Auto Notch Revisited.

[wa9fvp]

It's been 2 years since there were complaints on this forum about the K3 auto-notch.  Apparently it was never fixed.  

The other day I was working a Ham in Tel Aviv when a carrier came on and covered his signal.  The Auto notch worked well but the guys voice was very distorted.  To me that's unacceptable.  

This year at the Dayton Hamvention I talked to someone from Elecraft about the DSP problems and he agreed that the auto notch needs some improvement.  I think he was a the product manager.

Back in the early 90's I worked with another Engineer on a project we called "The Hamblaster". I published two articles in QEX (October 1991 and January 1992). We developed a PC based sound card that connects to the receiver's audio and performed, among other things,  an auto-notch and noise reduction (NR).  In our DSP software, the auto-notch was generated by summing the inverted NR output to the input signal.  Whether it's a noise reduction or an auto-notch we still used a software algorithm called the LMS (Least Means Square).  

Most Ham transceiver use the same LMS algorithm and I never heard distorted audio when the notch was engaged.  That's especially true with Yaesu, Icom or Kenwood. I'm not sure about the other American brands but I bet they are OK as well.

My second complaint is the K3's NR control.  Most other manufacturers have an analog like control that simply changes the NR level.  I don't understand the logic of having several steps from F1-1 to F4-4 and F5-1 (mixed) to F8-4 (mixed).  I would rather have two separate settings.  F0 to F9 for the level and if you want a to fiddle with the delay, D0 to D9 in the main menu.  I think the level control on other radios is simply a mix of the input signal with the NR output and is similar to the K3's mF5-1 to mF8-4

To me it sounds as if there's a dynamic range problem on the K3 whereby the numbers in the math are over-ranging when the notch is engaged and is causing a "flat-topping" in the audio signal.  But that's just a guess!  

I hope someone at Elecraft reads this and gets the ball rolling to fix the problem!

Jack WA9FVP
Willco Electronics  
[e-mail]

[Bill-3]

I completely agree - the K3 is very lacking with their auto-notch. It
requires fiddling with the AGC menus to force it to function without
ruining the fidelity of a SSB signal. The NR system is very complex with
many settings - none of which I have found to be very helpful -
certainly no better than just using my ears.

The subject has been brought up several times since I became interested
in the K3 and started following the various reflectors and groups. They
are both weak points of the K3 and should be addressed.

Most other currently available rigs are easier to operate in the NR
arena and much more pleasing to listen to in the auto-notch arena.

I have found some work-arounds and mentioned them in previous posts.
That said, why are work-arounds needed???

Bill W2BLC K-Line



______________________________________________________________
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
Message delivered to [hidden email]

[Tim Tucker]

I agree with the majority of your assessment.  I also brought up the Auto
notch issue several years ago and haven't seen much, if any improvement.
 As a result, I nearly always just use manual notch.  I also have the same
complaint with the way the NR in the K3 works.  The KX3 implementation is
far superior, IMO.  I've actually considered coupling an AF DSP speaker
product from West Mountain Radio to the K3 to overcome the K3 autonotch and
NR limitations.  I've used one of their speakers mobile for many years
coupled with my IC-7000 with a lot of success.


On Thu, Jul 31, 2014 at 2:01 PM, wa9fvp <[hidden email]> wrote:

> It's been 2 years since there were complaints on this forum about the K3
> auto-notch.  Apparently it was never fixed.
>
> The other day I was working a Ham in Tel Aviv when a carrier came on and
> covered his signal.  The Auto notch worked well but the guys voice was very
> distorted.  To me that's unacceptable.
>
> This year at the Dayton Hamvention I talked to someone from Elecraft about
> the DSP problems and he agreed that the auto notch needs some improvement.
> I think he was a the product manager.
>
> Back in the early 90's I worked with another Engineer on a project we
> called
> "The Hamblaster". I published two articles in QEX (October 1991 and January
> 1992). We developed a PC based sound card that connects to the receiver's
> audio and performed, among other things,  an auto-notch and noise reduction
> (NR).  In our DSP software, the auto-notch was generated by summing the
> inverted NR output to the input signal.  Whether it's a noise reduction or
> an auto-notch we still used a software algorithm called the LMS (Least
> Means
> Square).
>
> Most Ham transceiver use the same LMS algorithm and I never heard distorted
> audio when the notch was engaged.  That's especially true with Yaesu, Icom
> or Kenwood. I'm not sure about the other American brands but I bet they are
> OK as well.
>
> My second complaint is the K3's NR control.  Most other manufacturers have
> an analog like control that simply changes the NR level.  I don't
> understand
> the logic of having several steps from F1-1 to F4-4 and F5-1 (mixed) to
> F8-4
> (mixed).  I would rather have two separate settings.  F0 to F9 for the
> level
> and if you want a to fiddle with the delay, D0 to D9 in the main menu.  I
> think the level control on other radios is simply a mix of the input signal
> with the NR output and is similar to the K3's mF5-1 to mF8-4
>
> To me it sounds as if there's a dynamic range problem on the K3 whereby the
> numbers in the math are over-ranging when the notch is engaged and is
> causing a "flat-topping" in the audio signal.  But that's just a guess!
>
> I hope someone at Elecraft reads this and gets the ball rolling to fix the
> problem!
>
> Jack WA9FVP
> Willco Electronics
> [hidden email]
>
>
>
>
> -----
> Jack WA9FVP
>
> Sent from my TRS-80 :-)
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/Auto-Notch-Revisited-tp7591810.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

--
Owner, worldwidedx.com
AE6LX, Amateur Radio
NNN0ITA, Navy MARS
NNN0GAF FOUR, Southern CA Director Assistant for Training, Navy MARS
______________________________________________________________
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
Message delivered to [hidden email]

[NK7Z]

Hello,
I find I must also agree with the complaints regarding notching...  I
just cam from a Icom 756 P3, and the notching was far superior to the
K3.
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info


On Thu, 2014-07-31 at 17:28 -0400, Bill W2BLC wrote:

> I completely agree - the K3 is very lacking with their auto-notch. It
> requires fiddling with the AGC menus to force it to function without
> ruining the fidelity of a SSB signal. The NR system is very complex with
> many settings - none of which I have found to be very helpful -
> certainly no better than just using my ears.
>
> The subject has been brought up several times since I became interested
> in the K3 and started following the various reflectors and groups. They
> are both weak points of the K3 and should be addressed.
>
> Most other currently available rigs are easier to operate in the NR
> arena and much more pleasing to listen to in the auto-notch arena.
>
> I have found some work-arounds and mentioned them in previous posts.
> That said, why are work-arounds needed???
>
> Bill W2BLC K-Line
>
>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

______________________________________________________________
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
Message delivered to [hidden email]

[Johnny Siu]

Hello David,

I concur with your observation.  There are many areas that K3 are better than ic756 pro 3 but the NR, manual notch and auto notch of K3 have much rooms for improvement.

When there is a strong undesirable carrier next to a weak DX, in 756pro3, I can use manual notch to 'kill' the carrier and eliminate the pumping effect on AGC.

Every radio has its own merit.  We have to accept their weakness while we are enjoying their strength.

Anyway, I would like the NR of K3 will be as good as the NR of KX3.  At one time, I nearly sold the K3 and just kept the KX3.  On reflection, K3 is still a good contesting machine at desktop size, hence I still keep my K3.

73

Johnny VR2XMC
 

________________________________
 寄件人︰ David Cole <[hidden email]>
收件人︰ [hidden email]
傳送日期︰ 2014年08月1日 (週五) 6:12 AM
主題︰ Re: [Elecraft] Auto Notch Revisited.
 

