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noise blanker with ISCAT/FSK

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  • TLC_Carney
    Greetings all I m in one of those neighborhoods where there is frequently some form of man made noise on 6M. I ve noticed that turning on the noise blanker
    Message 1 of 11 , Feb 10, 2011
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      Greetings all

      I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.

      I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?

      73,

      Tom K6EU
    • Curt Nixon
      Hi Tom: I m a relative newcomer to MS and have similar noise issues on 6. I use an old IC-551 and have found that the noise blanker can inhibit decodes of FSK
      Message 2 of 11 , Feb 10, 2011
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        Hi Tom:

        I'm a relative newcomer to MS and have similar noise issues on 6. I use
        an old IC-551 and have found that the noise blanker can inhibit decodes
        of FSK signals. My theory is that FSK signals occur fast enough that
        choping them up via the blanker messes them up. The software does a good
        job of sorting the wheat from the chaf so to speak even though it is not
        apparent by listening.

        I have not spent enough time with ISCAT to know if it behaves the same
        but it seems to transition slower so might be ok ...

        I suspect that most of the wisdom will suggest that the NB be OFF on the
        rig.

        FWIW

        Curt
        KU8L

        TLC_Carney wrote:
        >
        > Greetings all
        >
        > I'm in one of those neighborhoods where there is frequently some form
        > of man made noise on 6M. I've noticed that turning on the noise
        > blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
        >
        > I wonder, does it really do any good? IE can decode ISCAT/FSK signals
        > that I couldn't decode with the noise blanker off?
        >
        > 73,
        >
        > Tom K6EU
        >
        >
      • Barry Garratt
        Hey Tom, I m in a very quiet location but occasionally get some noise when I m pointing west because of a mall out that way. I run my K3 with both preamps on
        Message 3 of 11 , Feb 10, 2011
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          Hey Tom,

           

          I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz  bandpass filter the output of which then goes back into the K3.

           

          I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 – 2700 Hz and run the K3 with the 1800 Hz filter.

           

          Just my way of doing things Tom. As the saying goes your mileage may vary.

           

          73,

           

          Barry KS7DX  

           

          From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
          Sent: Thursday, February 10, 2011 5:40 PM
          To: wsjtgroup@yahoogroups.com
          Subject: [wsjtgroup] noise blanker with ISCAT/FSK

           

           

          Greetings all

          I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.

          I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?

          73,

          Tom K6EU

        • Bill VanAlstyne W5WVO
          Tom, Barry, et al., This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
          Message 4 of 11 , Feb 10, 2011
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            Tom, Barry, et al.,
             
            This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
             
            In general I have not seen bad effects of a noise blanker on FSK441 signals.  I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured.  I'd say you should experiment and decide for your own system.”
             
            Well, I’d already been doing that, of course.
             
            Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
             
            The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
             
            Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
             
            But as far as unscientific, subjective experience is concerned – I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-)  Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly – nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question – no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
             
            Bill W5WVO
             
             
            Sent: Friday, February 11, 2011 02:14
            Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
             
             

            Hey Tom,

            I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz  bandpass filter the output of which then goes back into the K3.

            I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 – 2700 Hz and run the K3 with the 1800 Hz filter.

            Just my way of doing things Tom. As the saying goes your mileage may vary.

            73,

            Barry KS7DX 

            From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
            Sent: Thursday, February 10, 2011 5:40 PM
            To: wsjtgroup@yahoogroups.com
            Subject: [wsjtgroup] noise blanker with ISCAT/FSK

             

            Greetings all

            I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.

            I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?

            73,

            Tom K6EU

          • Clay W7CE
            I don t have any ISCAT experience, but I have done a fair amount of testing with and without noise blankers on FSK441, JT65A and JT65B. I m currently capable
            Message 5 of 11 , Feb 10, 2011
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              I don't have any ISCAT experience, but I have done a fair amount of testing with and without noise blankers on FSK441, JT65A and JT65B.  I'm currently capable of using up to three receivers simultaneously.  Two are in my Flex 5000A and have independent noise blankers.  For the third I usually run a Flex 1500.  When local noise, typically from power lines, is a problem I can get decodes from the receivers with the Noise Blanker turned on when the receiver with the noise blanker turned off doesn't even show a trace in SpecJT.  As soon as I turn the NB back on then the decodes are similar.  I've also tried this experiment with a Flex 3000, a VHF Ensemble SDR (soft rock-type design), a K3 and an IC-765ProIII with similar results, although the 756PRoIII noise blanker is mostly useless for power line noise and seems to be optimized for ignition noise when used mobile.  I almost always run with the 5000A noise blankers turned on now, since for each power line noise source that is located and repaired, there seem to be two more waiting to take its place.

