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K3s Notch Filter

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Richard-6

K3s Notch Filter

Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?

Don’t like what AGC does.

Cheers!
Richard Kunc - W4KBX
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hbjr

Re: K3s Notch Filter

Unfortunately you can’t. I miss that feature from several other lesser radios. You could target a particular audio frequency and set the width of the notch filter and make the offending sound go away!

Hank
K4HYJ

From: Richard
Sent: Sunday, May 12, 2019 6:24 PM
To: Elecraft Reflector
Subject: [Elecraft] K3s Notch Filter

Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?

Don’t like what AGC does.

Cheers!
Richard Kunc - W4KBX
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Richard-6

Re: K3s Notch Filter

In reply to this post by Richard-6

Yes, I really wish the K3s could do that. I also wish it had multiple notch filters.

As it is, it’s so wide that you can’t help silencing a good size chunk of the band. Hardly practical.

Maybe corporate feels that FT8 is just an evanescent craze that will soon go away, thus no need for narrower notches.

But hey! A boy can dream.

Richard

> On May 12, 2019, at 6:27 PM, HB <[hidden email]> wrote:
>
> Unfortunately you can’t. I miss that feature from several other lesser radios. You could target a particular audio frequency and set the width of the notch filter and make the offending sound go away!
>
> Hank
> K4HYJ
>
> From: Richard <mailto:[hidden email]>
> Sent: Sunday, May 12, 2019 6:24 PM
> To: Elecraft Reflector <mailto:[hidden email]>
> Subject: [Elecraft] K3s Notch Filter
>
> Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
>
> Don’t like what AGC does.
>
> Cheers!
> Richard Kunc - W4KBX
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft <http://mailman.qth.net/mailman/listinfo/elecraft>
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Bob McGraw - K4TAX

Re: K3s Notch Filter

In reply to this post by Richard-6

It appears from my measurements that the manual notch is about 200 Hz
wide at the 6 dB points. That's the width of only 2 FT-8 signals and
the depth of the notch is about 40 dB. Certainly will take out 1 or 2
signals and not affect others in the 2.7 kHz BW of the normal FT-8
receiver bandwidth.

As to the bleeding ears, turn the volume down.   I don't find it
necessary to hear any FT-8 data.   Also, correct attention to AGC
parameters does a lot to deal with strong signals in the midst of weaker
signals.   Also the use of ATTN and RF Gain reduction is a big
advantage, specially on 160M - 40M and to some extent on 20M.

As to those running "legal limit", that depends on band and conditions,
thus one may find legal limit is necessary to make contacts.   It is a
weak signal mode not a low power mode. {Flame shields up.}

73

Bob, K4TAX

On 5/12/2019 5:27 PM, HB wrote:

> Unfortunately you can’t. I miss that feature from several other lesser radios. You could target a particular audio frequency and set the width of the notch filter and make the offending sound go away!
>
> Hank
> K4HYJ
>
> From: Richard
> Sent: Sunday, May 12, 2019 6:24 PM
> To: Elecraft Reflector
> Subject: [Elecraft] K3s Notch Filter
>
> Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
>
> Don’t like what AGC does.
>
> Cheers!
> Richard Kunc - W4KBX
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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Rick WA6NHC-2

Re: K3s Notch Filter

1). The design of the K3 notch filter predates most digital modes currently used (excluding RTTY). Earlier digital modes, were wider. It may be possible to change the behavior.

2). The use of legal limit or not isn’t the issue; as it may be needed to make the DESIRED contact, typically often required on the lower bands. Your ability to hear such a strong signal has many factors, including band conditions and proximity.

3). I defy anyone to determine without going to the other station or asking, if the ‘offending’ station is using a 10 dB amp or 10 dB gain antenna. Gain=gain, the means isn’t important. Use what is needed to complete the contact.

Without an amp, I would not have been able to work enough stations this past winter, for a 160 M DXCC (inverted L, 600 watts, 108 worked). It would have been simpler has most of those I worked, also had more signal. Full legal limit is very common there.

I don’t listen to the digital modes but enjoy the quiet, volume down, ears safe (too late now). I also run with AGC off, which doesn’t stop the audio system from using its AGC and causing blocking.

However, FT4 and FT8 are very adept at hearing around the very strong, to hear the very weak.