Hello,
I find I must also agree with the complaints regarding notching...  I
just cam from a Icom 756 P3, and the notching was far superior to the
K3.
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info


On Thu, 2014-07-31 at 17:28 -0400, Bill W2BLC wrote:

> I completely agree - the K3 is very lacking with their auto-notch. It
> requires fiddling with the AGC menus to force it to function without
> ruining the fidelity of a SSB signal. The NR system is very complex with
> many settings - none of which I have found to be very helpful -
> certainly no better than just using my ears.
>
> The subject has been brought up several times since I became interested
> in the K3 and started following the various reflectors and groups. They
> are both weak points of the K3 and should be addressed.
>
> Most other currently available rigs are easier to operate in the NR
> arena and much more pleasing to listen to in the auto-notch arena.
>
> I have found some work-arounds and mentioned them in previous posts.
> That said, why are work-arounds needed???
>
> Bill W2BLC K-Line
>
>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

______________________________________________________________
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
Message delivered to [hidden email]
______________________________________________________________
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
Message delivered to [hidden email]

[Gary Gregory-2]

Agreed, now let's hope somebody IS listening and get this long term issue
resolved.

The Manual Notch eliminates a CW carrier nicely but it too requires button
presses and adjustment that could be simplified surely?

Gary


On 1 August 2014 08:57, Johnny Siu <[hidden email]> wrote:

> Hello David,
>
> I concur with your observation.  There are many areas that K3 are better
> than ic756 pro 3 but the NR, manual notch and auto notch of K3 have much
> rooms for improvement.
>
> When there is a strong undesirable carrier next to a weak DX, in 756pro3,
> I can use manual notch to 'kill' the carrier and eliminate the pumping
> effect on AGC.
>
> Every radio has its own merit.  We have to accept their weakness while we
> are enjoying their strength.
>
> Anyway, I would like the NR of K3 will be as good as the NR of KX3.  At
> one time, I nearly sold the K3 and just kept the KX3.  On reflection, K3 is
> still a good contesting machine at desktop size, hence I still keep my K3.
>
> 73
>
> Johnny VR2XMC
>
>
> ________________________________
>  寄件人︰ David Cole <[hidden email]>
> 收件人︰ [hidden email]
> 傳送日期︰ 2014年08月1日 (週五) 6:12 AM
> 主題︰ Re: [Elecraft] Auto Notch Revisited.
>
>
> Hello,
> I find I must also agree with the complaints regarding notching...  I
> just cam from a Icom 756 P3, and the notching was far superior to the
> K3.
> --
> Thanks and 73's,
> For equipment, and software setups and reviews see:
> www.nk7z.net
> for MixW support see;
> http://groups.yahoo.com/neo/groups/mixw/info
> for Dopplergram information see:
> http://groups.yahoo.com/neo/groups/dopplergram/info
> for MM-SSTV see:
> http://groups.yahoo.com/neo/groups/MM-SSTV/info
>
>
> On Thu, 2014-07-31 at 17:28 -0400, Bill W2BLC wrote:
> > I completely agree - the K3 is very lacking with their auto-notch. It
> > requires fiddling with the AGC menus to force it to function without
> > ruining the fidelity of a SSB signal. The NR system is very complex with
> > many settings - none of which I have found to be very helpful -
> > certainly no better than just using my ears.
> >
> > The subject has been brought up several times since I became interested
> > in the K3 and started following the various reflectors and groups. They
> > are both weak points of the K3 and should be addressed.
> >
> > Most other currently available rigs are easier to operate in the NR
> > arena and much more pleasing to listen to in the auto-notch arena.
> >
> > I have found some work-arounds and mentioned them in previous posts.
> > That said, why are work-arounds needed???
> >
> > Bill W2BLC K-Line
> >
> >
> >
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]
>
>
>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

--



*Gary - VK1ZZ, K3NHLSkype: Gary.VK1ZZhttp://www.qsl.net/vk1zz
<http://www.qsl.net/vk1zz>Motorhome Portable*
*"Grumpy's House"*


*Elecraft K3KPA500FTKAT500FT*
______________________________________________________________
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
Message delivered to [hidden email]

[k6dgw]

I rarely use the manual notch on CW, I've had other rigs with notch
filters, and I rarely used them either ... it seems that the filter in
my head is enough.

