Topics

CW narrow filter


john ni0k
 

Operating the CW WW CQ contest makes me wish for something narrower than the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz filter but is there something else that people are using?

73,
-John NI0K


ve3ki
 

To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K


Bill Maddock
 

John,

I have the 6 pole 200 hz filter in my K3 , which i used for search and pounce in the contest. I upgraded from the 5 pole 200 hz filter. Didnt really notice much difference. I have the old 200 hz filter for sale if your interested. The 200 hz filter really helped during the contest.
73 de Bill W4RTN


On Mon, Nov 26, 2018 at 9:46 AM, john ni0k
<jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K




Joe Subich, W4TV
 

If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower
than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>).

I would choose to believe the measurements made by Elecraft at:
<https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves>


The Elecraft curves show the -6 dB response points at roughly 480 Hz
for the "400 Hz" filter (KFL3C-400) and 370 Hz for the "250 Hz" filter
(KFL3A-250) both of which are actually made for/imported by INRAD.

The Elecraft application note also includes a comparison of the
KLF3A-250 vs. KFL3C-200 which shows the 200 Hz filter is tighter
than the 250 Hz filter to at least -50 dB (where the bandwidth
of both is approximately 700 Hz).

73,

... Joe, W4TV


On 2018-11-26 11:53 AM, ve3ki wrote:
To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.
If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.
73,
Rich VE3KI
On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:


Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K


ve3ki
 

Thank you, Joe. I wanted to be able to point to the Elecraft plots, but I was unsuccessful when trying to find them on the new web site - thanks for the link.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 02:49 PM, Joe Subich, W4TV wrote:
If you find you really need one, I'd suggest the 200 Hz filter,
because the 250 Hz filter is actually not all that much narrower
than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to
> <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>).


I would choose to believe the measurements made by Elecraft at:
<https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves>


The Elecraft curves show the -6 dB response points at roughly 480 Hz
for the "400 Hz" filter (KFL3C-400) and 370 Hz for the "250 Hz" filter
(KFL3A-250) both of which are actually made for/imported by INRAD.

The Elecraft application note also includes a comparison of the
KLF3A-250 vs. KFL3C-200 which shows the 200 Hz filter is tighter
than the 250 Hz filter to at least -50 dB (where the bandwidth
of both is approximately 700 Hz).

73,

... Joe, W4TV


On 2018-11-26 11:53 AM, ve3ki wrote:
To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI

On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:


Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K


Michael Kopec
 

Hello Rich VE3KI.  To get the filter specs now, according to elecraft webmaster, you must email tech support and they will send them to u de Mike K8NS

On Monday, November 26, 2018, 5:54:46 PM EST, ve3ki <ve3iay@...> wrote:


Thank you, Joe. I wanted to be able to point to the Elecraft plots, but I was unsuccessful when trying to find them on the new web site - thanks for the link.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 02:49 PM, Joe Subich, W4TV wrote:
If you find you really need one, I'd suggest the 200 Hz filter,
because the 250 Hz filter is actually not all that much narrower
than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to
> <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>).


I would choose to believe the measurements made by Elecraft at:
<https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves>


The Elecraft curves show the -6 dB response points at roughly 480 Hz
for the "400 Hz" filter (KFL3C-400) and 370 Hz for the "250 Hz" filter
(KFL3A-250) both of which are actually made for/imported by INRAD.

The Elecraft application note also includes a comparison of the
KLF3A-250 vs. KFL3C-200 which shows the 200 Hz filter is tighter
than the 250 Hz filter to at least -50 dB (where the bandwidth
of both is approximately 700 Hz).

73,

... Joe, W4TV


On 2018-11-26 11:53 AM, ve3ki wrote:
To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI

On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:


Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K


Michael Murphy
 

I have the 250hz filter in mine but have only used it maybe 2 times in the years that I've had my K3.  The 400 served me well last weekend in CQWW.

