Let's Try This Again -- was "[K3] ... A 750 Hz, 8-Pole ... Filter?"

[Gary Hvizdak]

Referring to http://mailman.qth.net/pipermail/elecraft/2010-June/131426.html
recently I posted several reasons why K3 owners might be interested in a 750
Hz 8-pole INRAD roofing filter.  The response to that post was immediate and
enthusiastic, but it wasn't sufficient for us to commission INRAD to begin
production.

Perhaps the reason for the limited response was that folks were already
firmly focused on Field Day?  Whatever the reason ... once again ... if you
are interested in a 750 Hz 8-pole INRAD roofing filter for your K3, please
email me (off-Reflector) at [hidden email] to express your interest.

If instead you think that there might be a greater demand for some other
bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
let me know that width and include your reasoning for desiring that other
width.

73 and TNX for the B/W,
Gary  KI4GGX
K3 #2724

P.S.  Keep in mind that if Wayne and company ever do get around to offering
a few choices of their long-promised dual-width (formerly variable-width)
filters, that those filters will almost certainly be of the same 5-pole
design as the three existing Elecraft roofing filters.

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[Guy, K2AV]

You might consider that it's not a contesting bandwidth, more a
pleasant casual operating bandwidth. And in casual conditions my SSB
1.8 roofing filter with DSP set to 750 does as well, which I do.  It's
only in contests that I get a 35 over 9 signal up 350 Hz that I need
to keep out of the hardware AGC.

73, Guy.

On Tue, Jul 13, 2010 at 10:36 PM, Gary Hvizdak <[hidden email]> wrote:

> Referring to http://mailman.qth.net/pipermail/elecraft/2010-June/131426.html
> recently I posted several reasons why K3 owners might be interested in a 750
> Hz 8-pole INRAD roofing filter.  The response to that post was immediate and
> enthusiastic, but it wasn't sufficient for us to commission INRAD to begin
> production.
>
> Perhaps the reason for the limited response was that folks were already
> firmly focused on Field Day?  Whatever the reason ... once again ... if you
> are interested in a 750 Hz 8-pole INRAD roofing filter for your K3, please
> email me (off-Reflector) at [hidden email] to express your interest.
>
> If instead you think that there might be a greater demand for some other
> bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
> let me know that width and include your reasoning for desiring that other
> width.
>
> 73 and TNX for the B/W,
> Gary  KI4GGX
> K3 #2724
>
> P.S.  Keep in mind that if Wayne and company ever do get around to offering
> a few choices of their long-promised dual-width (formerly variable-width)
> filters, that those filters will almost certainly be of the same 5-pole
> design as the three existing Elecraft roofing filters.
>
> ______________________________________________________________
> 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
>

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[Jim Brown-10]

On Wed, 14 Jul 2010 09:06:04 -0400, Guy Olinger K2AV wrote:

>You might consider that it's not a contesting bandwidth, more a
>pleasant casual operating bandwidth. And in casual conditions my SSB
>1.8 roofing filter with DSP set to 750 does as well, which I do.  It's
>only in contests that I get a 35 over 9 signal up 350 Hz that I need
>to keep out of the hardware AGC.

Guy is right. You're trying to solve a problem that doesn't exist, at least
not for most of us.

73, Jim K9YC


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[Gary Hvizdak]

Wed Jul 14 09:06:04 EDT 2010  Guy Olinger (K2AV) wrote ...

... it's not a contesting bandwidth, more a pleasant casual operating
bandwidth ... my SSB 1.8 roofing filter with DSP set to 750 does as well ...

Wed Jul 14 09:36:33 EDT 2010 Jim Brown (K9YC) wrote ...

You're trying to solve a problem that doesn't exist, at least not for most
of us.

--- - - - ---

Guy,

    Not everyone has a 1.8 kHz filter and not everyone operates CW contests.
And yes the whole idea for 750 Hz was that it offers a "pleasant casual
operating" width, and for some operators might be preferred versus INRAD's
existing 500 Hz filter (which is too narrow) and their 1 kHz filter (which
is too wide).


