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K3 APF Effectiveness

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wb6rse1

K3 APF Effectiveness

There are many variables at work with regard to judging the effectiveness of the K3 APF. In addition to the discussions of noise and careful tuning, there are user preferences to consider:

1) Headphones vs speakers
2) Enhancing a weak signal to "pop up" that would otherwise be copyable with adjustment of NR, NB, bandwidth/shift and/or the use of diversity RX.
3) Enhancing a truly weak signal that would otherwise be impossible to copy.

When commenting on the effectiveness of the APF, it would be useful to know what other of the K3's tools are in use and how they are adjusted.

73 - Steve WB6RSE
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k.igor

Re: K3 APF Effectiveness

Sure, you are right, but you would not deny that using same set of
parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22 should
give very similar results since the code of APF remains the same. After
playing few days with 4.22 I find myself having to turn off APF to better
receive weak CW stations. I don't have explanation for this. With APF on I
find it difficult to distinguish dits and dahs of weak signals. With 4.17 it
was much better for me. That should be apples-to apples comparison, I think.
I don't claim to be expert though, listening is very subjective IMHO.

Regards,

Igor, N1YX

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Wednesday, November 17, 2010 3:10 PM
To: Elecraft Reflector
Subject: [Elecraft] K3 APF Effectiveness

There are many variables at work with regard to judging the effectiveness of
the K3 APF. In addition to the discussions of noise and careful tuning,
there are user preferences to consider:

1) Headphones vs speakers
2) Enhancing a weak signal to "pop up" that would otherwise be copyable with
adjustment of NR, NB, bandwidth/shift and/or the use of diversity RX.
3) Enhancing a truly weak signal that would otherwise be impossible to copy.

When commenting on the effectiveness of the APF, it would be useful to know
what other of the K3's tools are in use and how they are adjusted.

73 - Steve WB6RSE
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Don Cunningham

Re: K3 APF Effectiveness

Gentlemen,
I am not a CW operator (yet) as I have let my 1960's Navy training go to
pot, but might I suggest that something might be overlooked in this
situation with the APF seeming less effective?? The common thing mentioned
is that "changes on one area often effect other areas" in the firmware. Is
it possible that the change to width (I believe that was the parameter) from
10 hz to 5 hz could be somehow causing this "difference" that some are
seeing?? Just a possibility from a bystander.
73,
Don, WB5HAK

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John Seney

Re: K3 APF Effectiveness

In reply to this post by k.igor

Hi All:

I have the same experience as Igor. There is an APF sweet spot that either moved or
disappeared.

Would it be helpful if there was a GUI that let us save, load, share, and see all of
the various K3 parameter settings that we are adjusting?

On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:

> Sure, you are right, but you would not deny that using same set of
> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22 should
> give very similar results since the code of APF remains the same. After
> playing few days with 4.22 I find myself having to turn off APF to better
> receive weak CW stations. I don't have explanation for this. With APF on I
> find it difficult to distinguish dits and dahs of weak signals. With 4.17 it
> was much better for me. That should be apples-to apples comparison, I think.
> I don't claim to be expert though, listening is very subjective IMHO.
>
> Regards,
>
> Igor, N1YX

73,

John Seney
ARS WD1V (fn42gw)
603 785-2413

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Mike Reublin

Re: K3 APF Effectiveness

John,

For me also.
K3 EZ gives you a lot of the parms. http://home.roadrunner.com/~n2bc/SW.htm

73, Mike NF4L

On 11/20/2010 3:16 PM, John Seney wrote:

> Hi All:
>
> I have the same experience as Igor. There is an APF sweet spot that either moved or
> disappeared.
>
> Would it be helpful if there was a GUI that let us save, load, share, and see all of
> the various K3 parameter settings that we are adjusting?
>
> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>
>> Sure, you are right, but you would not deny that using same set of
>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22 should
>> give very similar results since the code of APF remains the same. After
>> playing few days with 4.22 I find myself having to turn off APF to better
>> receive weak CW stations. I don't have explanation for this. With APF on I
>> find it difficult to distinguish dits and dahs of weak signals. With 4.17 it
>> was much better for me. That should be apples-to apples comparison, I think.
>> I don't claim to be expert though, listening is very subjective IMHO.
>>
>> Regards,
>>
>> Igor, N1YX
>
> 73,
>
> John Seney
> ARS WD1V (fn42gw)
> 603 785-2413
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
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wayne burdick

Final K3 APF Lab Test Results

Administrator

In reply to this post by John Seney

We just did a *very* accurate sweep of the APF passband from the original (4.17) and new (4.22) beta releases. Lyle has the data in spreadsheet form and will send it out on request. It's too big to attach to a reflector posting.

