Noise Filters Not Effective

Rick

I'm using a 6300 with SSDR v. 1.7.3.2. I hear no real noise reduction using either the NB or NR features. Is it me or are these still not really implemented? I've seen previous discussions on this and just want to make sure that it's not a shortcoming unique to my system. 73
Rick, W2JAZ

DrTeeth

I could **just** about hear a reduction with one of them. I cannot remember which one as I mainly use digimodes. It's not you if your hearing is otherwise fine.

David

I believe this is combination of user and environment. I have found the NB, NR, and ANF all to have an affect to quieting the noise when along with the AGC. The WNB is more challenging to determine the impact but I believe I have heard the quieting. From the comments I have seen, the level of these filters provide can depend on what your noise sources are. The setting I find to work well in the North Central NJ area as a starting point to make things quiet are WNB: 25, NB: 50, NR: 25, AGC Fast 40-50. ANF:0 can sometimes help all depends. As you note there are many threads on this topic and when they initially implemented the WNB and removed NB there were many concerns. Fortunately they added the NB back. Tim and others from FlexRadio have provided more technical explanations on how to optimally use the settings.

Rick

Thanks for suggesting these parameters which have improved things here. I have an inordinate amount of hash here in SNJ especially on 20. The NB seems to be helping quite a bit now. I also adjusted the AGC a bit more. TNX
Rick, W2JAZ 

KC7ES

I find the WNB at its nearly full settling is very effective at killing off some local grow light noise or similar that seemingly wipes out 80-6m late in the evening. YMMV, but it's the difference between operating vs not for me.

David

Glad that helped. Those are just starting points and tweaking for each of the filters for different conditions is necessary. The other setting I find helpful is bandwidth of 2.4K and sometime bringing the bottom up from 100 to 200/250 to improve clarity on stations with more bass in the audio. Of course all of this differs from person to person, environment and station setup.

EA4GLI

This is what WNB does in my location. The voice over is in Spanish but you can visually get an idea.


https://www.youtube.com/watch?v=guBdpxOLRE4

Jay Nation

There is a difference between noise heard, and listening to far into the noise floor. Nothings going to turn off the noise floor, it's where the signals come from. Signals down in or close to the noise floor will sound noisier than signals that aren't, the AGC-T control has been provided to give us some control over RX SNR.  When your hearing more noise than you want, try lowering the AGC-T to see if the noise reduces, yet you are still hearing the signal. After that's adjusted then try the DSP filters to see if they help even more. For a rig with no knobs Flexradio's are very adjustable.

At the moment, I'm listening to 20m digital with 2 slices, PSK, and JT. I'm not hearing "any" noise just the signals. Not sure why I'm even listening to the signals my brain can't decode them.

73, Jay - NO5J

Rick

It's all very much based on your environment. Here in SNJ, suburbs of Philadelphia, there is always noise especially it seems on 20m. I live with it and make the adjustments as suggested. But it's a rare day when the noise floor drops significantly I'm afraid....Rick W2JAZ

EA4GLI

In my case I go from a noise floor of S5 to 5+ to an S3 to 4 enabling WNB.

EA4GLI

I placed 10Hz TNF at the Band edges and then right click on them and save them. It is like getting band edges. They are persistent on power off and will display on the Maestro. I have had them since versión 1.6 (or maybe even 1.5) and no need to redo them on upgrades.

Jay Nation

Rick 

You may already be aware of most of the word salad below ...

But If your not ...

I'm rural, your not. Our noise floors and everything about what's in them are very different.

First things first, Do you have a pre-amp, and is it set correctly for the band your using. 160m, 80m, 40m, and 30m you almost always need it turned off.  20m you get to decide, 17m, 15m, 12m, 10m and up you almost always need it on.

Second. Have you got the bandwidth of your pass band adjusted as tight against the signal as you can get it, remember any portion of the pass band that doesn't have a signal in it, is just noise so adjust it out, If the signals 3k wide chopping off a little might even sound better. Do you really need to hear the all the fan noise he's transmitting?