Jim,

    The fact that the problem "doesn't exist" "for most of us" doesn't
negate the fact that there are folks who feel differently.  Some simply
think it's a good idea, while others are eager to purchase such a filter
today if were it available!


73,
Gary  KI4GGX
K3 #2724

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[John King-10]

As another data point in this discussion...

I operate 100% CW with my K3, which is equipped with 200, 500, 1000, and
2.7KHz filters.

During FD 2010 I made 400+ CW QSO's during my two 4 hour operating shifts.
The great majority of that operating time was spent with the DSP bandwidth
at 600-700 Hz (and the 1KHz crystal filter.) Only once, when digging out a
weak one, did I narrow the bandwidth tight enough to engage the 200Hz
crystal filter. FD may not be the ultimate contest environment test, but
it's busy. Calling stations are often pretty far off zero beat in FD, so one
needs a fairly wide bandwidth to hear many of them. The 1KHz crystal filter
combined with the K3 DSP did a swimmingly good job this year and in FD's 09
and 08. Would a 750 Hz crystal filter be better? Perhaps, but I'm quite
happy with what I have now.

73,
  john WA1ABI


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[Bob Naumann W5OV]

Gary, you said:

"existing 500 Hz filter (which is too narrow)and their 1 kHz filter (which
is too wide)".

500 Hz is too narrow? For what? 1 kHz too wide? For what? What's in this
bandwidth gap?

I have both the 500Hz and 1kHz filters in my K3, and they are perfect for
their intended purpose. I see no need or potential benefit in creating
something that would be somewhere in between the two.

I'm puzzled by your conclusion that 750 Hz will provide something special.
For what and for who?

73,

Bob W5OV


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[W8JI]

I would have no use for a 750 Hz filter. 99% of the time I use SSB bandwidth
on emty CW bands, or less than 500 Hz BW.

I have my filters set so the 500 Hz roofing kicks in at 600 Hz BW, my 250
roofing in at 350.

This is in an attempt to soften the big 50 Hz selectivity steps when using
narrow filters. The only "selectivity thing" I would like to change is the
huge percentage of step change at narrow selectivity.  I find the steps much
too abrupt, especially when the DSP changes at the same time the roofing
filter does in a step. :-)

The 50 Hz steps really annoy me at narrow CW selectivities.


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[David Gilbert]

We're talking roofing filters here, not operating bandwidth.  The
functional difference between a 750 Hz roofing filter and a DSP setting
of 750Hz versus a 1000 Hz roofing filter and a DSP setting of 750Hz is
just plain trivial ... ESPECIALLY in a non-contest environment.  At
least it seems Inrad understands that.

73,
Dave   AB7E



On 7/14/2010 7:21 AM, Gary Hvizdak wrote:

> Guy,
>
>      Not everyone has a 1.8 kHz filter and not everyone operates CW contests.
> And yes the whole idea for 750 Hz was that it offers a "pleasant casual
> operating" width, and for some operators might be preferred versus INRAD's
> existing 500 Hz filter (which is too narrow) and their 1 kHz filter (which
> is too wide).
>
>
> Jim,
>
>      The fact that the problem "doesn't exist" "for most of us" doesn't
> negate the fact that there are folks who feel differently.  Some simply
> think it's a good idea, while others are eager to purchase such a filter
> today if were it available!
>
>
> 73,
> Gary  KI4GGX
> K3 #2724
>
>    

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[Gary Hvizdak]

Wed Jul 14 1130 EDT John King (WA1ABI) wrote ...

During FD 2010 I made 400+ CW QSO's ... the great majority ... with the DSP
bandwidth at 600-700 Hz ...


Hi John,

    I appreciate your comments and I wouldn't expect you to want to make a
change for a 25% narrower filter.  Rather my intention is to offer another
choice for folks who still have four empty slots, or don't yet even have a
K3.

73,
Gary  KI4GGX
K3 #2724

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[Dunc Carter - W5DC]

I respectfully disagree that Inrad's 500 Hz roofing filter is too
narrow.  In my opinion, you are trying to market a solution to a problem
that doesn't exist.

Dunc, W5DC.
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[Bill W4ZV]

Gary Hvizdak wrote

If instead you think that there might be a greater demand for some other
bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
let me know that width and include your reasoning for desiring that other
width.