I'm not on SSB very much [compromised hearing, not mode-aversion], and
I've occasionally used the auto-notch on SSB when in
longer-than-a-contest-QSO mode.  It's always worked very well for me.  I
suppose there is some accompanying distortion, that's what happens when
you punch out a narrow part of the baseband, but honestly, it reduced
the carrier to where I couldn't hear it.

I think, but do not know, that the performance of several of the K3 DSP
"features" are closely related to the AGC parameters being used.  This
makes sense, the AGC is distorting the signal possibly before the other
"features" are getting the number stream.  All of that is above my pay
grade.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 7/31/2014 3:12 PM, David Cole wrote:
> Hello,
> I find I must also agree with the complaints regarding notching...  I
> just cam from a Icom 756 P3, and the notching was far superior to the
> K3.
>


______________________________________________________________
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
Message delivered to [hidden email]

[John_N1JM]

The trouble with the K3 notch is that it is outside the agc loop(audio notch) unlike the Icom radio. It may notch out the tone but not the carrier. A huge signal will still swamp the receiver. You will get arguments that this is better on receiver imd performance but I think I could live with receiver imd degradradation for the small if not brief time I would use the  inside the agc loop notch.

73, John N1JM

k6dgw wrote

I rarely use the manual notch on CW, I've had other rigs with notch
filters, and I rarely used them either ... it seems that the filter in
my head is enough.

I'm not on SSB very much [compromised hearing, not mode-aversion], and
I've occasionally used the auto-notch on SSB when in
longer-than-a-contest-QSO mode.  It's always worked very well for me.  I
suppose there is some accompanying distortion, that's what happens when
you punch out a narrow part of the baseband, but honestly, it reduced
the carrier to where I couldn't hear it.

I think, but do not know, that the performance of several of the K3 DSP
"features" are closely related to the AGC parameters being used.  This
makes sense, the AGC is distorting the signal possibly before the other
"features" are getting the number stream.  All of that is above my pay
grade.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 7/31/2014 3:12 PM, David Cole wrote:
> Hello,
> I find I must also agree with the complaints regarding notching...  I
> just cam from a Icom 756 P3, and the notching was far superior to the
> K3.
>


______________________________________________________________
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
Message delivered to [hidden email]

[Grant Youngman]

The Icom’s manual notch is inside the AGC loop, but not the auto notch.

The early (Version 1) Orion firmware had the auto notch inside the AGC loop, and it was one of the many great features of that radio.  In AM mode, you could punch in audo-notch and it would remove the carrier to let just the sideband energy drive the AGC — which often made uncopyable low-modulation percentage AM signals readable.  And of course, auto-notched interfering carriers would not affect AGC.  When Ten-tec completely rewrote the software (Version 2) they moved the auto notch outside the loop, and there were universal complaints (at least compared to how the notch worked in V1 firmware). It’s unfortunate that there were other factors that eventually led to the rewrite.

Obviously there are design tradeoffs, and I don’t fully understand them all.  But it does seem that it’s feasible to put a manual (e.g. non-adaptive) notch inside the AGC loop without doing too much damage to IMD or other specs. Maybe even do it as a menu selectable option if there are performance tradeoffs.

Grant NQ5T


On Jul 31, 2014, at 9:23 PM, John_N1JM <[hidden email]> wrote:

> The trouble with the K3 notch is that it is outside the agc loop(audio notch)
> unlike the Icom radio. It may notch out the tone but not the carrier. A huge
> signal will still swamp the receiver. You will get arguments that this is
> better on receiver imd performance but I think I could live with receiver
> imd degradradation for the small if not brief time I would use the  inside
> the agc loop notch.
>
>>
>> On 7/31/2014 3:12 PM, David Cole wrote:
>>> Hello,
>>> I find I must also agree with the complaints regarding notching...  I
>>> just cam from a Icom 756 P3, and the notching was far superior to the
>>> K3.