              It's interesting to note that when running multiple receivers, I usually get a higher rate of decodes compared to running only one receiver.  It is quite common to have one receiver decode the signal when another one doesn't.  Next time it might be the other way around.  I've made half a dozen or more 6M EME contacts that would not have happened with only one receiver.

              73,
              Clay  W7CE


              On 2/10/2011 7:50 PM, Bill VanAlstyne W5WVO wrote:
               

              Tom, Barry, et al.,
               
              This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
               
              In general I have not seen bad effects of a noise blanker on FSK441 signals.  I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured.  I'd say you should experiment and decide for your own system.”
               
              Well, I’d already been doing that, of course.
               
              Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
               
              The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
               
              Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
               
              But as far as unscientific, subjective experience is concerned – I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-)  Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly – nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question – no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
               
              Bill W5WVO
               
               
              Sent: Friday, February 11, 2011 02:14
              Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
               
               

              Hey Tom,

              I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz  bandpass filter the output of which then goes back into the K3.

              I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 – 2700 Hz and run the K3 with the 1800 Hz filter.

              Just my way of doing things Tom. As the saying goes your mileage may vary.

              73,

              Barry KS7DX 

              From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
              Sent: Thursday, February 10, 2011 5:40 PM
              To: wsjtgroup@yahoogroups.com
              Subject: [wsjtgroup] noise blanker with ISCAT/FSK

               

              Greetings all

              I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.

              I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?

              73,

              Tom K6EU


            • TLC_Carney
              Thanks for all of those who responded. I ve been experimenting a bit but as Bill says, it s hard to tell. So far I haven t seen any evidence of bad decodes
              Message 6 of 11 , Feb 12, 2011
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                Thanks for all of those who responded.

                I've been experimenting a bit but as Bill says, it's hard to tell. So far I haven't seen any evidence of "bad decodes" with the NB on. I did see one FSK ping that was below the "noise blanker off" floor decoded with the blanker on. Not much of a sample size.

                My K3 Nb setting is IF off, DSP 3-5. I assume 3-5 is fairly aggressive but 3-4 has not effect on the noise.

                Will continue to play with this.

                73,

                Tom K6EU



                --- In wsjtgroup@yahoogroups.com, "Bill VanAlstyne W5WVO" <w5wvo@...> wrote:
                >
                > Tom, Barry, et al.,
                >
                > This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
                >
                > “ In general I have not seen bad effects of a noise blanker on FSK441 signals. I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured. I'd say you should experiment and decide for your own system.”
                >
                > Well, I’d already been doing that, of course.
                >
                > Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                >
                > The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                >
                > Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                >
                > But as far as unscientific, subjective experience is concerned â€" I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-) Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly â€" nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question â€" no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                >
                > Bill W5WVO
                >
                >
                > From: Barry Garratt
                > Sent: Friday, February 11, 2011 02:14
                > To: 'TLC_Carney' ; wsjtgroup@yahoogroups.com
                > Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                >
                >
                >
                > Hey Tom,
                >
                >
                > I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz bandpass filter the output of which then goes back into the K3.
                >
                >
                > I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 â€" 2700 Hz and run the K3 with the 1800 Hz filter.
                >
                >
                > Just my way of doing things Tom. As the saying goes your mileage may vary.
                >
                >
                > 73,
                >
                >
                > Barry KS7DX
                >
                >
                > From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
                > Sent: Thursday, February 10, 2011 5:40 PM
                > To: wsjtgroup@yahoogroups.com
                > Subject: [wsjtgroup] noise blanker with ISCAT/FSK
                >
                >
                >
                >
                > Greetings all
                >
                > I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
                >
                > I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?
                >
                > 73,
                >
                > Tom K6EU
                >
              • Bill VanAlstyne W5WVO
                I’m resurrecting this old thread as I have some new anecdotal data on it. As suggested by Joe Taylor (see thread below), I’ve been experimenting with the
                Message 7 of 11 , Jul 24, 2011
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                  I’m resurrecting this old thread as I have some new anecdotal data on it.
                   
                  As suggested by Joe Taylor (see thread below), I’ve been experimenting with the K3 noise blankers (DSP and conventional analog) to see which one performs the best with FSK441 on meteor scatter signals.
                   
                  Over and over, I’ve found that running the DSP noise blanker on the K3 at any useful level creates artifacts or behaviors that seem to interfere with FSK441 decoding of weak to moderate signals. Strong signals that are well above the ambient noise level are not affected by the DSP noise blanker, but of course the NB is, in such a case, unnecessary anyway. But any signal that would be no more than a dB or two above the noise without the NB on does not decode cleanly with the DSP NB set to any useful noise-blanking level.
                   
