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K3: Noise reduction tutorial/primer available?

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Jeff Hall, W6UX

K3: Noise reduction tutorial/primer available?

Hi, I've been searching for some operating tips on how to strategically
employ the following K3 controls:

- NOTCH
- NR
- NB
- WIDTH
- SHIFT

As good as the manual is, I still feel like I don't understand how these
really work and when I should use them to get the best possible results. To
date, I've been randomly turning them on and off, adjusting their various
settings to see what they do. But I'm hoping some of the experts here can
explain how and when they like to use each of these controls.

I have been using my K3 for about 4 months. Lately, 40m has been a little
more noisy for me (about 4 bars of noise). I suspect its QRN, but there may
be some QRM as well. Activating the noise blanker (NB) will usually drop
the noise by 1 S unit. Recently, I've been fiddling with the NR settings to
improve the signal quality (this was very helpful on last night's 3905 40m
SSB net - the noise without NR on was just horrible).

I don't understand what the different NR settings are doing, as you move
from 1-1 thru 3-7. Going from 1-1 to 1-4, it sounds like the person on the
other end is moving farther down a long hallway - the signal gets more
faint, disappearing into a surrounding quietness. 2-1 and 3-1 sound very
similar to 1-1. And, I don't understand what NAR1,NAR2,NAR3 through WIDE1,
WIDE2, WIDE3 settings on the NR feature are doing for me. I don't notice
much difference no matter what I select with those.

What about NOTCH? I don't seem to notice any difference whether it is
engaged or not.

Finally, I can sometimes use the WIDTH control to reduce interference from
nearby signals, but if someone is booming in 2 kHz away, I can't seem to
shut them out. Anything else I can do here? I am not sure what SHIFT is
used for, perhaps this can be utilized? I have the 2.7kHz, 1.8 kHz and 400
Hz filters installed.

Thanks for helping a newbie!

73 de Jeff, W6UX
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Gary Dezern

Re: K3: Noise reduction tutorial/primer available?

I can help with some of these (though I'm clueless on the NB...)

It helps if you visualize the "passband" of the receiver as a small part of the entire RF spectrum that the radio lets into your speaker (or headphone.) This would be similar to a movable and resizable window on your house - so you can move the window to different places on your house to see different things outside (or make it larger/smaller to see more at once or less at once.) This window analogy, being visual, makes things easier to visualize...

Notch: This is like blocking out just a tiny portion of your "window." For me, it's most useful for those times that a LID decides to spend an hour tuning up and their tuning carrier is right in the middle of my "window." In SSB, the K3 will (by default) use "auto-notch" - so it'll look for a carrier within your passband (window) and automatically block it out. The best analogy I can come up with would be that the sun is shining directly into your window, so you put your hand between your eyes and the sun. Thats a "notch filter."

Width: Simply, this is the size of your window. Usually, you only want to "see" one thing at a time, and for SSB, that width is 2.7. However, when stations are too close together, you can make that window smaller so that adjacent stations aren't interfering with your view. (If that adjacent station is putting out splatter or a really wide signal, this might not help...) I usually end up shifting (see below) when messing with the width.

Shift: This is just moving your window around on your house. If you look out your window and there is a naked guy that you don't want to see on the left side of the window, you can just move the window a bit to the right. Of course, now you might be seeing something undesirable on the right side... Ideally, a combination of shifting the window and making it narrower (width) will let you see only what you want to see.

NB: No idea how this works on the K3. The documentation suggests the NAR/MED/WID "if" settings are useful for some types of noise and the DSP settings are useful for other types of noise - but I haven't seen anything that narrows it down more than that.

NR (noise reduction) is a mechanism of pushing the audio through a "DSP" (computer program) to try and clean it up. My understanding is that the DSP works by analyzing the audio and only letting through audio that forms certain patterns (such as speech) as opposed to completely random audio. The different settings for NR use slightly different mechanisms to try and clean thing up, some more aggressive than others. The more aggressive mechanisms tend to be more "destructive" to the audio which gives it that "hollow" or "echoing" sound.