Bottom line: There is no difference between the two. This is not surprising, since we did not change the filter algorithm.

Any difference must be attributed to noise and signal conditions, filter bandwidth settings, or APF tuning vs. actual signal pitch. This is the nature of APF; it is most effective under specific conditions. Try turning it on, and if it doesn't help, leave it off.

73,
Wayne
N6KR

----
http://www.elecraft.com

On Nov 20, 2010, at 12:16 PM, John Seney <[hidden email]> wrote:

> Hi All:
>
> I have the same experience as Igor. There is an APF sweet spot that either moved or
> disappeared.
>
> Would it be helpful if there was a GUI that let us save, load, share, and see all of
> the various K3 parameter settings that we are adjusting?
>
> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>
>> Sure, you are right, but you would not deny that using same set of
>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22 should
>> give very similar results since the code of APF remains the same. After
>> playing few days with 4.22 I find myself having to turn off APF to better
>> receive weak CW stations. I don't have explanation for this. With APF on I
>> find it difficult to distinguish dits and dahs of weak signals. With 4.17 it
>> was much better for me. That should be apples-to apples comparison, I think.
>> I don't claim to be expert though, listening is very subjective IMHO.
>>
>> Regards,
>>
>> Igor, N1YX
>
>
> 73,
>
> John Seney
> ARS WD1V (fn42gw)
> 603 785-2413
>
>
> ______________________________________________________________
> 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

Kok Chen

Re: Final K3 APF Lab Test Results

On Nov 20, 2010, at 12:43 PM, Wayne Burdick wrote:

> Any difference must be attributed to noise and signal conditions, filter bandwidth settings, or APF tuning vs. actual signal pitch. This is the nature of APF; it is most effective under specific conditions. Try turning it on, and if it doesn't help, leave it off.

Those running Mac OS X 10.6 (Snow Leopard) on your computers might want to play with this application to hear what changing filter parameters does to an "APF":

http://homepage.mac.com/chen/w7ay/cocoaFilter/index.html

The "stock" IIR filter in the program has adjustable Q and center frequencies, with a GUI so you can see the transfer function and compare different settings with what you "hear." There is also an experimental FIR filter in it that attempts to achieve better SNR than the IIR without introducing the "hollow" flat-topped narrow bandpass DSP sound.

The IIR that is in the program is just a simple analog second order bandpass filter that is transformed into the digital domain. But you can change both the FIR and IIR filters with just a few lines of C code to experiment with something other than the "stock" filters.

cocoaFilter is not intended as an end-user program, but as a sandbox for people to try other filter ideas without having to learn all of Cocoa and Core Audio. if you are familiar with DSP but don't want to deal with the Mac OS Core Audio or the Cocoa user interface, this framework should make it easy -- you only need to modify a few lines of the filter code.

Just think of the "stock" filters as a starting point. Go build your own "INRADS" :-).

Modern computers are so fast that you don't need a DSP chip to experiment with real time audio filters -- the "stock" filters in cocoaFilter use only about 2% of the processor load of *one* core of my Nehalem-based MacPro, and I didn't attempt *any* optimization (audio is filtered one sample at a time with the dynamic messaging of Objective-C; that is as inefficient as you can get). Only when you start building audio filters that are 10 times more complex, will you need to use Mac OS X's Grand Central Dispatch in your filters to spread the work among the cores of your processor.

Audio Units and the AU Lab program in the Mac OS X Developer disk (it is on every Mac OS X Installer DVD) is another platform you can use to experiment with filters. It is probably a bit more complex than changing a few lines of code in cocoaFilter. cocoaFilter uses Audio Unit calls but you don't *need* to understand that code to experiment with other filters :-).

73
Chen, W7AY

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Dave Perry N4QS

Re: K3 APF Effectiveness

In reply to this post by John Seney

I agree that the signal doesn't pop out anymore with 4.22, but I think it is
due to the change to 5 Hz tuning. It is harder to hear the peak in the
signal with the 5 Hz steps in the Shift tuning. I think we should go back
to 10 Hz per click. Just my opinion.