It really is too narrow for me.

Mike - KI8R

On Mon, Nov 26, 2018 at 10:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K





--
-----------------------------------------------
Michael Murphy - KI8R

mike@...

www.ki8r.com

614-371-8265 (cell)

-----------------------------------------------


Jim English
 

The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.

73,

Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K




Bob McGraw - K4TAX
 

And........very narrow filters, due to group delay, will take a noise pulse or spike and it will go SPLAT across the passband.   Hence the filter makes the spike much wider than the original width of the spike.    For the most part, random or broadband noise is unaffected.    Just opening up the passband to the point where the narrow filter switches out can make noticeable improvement in receiving conditions.   I prefer to use a narrow DSP passband and manually select a wider roofing filter.   My K3S makes for a super sweet receiver in this regard.

73

Bob, K4TAX



On 11/26/2018 6:23 PM, Jim English wrote:
The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.

73,

Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K





Rob Sherwood
 

I had trouble navigating their website just now, as it appears to be in transition.

The 6-pole 200-Hz roofing filter was designed to have lower passive intermodulation.

I have not tested one since one of their crystal suppliers, ICM, went out of business.

There is more to selecting a roofing filter than just the bandwidth.

Rob

NC0B

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of ve3ki
Sent: Monday, November 26, 2018 3:55 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] CW narrow filter

 

Thank you, Joe. I wanted to be able to point to the Elecraft plots, but I was unsuccessful when trying to find them on the new web site - thanks for the link.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 02:49 PM, Joe Subich, W4TV wrote:

If you find you really need one, I'd suggest the 200 Hz filter,
because the 250 Hz filter is actually not all that much narrower
than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to

> <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>).


I would choose to believe the measurements made by Elecraft at:
<https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves>


The Elecraft curves show the -6 dB response points at roughly 480 Hz
for the "400 Hz" filter (KFL3C-400) and 370 Hz for the "250 Hz" filter
(KFL3A-250) both of which are actually made for/imported by INRAD.

The Elecraft application note also includes a comparison of the
KLF3A-250 vs. KFL3C-200 which shows the 200 Hz filter is tighter
than the 250 Hz filter to at least -50 dB (where the bandwidth
of both is approximately 700 Hz).

73,

... Joe, W4TV


On 2018-11-26 11:53 AM, ve3ki wrote:

To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI

On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:


Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K

 


If this email is spam, report it to www.OnlyMyEmail.com


john ni0k
 

Rob and all:

Thanks for the replies from everyone. There is a link below to the Elecraft filter data, but the graphs on the Elecraft site are very blurry and hard to read. Before I sent the link I sent a request to Elecraft for filter specs. Yes, they have a new website and it is completely different to navigate than the old one.

I'm leaning towards the 200 Hz filter based on the info so far.

-John NI0K

Rob Sherwood wrote:

I had trouble navigating their website just now, as it appears to be in transition.

The 6-pole 200-Hz roofing filter was designed to have lower passive intermodulation.

I have not tested one since one of their crystal suppliers, ICM, went out of business.

There is more to selecting a roofing filter than just the bandwidth.

Rob

NC0B

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of ve3ki
Sent: Monday, November 26, 2018 3:55 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] CW narrow filter

 

Thank you, Joe. I wanted to be able to point to the Elecraft plots, but I was unsuccessful when trying to find them on the new web site - thanks for the link.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 02:49 PM, Joe Subich, W4TV wrote:

If you find you really need one, I'd suggest the 200 Hz filter,
because the 250 Hz filter is actually not all that much narrower
than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to

> <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>).


I would choose to believe the measurements made by Elecraft at:
<https://elecraft.com/pages/k3s-8-215-mhz-first-if-crystal-filter-response-curves>


The Elecraft curves show the -6 dB response points at roughly 480 Hz
for the "400 Hz" filter (KFL3C-400) and 370 Hz for the "250 Hz" filter
(KFL3A-250) both of which are actually made for/imported by INRAD.

