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Variable bandwidth crystal filter

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joachim.groeger

Variable bandwidth crystal filter

I seem to remember talk some time ago about a variable bandwidth crystal
filter becoming available for the K3 at some stage. Anyone know the
status of its development?

J R Groeger
DK3NG, G4XXW, EL0AA/MM

K1, K2, K3
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Chuck Guenther

Re: Variable bandwidth crystal filter

J.R. Groeger wrote:

"I seem to remember talk some time ago about a variable bandwidth
crystal filter becoming available for the K3 at some stage. Anyone know
the status of its development?"

With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
talked about), I certainly wouldn't see much need for a variable BW
roofing filter.

73,
Chuck NI0C
K2, K3
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Joe Subich, W4TV-4

Re: Variable bandwidth crystal filter

> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
> talked about), I certainly wouldn't see much need for a variable BW
> roofing filter.

10 Hz steps for DSP does not eliminate the need for a variable BW
roofing filter. It would certainly be nice to have something that
went from "narrow SSB" to "wide CW" ... to fill the hole between
2.7/2.8 and 500 HZ.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Chuck Guenther
> Sent: Wednesday, August 05, 2009 7:51 PM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] Variable bandwidth crystal filter
>
>
> J.R. Groeger wrote:
>
> "I seem to remember talk some time ago about a variable bandwidth
> crystal filter becoming available for the K3 at some stage.
> Anyone know
> the status of its development?"
>
> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
> talked about), I certainly wouldn't see much need for a variable BW
> roofing filter.
>
> 73,
> Chuck NI0C
> K2, K3

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joachim.groeger

Re: Variable bandwidth crystal filter

Joe,

Walter Cronkite would have likely endorsed your view by saying:
"And that's the way it is"

Tks es 73

JRG

Joe Subich, W4TV schrieb:

>
>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>> talked about), I certainly wouldn't see much need for a variable BW
>> roofing filter.
>>
>
> 10 Hz steps for DSP does not eliminate the need for a variable BW
> roofing filter. It would certainly be nice to have something that
> went from "narrow SSB" to "wide CW" ... to fill the hole between
> 2.7/2.8 and 500 HZ.
>
> 73,
>
> ... Joe, W4TV
>
>
>
>
>
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]] On Behalf Of Chuck Guenther
>> Sent: Wednesday, August 05, 2009 7:51 PM
>> To: [hidden email]
>> Cc: [hidden email]
>> Subject: Re: [Elecraft] Variable bandwidth crystal filter
>>
>>
>> J.R. Groeger wrote:
>>
>> "I seem to remember talk some time ago about a variable bandwidth
>> crystal filter becoming available for the K3 at some stage.
>> Anyone know
>> the status of its development?"
>>
>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>> talked about), I certainly wouldn't see much need for a variable BW
>> roofing filter.
>>
>> 73,
>> Chuck NI0C
>> K2, K3
>>
>
>
>
>

HowardZ

Re: Variable bandwidth crystal filter

In reply to this post by Chuck Guenther

It appears that the only way the K3 achieves its high test scores in dynamic range is when the offending signal is outside the roofing filter's bandwidth. Only the roofing filter yields this high performance.

For example, if your roofing filter is 2.8Khz, but you hear an unwanted nearby signal, and you use DSP to narrow it to 2.0khz, the reduction of the unwanted signal will not be as great as if you switched to your 2.0khz roofing filter (which you had not purchased yet). This is because the offending signal is within the roofing filter's 2.8khz bandwidth.

Thus following this example, the Flex 5000 has the same dynamic range regardless of the DSP filter bandwith khz, and will outperform the K3 when the offending signal is within the K3's roofing filter bandwidth. The Flex's DSP filter yields dynamic range of 96db. So with the Flex, you'll have 96db of dynamic range regardless of the DSP bandwidth selected. But with the K3, such high dynamic range is only achieved when the offending signal is being blocked by a roofing filter.