                  To my amazement, however, the analog NB seems to have no such problems. While it reduces the dynamic range of the receiver chain (as does any analog IF NB), this is typically not a problem when working weak-signal modes. I have cleanly decoded weak FSK441 sigs that would have been in the noise had the K3 analog NB not been invoked.
                   
                  So tentatively, if you use a K3, turn OFF the DSP NB and turn ON the analog NB. Set it to the least aggressive position that produces a maximum of noise reduction. K3 m/s ops, let me know your experiences with this.
                   
                  Again, to emphasize, this is with regard to FSK441 VHF meteor-scatter operation with the Elecraft K3. Not anything else.
                   
                  Bill W5WVO
                   
                   
                   
                  Sent: Friday, February 11, 2011 03:50
                  Subject: Re: [wsjtgroup] noise blanker with ISCAT/FSK
                   
                   

                  Tom, Barry, et al.,
                   
                  This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
                   
                  In general I have not seen bad effects of a noise blanker on FSK441 signals.  I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured.  I'd say you should experiment and decide for your own system.”
                   
                  Well, I’d already been doing that, of course.
                   
                  Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                   
                  The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                   
                  Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                   
                  But as far as unscientific, subjective experience is concerned – I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-)  Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly – nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question – no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                   
                  Bill W5WVO
                   
                   
                  Sent: Friday, February 11, 2011 02:14
                  Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                   
                   

                  Hey Tom,

                  I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz  bandpass filter the output of which then goes back into the K3.

                  I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 – 2700 Hz and run the K3 with the 1800 Hz filter.

                  Just my way of doing things Tom. As the saying goes your mileage may vary.

                  73,

                  Barry KS7DX 

                  From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
                  Sent: Thursday, February 10, 2011 5:40 PM
                  To: wsjtgroup@yahoogroups.com
                  Subject: [wsjtgroup] noise blanker with ISCAT/FSK

                   

                  Greetings all

                  I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.

                  I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?

                  73,

                  Tom K6EU

                • TLC_Carney
                  Thanks for the follow up Bill. My experience is exactly the same as your with the DSP based noise blanker. I didn t try the IF blanker as, even cranked all
                  Message 8 of 11 , Jul 24, 2011
                  • 0 Attachment
                    Thanks for the follow up Bill. My experience is exactly the same as your with the DSP based noise blanker. I didn't try the IF blanker as, even cranked all the way up, it had very little effect on the noise in my neighborhood. I tried it again this morning and while it still has little effect on the worst noise source, it does reduce the noise of other sources in the neighborhood.

                    I'll try some experimenting over the next week and post the results.