Take care
Gary / k3wow

On Jul 8, 2010, at 1:34 PM, Jeff Hall (W6UX) wrote:

> Hi, I've been searching for some operating tips on how to strategically
> employ the following K3 controls:
>
> - NOTCH
> - NR
> - NB
> - WIDTH
> - SHIFT
>
> As good as the manual is, I still feel like I don't understand how these
> really work and when I should use them to get the best possible results. To
> date, I've been randomly turning them on and off, adjusting their various
> settings to see what they do. But I'm hoping some of the experts here can
> explain how and when they like to use each of these controls.
>
> I have been using my K3 for about 4 months. Lately, 40m has been a little
> more noisy for me (about 4 bars of noise). I suspect its QRN, but there may
> be some QRM as well. Activating the noise blanker (NB) will usually drop
> the noise by 1 S unit. Recently, I've been fiddling with the NR settings to
> improve the signal quality (this was very helpful on last night's 3905 40m
> SSB net - the noise without NR on was just horrible).
>
> I don't understand what the different NR settings are doing, as you move
> from 1-1 thru 3-7. Going from 1-1 to 1-4, it sounds like the person on the
> other end is moving farther down a long hallway - the signal gets more
> faint, disappearing into a surrounding quietness. 2-1 and 3-1 sound very
> similar to 1-1. And, I don't understand what NAR1,NAR2,NAR3 through WIDE1,
> WIDE2, WIDE3 settings on the NR feature are doing for me. I don't notice
> much difference no matter what I select with those.
>
> What about NOTCH? I don't seem to notice any difference whether it is
> engaged or not.
>
> Finally, I can sometimes use the WIDTH control to reduce interference from
> nearby signals, but if someone is booming in 2 kHz away, I can't seem to
> shut them out. Anything else I can do here? I am not sure what SHIFT is
> used for, perhaps this can be utilized? I have the 2.7kHz, 1.8 kHz and 400
> Hz filters installed.
>
> Thanks for helping a newbie!
>
> 73 de Jeff, W6UX
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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Jeff Hall, W6UX

Re: K3: Noise reduction tutorial/primer available?

In reply to this post by Jeff Hall, W6UX

Thanks Gary and "The Smiths" (great 80s band, BTW!) for those very helpful
pointers! Can't wait to try those techniques out tonight!

73 de Jeff, W6UX
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Don Wilhelm-4

Re: K3: Noise reduction tutorial/primer available?

In reply to this post by Jeff Hall, W6UX

Jeff,

I see you have gotten a few helpful answers. Let me add something to
your questions about shift and width.
The shift and width are mostly helpful for CW and possibly DATA modes -
the SHIFT centers your receive passband. A rough estimate of the
passband is shown in the lower left graphic on the LCD display. You
should always keep some part of your passband at the CW pitch you are
listening to (the sidetone pitch), otherwise the signal you wish to
receive will be attenuated because it is outside the passband.

The width simply narrows the passband - and it narrows it from both
sides, so as you attempt to use more narrow widths, the setting of the
shift control becomes more critical. That is about all there is to
shift and width.

Now, for SSB, you will find the shift and width more cumbersome to use
while trying to maintain SSB intelligibility. The cure is to tap either
the shift or width buttons so they become LO CUT and HI CUT instead.
Set the LO CUT at 200 to 300 Hz and leave it there. Control the width
of the SSB passband only with the HI CUT knob and you will maintain
intelligibility as you narrow the passband.
If the band is not crowded and you have no QRM on your desired SSB
signal, reduce the LO CUT to 150 Hz, and increase the HI CUT to 3.00 kHz
(or even 3.50) to achieve the best fidelity. If an interfering signal
comes in on the (audio) high frequency side of the desired station,
reduce the HI CUT to try to minimize the QRM - conversely, if the
interfering signal is on the low frequency end, increase the frequency
of the LO CUT to eliminate the QRM - one caution, go slowly with the LO
CUT because if the low end of the passband is much above 350 Hz, you
will sacrifice a lot of intelligibility for the desired station.

I hope that is helpful. If you did not understand, please ask again.

73,
Don W3FPR

Jeff Hall (W6UX) wrote:

The Smiths

Re: K3: Noise reduction tutorial/primer available?