Dave, N4QS

----- Original Message -----
From: "John Seney" <[hidden email]>
To: "Igor Kosvin" <[hidden email]>
Cc: "'Elecraft Reflector'" <[hidden email]>
Sent: Saturday, November 20, 2010 2:16 PM
Subject: Re: [Elecraft] K3 APF Effectiveness

> Hi All:
>
> I have the same experience as Igor. There is an APF sweet spot that either
> moved or
> disappeared.
>
> Would it be helpful if there was a GUI that let us save, load, share, and
> see all of
> the various K3 parameter settings that we are adjusting?
>
> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>
>> Sure, you are right, but you would not deny that using same set of
>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22
>> should
>> give very similar results since the code of APF remains the same. After
>> playing few days with 4.22 I find myself having to turn off APF to better
>> receive weak CW stations. I don't have explanation for this. With APF on
>> I
>> find it difficult to distinguish dits and dahs of weak signals. With 4.17
>> it
>> was much better for me. That should be apples-to apples comparison, I
>> think.
>> I don't claim to be expert though, listening is very subjective IMHO.
>>
>> Regards,
>>
>> Igor, N1YX
>
>
> 73,
>
> John Seney
> ARS WD1V (fn42gw)
> 603 785-2413
>
>
> ______________________________________________________________
> 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
>

David Christ

Re: K3 APF Effectiveness

Just do two clicks at a time and you have 10 Hz steps, no? What am I missing?

David K0LUM

At 8:54 PM -0600 11/20/10, Dave Perry N4QS wrote:
>I agree that the signal doesn't pop out anymore with 4.22, but I think it is
>due to the change to 5 Hz tuning. It is harder to hear the peak in the
>signal with the 5 Hz steps in the Shift tuning. I think we should go back
>to 10 Hz per click. Just my opinion.
>
>Dave, N4QS
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wayne burdick

Re: K3 APF Effectiveness

Administrator

In reply to this post by Dave Perry N4QS

5-Hz steps simply make it easier to tune the APF. This has absolutely no
effect on the filter passband, Q, etc. Going back to 10-Hz steps would just make it harder to center signals when using SHIFT, as was the case with 4.17. Many operators requested the finer step size.

73,
Wayne

----
http://www.elecraft.com

On Nov 20, 2010, at 6:54 PM, "Dave Perry N4QS" <[hidden email]> wrote:

>
> I agree that the signal doesn't pop out anymore with 4.22, but I think it is
> due to the change to 5 Hz tuning. It is harder to hear the peak in the
> signal with the 5 Hz steps in the Shift tuning. I think we should go back
> to 10 Hz per click. Just my opinion.
>
> Dave, N4QS
>
> ----- Original Message -----
> From: "John Seney" <[hidden email]>
> To: "Igor Kosvin" <[hidden email]>
> Cc: "'Elecraft Reflector'" <[hidden email]>
> Sent: Saturday, November 20, 2010 2:16 PM
> Subject: Re: [Elecraft] K3 APF Effectiveness
>
>
>> Hi All:
>>
>> I have the same experience as Igor. There is an APF sweet spot that either
>> moved or
>> disappeared.
>>
>> Would it be helpful if there was a GUI that let us save, load, share, and
>> see all of
>> the various K3 parameter settings that we are adjusting?
>>
>> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>>
>>> Sure, you are right, but you would not deny that using same set of
>>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22
>>> should
>>> give very similar results since the code of APF remains the same. After
>>> playing few days with 4.22 I find myself having to turn off APF to better
>>> receive weak CW stations. I don't have explanation for this. With APF on
>>> I
>>> find it difficult to distinguish dits and dahs of weak signals. With 4.17
>>> it
>>> was much better for me. That should be apples-to apples comparison, I
>>> think.
>>> I don't claim to be expert though, listening is very subjective IMHO.
>>>
>>> Regards,
>>>
>>> Igor, N1YX
>>
>>
>> 73,
>>
>> John Seney
>> ARS WD1V (fn42gw)
>> 603 785-2413
>>
>>
>> ______________________________________________________________
>> 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
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
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k.igor

Re: Final K3 APF Lab Test Results

In reply to this post by wayne burdick

Wayne,

My intuition says that the problem is not in the filter algorithm. Could be
that the APF just not engages in 4.22? Could be that instead of APF it is
still does Dual PB or something? Can you try to listen to the weak CW with 2
rigs - one with 4.17 and one with 4.22? When I engage 4.22 APF I hear high
pitch noise at frequency range close to the CW pitch, which makes hearing CW
signal very hard. The 4.17 (and 4.18) did not have this. I have 400Hz 8-pole
and 250 Hz 8-pole filters, I tried with both - same problem.

73,

Igor, N1YX

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Saturday, November 20, 2010 3:44 PM
To: [hidden email]
Subject: [Elecraft] Final K3 APF Lab Test Results

We just did a *very* accurate sweep of the APF passband from the original
(4.17) and new (4.22) beta releases. Lyle has the data in spreadsheet form
and will send it out on request. It's too big to attach to a reflector
posting.

Bottom line: There is no difference between the two. This is not surprising,
since we did not change the filter algorithm.