Third. All of our AGC-T Automatic Gain Control Threshold controls are exactly the same. AGC is just a software amplifier. The threshold slider just sets the the lowest signal level you want amplified. The noise floor isn't constant it bounces around, so we have to allow for that. So one setting at one moment will be a maladjusted setting the next, unless enough distance is kept between the threshold and the audible noise floor. The squiggly line visible in the panadater doesn't accurately represent what's really going on. any weaker signals below that squiggly line cannot be heard, period. Signals peaking inside the width of the squiggly line can be heard as very noisy signals. Signals  peaking above the squiggly line will be heard, but they can be noisy too, because the noise floor is always bouncing a little even though the display averaging hides that fact.The weakest signals are wrapped in noise. The threshold setting can be tweaked slightly sometimes to improve the quality of the audio if the signals are far enough above the noise. When your hearing a constant noise your threshold is set too low, because the threshold slider is set to high. which seems backwards, think of the slider as having an alternate label, think of it as the "more" noise control. It's also amplifying the noise,  the slider adjustment scale is 1 - 100 units/clicks think percentage when adjusting it. A weak noisy signal may sound better at 24% than it does at 23% and might sound even better at 25% or 26%. as long as you compensate by adjusting the slice volume level as you adjust the threshold. Raising the threshold lowers the signal level cutoff point, and adds more noise. so what do you do when you've eliminated  as much noise as you can, and now the signal is so weak it can't be heard clearly. Now you should raise the slice volume slightly a percentage point or two. If the noise bumps up drop the threshold a percentage point to see if it helps any. It's a lot like adjusting an antenna tuner or dipping/peaking the load and plate controls of a tube amplifier, because what your trying to do is tune the signal in, and the noise out. 

When I'm working Digital on 20m my AGC-T is set ranging from 9 - 18 depending on the band conditions. Fldigi needs more up to a 36% AGC-T level, WSJT-X needs the least. DAX RX stays set to 50% for both, by personal preference. I don't ever touch the WSJT-X level slider it stays at 0dB.


Fourth. You've done all the above to eliminate as much noise as you can, and it's still noisy. Try enabling the NR and tweaking its level slider. you do this last, because every adjustment prior to this affects the adjustment of the NR. So eliminate as much of the noise as possible. the NR being a DSP filter will affect the "quality?" of the audio a little so you want to use the least amount of NR possible.
It will reduce any remaining hiss further but it also remove portions of the signal too. If it sounds worse to your ear now, either tweak it some more or turn it back off. It helps in some cases and not others.

There is no "Magic" noise button, unless your willing to include the mute button among the noise control features (It's really the most effective). You, yourself are the real "Magic" noise control. Adjust your operating methods, and stop tuning into the noise, try a signal instead.

Maybe the speaker volume can be reduced too.

They're your ears you decide what goes in them.
 
Maybe some of the above helps, it was intended to.

73, Jay - NO5J     

Jay Nation

Kevin

Apologies for the additional word salad.

Yes that's it. The secret is to avoid feeding noise to any of the gain stages and do that first. then tweak the AGC-T to improve the remaining noise.

I've considered trying to create a video that could allow some A/B comparisons. I just haven't figured out how to instantly switch from one to the other yet. I also haven't got much experience with creating desktop videos, It sounds like another project to play with though.

The thing I really didn't emphasize enough is that, the settings that work at 4 pm on band X will be different, both on band Y and at 8 pm. You will have to master the technique well enough to be able to repeat the adjustments when the noise levels change.

A thunderstorm really complicates things, but the method will still be valid, even though the results may not be useable. Sometimes you just have to accept that. 

When you hear noise, it's time to adjust something. Knowing what to adjust can be learned with enough practice. 

I also forgot to explain that all this applies to atmospheric noise, the hiss that's always there.

If your dealing with impulse noise, you should enable the NB and hope it helps.