(When the offending signal is 20khz, 50khz, etc away - the K3's dynamic range will be superior to the Flex, since the Flex is always 96db regardless of how far away the offending signal is.)

Loading up the radio (and second receiver) with roofing filters makes the expensive K3 radio even more expensive.

Thus the interest in the "variable bandwidth crystal" roofing filter as a major money saver - if it ever comes to fuition.

Howard

Chuck Guenther wrote

J.R. Groeger wrote:

"I seem to remember talk some time ago about a variable bandwidth
crystal filter becoming available for the K3 at some stage. Anyone know
the status of its development?"

With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
talked about), I certainly wouldn't see much need for a variable BW
roofing filter.

73,
Chuck NI0C
K2, K3
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Ed K1EP

Re: Variable bandwidth crystal filter

In reply to this post by Chuck Guenther

At 8/5/2009 07:51 PM, Chuck Guenther wrote:

> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>talked about), I certainly wouldn't see much need for a variable BW
>roofing filter.

Can you explain that relationship?

>73,
>Chuck NI0C
>K2, K3

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AC7AC

Re: Variable bandwidth crystal filter

In reply to this post by HowardZ

CONTENTS DELETED

The author has deleted this message.

Steve Ellington

Re: Variable bandwidth crystal filter

In reply to this post by HowardZ

Howardz:
There's little one catch with the Flex test results. There's a control on
the PowerSDR screen called AGC-T which stands for Automatic Gain Control
Threshold. When signals are strong, you must manually adjust that control
much like you would adjust an RF Gain control so the receiver doesn't
overload. When they run all those test, they fiddle with that AGC-T for best
performance with any given signal. I've used the Flex 5k several times and
it always seems to crude to be forced to adjust AGC-T to compensate for
bands, band conditions and signal levels. If Flex had roofing filters then I
doubt that this manual adjustment would be necessary because the A/D
converter would be protected. So when those dynamic ranges test are run, you
can bet that someone tweaks that AGC-T control, otherwise the results would
be horrible.

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "HowardZ" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, August 06, 2009 5:47 PM
Subject: Re: [Elecraft] Variable bandwidth crystal filter

>
> It appears that the only way the K3 achieves its high test scores in
> dynamic
> range is when the noise is outside the roofing filter's bandwidth. Only
> the
> roofing filter yields this high performance.
>
> For example, if your roofing filter is 2.8Khz, but you hear an unwanted
> nearby signal, and you use DSP to narrow it to 2.0khz, the reduction of
> the
> unwanted signal will not be as great as if you switched to your 2.0khz
> roofing filter (which you had not purchased yet). This is because the
> offending signal is within the roofing filter's 2.8khz bandwidth.
>
> Thus following this example, the Flex 5000 has the same dynamic range
> regardless of the DSP filter bandwith khz, and will outperform the K3 when
> the offending signal is within its DSP bandwidth. So with the Flex,
> you'll
> have 96db of dynamic range regardless of the DSP bandwidth selected. But
> with the K3, such high dynamic range is only achieved when the offending
> signal is being blocked by a roofing filter.
>
> (When the offending signal is 20khz, 50khz, etc away - the K3's dynamic
> range will be superior to the Flex, since the Flex is always 96db
> regardless
> of how far away the offending signal is.)
>
> Loading up the radio (and second receiver) with roofing filters makes the
> expensive K3 radio even more expensive.
>
> Thus the interest in the "variable bandwidth crystal" roofing filter as a
> major money saver - if it ever comes to fuition.
>
> Howard
>
>
>
> Chuck Guenther wrote:
>>
>> J.R. Groeger wrote:
>>
>> "I seem to remember talk some time ago about a variable bandwidth
>> crystal filter becoming available for the K3 at some stage. Anyone know
>> the status of its development?"
>>
>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>> talked about), I certainly wouldn't see much need for a variable BW
>> roofing filter.
>>
>> 73,
>> Chuck NI0C
>> K2, 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
>>
>>
>
> --
> View this message in context:
> http://n2.nabble.com/Variable-bandwidth-crystal-filter-tp3394075p3400928.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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Chuck Guenther

