasty bug in the wfm_rcv_pll.py code. The pilot tone pll should return the recovered carrier, For this you should use gr.pll_refout_cc, not gr.pll_carriertracking_cc. pll_carriertracking returns the input transformed to baseband using the recovered carrier. pll_refout returns the recovered carrier. Great catch, Martin. With the fixed code I now actually get stereo. (Before you would get a kind of attenuated, distorted, spectrum inverted stereo) Can you check it in? Done I tested it with a stereo-coder I wrote in gnuradio, and now I seem to actually get stereo seperation. (stereo modulater is attached) But now I do get a lot of noise when decoding stereo. I also don't quite understand why double side band suppressed carrier Left-Right audio is attenuated and needs a factor 20 for gain. (It seems to be correct or at least close) I would try this with the regular (non-PLL) FM demod. I think the rolloff of the PLL tracking loop is what is giving you the lower gain. The code comments say 10 dB The actual code uses a factor 20 which corresponds to 20 *log10(20)= 26 dB. This 26 dB seems to be quite accurate, but where is this number based on? can you give me a link to more info or the stereo FM specs on this. # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0, Greetings, Martin fix for wrong pll is below: --- gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll.py 2007-06-11 18:12:55.0 +0200 +++ gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll_fixed.py 2007-06-17 08:07:43.0 +0200 @@ -131,8 +131,8 @@ max_freq = -2.0*math.pi*18990/audio_rate; min_freq = -2.0*math.pi*19010/audio_rate; -self.stereo_carrier_pll_recovery = gr.pll_carriertracking_cc(alpha,beta,max_freq,min_freq); -self.stereo_carrier_pll_recovery.squelch_enable(False); +self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq); +#self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now # set up mixer (multiplier) to get the L-R signal at baseband ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
Hi Martin, Goto http://www.itu.int/rec/R-REC-BS.450-3-200111-I/en and click on the electronic bookshop. After that register for 3 free download. Regards, Hew --- Martin Dvh [EMAIL PROTECTED] wrote: Hew How Chee wrote: Hi, This document might be useful. RECOMMENDATION ITU-R BS.450-3 Transmission standards for FM sound broadcasting at VHF Is it downloadable somewhere? I already found that this is the standard I need, but could not find a place where I could download it. Greetings, Martin Regards, Hew --- Martin Dvh [EMAIL PROTECTED] wrote: can you give me a link to more info or the stereo FM specs on this. Greetings, Martin Pinpoint customers who are looking for what you sell. http://searchmarketing.yahoo.com/ ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
Hew How Chee wrote: Hi, This document might be useful. RECOMMENDATION ITU-R BS.450-3 Transmission standards for FM sound broadcasting at VHF Is it downloadable somewhere? I already found that this is the standard I need, but could not find a place where I could download it. Greetings, Martin Regards, Hew --- Martin Dvh [EMAIL PROTECTED] wrote: can you give me a link to more info or the stereo FM specs on this. Greetings, Martin Take the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news, photos more. http://mobile.yahoo.com/go?refer=1GNXIC ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
Matt Ettus wrote: Martin Dvh wrote: Hi, I found a nasty bug in the wfm_rcv_pll.py code. The pilot tone pll should return the recovered carrier, For this you should use gr.pll_refout_cc, not gr.pll_carriertracking_cc. pll_carriertracking returns the input transformed to baseband using the recovered carrier. pll_refout returns the recovered carrier. Great catch, Martin. With the fixed code I now actually get stereo. (Before you would get a kind of attenuated, distorted, spectrum inverted stereo) Can you check it in? Sure, I will change the example(s) too, because they try to enable the squelch which the pll_refout does not have. (I will disable the squelch for now. Probably implement squelch in pll_refout later) I am working on an improved FM-stereo-receiver and a stereo-fm transmitter too. So I will get back on this when it is finished and add it to the examples. I tested it with a stereo-coder I wrote in gnuradio, and now I seem to actually get stereo seperation. (stereo modulater is attached) But now I do get a lot of noise when decoding stereo. I also don't quite understand why double side band suppressed