The Elecraft application note also includes a comparison of the
KLF3A-250 vs. KFL3C-200 which shows the 200 Hz filter is tighter
than the 250 Hz filter to at least -50 dB (where the bandwidth
of both is approximately 700 Hz).

73,

... Joe, W4TV


On 2018-11-26 11:53 AM, ve3ki wrote:

To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI

On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:


Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K

 


If this email is spam, report it to www.OnlyMyEmail.com



David Box
 

Bob

How have you setup the filter selection on your K3?  When I use the XFIL button to change roofing filter the DSP bandwidth also increases.  Looking through the manual I don't see how you can set a roofing filter to stay fixed while changing to narrow DSP so know I am missing something, would like to minimize ringing by using as wide a roofing filter as I can.

de Dave K5MWR

On 11/26/2018 6:53 PM, Bob McGraw - K4TAX wrote:

And........very narrow filters, due to group delay, will take a noise pulse or spike and it will go SPLAT across the passband.   Hence the filter makes the spike much wider than the original width of the spike.    For the most part, random or broadband noise is unaffected.    Just opening up the passband to the point where the narrow filter switches out can make noticeable improvement in receiving conditions.   I prefer to use a narrow DSP passband and manually select a wider roofing filter.   My K3S makes for a super sweet receiver in this regard.

73

Bob, K4TAX



On 11/26/2018 6:23 PM, Jim English wrote:
The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.

73,

Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K





ve3ki
 

You select the DSP bandwidth with the WIDTH control. This also automatically selects the roofing filter, based on the filter bandwidths you have entered into the filter configuration using either the K3 Utility or the CONFIG:FLx BW settings. If you have a roofing filter set to switch in at a particular width, it will be selected automatically at that DSP width and below. The FLx BW settings do not have to match the designation on the filter; you can set each roofing filter to be switched in at the bandwidth of your choice.

If you want to use narrow DSP settings using a wider roofing filter than the one that would normally switch in based on its designation, you need to go into the filter configuration and change the bandwidth at which the narrower roofing filter is selected. For example, if you have a 400 Hz roofing filter but you don't want it ti be selected at DSP bandwidths above 300 Hz, then in the CONFIG:FLx BW menu for the 400 Hz roofing filter, select 0.30 instead of 0.40. You can go the other way as well: if you have a 250 Hz roofing filter but you want it to be selected at 350 Hz and below, set CONFIG:FLx BW to 0.35 instead of 0.25.

73,
Rich VE3KI


On Tue, Nov 27, 2018 at 09:04 AM, David Box wrote:

Bob

How have you setup the filter selection on your K3?  When I use the XFIL button to change roofing filter the DSP bandwidth also increases.  Looking through the manual I don't see how you can set a roofing filter to stay fixed while changing to narrow DSP so know I am missing something, would like to minimize ringing by using as wide a roofing filter as I can.

de Dave K5MWR

On 11/26/2018 6:53 PM, Bob McGraw - K4TAX wrote:

And........very narrow filters, due to group delay, will take a noise pulse or spike and it will go SPLAT across the passband.   Hence the filter makes the spike much wider than the original width of the spike.    For the most part, random or broadband noise is unaffected.    Just opening up the passband to the point where the narrow filter switches out can make noticeable improvement in receiving conditions.   I prefer to use a narrow DSP passband and manually select a wider roofing filter.   My K3S makes for a super sweet receiver in this regard.

73

Bob, K4TAX

 


On 11/26/2018 6:23 PM, Jim English wrote:
The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.
 