Re: Variable bandwidth crystal filter

In reply to this post by Ed K1EP

I simply meant that if folks were looking for a more or less
continuously variable selectivity in the K3, then the 10 Hz increment
DSP filters would provide that, for all practical purposes.
73,
Chuck NI0C

Ed K1EP wrote:

> At 8/5/2009 07:51 PM, Chuck Guenther wrote:
>
>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>> talked about), I certainly wouldn't see much need for a variable BW
>> roofing filter.
>
> Can you explain that relationship?
>
>
>> 73,
>> Chuck NI0C
>> K2, K3
>
>

Don Wilhelm-4

Re: Variable bandwidth crystal filter

Chuck,

True, true *BUT* the roofing filter can suppress signals before they get
to the hardware AGC. If one is happy with only the DSP filtering alone,
then do not purchase any roofing filters at all, just go with the stock
2.7 kHz roofing filter. Different strokes for different folks, some
need the additional filtering, others do not - and others will purchase
a full set of filters just to have them available - the choice depends
on your operating habits and expectations as well as your ham radio
budget. The casual operators will have great success with only the 2.7
kHz filter, but a contester will want a full complement of roofing
filters to fight those 'tough times'.

73,
Don W3FPR

Chuck Guenther wrote:

> I simply meant that if folks were looking for a more or less
> continuously variable selectivity in the K3, then the 10 Hz increment
> DSP filters would provide that, for all practical purposes.
> 73,
> Chuck NI0C
>
>
> Ed K1EP wrote:
>
>> At 8/5/2009 07:51 PM, Chuck Guenther wrote:
>>
>>
>>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>>> talked about), I certainly wouldn't see much need for a variable BW
>>> roofing filter.
>>>
>> Can you explain that relationship?
>>
>>
>>
>>> 73,
>>> Chuck NI0C
>>> K2, K3
>>>
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.392 / Virus Database: 270.13.45/2285 - Release Date: 08/06/09 05:57:00
>
>

Chuck Guenther

Re: Variable bandwidth crystal filter

Good review of the flexibility of the K3, Don!

My K3 filter slots are all filled: 2.7, 2.1, 400, 250, and 200. Using
the K3 Utility, I can set the 250 Hz filter to kick in at a DSP
bandwidth of 300 Hz, 250 Hz, or 200 Hz. But with the upcoming firmware
upgrades, the flexibility will be enhanced, so I can make the 250 Hz
filter kick in at, say 240 Hz, if I want to. At least, that's my
understanding of what's coming up. This is a significant enhancement,
especially at narrow CW bandwidths-- and in my opinion-- much more
desirable than a new variable bandwidth roofing filter.
73,
Chuck NI0C
K2-10 s/n 5853 K3-100 s/n 1061

Don Wilhelm wrote:

> Chuck,
>
> True, true *BUT* the roofing filter can suppress signals before they
> get to the hardware AGC. If one is happy with only the DSP filtering
> alone, then do not purchase any roofing filters at all, just go with
> the stock 2.7 kHz roofing filter. Different strokes for different
> folks, some need the additional filtering, others do not - and others
> will purchase a full set of filters just to have them available - the
> choice depends on your operating habits and expectations as well as
> your ham radio budget. The casual operators will have great success
> with only the 2.7 kHz filter, but a contester will want a full
> complement of roofing filters to fight those 'tough times'.
>
> 73,
> Don W3FPR
>
> Chuck Guenther wrote:
>> I simply meant that if folks were looking for a more or less
>> continuously variable selectivity in the K3, then the 10 Hz increment
>> DSP filters would provide that, for all practical purposes.
>> 73,
>> Chuck NI0C
>>
>>
>> Ed K1EP wrote:
>>
>>> At 8/5/2009 07:51 PM, Chuck Guenther wrote:
>>>
>>>
>>>> With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being
>>>> talked about), I certainly wouldn't see much need for a variable BW
>>>> roofing filter.
>>>>
>>> Can you explain that relationship?
>>>
>>>
>>>
>>>> 73,
>>>> Chuck NI0C
>>>> K2, 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
>> ------------------------------------------------------------------------
>>
>>
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com Version: 8.5.392 / Virus Database:
>> 270.13.45/2285 - Release Date: 08/06/09 05:57:00
>>
>>
>