In reply to this post by Jeff Hall, W6UX

Some of you were interested in what the Filters and such did on the K3 so I wrote this little bit of information up to help you out. I hope you find it useful. If you have any questions feel free to ask off the reflector. Thanks;

In brief:

Notch:

The Notch has an Auto (for SSB use) and a manual setting for CW. This can be used to take out a tone (carrier) or other noise that is sitting in the middle or near your pass band area (the freq. you're listening to). It can also be used in CW mode to reduce the amount of noise you hear in the upper or lower part of the pass band area. Setting it up to do this takes SOME understanding of what a notch filter does, and how to adjust it. You may not hear any difference between having it on, and off depending on the noise, and on the settings that you have selected. Along with turning it on you also have to adjust the Freq. manually when using it in CW mode.
Sometimes Notching out (CUTTING out) a selected signal can help with reception. For example if you are on CW and you have a lot of LOW end rumbling in headphones and you want to get rid of it, depending on your PITCH freq. you can turn on the NOTCH filter and set it to 300Hz for example. This will NOTCH out (cut out) all of the sound on and around the 300Hz freq. area.
One thing you have to watch out for is setting the Notch freq in the menu to match, or come too close to your PITCH freq. If you do you will have essentially Notched out your Target freq that you're listening for. Not good.

NR:

The NR is used to reduce noise. As you've noticed it has settings as well. Settings 1-1 through 4-1 are normally used with CW, because of the "long hallway" effect that you've already experienced on SSB. Settings 5-1 through 8-4 are generally used with SSB because they don't tend to cause this kind of effect on the voices.
You should always try to use the LEAST (or lowest) NR value you can IE 5-1 or 1-1... If it helps at 1-1 and is good enough, there is no need to process more than you need. Too much of ANYTHING is a bad thing.

Even though it wasn't mentioned in the original question, the RF gain is another one of your BEST noise reducing tools you have... When used in conjunction with the NR filter, if you reduce your RF gain down to 4 or even 5 bars on the scale when the nose on 40 is 4 bars high (as you indicated it was) you will notice that your NR works exponentially better! This is because the DSP no longer has to process nearly as much noise along with signal.
Don't worry, you will find that even when you turn the RF gain down on a signal that is S5 along with an S4 (4 bars) noise level you will NOT make the signal you're listening for go away. Just turn it down slowly as to hear when the person starts to get too low. If you start reducing their signal by more than the NR is reducing your noise level you know you've gone too far. You'll have to play around with this one some.. It's all about technique.
Keep in mind that it may take 10 seconds or so before your NR starts to clean up the noise as you drop the RF gain, so try only dropping it as much as 1 bar less than the noise level at first, if you need to drop the RF gain lower then go ahead and then listen again for a few second more.

NB:

The NB generally works for Electrical noise and other pulsing type noises... You have already noticed that when you turn it on it can drop your S meter by as much as 1 S unit. With the proper settings (DSP/IF) you may be able to get that down to as much as 3 S units (bars) of noise reduction. However, keep in mind, with the reduction of noise with this method you will also have adverse affects on the signals you're trying to listen to. Such as a clicky sound on the CW tones, or flutter on a voice.
Again, like the NR you always want to use as little as you can get away with. Starting with the lower numbers for DSP, and the Narrow modes for IF.
Just for a starting spot, in my area I find that 2-5 with Med 2 seems to work very well at reducing the QRM/QRN. However, if I move it to 2-7, Med 2 I find that the noise level drops down 3 bars, but trying the have a QSO with a weak station is almost impossible. As well as the noise it tends to "remove" the sender as well.
Try NOT to use your S meter as your gauge of where you should have your NB set to. For example, Turn off the IF NB, start with the DSP (because this seems to work best at removing noise) Next, Close your eyes and start to VERY slowly turn the DSP part of the NB starting at the lowest number (setting). LISTEN to when the noise is reduced to your satisfaction. It may take some going back and forth to get this right, or even hear a difference. When you are done, if you are not completely satisfied with the noise reduction continue this process using the IF part of the settings. Keep the DSP portion exactly where you found it to work best. When you find the best IF noise reduction you will have your combination set.
It is important to listen to some signals and turn on and off the NB to make sure that you haven't over compensated for the noise and distorted the signal you are trying to receive. Be sure to test this with some weak signals as well, as they are not only distorted, but can be removed completely.