______________________________________________________________
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
Message delivered to [hidden email]

[wa9fvp]

A feature that we added to the Hamblaster was something I called a Filter Freeze button.  It was something I suggested and turned out to be very affective.

It wasn't really physical a button. It was actually an on screen control that passed a parameter to the Hamblaster telling the LMS algorithm to stop up dating.  The LMS algorithm converged on the carrier and then stopped updating it's coefficients .  It locked the auto-notch frequency and killed the carrier without affecting the voice.

The Idea was to have a semi-automatic filter that you can press a button, quickly notch the carrier and lock the null frequency and depth.  A manual adjustable notch was too cumbersome and would required fiddling with the frequency adjustment knob while trying to null the carrier.  


I would love to see this feature added to the K3.  

Jack WA9FVP
Willco Electronics
[e-mail]

[David Woolley (E.L)]

Whilst summing the inverted NR output doesn't sound logically any
different from applying a custom filter, the tactic used by hearing aids
(at least Oticon ones) is actually to determine the frequency and phase
of the presumed interfering signal (howl round in that case) and add in
an inverted version.

That does, have the disadvantage that if the tone is really external and
than goes away, the cancelling tone remains for a while and you actually
get an interfering signal as an artifact.  That would mean that it would
not work well for modulated tones, e.g. morse signals, rather than pure
carriers.

I don't really understand all the references to least squares.  Least
squares is basically about the simplest way of matching parameters of an
expected signal to an actual signal in noise.  What is interesting is
the choice of parameters being fitted, and the expected form of the
signa, not that there is a least squares fit.

If what is really being described here is to do a least squares fit of a
sine wave and then add the inverted version of this, that would work
better than an automated notch filter for continuous carriers
(essentially because it would be extremely narrow bandwidth, much
narrower than could be achieved with acceptable group delays with a
filter), and would not impact on speech, but would not work at all well
for modulated carriers (effectively its bandwidth is much lower than
that of a morse signal).

Incidentally, the real research funding for noise reduction of speech is
in the hearing aid industry - that's essentially what modern digital
aids are about.  People with moderate to severe through profound loss
often complain about the artefacts produced by the noise reduction and
speech compression.  People with profound loss, who have previously used
analogue aids, often have difficulty moving to digital aids because they
can't get used to the artefacts.

--
David Woolley
Owner K2 06123


On 31/07/14 22:01, wa9fvp wrote:

> Back in the early 90's I worked with another Engineer on a project we called
> "The Hamblaster". I published two articles in QEX (October 1991 and January
> 1992). We developed a PC based sound card that connects to the receiver's
> audio and performed, among other things,  an auto-notch and noise reduction
> (NR).  In our DSP software, the auto-notch was generated by summing the
> inverted NR output to the input signal.  Whether it's a noise reduction or
> an auto-notch we still used a software algorithm called the LMS (Least Means
> Square).
>
> Most Ham transceiver use the same LMS algorithm and I never heard distorted
> audio when the notch was engaged.  That's especially true with Yaesu, Icom
> or Kenwood. I'm not sure about the other American brands but I bet they are
> OK as well.

______________________________________________________________
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
Message delivered to [hidden email]

[k6dgw]

I have severe traumatic hearing loss from one night many years ago when
I still thought I was bulletproof and immortal and I'm pretty deaf above
about 1200 Hz.  The Dept of Veterans' Affairs gives me hearing aids,
replacing them every 5 or so years [Thank you US Taxpayers, you change
my life!].  They are quite amazing, mine are Phonak.

They will "notch out" the siren on a fire truck.  They don't take it all
the way out [sort of unsafe not to hear it at all], they do it almost
instantly over some threshold amplitude, and the "notch" follows the
pitch of the siren.  I suspect they are doing what Jim, K9YC, suggested
in another email on this thread.