I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250" is actually 370 Hz BW and I don't want that).

73,  Bill

[Eric Swartz - WA6HHQ]

Let's end this thread for now. If you have further questions or
comments, please correspond directly with Gary.

73, Eric  WA6HHQ
Elecraft List Modulator

-----
On 7/14/2010 11:40 AM, Duncan Carter wrote:
> I respectfully disagree that Inrad's 500 Hz roofing filter is too
> narrow.  In my opinion, you are trying to market a solution to a problem
> that doesn't exist.
>
> Dunc, W5DC.
>
>    
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[David Gilbert]

I never said that it was, and I'm not the guy who thinks a 750Hz filter
is an important additional option.  I use the 250 Hz 8-pole filter in my
K3 when I need a narrow filter for CW, and I use the 1.5 KHz 8-pole
filter any time I have the DSP set for greater than 300 Hz.  Both work
great.

73,
Dave   AB7E



On 7/14/2010 11:40 AM, Duncan Carter wrote:
> I respectfully disagree that Inrad's 500 Hz roofing filter is too
> narrow.  In my opinion, you are trying to market a solution to a
> problem that doesn't exist.
>
> Dunc, W5DC.
>
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[gm3sek]

Bill W4ZV wrote:

>
>
>Gary Hvizdak wrote:
>>
>> If instead you think that there might be a greater demand for some other
>> bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
>> let me know that width and include your reasoning for desiring that other
>> width.
>>
>
>I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>is actually 370 Hz BW and I don't want that).

Yes, the real gap in the available range of roofing filters is an 8-pole
with a *true* 6dB BW of 250Hz.

As for the choice between 250Hz and 200Hz, I have tried both bandwidths
by modifying a stock 200Hz 5-pole filter (with design help from Wayne).

In real-life contest QRM there is no noticeable difference between the
two bandwidths on CW, but there is a huge difference for RTTY.  With
170Hz shift, a 250Hz filter is very close to the lower limit of usable
bandwidth, but definitely on the right side of the line - in heavy RTTY
QRM, a 250Hz filter can be a game changer. But 200Hz is below that
limit, not usable at all.

For those reasons I would support 250Hz because it would meet the needs
of more users, but would vote against 200Hz (and in this, I do literally
mean "vote with my pocketbook").


--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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[Joe Subich, W4TV-4]

 > For those reasons I would support 250Hz because it would meet
 > the needs of more users, but would vote against 200Hz (and in
 > this, I do literally mean "vote with my pocketbook").

I agree with Ian here ... a filter with a reliable 270 Hz bandwidth
would be nearly ideal for RTTY and far better than the so called
"250 Hz" 8 pole filter.   I would almost certainly replace the
5-pole 200 Hz filters with 8-pole 250-270 Hz filters.

73,

    ... Joe, W4TV


On 7/14/2010 5:05 PM, Ian White GM3SEK wrote:

> Bill W4ZV wrote:
>>
>>
>> Gary Hvizdak wrote:
>>>
>>> If instead you think that there might be a greater demand for some other
>>> bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
>>> let me know that width and include your reasoning for desiring that other
>>> width.
>>>
>>
>> I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>> is actually 370 Hz BW and I don't want that).
>
> Yes, the real gap in the available range of roofing filters is an 8-pole
> with a *true* 6dB BW of 250Hz.
>
> As for the choice between 250Hz and 200Hz, I have tried both bandwidths
> by modifying a stock 200Hz 5-pole filter (with design help from Wayne).
>
> In real-life contest QRM there is no noticeable difference between the
> two bandwidths on CW, but there is a huge difference for RTTY.  With
> 170Hz shift, a 250Hz filter is very close to the lower limit of usable
> bandwidth, but definitely on the right side of the line - in heavy RTTY
> QRM, a 250Hz filter can be a game changer. But 200Hz is below that
> limit, not usable at all.
>
> For those reasons I would support 250Hz because it would meet the needs
> of more users, but would vote against 200Hz (and in this, I do literally
> mean "vote with my pocketbook").
>
>

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[N5GE]

On Wed, 14 Jul 2010 12:01:30 -0700 (PDT), Bill W4ZV
<[hidden email]> wrote:

I second that.  I wonder why they don't label them as the width they
really are?