Rick WA6NHC

Smell Czech correction happen

> On May 12, 2019, at 3:47 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>
> It appears from my measurements that the manual notch is about 200 Hz wide at the 6 dB points. That's the width of only 2 FT-8 signals and the depth of the notch is about 40 dB. Certainly will take out 1 or 2 signals and not affect others in the 2.7 kHz BW of the normal FT-8 receiver bandwidth.
>
> As to the bleeding ears, turn the volume down. I don't find it necessary to hear any FT-8 data. Also, correct attention to AGC parameters does a lot to deal with strong signals in the midst of weaker signals. Also the use of ATTN and RF Gain reduction is a big advantage, specially on 160M - 40M and to some extent on 20M.
>
> As to those running "legal limit", that depends on band and conditions, thus one may find legal limit is necessary to make contacts. It is a weak signal mode not a low power mode. {Flame shields up.}
>
> 73
>
> Bob, K4TAX
>
>
>> On 5/12/2019 5:27 PM, HB wrote:
>> Unfortunately you can’t. I miss that feature from several other lesser radios. You could target a particular audio frequency and set the width of the notch filter and make the offending sound go away!
>>
>> Hank
>> K4HYJ
>>
>> From: Richard
>> Sent: Sunday, May 12, 2019 6:24 PM
>> To: Elecraft Reflector
>> Subject: [Elecraft] K3s Notch Filter
>>
>> Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
>>
>> Don’t like what AGC does.
>>
>> Cheers!
>> Richard Kunc - W4KBX
>> ______________________________________________________________
>> 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
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>
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>> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
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Jim Brown-10

Re: K3s Notch Filter

In reply to this post by Bob McGraw - K4TAX

On 5/12/2019 3:47 PM, Bob McGraw K4TAX wrote:
> Certainly will take out 1 or 2 signals and not affect others in the
> 2.7 kHz BW of the normal FT-8 receiver bandwidth.

Not quite -- there's a lot of phase shift associated with the amplitude
response change of the notch, so it degrades docoding of signals for
some unknown bandwidth on both sides of the notch. K1JT warns against
using any filtering ahead of the WSJT-X decoders for this reason.

73, Jim K9YC

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Jim Brown-10

Re: K3s Notch Filter

In reply to this post by Rick WA6NHC-2

On 5/12/2019 4:17 PM, Rick Bates (WA6NHC) wrote:
> The use of legal limit or not isn’t the issue; as it may be needed to make the DESIRED contact, typically often required on the lower bands. Your ability to hear such a strong signal has many factors, including band conditions and proximity.

Right. As to decoding weak stations around much, much stronger ones -- I
face that often on 160M and 6M, which is 99.9% of my FT8 activity. My
solution is to set the input gain to the decoder so that the strongest
signals don't cause the A/D to clip, but raise the level of the weaker
stations so they are above the bottom of the A/D. The indicated input
level is then about 70 dB. Clipping is indicated by the green vertical
bar turning red. And I run with slow AGC.

73, Jim K9YC

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Arie Kleingeld PA3A-2

Re: K3s Notch Filter

<snip>

Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
<snip>

Well, the K3's nothfilter may not be the best for FT8. Besides that,
when the notch is engaged, the AGC is still responding to that strong
signal. That's in the design...

73.
Arie PA3A

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Richard Lamont

Re: K3s Notch Filter

In reply to this post by Richard-6

On 12/05/2019 23:22, Richard wrote:

> Is there any way to make the manual notch filter really narrow to keep morons running legal limit on FT8 from wiping out my waterfall and making my ears bleed?
>
> Don’t like what AGC does.

Probably not, but both the notch filter and AGC are the wrong tools for
the job.

The WSJT-X decoder has huge dynamic range (16-bit 48000 samples/sec
input decimated to 12000 samples/sec, so over 90 dB), so it's best to
use the RX as a dumb converter and let the decoder deal with it. It's
the right tool for the job.

This means keeping the bandwidth of the RX at least as wide as the band
displayed on the waterfall and avoiding the use of anything in the K3
that might improve the signal for aural CW/SSB reception such as notch
filtering, equalisation, noise blanking and noise reduction.

AGC should be avoided because the level of every FT8 signal in the
passband will be modulated by fading on the strongest signal, which
makes the decoder's job harder. The AGC recovery time may also cause the
loss of more symbols than necessary when there's impulsive interference
such as lightning static.

The trick is to set the gain manually through the chain, from the RF
gain knob on the RX right through to the waterfall settings, so that
levels are matched and no one stage in the chain is either clipping
strong signals or pushing weak ones below the noise floor.

If you ears are still bleeding then turn the AF gain down. If the WSJT-X
'thermometer' is in the red turn the RF gain down. If the waterfall
isn't showing both the weakest and strongest signals properly, adjust
the waterfall zero and gain controls accordingly.