                    73,

                    Tom K6EU



                    --- In wsjtgroup@yahoogroups.com, "Bill VanAlstyne W5WVO" <w5wvo@...> wrote:
                    >
                    > I’m resurrecting this old thread as I have some new anecdotal data on it.
                    >
                    > As suggested by Joe Taylor (see thread below), I’ve been experimenting with the K3 noise blankers (DSP and conventional analog) to see which one performs the best with FSK441 on meteor scatter signals.
                    >
                    > Over and over, I’ve found that running the DSP noise blanker on the K3 at any useful level creates artifacts or behaviors that seem to interfere with FSK441 decoding of weak to moderate signals. Strong signals that are well above the ambient noise level are not affected by the DSP noise blanker, but of course the NB is, in such a case, unnecessary anyway. But any signal that would be no more than a dB or two above the noise without the NB on does not decode cleanly with the DSP NB set to any useful noise-blanking level.
                    >
                    > To my amazement, however, the analog NB seems to have no such problems. While it reduces the dynamic range of the receiver chain (as does any analog IF NB), this is typically not a problem when working weak-signal modes. I have cleanly decoded weak FSK441 sigs that would have been in the noise had the K3 analog NB not been invoked.
                    >
                    > So tentatively, if you use a K3, turn OFF the DSP NB and turn ON the analog NB. Set it to the least aggressive position that produces a maximum of noise reduction. K3 m/s ops, let me know your experiences with this.
                    >
                    > Again, to emphasize, this is with regard to FSK441 VHF meteor-scatter operation with the Elecraft K3. Not anything else.
                    >
                    > Bill W5WVO
                    >
                    >
                    >
                    > From: Bill VanAlstyne W5WVO
                    > Sent: Friday, February 11, 2011 03:50
                    > To: 'TLC_Carney' ; wsjtgroup@yahoogroups.com ; Barry Garratt
                    > Subject: Re: [wsjtgroup] noise blanker with ISCAT/FSK
                    >
                    >
                    >
                    > Tom, Barry, et al.,
                    >
                    > This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
                    >
                    > “ In general I have not seen bad effects of a noise blanker on FSK441 signals. I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured. I'd say you should experiment and decide for your own system.”
                    >
                    > Well, I’d already been doing that, of course.
                    >
                    > Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                    >
                    > The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                    >
                    > Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                    >
                    > But as far as unscientific, subjective experience is concerned â€" I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-) Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly â€" nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question â€" no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                    >
                    > Bill W5WVO
                    >
                    >
                    > From: Barry Garratt
                    > Sent: Friday, February 11, 2011 02:14
                    > To: 'TLC_Carney' ; wsjtgroup@yahoogroups.com
                    > Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                    >
                    >
                    >
                    > Hey Tom,
                    >
                    >
                    > I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz bandpass filter the output of which then goes back into the K3.
                    >
                    >
                    > I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 â€" 2700 Hz and run the K3 with the 1800 Hz filter.
                    >
                    >
                    > Just my way of doing things Tom. As the saying goes your mileage may vary.
                    >
                    >
                    > 73,
                    >
                    >
                    > Barry KS7DX
                    >
                    >
                    > From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of TLC_Carney
                    > Sent: Thursday, February 10, 2011 5:40 PM
                    > To: wsjtgroup@yahoogroups.com
                    > Subject: [wsjtgroup] noise blanker with ISCAT/FSK
                    >
                    >
                    >
                    >
                    > Greetings all
                    >
                    > I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
                    >
                    > I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?
                    >
                    > 73,
                    >
                    > Tom K6EU
                    >
                  • Bill VanAlstyne W5WVO
                    Tom, Analog noise blankers tend to work best on “impulse”-type noise – the kind of noise you get from sparks (ignition systems, power line arcing, etc.).
                    Message 9 of 11 , Jul 24, 2011
                    • 0 Attachment
                      Tom,
                       
                      Analog noise blankers tend to work best on “impulse”-type noise – the kind of noise you get from sparks (ignition systems, power line arcing, etc.). Electronically generated broadband noise is typically not reduced a lot, if any, by this kind of NB, which is why Elecraft put in a DSP-based NB as well. The noise I tried the analog NB on sounded like power-line noise to me.
                       
                      Bill W5WVO
                       
                       
                      Sent: Sunday, July 24, 2011 16:28
                      Subject: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK
                       
                       

                      Thanks for the follow up Bill. My experience is exactly the same as your with the DSP based noise blanker. I didn't try the IF blanker as, even cranked all the way up, it had very little effect on the noise in my neighborhood. I tried it again this morning and while it still has little effect on the worst noise source, it does reduce the noise of other sources in the neighborhood.

                      I'll try some experimenting over the next week and post the results.

                      73,

                      Tom K6EU

                      --- In mailto:wsjtgroup%40yahoogroups.com, "Bill VanAlstyne W5WVO" <w5wvo@...> wrote:

                      >
                      > I’m
                      resurrecting this old thread as I have some new anecdotal data on it.
                      >
                      > As suggested by Joe Taylor (see thread below), I’ve been
                      experimenting with the K3 noise blankers (DSP and conventional analog) to see which one performs the best with FSK441 on meteor scatter signals.
                      >
                      > Over and over, I’ve found that running the DSP noise blanker on the
                      K3 at any useful level creates artifacts or behaviors that seem to interfere with FSK441 decoding of weak to moderate signals. Strong signals that are well above the ambient noise level are not affected by the DSP noise blanker, but of course the NB is, in such a case, unnecessary anyway. But any signal that would be no more than a dB or two above the noise without the NB on does not decode cleanly with the DSP NB set to any useful noise-blanking level.
                      >
                      >
                      To my amazement, however, the analog NB seems to have no such problems. While it reduces the dynamic range of the receiver chain (as does any analog IF NB), this is typically not a problem when working weak-signal modes. I have cleanly decoded weak FSK441 sigs that would have been in the noise had the K3 analog NB not been invoked.
                      >
                      > So tentatively, if you use a K3, turn OFF the
                      DSP NB and turn ON the analog NB. Set it to the least aggressive position that produces a maximum of noise reduction. K3 m/s ops, let me know your experiences with this.
                      >
                      > Again, to emphasize, this is with regard to FSK441
                      VHF meteor-scatter operation with the Elecraft K3. Not anything else.
                      >
                      > Bill W5WVO
                      >
                      >
                      >
                      > From: Bill VanAlstyne
                      W5WVO
                      > Sent: Friday, February 11, 2011 03:50
                      > To: 'TLC_Carney' ;
                      mailto:wsjtgroup%40yahoogroups.com ; Barry Garratt
                      > Subject: Re: [wsjtgroup] noise blanker with
                      ISCAT/FSK
                      >
                      >
                      >
                      > Tom, Barry, et al.,
                      >
                      > This question about noise blankers and FSK441 has occurred to me as
                      well. I wrote to Joe Taylor about it, in fact. This is what he said:
                      >
                      > “ In general I have not seen bad effects of a noise blanker on FSK441
                      signals. I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured. I'd say you should experiment and decide for your own system.”
                      >
                      > Well, I’d already been doing that, of
                      course.
                      >
                      > Barry and I both run K3s, and the K3 actually has two
                      independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                      >
                      > The problem with “experimenting” with
                      meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                      >
                      > Now, I don’t have such a
                      “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                      >
                      > But as far as unscientific, subjective experience is concerned â€" I
                      believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-) Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly â€" nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question â€" no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                      >
                      > Bill W5WVO
                      >
                      >
                      > From: Barry
                      Garratt
                      > Sent: Friday, February 11, 2011 02:14
                      > To: 'TLC_Carney'
                      ; mailto:wsjtgroup%40yahoogroups.com
                      > Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                      >
                      >
                      >
                      > Hey Tom,
                      >
                      >
                      > I’m in a very quiet
                      location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz bandpass filter the output of which then goes back into the K3.
                      >
                      >
                      > I run it
                      like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 â€" 2700 Hz and run the K3 with the 1800 Hz filter.
                      >
                      >
                      > Just my way
                      of doing things Tom. As the saying goes your mileage may vary.
                      >
                      >
                      > 73,
                      >
                      >
                      > Barry KS7DX
                      >
                      >
                      >
                      From: mailto:wsjtgroup%40yahoogroups.com [mailto:mailto:wsjtgroup%40yahoogroups.com] On Behalf Of TLC_Carney
                      > Sent: Thursday, February 10, 2011 5:40
                      PM
                      > To:
                      href="mailto:wsjtgroup%40yahoogroups.com">mailto:wsjtgroup%40yahoogroups.com
                      >
                      Subject: [wsjtgroup] noise blanker with ISCAT/FSK
                      >
                      >
                      >
                      >
                      > Greetings all
                      >
                      > I'm in one of those
                      neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
                      >
                      > I wonder, does it really do any
                      good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?
                      >
                      > 73,
                      >
                      > Tom
                      K6EU
                      >

                    • Dan Bates
                      Just as a reference, I have a very nasty power line buzz that starts popping on hot afternoons until it becomes solid then goes away after sundown. I have the
                      Message 10 of 11 , Jul 25, 2011
                      • 0 Attachment

                        Just as a reference, I have a very nasty power line buzz that starts popping on hot afternoons until it becomes solid then goes away after sundown.

                         

                        I have the K3 NB set to DSP t3-6, and IF Med4.  This completely knocks out the noise, and I notice no problems with decoding ISCAT. The other thing I do is turn off AGC which keeps the noise pulses from shutting down the rf gain.  I also only run the external preamp and leave the internal preamp off.  I notice no decrease in SNR, but an improved noise floor..

                         

                        I’d appreciate anyone else’s experience.

                         

                        Dan n5tm

                         

                        From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Bill VanAlstyne W5WVO
                        Sent: Sunday, July 24, 2011 5:07 PM
                        To: wsjtgroup@yahoogroups.com; TLC_Carney
                        Subject: Re: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK

                         

                         

                        Tom,

                         

                        Analog noise blankers tend to work best on “impulse”-type noise – the kind of noise you get from sparks (ignition systems, power line arcing, etc.). Electronically generated broadband noise is typically not reduced a lot, if any, by this kind of NB, which is why Elecraft put in a DSP-based NB as well. The noise I tried the analog NB on sounded like power-line noise to me.

                         

                        Bill W5WVO

                         

                         

                        From: TLC_Carney

                        Sent: Sunday, July 24, 2011 16:28

                        Subject: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK

                         

                         

                        Thanks for the follow up Bill. My experience is exactly the same as your with the DSP based noise blanker. I didn't try the IF blanker as, even cranked all the way up, it had very little effect on the noise in my neighborhood. I tried it again this morning and while it still has little effect on the worst noise source, it does reduce the noise of other sources in the neighborhood.

                        I'll try some experimenting over the next week and post the results.

