[Elecraft] K3: DSP NR for Data A mode?
Is it possible to implement Noise Reduction in the DSP for Data A mode? Or is it a really stupid idea? The PSK software I use -- cocoaModem for the Mac -- has a noise reduction mode which works reasonably well when it is receiving a broad spectrum signal -- 2 KHz or more. It does not work well at all when I narrow the DSP bandwidth to eliminate strong nearby signals. This situation leads to the annoying situation where I can copy a weak station when the bandwidth is broad, but not when I have narrowed it to eliminate strong nearby stations. The strong nearby stations overload my SignaLink AtoD converter which keeps me from copying the station. It seems to me the DSP is in a position to apply noise reduction before the narrow band filter, if that is the best way to perform noise reduction. Cheers - Bill, AE6JV - Bill Frantz| Airline peanut bag: Produced | Periwinkle (408)356-8506 | in a facility that processes | 16345 Englewood Ave www.pwpconsult.com | peanuts and other nuts. - Duh | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K3: DSP NR for Data A mode?
Have you tried using a narrower filter in the K3 or using the K3 NR? Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 20 Jul 2012 09:03:20 -0700, Bill Frantz fra...@pwpconsult.com wrote: Is it possible to implement Noise Reduction in the DSP for Data A mode? Or is it a really stupid idea? The PSK software I use -- cocoaModem for the Mac -- has a noise reduction mode which works reasonably well when it is receiving a broad spectrum signal -- 2 KHz or more. It does not work well at all when I narrow the DSP bandwidth to eliminate strong nearby signals. This situation leads to the annoying situation where I can copy a weak station when the bandwidth is broad, but not when I have narrowed it to eliminate strong nearby stations. The strong nearby stations overload my SignaLink AtoD converter which keeps me from copying the station. It seems to me the DSP is in a position to apply noise reduction before the narrow band filter, if that is the best way to perform noise reduction. Cheers - Bill, AE6JV - Bill Frantz| Airline peanut bag: Produced | Periwinkle (408)356-8506 | in a facility that processes | 16345 Englewood Ave www.pwpconsult.com | peanuts and other nuts. - Duh | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K3: DSP NR for Data A mode?
Note that NR is not available in DATA A mode -- K3 manual p25: NR turns noise reduction on. It doesn’t apply to DATA or FM modes, or with AGC turned off. Ray identified why I would like the K3 NR to work in DATA A when he said, NR algorithms -need- a broad chunk of spectrum. If the DSP NR could work on a broad spectrum before filtering it would have enough data to separate signal from noise. I'm not trying to get NR to deal with strong nearby signals, but when I narrow the bandwidth to get rid of them, my post-narrowing NR no longer works so I'm looking for pre-narrowing NR. I have used the notch filter, but it takes time to deploy, and can't deal with two separate loud signals. By experience, narrowing the DSP bandwidth is operationally easier and more effective. I suppose I should bite the bullet and get a 24 bit USB sound card. Does anyone have any recommendations? [It hurts to spend money for a 24 bit A/D converter which is going to convert analog the radio has produced using a 24 bit D/A converter. It's just unaesthetic.] Cheers - Bill, AE6JV On 7/20/12 at 10:43, li...@n5ge.com (N5GE) wrote: Have you tried using a narrower filter in the K3 or using the K3 NR? On 7/20/12 at 11:11, raysil...@verizon.net (Ray Sills) wrote: Well, the way I see it Noise Reduction won't help you get rid of strong nearby (in frequency and/or QTH) signals. That would be the job of a notch filter. In fact, I think NR algorithms -need- a broad chunk of spectrum, so as to be able to identify what is signal and what is noise. If you narrow the DSP bandwidth, the software many not have enough noise to work with. If those strong signals are overloading the A/D converter, you would be better off lowering the level fed to the converter. I think the SignaLink uses a 16 bit converter, and this is where a 24 bit converter would work much better, since it has 24 dB more dynamic range (before clipping). --- Bill Frantz| The only thing we have to | Periwinkle (408)356-8506 | fear is fear itself. - FDR | 16345 Englewood Ave www.pwpconsult.com | Inaugural address, 3/4/1933 | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K3: DSP NR for Data A mode?
Bill, I have not found 24 bit soundcards to be a requirement for data modes. 16 bit soundcards will do just fine. Yes, NR is not available in Data modes because it distorts the signal and would result in reduced copyability. The object is to produce as clean a signal as possible to the soundcard. What you observed is a true consequence of how most noise reduction algorithms work. They assume that the noise is distributed evenly across the bandwidth they are receiving, and configure a filter to reduce that noise. If you narrow the bandwidth, that noise begins to appear (to the mathematics) more and more like a signal that should not be interfered with. I would suggest that the best solution is to allow the data mode software to sort things out to the best of its ability. If you reduce the signal width sufficiently to home in to the desired signal, then I would expect the data software to be able to decode properly (at its limits of rejection) using a wide bandwidth, and also be able to decode quite well with a very narrow bandwidth, but at intermediate widths, the datamode application software will not have enough bandwidth to properly discern what is noise and which is a proper signal. The noise reduction in many data mode applications is actually quite good. So my suggestion is to allow that data mode application to use its noise reduction capability (which requires a wide bandwidth), but if you are struggling to receive a signal, narrow the RX bandwidth to the narrowest possible and see if the QSO can continue. 73, Don W3FPR On 7/20/2012 5:57 PM, Bill Frantz wrote: Note that NR is not available in DATA A mode -- K3 manual p25: NR turns noise reduction on. It doesn’t apply to DATA or FM modes, or with AGC turned off. Ray identified why I would like the K3 NR to work in DATA A when he said, NR algorithms -need- a broad chunk of spectrum. If the DSP NR could work on a broad spectrum before filtering it would have enough data to separate signal from noise. I'm not trying to get NR to deal with strong nearby signals, but when I narrow the bandwidth to get rid of them, my post-narrowing NR no longer works so I'm looking for pre-narrowing NR. I have used the notch filter, but it takes time to deploy, and can't deal with two separate loud signals. By experience, narrowing the DSP bandwidth is operationally easier and more effective. I suppose I should bite the bullet and get a 24 bit USB sound card. Does anyone have any recommendations? [It hurts to spend money for a 24 bit A/D converter which is going to convert analog the radio has produced using a 24 bit D/A converter. It's just unaesthetic.] Cheers - Bill, AE6JV On 7/20/12 at 10:43, li...@n5ge.com (N5GE) wrote: Have you tried using a narrower filter in the K3 or using the K3 NR? On 7/20/12 at 11:11, raysil...@verizon.net (Ray Sills) wrote: Well, the way I see it Noise Reduction won't help you get rid of strong nearby (in frequency and/or QTH) signals. That would be the job of a notch filter. In fact, I think NR algorithms -need- a broad chunk of spectrum, so as to be able to identify what is signal and what is noise. If you narrow the DSP bandwidth, the software many not have enough noise to work with. If those strong signals are overloading the A/D converter, you would be better off lowering the level fed to the converter. I think the SignaLink uses a 16 bit converter, and this is where a 24 bit converter would work much better, since it has 24 dB more dynamic range (before clipping). --- Bill Frantz| The only thing we have to | Periwinkle (408)356-8506 | fear is fear itself. - FDR | 16345 Englewood Ave www.pwpconsult.com | Inaugural address, 3/4/1933 | Los Gatos, CA 95032 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