Any difference must be attributed to noise and signal conditions, filter
bandwidth settings, or APF tuning vs. actual signal pitch. This is the
nature of APF; it is most effective under specific conditions. Try turning
it on, and if it doesn't help, leave it off.

73,
Wayne
N6KR

----
http://www.elecraft.com

On Nov 20, 2010, at 12:16 PM, John Seney <[hidden email]> wrote:

> Hi All:
>
> I have the same experience as Igor. There is an APF sweet spot that either
moved or
> disappeared.
>
> Would it be helpful if there was a GUI that let us save, load, share, and
see all of
> the various K3 parameter settings that we are adjusting?
>
> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>
>> Sure, you are right, but you would not deny that using same set of
>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22
should
>> give very similar results since the code of APF remains the same. After
>> playing few days with 4.22 I find myself having to turn off APF to better
>> receive weak CW stations. I don't have explanation for this. With APF on
I
>> find it difficult to distinguish dits and dahs of weak signals. With 4.17
it
>> was much better for me. That should be apples-to apples comparison, I
think.

>> I don't claim to be expert though, listening is very subjective IMHO.
>>
>> Regards,
>>
>> Igor, N1YX
>
>
> 73,
>
> John Seney
> ARS WD1V (fn42gw)
> 603 785-2413
>
>
> ______________________________________________________________
> 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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KK7P

Re: Final K3 APF Lab Test Results

The APF engages. I measured it in 4.22. It is no different than in 4.17.

Of course, you must set the feature to operate, or it will indeed be the
old DUAL PB algorithm. CONFIG:DUAL PB must be set to APF and not set
to NOR.

73,

Lyle KK7P
> My intuition says that the problem is not in the filter algorithm. Could be
> that the APF just not engages in 4.22? Could be that instead of APF it is
> still does Dual PB or something?

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N2TK

Re: K3 APF Effectiveness

In reply to this post by wayne burdick

APF worked great this morning. Was hunting for the KH2 on 160m and couldn't
hear him. Turned on the APF and used 3-digit resolution on the VFO (10HZ
steps) and he popped out as I tuned across him. Worked him with two calls.
New one on topband.

I installed 4.17 on #311 and have 4.22 on #1435. So far I can't hear a
difference when using the APF on very weak signals on topband.
73,
N2TK, Tony

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Sunday, November 21, 2010 12:45 AM
To: Dave Perry N4QS
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 APF Effectiveness

5-Hz steps simply make it easier to tune the APF. This has absolutely no
effect on the filter passband, Q, etc. Going back to 10-Hz steps would just
make it harder to center signals when using SHIFT, as was the case with
4.17. Many operators requested the finer step size.

73,
Wayne

----
http://www.elecraft.com

On Nov 20, 2010, at 6:54 PM, "Dave Perry N4QS" <[hidden email]> wrote:

>
> I agree that the signal doesn't pop out anymore with 4.22, but I think it
is
> due to the change to 5 Hz tuning. It is harder to hear the peak in the
> signal with the 5 Hz steps in the Shift tuning. I think we should go back

> to 10 Hz per click. Just my opinion.
>
> Dave, N4QS
>
> ----- Original Message -----
> From: "John Seney" <[hidden email]>
> To: "Igor Kosvin" <[hidden email]>
> Cc: "'Elecraft Reflector'" <[hidden email]>
> Sent: Saturday, November 20, 2010 2:16 PM
> Subject: Re: [Elecraft] K3 APF Effectiveness
>
>
>> Hi All:
>>
>> I have the same experience as Igor. There is an APF sweet spot that

either
>> moved or
>> disappeared.
>>
>> Would it be helpful if there was a GUI that let us save, load, share, and

>> see all of
>> the various K3 parameter settings that we are adjusting?
>>
>> On Nov 17, 2010, at 11:53 PM, Igor Kosvin wrote:
>>
>>> Sure, you are right, but you would not deny that using same set of
>>> parameters (NR/NB, WIDTH, PITCH, RF, etc) the APF circa 4.17 and 4.22
>>> should
>>> give very similar results since the code of APF remains the same. After
>>> playing few days with 4.22 I find myself having to turn off APF to

better
>>> receive weak CW stations. I don't have explanation for this. With APF on

>>> I
>>> find it difficult to distinguish dits and dahs of weak signals. With
4.17

>>> it
>>> was much better for me. That should be apples-to apples comparison, I
>>> think.
>>> I don't claim to be expert though, listening is very subjective IMHO.
>>>
>>> Regards,
>>>
>>> Igor, N1YX
>>
>>
>> 73,
>>
>> John Seney
>> ARS WD1V (fn42gw)
>> 603 785-2413
>>
>>
>> ______________________________________________________________
>> 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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> Post: mailto:[hidden email]
>
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