                        73,

                        Tom K6EU

                        --- In mailto:wsjtgroup%40yahoogroups.com, "Bill VanAlstyne W5WVO" <w5wvo@...> wrote:
                        >
                        > I’m resurrecting this old thread as I have some new anecdotal data on it.
                        >
                        > As suggested by Joe Taylor (see thread below), I’ve been experimenting with the K3 noise blankers (DSP and conventional analog) to see which one performs the best with FSK441 on meteor scatter signals.
                        >
                        > Over and over, I’ve found that running the DSP noise blanker on the K3 at any useful level creates artifacts or behaviors that seem to interfere with FSK441 decoding of weak to moderate signals. Strong signals that are well above the ambient noise level are not affected by the DSP noise blanker, but of course the NB is, in such a case, unnecessary anyway. But any signal that would be no more than a dB or two above the noise without the NB on does not decode cleanly with the DSP NB set to any useful noise-blanking level.
                        >
                        > To my amazement, however, the analog NB seems to have no such problems. While it reduces the dynamic range of the receiver chain (as does any analog IF NB), this is typically not a problem when working weak-signal modes. I have cleanly decoded weak FSK441 sigs that would have been in the noise had the K3 analog NB not been invoked.
                        >
                        > So tentatively, if you use a K3, turn OFF the DSP NB and turn ON the analog NB. Set it to the least aggressive position that produces a maximum of noise reduction. K3 m/s ops, let me know your experiences with this.
                        >
                        > Again, to emphasize, this is with regard to FSK441 VHF meteor-scatter operation with the Elecraft K3. Not anything else.
                        >
                        > Bill W5WVO
                        >
                        >
                        >
                        > From: Bill VanAlstyne W5WVO
                        > Sent: Friday, February 11, 2011 03:50
                        > To: 'TLC_Carney' ; mailto:wsjtgroup%40yahoogroups.com ; Barry Garratt
                        > Subject: Re: [wsjtgroup] noise blanker with ISCAT/FSK
                        >
                        >
                        >
                        > Tom, Barry, et al.,
                        >
                        > This question about noise blankers and FSK441 has occurred to me as well. I wrote to Joe Taylor about it, in fact. This is what he said:
                        >
                        > “ In general I have not seen bad effects of a noise blanker on FSK441 signals. I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured. I'd say you should experiment and decide for your own system.”
                        >
                        > Well, I’d already been doing that, of course.
                        >
                        > Barry and I both run K3s, and the K3 actually has two independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                        >
                        > The problem with “experimenting” with meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                        >
                        > Now, I don’t have such a “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                        >
                        > But as far as unscientific, subjective experience is concerned â€" I believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-) Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly â€" nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question â€" no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                        >
                        > Bill W5WVO
                        >
                        >
                        > From: Barry Garratt
                        > Sent: Friday, February 11, 2011 02:14
                        > To: 'TLC_Carney' ; mailto:wsjtgroup%40yahoogroups.com
                        > Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                        >
                        >
                        >
                        > Hey Tom,
                        >
                        >
                        > I’m in a very quiet location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz bandpass filter the output of which then goes back into the K3.
                        >
                        >
                        > I run it like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 â€" 2700 Hz and run the K3 with the 1800 Hz filter.
                        >
                        >
                        > Just my way of doing things Tom. As the saying goes your mileage may vary.
                        >
                        >
                        > 73,
                        >
                        >
                        > Barry KS7DX
                        >
                        >
                        > From: mailto:wsjtgroup%40yahoogroups.com [mailto:mailto:wsjtgroup%40yahoogroups.com] On Behalf Of TLC_Carney
                        > Sent: Thursday, February 10, 2011 5:40 PM
                        > To: mailto:wsjtgroup%40yahoogroups.com
                        > Subject: [wsjtgroup] noise blanker with ISCAT/FSK
                        >
                        >
                        >
                        >
                        > Greetings all
                        >
                        > I'm in one of those neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
                        >
                        > I wonder, does it really do any good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?
                        >
                        > 73,
                        >
                        > Tom K6EU
                        >

                      • Bill VanAlstyne W5WVO
                        Hi Dan, Thanks for the data point. Theoretically, I wouldn’t expect any problems decoding ISCAT with DSP NB on, because it is a much slower protocol, and
                        Message 11 of 11 , Jul 25, 2011
                        • 0 Attachment
                          Hi Dan,
                           
                          Thanks for the data point. Theoretically, I wouldn’t expect any problems decoding ISCAT with DSP NB on, because it is a much slower protocol, and thus much less likely to trigger the DSP algorithms. However, I use ISCAT only occasionally, since meteor scatter has been my main pursuit, and ISCAT is typically too slow for brief (< 200 ms) m/s pings.
                           
