ANF Causing SSB Audio Distortion

  • 3
  • Problem
  • Updated 4 years ago
  • Acknowledged
I looked for previous messages and did not see this mentioned specifically.  

When enabling the ANF (Auto Notch Filter) on the DSP menu (not to be confused with the TNF or Tracking Notch Filter), SSB audio becomes fuzzy and/or distorted as the gain is increased on the ANF slider control.  

From a subjective standpoint, the ANF does not appear to be as effective in removing offending carrier tones in SmartSDR as PowerSDR did on my old Flex 3000.

Are there any recommendations on how to best utilize this feature or work around the distortion while still mitigating offending carrier tones?  Is this a known issue?  Are there any plans to enhance the ANF feature?


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Jay -- N0FB, Elmer

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Posted 5 years ago

  • 3
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Jon - KF2E

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This has been discussed previously and Flex has admitted they need work. Here is one thread where it was discussed.

I guess it's "on the list" but no relief is in sight.

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Steve N4LQ

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Yes...Total distortion. I'm surprised ANF is even included if it's going to work like that.
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ANF and also TNF from the flex 3000/5000 is a lot better then my 6300!
Indeed,total distortion!
Lets hope that in the next update 1.4 all is ok!
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Ken - NM9P

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Instead of ANF, use the TNF which is sharper and doesn't distort much at all. They are working on ANF improvements.
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Steve N4LQ

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TNF is too much trouble to fiddle with. 
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Ken - NM9P

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.? Right click on offending carrier, select "add TNF" and drag it to fine-tune if needed. Drag up or down to narrow or widen the notch. Right click on the filter to select how deep it is and whether or not to make it permanent. It seems very simple and straightforward to me. I can get a notch on a carrier about as fast as the ANF can lock in. Then tweak it as necessary. But yes, it would be much nicer to be automatic. Still, ANF only gives one notch. With TNF I can filter out multiple carriers in the same voice bandwidth that are created by my router and switch.
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Tim - W4TME, Customer Experience Manager

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Official Response
This behavior has been reported previously in the Community and we have acknowledged it.  We are aware of the issues and will be working on the DSP noise mitigation features in an upcoming release.
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Jim KJ7S

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I found, as did some of the others that using the TNF rather than the ANF is far and away the better way to take care of the offending carrier...and you can set more than one TNF for a given passband to take care of most any offending carrier, to a point, all of which do a LOT better than the TNF. If that is too much of a "hassle" for you then you will have to weigh the hassle of that against the hassle of the offending carrier(s).
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Jim, KJ3P

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Not to dig up an old problem, but the Automatic Notch Filter (ANF) in v1.5.1 still imparts a "gravelly" distortion to received SSB audio, especially if the station has a prominent low-end response.

I also note that the ANF seems to un-mute briefly during parts of the received audio, so bits and pieces of the notched signal get through.  However, the notch mutes perfectly during periods of silence, even with mild QSB of the "offending" carrier.

I know that these things are always "works in progress" but wanted to register my observations for the record.

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Norm - W7CK

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NR also needs a lot of work.  I still can't use it to any degree of satisfaction.  Distorts (all lows and bassy) SSB voice and makes it very hard to understand.  My other rigs don't seem to have this problem.

I hope this has been reported and is going to be worked on soon?
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FRS is still under the weather with noise mitigation.