Width:

The width control is basically how much freq. you want to listen to at one time. Think about this one as if it were your hand was cupped over your ear. The wider you open your hand the more you're going to hear around the room.. The more you narrow in your hand over your ear the less you are going to hear from a broad range of area. So, for example, if you are trying to have a conversation with some one on 7.025 and there is someone at 7.026 you want to make sure that your (width) hand is closed by at least 800Hz... This way you are "focusing" specifically on those signals that are only within 800Hz of your target freq. By squeezing in your width (lower number) you will focus more on the signal that you're listening to.
When using CW the freq. you should tune your target to should match as close as possible to the Freq. that you have your "PITCH" set to. This would be what we call the CENTER of the pass band. You almost always want to try to "center" your pass band with the other person. There is another useful feature on your display that will help you do this when the "CWT" mode is on. You will notice a little "Goal post", when you have CENTERED the signal with your Pitch you will see that little goal post move to the center of the graph display.

Returning to Width, when you get the Width down to 50, or 50Hz this means you are ONLY able to hear things 25Hz to top, and 25Hz to the bottom of the signal you are focusing on. Again, this would be like you have your hand cupped VERY tight around your ear as to focus on something right in front of your ear.
The reason that this helps clean up the noise, is because you are listening to a very selective area. With SSB this area inherently can not be too narrow. For this reason you will notice that your Width control will not go as low as it does on CW. With SSB you will find that about 1.8Khz is about as low as you will be able to go before you start distorting the sound of the signal you are listening to.

In case you feel like you've gotten yourself lost, you can always push and hold down the SHIFT button until it resets you into the "NORM" or normalization mode. This just puts your Shift and WIDTH back to the default positions so you can try again.

Shift:

Keeping in mind the Width control, and my description of your hand cupped over your ear, the Shift knob works like a turn table for your head... Okay, this sounds funny I'm sure. What I mean is, Now that you have your ear cupped, you have to be able to focus your hearing on a target. The Shift knob allows you to rotate your head to the left or the right so that your ear is pointed in a particular direction. For example, if you have your filter down to 50 (50Hz) and you move your shift knob to the left you will then start to focus your target on a lower in Freq. You have still maintained that same cup "width" over your ear, but you are "searching" for signals within that area below (as in my example) or if you turn it to the right you will be focusing above the CENTER pass band freq. The center is marked by a little * next to the number.
This would be very similar to moving the VFO knob up or down, but in this case, you will not change your Transmitting freq. The Shit will only move you a designated amount above or below, and ONLY effect what YOU hear (focus on). It will not effect your Transmit area. The same thing can be done by moving the RIT knob as well, but it's not always recommended.
The reason that you would want to focus on something that is NOT in your pass band is because you may find that you have noise that is not able to be reduced, and you find that you can SHIFT the pass band (focus) to the side SLIGHTLY and find a clearer signal.
I find that when I have my Width set to 250Hz and I SHIFT my pass band area down about 20Hz I can more clearly hear the target signal. Again, this is technique and something you can experiment with. Put a signal in the CENTER of your pass band WIDTH, then narrow down to about 100 to 250Hz, and play with the shift moving up or down, you will hear what I'm talking about.

For SSB use there is a VERY helpful feature in combating noise. This is where you switch the WIDTH and SHIFT settings over to the "HI & LO" mode by pressing the buttons in quickly. Hi & Low will change how the voices sound just as they are labeled. The HI will adjust how much High freq. you can hear, and the LO will adjust how much Low Freq. you can here.
What you can't see in this mode, is that you are actually moving the pass band WIDTH and IF SHIFT around. If you exit the Hi & Lo mode and return to WIDTH and SHIFT you will see the changes that you have made.
The best way to use this is to move the Hi & Lo settings around until you have removed as much noise from the audio as you can, while still keeping the sound of the voice from being too distorted. In most cases you will find that you can remove a lot of the High end of the voice while tightening in the Low end of the voice and still copy what the station is saying very clearly. You'll also note that when you change back to the WIDTH and SHIFT modes that you've probably done what I was describing in the above paragraph... IE, you will have changed the SHIFT to a Lower Freq. and tightened the WIDTH down to a narrow pass band somewhere around 1.5KHz.

I hope that I have given you a pretty good idea of what each of these things can do for you, and how to use them. Of course if you need more help please feel free to email the group again. I'm sure there will be many more explanation of how these things work.. Hopefully not overly technical as you may be a nuebie. Have fun and 73
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