They have 5 different automatic "programs" for differing circumstances.
  One is for music which they somehow recognize after about 3-5 seconds.
  They will also suppress the wind noise in my truck in about 3-5
seconds. I think that suppression is just a roll-off of the very high
frequencies.

I rarely use the manual notch on CW.  I'm not on SSB very much but when
I am and in a non-contest environment, I have used the auto-notch and I
don't discern any artifacts from the K3.  On some bands, I use the NB
all the time on CW, it *does* knock down some repetitive components in
the power line hash.  I don't notice any artifacts, but I can create
them with very aggressive settings.  NR makes SSB signals sound a bit
strange and I rarely use it.

Incidentally, my hearing aids seem to have Bluetooth because they "talk
to each other," apparently negotiating when to change programs.  They do
all of this on 1.4 V from batteries about the size of a 10-32 nut.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 8/1/2014 2:48 AM, David Woolley wrote:

> Whilst summing the inverted NR output doesn't sound logically any
> different from applying a custom filter, the tactic used by hearing aids
> (at least Oticon ones) is actually to determine the frequency and phase
> of the presumed interfering signal (howl round in that case) and add in
> an inverted version.
>
> That does, have the disadvantage that if the tone is really external and
> than goes away, the cancelling tone remains for a while and you actually
> get an interfering signal as an artifact.  That would mean that it would
> not work well for modulated tones, e.g. morse signals, rather than pure
> carriers.

______________________________________________________________
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
Message delivered to [hidden email]

[wa9fvp]

A few years ago I uploaded sound files to the Elecraft/Yahoo news groups.  You can find them in the files section and they show a comparison of audio with no notch and with it on.

If your interested in some technical stuff, there's a very good tutorial about the LMS algorithm on the National Instruments web site.  The "Fast Block LMS" is the one we used in the Hamblaster.  

http://zone.ni.com/reference/en-XX/help/372357A-01/lvaftconcepts/aft_lms_algorithms/

[David Woolley (E.L)]

You need to qualify LMS with "for FIR adaptive filters", as least mean
square (least squares) has a much longer history in statistics.

If I understand it, it is the simple algorithm used in (early) modem
equalisation filters, because it is cheap to compute.  The problem with
it in the context of this thread is that it needs a value for d(n).
Although d(n) is confusingly defined in the actual article, I believe it
represents the "correct" (desired) output of the filter.

That is easy in a digital system, where you can determine it by slicing
the output of the filter (and possibly running forward error
correction), but the context of this thread was the use of the
auto-notch on voice signals.  In that case, it takes human intelligence
to work out the general nature of the correct signal, and even then that
doesn't give you the exact waveform.

What I guess you must be doing, for voice, is using an expected signal
of silence (d(n) = 0) and hoping that the voice signal is sufficiently
uncorrelated that the filter fails to converge on to it, but only onto
the, simpler, interfering carrier(s).

--
David Woolley
Owner K2 06123

On 02/08/14 01:39, wa9fvp wrote:
> If your interested in some technical stuff, there's a very good tutorial
> about the LMS algorithm on the National Instruments web site.  The "Fast
> Block LMS" is the one we used in the Hamblaster.
>
> http://zone.ni.com/reference/en-XX/help/372357A-01/lvaftconcepts/aft_lms_algorithms/

______________________________________________________________
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
Message delivered to [hidden email]

[Sverre Holm (LA3ZA)]

In the context of the LMS filter for FIR notch filtering and noise cancellation, one common way to find the reference is by a simple delay of the input signal. If the purpose is to separate voice from a sinusoid, then one utilizes the fact that a sinusoid has a long correlation function in time compared to voice. If the delay is longer than usual correlation time for voice, one will get a reference for the desired signal - at least in the correlation domain which is what counts here.

For a noise reduction filter, the delay is often shorter, as noise has short correlation time compared to a voiced signal.

David Woolley (E.L) wrote

The problem with it in the context of this thread is that it needs a value for d(n).
Although d(n) is confusingly defined in the actual article, I believe it
represents the "correct" (desired) output of the filter.