Re: [Flexradio] 1.18.1 Audio Limiting
I've made multiple recordings and I had Eric make recordings of a 60 over S9 AM station. I am unable to duplicate what you are seeing. What I need for diagnosis of the issue is an IQ recording so I can see the problem in action. This will be a large file that probably won't fit through email so one will need to figure out how to make the recording available for download. 73's Bob N4HY Frank Mayer wrote: Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ -- (Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. You don't need to see the whole staircase, just take the first step., MLK. Twitter:rwmcgwier Active: Facebook,Myspace,LinkedIn ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
But this is not a fix, it is a bandaid. I need an IQ recording of the problem happening. I am unhappy that Frank is having to set the AGC threshold to a pretty ridiculous level. What this says to me is that there is something wrong with attack and it needs to be investigated. I am very proud of SAM/AM so I don't want it to have problems like this. Bob N4HY Tim Ellison wrote: Look like you found the fix. The AGC was improved in the 1.18.x releases so this making this parameter change is very reasonable. -Tim -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Frank Mayer Sent: Saturday, June 20, 2009 4:22 PM To: Frank Mayer; flexradio@flex-radio.biz Subject: Re: [Flexradio] 1.18.1 Audio Limiting A point of interest. I am able to stop this audio limiting effect on AM by reducing the AGC-T control from the nominal setting of 90 to 60 and below, depending on the strength of the RX signal. This was unnecessary previously in 1.16.2 and earlier. -- (Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. You don't need to see the whole staircase, just take the first step., MLK. Twitter:rwmcgwier Active: Facebook,Myspace,LinkedIn ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
We completely agree. Frank Mayer wrote: It's not really a fix. It requires constant adjustment of the AGC-T and/or Preamp level to avoid the limiting effect on AM depending on the strength of the signal. - Original Message - From: Tim Ellison telli...@itsco.com To: Frank Mayer wa3...@usa.com; flexradio@flex-radio.biz Sent: Saturday, June 20, 2009 5:06 PM Subject: RE: [Flexradio] 1.18.1 Audio Limiting Look like you found the fix. The AGC was improved in the 1.18.x releases so this making this parameter change is very reasonable. -Tim -- (Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. You don't need to see the whole staircase, just take the first step., MLK. Twitter:rwmcgwier Active: Facebook,Myspace,LinkedIn ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
Whoops - the upward shifts I was referring to are noise floor shifts in the pan display. Bob On Jun 21, 2009, at 8:39 AM, Bob McGwier wrote: But this is not a fix, it is a bandaid. I need an IQ recording of the problem happening. I am unhappy that Frank is having to set the AGC threshold to a pretty ridiculous level. What this says to me is that there is something wrong with attack and it needs to be investigated. I am very proud of SAM/AM so I don't want it to have problems like this. Bob N4HY Tim Ellison wrote: Look like you found the fix. The AGC was improved in the 1.18.x releases so this making this parameter change is very reasonable. -Tim -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz ] On Behalf Of Frank Mayer Sent: Saturday, June 20, 2009 4:22 PM To: Frank Mayer; flexradio@flex-radio.biz Subject: Re: [Flexradio] 1.18.1 Audio Limiting A point of interest. I am able to stop this audio limiting effect on AM by reducing the AGC-T control from the nominal setting of 90 to 60 and below, depending on the strength of the RX signal. This was unnecessary previously in 1.16.2 and earlier. -- (Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. You don't need to see the whole staircase, just take the first step., MLK. Twitter:rwmcgwier Active: Facebook,Myspace,LinkedIn ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