                          Your K3 setup is pretty much the way I have mine set up also for WSJT – AGC OFF, PR-6 inline, internal preamp off. Sometimes lightning crashes are too high in amplitude to run with AGC OFF, but in those cases, the overall noise profile is such that operating at all is unproductive, not to mention somewhat risky because of the proximity of lightning discharges, so I pull the switch and disconnect. :-)
                           
                          Bill W5WVO
                           
                           
                          From: Dan Bates
                          Sent: Monday, July 25, 2011 18:18
                          Subject: RE: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK
                           

                          Just as a reference, I have a very nasty power line buzz that starts popping on hot afternoons until it becomes solid then goes away after sundown.

                           

                          I have the K3 NB set to DSP t3-6, and IF Med4.  This completely knocks out the noise, and I notice no problems with decoding ISCAT. The other thing I do is turn off AGC which keeps the noise pulses from shutting down the rf gain.  I also only run the external preamp and leave the internal preamp off.  I notice no decrease in SNR, but an improved noise floor..

                           

                          I’d appreciate anyone else’s experience.

                           

                          Dan n5tm

                           

                          From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Bill VanAlstyne W5WVO
                          Sent: Sunday, July 24, 2011 5:07 PM
                          To: wsjtgroup@yahoogroups.com; TLC_Carney
                          Subject: Re: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK

                           

                           

                          Tom,

                           

                          Analog noise blankers tend to work best on “impulse”-type noise – the kind of noise you get from sparks (ignition systems, power line arcing, etc.). Electronically generated broadband noise is typically not reduced a lot, if any, by this kind of NB, which is why Elecraft put in a DSP-based NB as well. The noise I tried the analog NB on sounded like power-line noise to me.

                           

                          Bill W5WVO

                           

                           

                          From: TLC_Carney

                          Sent: Sunday, July 24, 2011 16:28

                          Subject: [wsjtgroup] Re: K3 noise blanker with ISCAT/FSK

                           

                           

                          Thanks for the follow up Bill. My experience is exactly the same as your with the DSP based noise blanker. I didn't try the IF blanker as, even cranked all the way up, it had very little effect on the noise in my neighborhood. I tried it again this morning and while it still has little effect on the worst noise source, it does reduce the noise of other sources in the neighborhood.

                          I'll try some experimenting over the next week and post the results.

                          73,

                          Tom K6EU

                          --- In mailto:wsjtgroup%40yahoogroups.com, "Bill VanAlstyne W5WVO" <w5wvo@...> wrote:

                          >
                          > I’m
                          resurrecting this old thread as I have some new anecdotal data on it.
                          >
                          > As suggested by Joe Taylor (see thread below), I’ve been
                          experimenting with the K3 noise blankers (DSP and conventional analog) to see which one performs the best with FSK441 on meteor scatter signals.
                          >
                          > Over and over, I’ve found that running the DSP noise blanker on the
                          K3 at any useful level creates artifacts or behaviors that seem to interfere with FSK441 decoding of weak to moderate signals. Strong signals that are well above the ambient noise level are not affected by the DSP noise blanker, but of course the NB is, in such a case, unnecessary anyway. But any signal that would be no more than a dB or two above the noise without the NB on does not decode cleanly with the DSP NB set to any useful noise-blanking level.
                          >
                          >
                          To my amazement, however, the analog NB seems to have no such problems. While it reduces the dynamic range of the receiver chain (as does any analog IF NB), this is typically not a problem when working weak-signal modes. I have cleanly decoded weak FSK441 sigs that would have been in the noise had the K3 analog NB not been invoked.
                          >
                          > So tentatively, if you use a K3, turn OFF the
                          DSP NB and turn ON the analog NB. Set it to the least aggressive position that produces a maximum of noise reduction. K3 m/s ops, let me know your experiences with this.
                          >
                          > Again, to emphasize, this is with regard to FSK441
                          VHF meteor-scatter operation with the Elecraft K3. Not anything else.
                          >
                          > Bill W5WVO
                          >
                          >
                          >
                          > From: Bill VanAlstyne
                          W5WVO
                          > Sent: Friday, February 11, 2011 03:50
                          > To: 'TLC_Carney' ;
                          mailto:wsjtgroup%40yahoogroups.com ; Barry Garratt
                          > Subject: Re: [wsjtgroup] noise blanker with
                          ISCAT/FSK
                          >
                          >
                          >
                          > Tom, Barry, et al.,
                          >
                          > This question about noise blankers and FSK441 has occurred to me as
                          well. I wrote to Joe Taylor about it, in fact. This is what he said:
                          >
                          > “ In general I have not seen bad effects of a noise blanker on FSK441
                          signals. I think it generally unlikely, but in detail it must depend on how the blanker is implemented and configured. I'd say you should experiment and decide for your own system.”
                          >
                          > Well, I’d already been doing that, of
                          course.
                          >
                          > Barry and I both run K3s, and the K3 actually has two
                          independent noise blankers -- one being a standard-design IF hardware noise blanker (albeit with numerous available threshold and time-slice settings), which like all such NBs introduces considerable non-linearity into the IF path; and a second DSP-implemented noise blanker which generally preserves receiver linearity and dynamic range, but still (as it must) “cuts out holes” in the received tones. So there is a lot of opportunity in the K3 for “experimenting.”
                          >
                          > The problem with “experimenting” with
                          meteor scatter, of course, is that it’s rather difficult to try different setups on the same m/s signal because they don’t last long enough, and in any case are subject to propagation vagaries of their own during the few seconds (at best) that they are heard. The only way to really test NB implementations would be to make use of a soundcard-and-software generator that can be set to emulate meteor pings at the radio frequencies being used. The audio thus generated is fed into a transmitter, the RF output attenuated to very low levels, and finally fed into a WSJT-equipped receiver.
                          >
                          > Now, I don’t have such a
                          “ping generator”, but I believe Joe has something like this that he uses during decoder development. One of these days I’m going to ask Joe if he would be willing to share that code and setup with the rest of the world. :-)
                          >
                          > But as far as unscientific, subjective experience is concerned â€" I
                          believe that running a noise blanker at aggressive levels can have a distorting effect on weak FSK441 pings that can render them difficult to decode. (I haven’t sensed any problems using more conservative NB settings.) The catch, of course, is that in many cases of severe man-made QRN, without the aggressively-set NB, you wouldn’t see or hear or decode the ping in the first place, because it would be way below the pumped-up noise floor. :-) Remember that FSK441 does take up a sizeable portion of the SSB reference passband, due both to its spread of audio tones and to its high speed. Because of these factors, encoded signals even slightly below the noise level will not decode cleanly â€" nothing at all like JT65 or even ISCAT, which are much slower (and in the case of JT65A, much narrower). So to speak to the other implied question â€" no, I don’t think using a NB would interfere significantly or at all with decoding ISCAT. And it definitely has no effect on decoding JT65 that I’ve ever observed.
                          >
                          > Bill W5WVO
                          >
                          >
                          > From: Barry
                          Garratt
                          > Sent: Friday, February 11, 2011 02:14
                          > To: 'TLC_Carney'
                          ; mailto:wsjtgroup%40yahoogroups.com
                          > Subject: RE: [wsjtgroup] noise blanker with ISCAT/FSK
                          >
                          >
                          >
                          > Hey Tom,
                          >
                          >
                          > I’m in a very quiet
                          location but occasionally get some noise when I’m pointing west because of a mall out that way. I run my K3 with both preamps on all the time by the way. Unless I’m pointing west my S meter barely flickers the S1 led at times. Even though I have that kind of noise level I will usually run the NB and also I have a Timewave ANC-4. It’s the 1st thing in the chain and it feeds the PRE-6 GasFet. That pre-amp then feeds a DCI 10 pole, 300 KHz bandpass filter the output of which then goes back into the K3.
                          >
                          >
                          > I run it
                          like that all the time usually just so I don’t forget to switch things on if I turn west. When it comes to weak signals every little bit helps. I also limit the audio to the sound card with an audio DSP, also by Timewave, to 700 â€" 2700 Hz and run the K3 with the 1800 Hz filter.
                          >
                          >
                          > Just my way
                          of doing things Tom. As the saying goes your mileage may vary.
                          >
                          >
                          > 73,
                          >
                          >
                          > Barry KS7DX
                          >
                          >
                          >
                          From: mailto:wsjtgroup%40yahoogroups.com [mailto:mailto:wsjtgroup%40yahoogroups.com] On Behalf Of TLC_Carney
                          > Sent: Thursday, February 10, 2011 5:40
                          PM
                          > To:
                          href="mailto:wsjtgroup%40yahoogroups.com">mailto:wsjtgroup%40yahoogroups.com
                          >
                          Subject: [wsjtgroup] noise blanker with ISCAT/FSK
                          >
                          >
                          >
                          >
                          > Greetings all
                          >
                          > I'm in one of those
                          neighborhoods where there is frequently some form of man made noise on 6M. I've noticed that turning on the noise blanker (K3) will usually reduce the noise floor by 2 to 3 db in SpecJT.
                          >
                          > I wonder, does it really do any
                          good? IE can decode ISCAT/FSK signals that I couldn't decode with the noise blanker off?
                          >
                          > 73,
                          >
                          > Tom
                          K6EU
                          >

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