73,
 
Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K




David Box
 

Rich

Appreciate this info, seems I need to be reminded about some of the features every now and then

de Dave K5MWR

On 11/27/2018 9:08 AM, ve3ki wrote:
You select the DSP bandwidth with the WIDTH control. This also automatically selects the roofing filter, based on the filter bandwidths you have entered into the filter configuration using either the K3 Utility or the CONFIG:FLx BW settings. If you have a roofing filter set to switch in at a particular width, it will be selected automatically at that DSP width and below. The FLx BW settings do not have to match the designation on the filter; you can set each roofing filter to be switched in at the bandwidth of your choice.

If you want to use narrow DSP settings using a wider roofing filter than the one that would normally switch in based on its designation, you need to go into the filter configuration and change the bandwidth at which the narrower roofing filter is selected. For example, if you have a 400 Hz roofing filter but you don't want it ti be selected at DSP bandwidths above 300 Hz, then in the CONFIG:FLx BW menu for the 400 Hz roofing filter, select 0.30 instead of 0.40. You can go the other way as well: if you have a 250 Hz roofing filter but you want it to be selected at 350 Hz and below, set CONFIG:FLx BW to 0.35 instead of 0.25.

73,
Rich VE3KI


On Tue, Nov 27, 2018 at 09:04 AM, David Box wrote:

Bob

How have you setup the filter selection on your K3?  When I use the XFIL button to change roofing filter the DSP bandwidth also increases.  Looking through the manual I don't see how you can set a roofing filter to stay fixed while changing to narrow DSP so know I am missing something, would like to minimize ringing by using as wide a roofing filter as I can.

de Dave K5MWR

On 11/26/2018 6:53 PM, Bob McGraw - K4TAX wrote:

And........very narrow filters, due to group delay, will take a noise pulse or spike and it will go SPLAT across the passband.   Hence the filter makes the spike much wider than the original width of the spike.    For the most part, random or broadband noise is unaffected.    Just opening up the passband to the point where the narrow filter switches out can make noticeable improvement in receiving conditions.   I prefer to use a narrow DSP passband and manually select a wider roofing filter.   My K3S makes for a super sweet receiver in this regard.

73

Bob, K4TAX

 


On 11/26/2018 6:23 PM, Jim English wrote:
The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.
 
73,
 
Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K




Bob McGraw - K4TAX
 

David et al;

I use the K3 Utility to change the filter configuration.  Easy as I have the utility on the desktop.  The 200 Hz filter resides as FL5 and the 500 Hz as FL4.  Normally both are enables for CW mode.  However, when QRN is an issue, just uncheck the 200 Hz filter in the CW mode only.  That way the DSP can go down to 50 Hz if/as needed with a 500 Hz roofing filter.

73

Bob, K4ATX


On 11/27/2018 8:04 AM, David Box wrote:

Bob

How have you setup the filter selection on your K3?  When I use the XFIL button to change roofing filter the DSP bandwidth also increases.  Looking through the manual I don't see how you can set a roofing filter to stay fixed while changing to narrow DSP so know I am missing something, would like to minimize ringing by using as wide a roofing filter as I can.

de Dave K5MWR

On 11/26/2018 6:53 PM, Bob McGraw - K4TAX wrote:

And........very narrow filters, due to group delay, will take a noise pulse or spike and it will go SPLAT across the passband.   Hence the filter makes the spike much wider than the original width of the spike.    For the most part, random or broadband noise is unaffected.    Just opening up the passband to the point where the narrow filter switches out can make noticeable improvement in receiving conditions.   I prefer to use a narrow DSP passband and manually select a wider roofing filter.   My K3S makes for a super sweet receiver in this regard.