Joe Subich, W4TV-4

Re: Variable bandwidth crystal filter

> But with the upcoming firmware upgrades, the flexibility will be
> enhanced, so I can make the 250 Hz filter kick in at, say 240 Hz,
> if I want to. At least, that's my understanding of what's coming
> up.

The beta firmware does not allow setting width in 10 Hz steps. Only
the center frequency (FC) is adjustable in 10 Hz steps.

> This is a significant enhancement, especially at narrow CW bandwidths
> -- and in my opinion-- much more desirable than a new variable bandwidth
> roofing filter

You will not see a big difference with a "DSP tracking" filter
on CW if you already have fixed 400, 250 and 200 Hz filters.

Where the capability becomes noticeable is on SSB due to the
wide steps between 2.8 KHz and 1.5 KHz and in digital modes
with the step between 2.8 KHz and 400 Hz. It is not possible (there
are not enough filter 'slots') to install roofing filters even every
500 Hz even though the filters are available - e.g. 2.8 KHz, 2.1 KHz,
1.8 KHz, 1.5 KHz, 1000 Hz, 500 Hz, and 250 Hz - particularly if you
want to operate FM and AM or ESSB where it is currently necessary
to tie up slots with BOTH the FM (13 KHz) and AM (6 KHz) filters.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Chuck Guenther
> Sent: Friday, August 07, 2009 9:00 AM
> To: [hidden email]
> Cc: [hidden email]; [hidden email]
> Subject: Re: [Elecraft] Variable bandwidth crystal filter
>
>
> Good review of the flexibility of the K3, Don!
>
> My K3 filter slots are all filled: 2.7, 2.1, 400, 250, and
> 200. Using
> the K3 Utility, I can set the 250 Hz filter to kick in at a DSP
> bandwidth of 300 Hz, 250 Hz, or 200 Hz. But with the
> upcoming firmware
> upgrades, the flexibility will be enhanced, so I can make the 250 Hz
> filter kick in at, say 240 Hz, if I want to. At least, that's my
> understanding of what's coming up. This is a significant
> enhancement,
> especially at narrow CW bandwidths-- and in my opinion-- much more
> desirable than a new variable bandwidth roofing filter.
> 73,
> Chuck NI0C
> K2-10 s/n 5853 K3-100 s/n 1061
>
>
>
> Don Wilhelm wrote:
> > Chuck,
> >
> > True, true *BUT* the roofing filter can suppress signals before they
> > get to the hardware AGC. If one is happy with only the DSP
> filtering
> > alone, then do not purchase any roofing filters at all,
> just go with
> > the stock 2.7 kHz roofing filter. Different strokes for different
> > folks, some need the additional filtering, others do not -
> and others
> > will purchase a full set of filters just to have them
> available - the
> > choice depends on your operating habits and expectations as well as
> > your ham radio budget. The casual operators will have
> great success
> > with only the 2.7 kHz filter, but a contester will want a full
> > complement of roofing filters to fight those 'tough times'.
> >
> > 73,
> > Don W3FPR
> >
> > Chuck Guenther wrote:
> >> I simply meant that if folks were looking for a more or less
> >> continuously variable selectivity in the K3, then the 10
> Hz increment
> >> DSP filters would provide that, for all practical purposes.
> >> 73,
> >> Chuck NI0C
> >>
> >>
> >> Ed K1EP wrote:
> >>
> >>> At 8/5/2009 07:51 PM, Chuck Guenther wrote:
> >>>
> >>>
> >>>> With the upoming 10 Hz resolution DSP upgrade (Firmware
> 3.23 being
> >>>> talked about), I certainly wouldn't see much need for a
> variable BW
> >>>> roofing filter.
> >>>>
> >>> Can you explain that relationship?
> >>>
> >>>
> >>>
> >>>> 73,
> >>>> Chuck NI0C
> >>>> K2, 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
> >>
> ---------------------------------------------------------------------
> >> ---
> >>
> >>
> >> No virus found in this incoming message.
> >> Checked by AVG - www.avg.com Version: 8.5.392 / Virus Database:
> >> 270.13.45/2285 - Release Date: 08/06/09 05:57:00
> >>
> >>
> >
>
> ______________________________________________________________
> 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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> Please help support this email list: http://www.qsl.net/donate.html