The WNB also has an affect on some types of atmospheric band noise, and can be enabled and tried before optimizing the AGC-T settings.  

Also keep in mind that this pertains to eliminating noise. AGC-T can also be used to balance the audio levels in SSB net ragchews where it's less about pulling signals out of the noise, and more about protecting you speakers and ears from the stronger signals while still being able to copy the weaker ones. That's a different technique. Learning how to combine the two is something I'm still trying to master.

Sometimes, you just have to blame noise on lousy band conditions, but you don't have to listen to the noise if you don't want to, most of the time.

The receivers in these radio let you pull signals out of the noise floor, "with" some noise that can be managed. There's usually more signals right below those. I've worked signals that I could neither see nor hear using WSJT-X pulling QSO's right out of nothing but hiss, I just mute the speakers most of the time when I'm trying to work digital.

My antenna a ZS6BKW is totally deaf on 15m and I can't really transmit there either, but if I tune to the JT portion even though nothings seen or heard on the panadapter, WSJT-X still decodes plenty of signals.

I really need to put up a 15m dipole soon.  I just need to throw some rope up into a couple of trees I guess, I've got plenty of trees, most of them are in the way though.
 
Jay - NO5J

Rick

TNX very much Jay. I've made a number of I,prove,mets since my initial post and in doing so am better acquainted with the various parameters. Truth be told, I was away from th radio for nearly a month using a legacy flex and PowerSDR at our lake cottage. When I returned I had to relearn everything and didn't realize that I hadn't set one control to any value at all so it was I'm properly adjusted . Duh! Anyway, I'm in better shape than I was and I appreciate all the suggestions and dialogue I generated by my post. It's a great group of hams and a great radio!

Jay Nation

Kevin
Your right about the Profiles, Memories, FRStack and DDUtil might get the rest done. Something else to practice before creating the video, I guess.

73, Jay - NO5J

Jay Nation

Kevin

Another Quick and Dirty technique that works for me on 20m using Fldigi is ...

Pre-amp off
DAX RX at 50%
AGC-T at 45% W/Fast selected.
The Fldigi waterfall looks pretty good using scope.pal with "both" of  the waterfall controls set to @32-33% then adjust the AGC-T percentage up and down a percent at a time till the waterfall background is completely black. If you start to see garbage in the Fldigi waterfall drop the AGC-T another percent. etc. You use the AGC-T to tweak for band conditions.

Using this setup is often good enough.

73, Jay - NO5J

AA0KM

More work needed  on ANF and NR.

 Hope soon. WNB is fine as well as NB is fine.

EA4GLI

Fantastic explanation Jay. I would like to add that I also use the RX EQ to make bad sounding weak stations legible.

Jay Nation

Salvador

Your right sometimes I do get brave enough to enable the RX EQ, At one time I insisted on graphic EQ's being used on any audio I listened too. I stand before you all as a recovering tweak addict. I saw the early Flexradio's as being an aid to my recovery due to their lack of knobs. All they really accomplished was that they helped a little with my knob addiction. I thought I'd succeeded in getting the tweak monkey off my back, then ... I bought a Maestro. Addictions are additive, sometimes they even multiply.

But yes rolling off the frequencies 2k and above does help, when atmospherics are involved. the EQ is just another adjustable gain stage in the RX audio chain. I'd still like to see a "real" flow chart of the into's and outta's in the RX audio chain. PowerSDR had such a thing.

73, Jay - NO5J 

Rick

I appreciated your thoughtful suggestions which I read through again this morning. Some good helpful conversation about this topic. After I made the first post I realized that I had been away from smartsdr so long while using PowerSDR at the vacation house that I had forgotten to move the noise reduction sliders! Duh! Anyway, very good suggestions from you and the group. 73 Rick W2JAZ

EA4GLI

Hi Guy, I just sent you an email. If you could check it when you get a chance it would be great. Speedy recovery, 73s. Sal.

Bill N5TU

Well stated. VY 73, Bill, N5TU