73

Bob, K4TAX



On 11/26/2018 6:23 PM, Jim English wrote:
The problem with very narrow CW filters is that they generally have very steep skirts which means the generally they have to be designed without regard to the group delay variation throughout the passband.  Most are based on Chebychev coefficients or some modification thereof.  As such, there is a significant amount of energy stored at the passband edges which cause ringing to be heard in the demodulated signal.  Receivers based on DSP in the signal processing stages generally don't suffer from this as the filters are a linear phase type that are constant group delay which do not have the ringing issue.  Where the AGC pickoff point is located may affect the performance but I must say that I love my (by now) old iron flex 5k transceiver.  Last month when everybody was trying to work the Ducie island station I had an issue where there was some lid operator QRMing.  However, he was close in frequency but not close enough.  I just cranked the bandwidth of the flex DSP filter down to about 50 Hz and that turkey was GONE.  Then I worked him of course.  I love my 5k so much that I bought a spare since they are nor being built anymore and are cheap now.  They do require a windows computer that can get out of its own way however and they are definitely not for the computer squeamish but getting past that I think they are the bomb!  The newer ones are probably better but being a HAM which stands for "haven't any money" I am too cheap to buy one.  At least now.

73,

Jim WO7V

On Mon, Nov 26, 2018 at 7:46 AM john ni0k <jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K






Dean LaClair
 

I would be interested in that 200 hz filter, if it were reasonable.
I'm dying to try a narrow cw filter
Let me know, tnx
Dean dot K2WW @ Gmail off list
73
Dean K2WW


On Mon, Nov 26, 2018, 11:59 Bill Maddock via Groups.Io <n4zi96=yahoo.com@groups.io> wrote:
John,

I have the 6 pole 200 hz filter in my K3 , which i used for search and pounce in the contest. I upgraded from the 5 pole 200 hz filter. Didnt really notice much difference. I have the old 200 hz filter for sale if your interested. The 200 hz filter really helped during the contest.
73 de Bill W4RTN


On Mon, Nov 26, 2018 at 9:46 AM, john ni0k
<jasimmons@...> wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K




Vic Owen
 

Not to hijack the thread, but this is kinda related...

I've been considering getting the upgraded synthesizer for my K3...for anyone that has done this, did you find the selectivity improvement for close-in interference worthwhile?

Thanks
--
Vic Owen
KB7GL


southdaleus
 

I was one of the first to upgrade this.  Yes I would highly recommend this upgrade.  The only time I would say keep your old board is if you are careful with your money and if you are a casual operator where you talk to friends in a casual setting.  In those settings you may not observe much difference.  

Dale, K9VUJ


On 30, Nov 2018, at 10:18, kb7gl@... wrote:

Not to hijack the thread, but this is kinda related...

I've been considering getting the upgraded synthesizer for my K3...for anyone that has done this, did you find the selectivity improvement for close-in interference worthwhile?

Thanks
--
Vic Owen
KB7GL


john ni0k
 

Dale,

I'm sure we are all interested to hear a description of the difference you noted.

-John NI0K

dalej via Groups.Io wrote:

I was one of the first to upgrade this.  Yes I would highly recommend this upgrade.  The only time I would say keep your old board is if you are careful with your money and if you are a casual operator where you talk to friends in a casual setting.  In those settings you may not observe much difference.  

Dale, K9VUJ


On 30, Nov 2018, at 10:18, kb7gl@... wrote:

Not to hijack the thread, but this is kinda related...

I've been considering getting the upgraded synthesizer for my K3...for anyone that has done this, did you find the selectivity improvement for close-in interference worthwhile?

Thanks
--
Vic Owen
KB7GL



 

* On 2018 30 Nov 21:10 -0600, john ni0k wrote:
Dale,

I'm sure we are all interested to hear a description of the difference you
noted.
In my case with the upgrade to the K3SYNA the K3 became the first radio
I owned that I could listen to CW for longer than an hour or so at a
crack.

Close-in selectivity likely improved, though it wasn't something I was
able to do a thorough A/B test on. With the 200 Hz filter installed, it
already was quite good. I do know that on phone I can cut QRM
completely away that is 2 kHz off my displayed frequency with Hi-Cut and
the 2.1 kHz filter installed.

In my opinion, the new synth board made an already fine radio even
better.

73, Nate

--

"The optimist proclaims that we live in the best of all
possible worlds. The pessimist fears this is true."

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