carrier Left-Right audio is attenuated and needs a factor 20 for gain. (It seems to be correct or at least close) I would try this with the regular (non-PLL) FM demod. I think the rolloff of the PLL tracking loop is what is giving you the lower gain. Yes, that seems to be the problem. For now I switched to using the non-PLL FM-demod. Do you know if/how I can make a PLL which does not have this high roll-of. I played with the pll-parameters but that doesn't seem to help. It is critically damped, so that is probably the best we can get with this pll. Would I need another type of pll with a higher order loop-filter or something like that. Greetings, Martin The code comments say 10 dB The actual code uses a factor 20 which corresponds to 20 *log10(20)= 26 dB. This 26 dB seems to be quite accurate, but where is this number based on? can you give me a link to more info or the stereo FM specs on this. # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0, Greetings, Martin fix for wrong pll is below: --- gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll.py 2007-06-11 18:12:55.0 +0200 +++ gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll_fixed.py 2007-06-17 08:07:43.0 +0200 @@ -131,8 +131,8 @@ max_freq = -2.0*math.pi*18990/audio_rate; min_freq = -2.0*math.pi*19010/audio_rate; -self.stereo_carrier_pll_recovery = gr.pll_carriertracking_cc(alpha,beta,max_freq,min_freq); -self.stereo_carrier_pll_recovery.squelch_enable(False); +self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq); +#self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now # set up mixer (multiplier) to get the L-R signal at baseband ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
I would try this with the regular (non-PLL) FM demod. I think the rolloff of the PLL tracking loop is what is giving you the lower gain. Yes, that seems to be the problem. For now I switched to using the non-PLL FM-demod. Do you know if/how I can make a PLL which does not have this high roll-of. I played with the pll-parameters but that doesn't seem to help. It is critically damped, so that is probably the best we can get with this pll. Would I need another type of pll with a higher order loop-filter or something like that. I think it's just a question of bandwidth. Have you confirmed that the PLL has at least 60 kHz of bandwidth? Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] bug in wfm_rcv_pll and fix, who has stereo FM specs/info and noise and gain issues
Martin Dvh wrote: Hi, I found a nasty bug in the wfm_rcv_pll.py code. The pilot tone pll should return the recovered carrier, For this you should use gr.pll_refout_cc, not gr.pll_carriertracking_cc. pll_carriertracking returns the input transformed to baseband using the recovered carrier. pll_refout returns the recovered carrier. Great catch, Martin. With the fixed code I now actually get stereo. (Before you would get a kind of attenuated, distorted, spectrum inverted stereo) Can you check it in? I tested it with a stereo-coder I wrote in gnuradio, and now I seem to actually get stereo seperation. (stereo modulater is attached) But now I do get a lot of noise when decoding stereo. I also don't quite understand why double side band suppressed carrier Left-Right audio is attenuated and needs a factor 20 for gain. (It seems to be correct or at least close) I would try this with the regular (non-PLL) FM demod. I think the rolloff of the PLL tracking loop is what is giving you the lower gain. The code comments say 10 dB The actual code uses a factor 20 which corresponds to 20 *log10(20)= 26 dB. This 26 dB seems to be quite accurate, but where is this number based on? can you give me a link to more info or the stereo FM specs on this. # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0, Greetings, Martin fix for wrong pll is below: --- gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll.py 2007-06-11 18:12:55.0 +0200 +++ gnuradio-core/src/python/gnuradio/blksimpl/wfm_rcv_pll_fixed.py 2007-06-17 08:07:43.0 +0200 @@ -131,8 +131,8 @@ max_freq = -2.0*math.pi*18990/audio_rate; min_freq = -2.0*math.pi*19010/audio_rate; -self.stereo_carrier_pll_recovery = gr.pll_carriertracking_cc(alpha,beta,max_freq,min_freq); -self.stereo_carrier_pll_recovery.squelch_enable(False); +self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq); +#self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now # set up mixer (multiplier) to get the L-R signal at baseband ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