Chuck Guenther

Re: Variable bandwidth crystal filter

Joe Subich, W4TV wrote:
>
> The beta firmware does not allow setting width in 10 Hz steps. Only
> the center frequency (FC) is adjustable in 10 Hz steps.
>
>

Joe, thanks for this information. Now I get it (I think).

Just to review, about a year ago, we got 10 Hz CW pitch increments with
firmware version 2.33. This allowed the pitch to be varied in 10 Hz
steps, keeping the signal centered in the passbands of both the roofing
filter and the DSP filter. However, the passband "SHIFT" control still
has the 50 Hz increments. The new firmware will provide us with 10 Hz
passband tuning, thus making the SHIFT control much more useful when
employing very narrow CW filters.

Please correct me if I'm wrong.

73,
Chuck NI0C

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Julian, G4ILO

Re: Variable bandwidth crystal filter

In reply to this post by Joe Subich, W4TV-4

Joe Subich, W4TV-4 wrote

Where the capability becomes noticeable is on SSB due to the
wide steps between 2.8 KHz and 1.5 KHz and in digital modes
with the step between 2.8 KHz and 400 Hz.

In digital modes it shouldn't be an issue because you don't, in theory, need narrow filtering. In theory you can run with the AGC off because you don't have to listen to the signals and the digimode software ignores all but the bit of the passband you're interested in.

In practise you can't, because the audio side doesn't seem to have the same dynamic range as the RF side of the K3. If a strong PSK31 signal comes on the air I see "ghost" images of it on the waterfall, often quite strong ones. If I back off the RF gain they disappear, but often I have to back it off far enough that I also lose the weakest signals.

Yes, I have done the mod to the KIO board. And I don't think it's the sound card, because I installed an SB Live 24 for radio use and the ghosts are still present.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Brett Howard

Re: Variable bandwidth crystal filter

Have you done the mod where you install the bigger L in the power leg to the
AF amp?

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Julian, G4ILO
Sent: Friday, August 07, 2009 8:17 AM
To: [hidden email]
Subject: Re: [Elecraft] Variable bandwidth crystal filter

Joe Subich, W4TV-4 wrote:
>
>
> Where the capability becomes noticeable is on SSB due to the
> wide steps between 2.8 KHz and 1.5 KHz and in digital modes
> with the step between 2.8 KHz and 400 Hz.
>
In digital modes it shouldn't be an issue because you don't, in theory, need
narrow filtering. In theory you can run with the AGC off because you don't
have to listen to the signals and the digimode software ignores all but the
bit of the passband you're interested in.

In practise you can't, because the audio side doesn't seem to have the same
dynamic range as the RF side of the K3. If a strong PSK31 signal comes on
the air I see "ghost" images of it on the waterfall, often quite strong
ones. If I back off the RF gain they disappear, but often I have to back it
off far enough that I also lose the weakest signals.

Yes, I have done the mod to the KIO board. And I don't think it's the sound
card, because I installed an SB Live 24 for radio use and the ghosts are
still present.

-----
Julian, G4ILO. K2 #392 K3 #222.
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

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l
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