I responded some time ago to this subject, saying that I didn't see any problem with my S-1000; since the topic continues open I though it twice and made some test before giving more opinions. Listening carefully to strong (and not so strong) AM voice transmissions, I must agree that the situation is not as good as I had stated before, my apologies for that. I think there are two causes: AGC and demodulation. 1.- AGC. It is clear that this radio uses something similar to the voice (or RF) derived AGC concept, with all the improvements explained by Phil Harman in his document about the SDR-1000 AGC, and the software reorganization incorporated in SVN 2797. This implementation works extremely well for SSB, CW and digital modes. But when listening to AM broadcasts this solution is not so good, since the current AGC raises the gain in speech pauses and you hear it (studio noises, in fact) and the effect can be very annoying. When dealing with AM you has at your disposal a constant reference of the transmitted signal, the carrier, which can be used as a pilot for the AGC instead of the audio (or IF signal). This is the old method of carrier derived AGC used since almost the beginning of broadcasting. Really the reason for its universal use was its simple implementation once the variable-mu tubes were introduced, but still has advantages when listening AM voice broadcasts, because the AGC still controls the gain in the speech pauses without recurring to very long time constants which are not desirable for SWL DX listening. So my suggestion is to include a Carrier derived AGC for AM and SAM, which could include some of the refinements to deal with impulse noise as already described. This AGC mode could be selected from the setup. 2.- Demodulation. Both the AM and SAM detectors recovers a non symmetrical signal. I just don't have an idea of the reason, but the test is easy: Tune an AM broadcast station transmitting speech, and look the audio on the scope or panascope display. Switch between AM an USB and see the result (select bandwidths of 6 kHz and 3 kHz to listen in the same conditions and set the scope time to 5000 us). If you listen carefully the audio quality improves when switching to USB/LSB. If you tune to an empty frequency you will see unsymmetrical noise also. This effect is not related to the AGC, even fixing the gain level the asymmetry remains. There are bug reports about this: 2240 and 2282. Also 2276 may be related. 73 de Ignacio, EB4APL Frank Mayer wrote: Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
Ignacio, all: Your observations are consistent with mine. My point of reference is a new Pwr SDR 1.18.0 with a F5Ka, compared to Hammarlund and Hallicrafters non-coherent AM detection (Hammarund wins, by the way). The F5Ka coherent AM detection is quite impressive in terms of its resistance to fading. The non-coherent detection and AGC action is pretty good, but maybe a little problematic. I have also observed that listening to AM in SSB mode, independent of bandwidth, as along as the comparison bandwidths are same, produces more pleasing audio quality. I have not taken the time to fiddle with the AGC threshold or time constants yet. But I will. In the grand scheme of things, I am not sure how important it is to emulate the performance and audio characteristics of the old, high quality AM receivers since AM transmission, even on the commercial, and propaganda side of things, is slowly dying. Sure, I would like to say that my new bleeding edge digital radio can perform like the best analog radios of yore, but I still have the old radios too (hi). Thanks for your insight. Bob KF6BC On Jun 21, 2009, at 11:52 AM, EB4APL wrote: I responded some time ago to this subject, saying that I didn't see any problem with my S-1000; since the topic continues open I though it twice and made some test before giving more opinions. Listening carefully to strong (and not so strong) AM voice transmissions, I must agree that the situation is not as good as I had stated before, my apologies for that. I think there are two causes: AGC and demodulation. 1.- AGC. It is clear that this radio uses something similar to the voice (or RF) derived AGC concept, with all the improvements explained by Phil Harman in his document about the SDR-1000 AGC, and the software reorganization incorporated in SVN 2797. This implementation works extremely well for SSB, CW and digital modes. But when listening to AM broadcasts this solution is not so good, since the current AGC raises the gain in speech pauses and you hear it (studio noises, in fact) and the effect can be very annoying. When dealing with AM you has at your disposal a constant reference of the transmitted signal, the carrier, which can be used as a pilot for the AGC instead of the audio (or IF signal). This is the old method of carrier derived AGC used since almost the beginning of broadcasting. Really the reason for its universal use was its simple implementation once the variable-mu tubes were introduced, but still has advantages when listening AM voice broadcasts, because the AGC still controls the gain in the speech pauses without recurring to very long time constants which are not desirable for SWL DX listening. So my suggestion is to include a Carrier derived AGC for AM and SAM, which could include some of the refinements to deal with impulse noise as already described. This AGC mode could be selected from the setup. 