The "morons" are not running legal limit to cause you trouble. We're
doing it (for example) because the loss on the 160m path between G and
JA is so high that we need legal limit to get even a faintly detectable
signal at the other end.

73,
Richard G4DYA
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Jim Brown-10

WSJT-X, AGC, Notch, and NB

On 5/13/2019 2:53 AM, Richard Lamont wrote:
> The WSJT-X decoder has huge dynamic range (16-bit 48000 samples/sec
> input decimated to 12000 samples/sec, so over 90 dB), so it's best to
> use the RX as a dumb converter and let the decoder deal with it. It's
> the right tool for the job.

Yes, BUT -- while the theoretical range of a 16 bit system is 96 dB,
non-linearities at the lower end of the dynamic range limit it to about
90 dB. That's still a lot, and it's why I recommend setting the audio
level as high as possible at the input of the A/D.

> This means keeping the bandwidth of the RX at least as wide as the band
> displayed on the waterfall and avoiding the use of anything in the K3
> that might improve the signal for aural CW/SSB reception such as notch
> filtering, equalisation, noise blanking and noise reduction.

I will offer an alternative view on use of the NB. Yesterday, AG6EE was
in a rare grid in northern NV on 6M, and there was VERY strong impulse
noise coming from his direction. Without the NB, WSJT-X could not decode
him. WITH the NB, it did, and I made the QSO. I would NOT recommend
general use of the NB, because it generates IMD that results in multiple
decodes of the same signal, but there are exceptions to every rule. :)

> AGC should be avoided because the level of every FT8 signal in the
> passband will be modulated by fading on the strongest signal, which
> makes the decoder's job harder.

I find that this is not a problem with AGC-S, primarily because in my
situation, the very strong signals are locals, not subject to QSB.

73, Jim K9YC

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Bob McGraw - K4TAX

Re: WSJT-X, AGC, Notch, and NB

I must agree with Jim on every point.    The noise blanker does work but
only on impulse signals. It does little to nothing on broad band noise
and in fact, as Jim stated, can be degrading to the decoding of signals
if used with broad band noise.

And I agree that reducing BW or changing SHIFT is not an ideal means,
but do use 2.7 kHz to 2.8 kHz for better receiver performance. Just let
the software do its job.   With wider bandwidths as opposed to filtering
to lesser bandwidths, with wider BW's there is less impact on the
decoding success of the software.   The software is designed to operate
within the normal SSB bandwidth of the spectrum.   If there are signals
higher in frequency or lower in frequency there is nothing wrong with
using the "big knob" on the radio to change frequency slightly to
receive those signals.   And again, the software knows what to do when
it comes time to transmit.

And I find the use of slow AGC is really a must. The electronics is
much better than I am for determining if gain needs to be adjusted.
Just let the superior electronics and software do the job.

73

Bob, K4TAX

On 5/13/2019 12:18 PM, Jim Brown wrote:

> On 5/13/2019 2:53 AM, Richard Lamont wrote:
>> The WSJT-X decoder has huge dynamic range (16-bit 48000 samples/sec
>> input decimated to 12000 samples/sec, so over 90 dB), so it's best to
>> use the RX as a dumb converter and let the decoder deal with it. It's
>> the right tool for the job.
>
> Yes, BUT -- while the theoretical range of a 16 bit system is 96 dB,
> non-linearities at the lower end of the dynamic range limit it to
> about 90 dB. That's still a lot, and it's why I recommend setting the
> audio level as high as possible at the input of the A/D.
>
>
>> This means keeping the bandwidth of the RX at least as wide as the band
>> displayed on the waterfall and avoiding the use of anything in the K3
>> that might improve the signal for aural CW/SSB reception such as notch
>> filtering, equalisation, noise blanking and noise reduction.
>
> I will offer an alternative view on use of the NB. Yesterday, AG6EE
> was in a rare grid in northern NV on 6M, and there was VERY strong
> impulse noise coming from his direction. Without the NB, WSJT-X could
> not decode him. WITH the NB, it did, and I made the QSO. I would NOT
> recommend general use of the NB, because it generates IMD that results
> in multiple decodes of the same signal, but there are exceptions to
> every rule. :)
>
>> AGC should be avoided because the level of every FT8 signal in the
>> passband will be modulated by fading on the strongest signal, which
>> makes the decoder's job harder.
>
> I find that this is not a problem with AGC-S, primarily because in my
> situation, the very strong signals are locals, not subject to QSB.
>
> 73, Jim K9YC
>
>
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