2.- Demodulation. Both the AM and SAM detectors recovers a non symmetrical signal. I just don't have an idea of the reason, but the test is easy: Tune an AM broadcast station transmitting speech, and look the audio on the scope or panascope display. Switch between AM an USB and see the result (select bandwidths of 6 kHz and 3 kHz to listen in the same conditions and set the scope time to 5000 us). If you listen carefully the audio quality improves when switching to USB/LSB. If you tune to an empty frequency you will see unsymmetrical noise also. This effect is not related to the AGC, even fixing the gain level the asymmetry remains. There are bug reports about this: 2240 and 2282. Also 2276 may be related. 73 de Ignacio, EB4APL Frank Mayer wrote: Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage:
Re: [Flexradio] 1.18.1 Audio Limiting
Bob, I can make a standard audio recording of it for you with 1.18.1 and then with again with the same staion with 1.62.2 and convert it to mp3 from wav, send it to you and you can hear the issue. It's not an IQ but it will clearly demonstrate the problem I am hearing. Please advise, Frank - Original Message - From: Bob McGwier rwmcgw...@gmail.com To: Frank Mayer wa3...@usa.com Cc: flexradio@flex-radio.biz Sent: Sunday, June 21, 2009 11:35 AM Subject: Re: [Flexradio] 1.18.1 Audio Limiting I've made multiple recordings and I had Eric make recordings of a 60 over S9 AM station. I am unable to duplicate what you are seeing. What I need for diagnosis of the issue is an IQ recording so I can see the problem in action. This will be a large file that probably won't fit through email so one will need to figure out how to make the recording available for download. 73's Bob N4HY Frank Mayer wrote: Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ -- (Co)Author: DttSP, Quiktrak, PowerSDR, GnuRadio Member: ARRL, AMSAT, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. You don't need to see the whole staircase, just take the first step., MLK. Twitter:rwmcgwier Active: Facebook,Myspace,LinkedIn ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
A point of interest. I am able to stop this audio limiting effect on AM by reducing the AGC-T control from the nominal setting of 90 to 60 and below, depending on the strength of the RX signal. This was unnecessary previously in 1.16.2 and earlier. - Original Message - From: Frank Mayer To: flexradio@flex-radio.biz Sent: Saturday, June 20, 2009 3:35 PM Subject: 1.18.1 Audio Limiting Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
Look like you found the fix. The AGC was improved in the 1.18.x releases so this making this parameter change is very reasonable. -Tim -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Frank Mayer Sent: Saturday, June 20, 2009 4:22 PM To: Frank Mayer; flexradio@flex-radio.biz Subject: Re: [Flexradio] 1.18.1 Audio Limiting A point of interest. I am able to stop this audio limiting effect on AM by reducing the AGC-T control from the nominal setting of 90 to 60 and below, depending on the strength of the RX signal. This was unnecessary previously in 1.16.2 and earlier. - Original Message - From: Frank Mayer To: flexradio@flex-radio.biz Sent: Saturday, June 20, 2009 3:35 PM Subject: 1.18.1 Audio Limiting Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] 1.18.1 Audio Limiting
It's not really a fix. It requires constant adjustment of the AGC-T and/or Preamp level to avoid the limiting effect on AM depending on the strength of the signal. - Original Message - From: Tim Ellison telli...@itsco.com To: Frank Mayer wa3...@usa.com; flexradio@flex-radio.biz Sent: Saturday, June 20, 2009 5:06 PM Subject: RE: [Flexradio] 1.18.1 Audio Limiting Look like you found the fix. The AGC was improved in the 1.18.x releases so this making this parameter change is very reasonable. -Tim -Original Message- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Frank Mayer Sent: Saturday, June 20, 2009 4:22 PM To: Frank Mayer; flexradio@flex-radio.biz Subject: Re: [Flexradio] 1.18.1 Audio Limiting A point of interest. I am able to stop this audio limiting effect on AM by reducing the AGC-T control from the nominal setting of 90 to 60 and below, depending on the strength of the RX signal. This was unnecessary previously in 1.16.2 and earlier. - Original Message - From: Frank Mayer To: flexradio@flex-radio.biz Sent: Saturday, June 20, 2009 3:35 PM Subject: 1.18.1 Audio Limiting Audio limiting on AM and SAM receive very evident in the new release, just like it was in the previous release 1.18.0 with the SDR-1000. This issue started with the SVN test branch, SVN 2797 when the changes were made to the AGC. Frank, WA3JBT ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