Tom, N5GE

K3 #806 with SUB RX, PR6,
KRC2 and K144XV
K3 #1055 with PR6 and XV432
W1, 2 W2's and other small kits

QCWA Life Member 35102

[hidden email]
http://www.n5ge.com
http://www.swotrc.net

>I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>is actually 370 Hz BW and I don't want that).
>
>73,  Bill

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[Dunc Carter - W5DC]

As I wrote in an earlier post, the 250 Hz filter skirts are
assymetrical, at least mine is.  On one side, they are about right for
using a 250 Hz dsp setting but on the other side, they are wider.  You
may also benefit from tweaking the filter center frequency which you can
do using the configuration utility; my 250 Hz filter Freq. Offset 0s-s
set at -.04 but you best setting may likely be something different; yes,
it's nit-picking but what else is an old geezer to to when the bands are
dead.   Usually, best/least ringing response is obtained with the filter
centered as best possible but you can also listen to noise.  I usually
set the default width for my 250 Hz filter at 200 Hz and the default
center frequency of the 500 Hz filter at 450 Hz which gives a slight
improvement in ringing response at 200 Hz and 450 Hz by getting the
filter corner frequencies further down the dsp skirts; most of the time
I just use either of these two default frequencies as I can toggle
between them and the 1.8 KHz with  the XFIL button.

Dunc, W5DC

Radio Amateur N5GE wrote:

> On Wed, 14 Jul 2010 12:01:30 -0700 (PDT), Bill W4ZV
> <[hidden email]> wrote:
>
> I second that.  I wonder why they don't label them as the width they
> really are?
>
> Tom, N5GE
>
> K3 #806 with SUB RX, PR6,
> KRC2 and K144XV
> K3 #1055 with PR6 and XV432
> W1, 2 W2's and other small kits
>
> QCWA Life Member 35102
>
> [hidden email]
> http://www.n5ge.com
> http://www.swotrc.net
>
>  
>> I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>> is actually 370 Hz BW and I don't want that).
>>
>> 73,  Bill
>>    
>
> ______________________________________________________________
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>
>  

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[Ted Roycraft]

That's the filter width at the 3db point.  From the filter plots it
looks pretty close.

At least it's not like buying a 2 X 4 which isn't close to being 2 X 4.

73, Ted, W2ZK

On 7/14/2010 10:47 PM, Radio Amateur N5GE wrote:

> On Wed, 14 Jul 2010 12:01:30 -0700 (PDT), Bill W4ZV
> <[hidden email]>  wrote:
>
> I second that.  I wonder why they don't label them as the width they
> really are?
>
> Tom, N5GE
>
> K3 #806 with SUB RX, PR6,
> KRC2 and K144XV
> K3 #1055 with PR6 and XV432
> W1, 2 W2's and other small kits
>
> QCWA Life Member 35102
>
> [hidden email]
> http://www.n5ge.com
> http://www.swotrc.net
>
>    
>> I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>> is actually 370 Hz BW and I don't want that).
>>
>> 73,  Bill
>>      
> ______________________________________________________________
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>
>
>    

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[gm3sek]

Joe Subich, W4TV wrote:

>
> > For those reasons I would support 250Hz because it would meet
> > the needs of more users, but would vote against 200Hz (and in
> > this, I do literally mean "vote with my pocketbook").
>
>I agree with Ian here ... a filter with a reliable 270 Hz bandwidth
>would be nearly ideal for RTTY and far better than the so called
>"250 Hz" 8 pole filter.   I would almost certainly replace the
>5-pole 200 Hz filters with 8-pole 250-270 Hz filters.
>

Agreed. 250-270Hz would be the "sweet spot" for an 8-pole filter, to
guarantee good sales for the manufacturer *and* good performance for a
range of users in heavy QRM.

Now let's see if Inrad or Elecraft take the bait :-)


73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek

>On 7/14/2010 5:05 PM, Ian White GM3SEK wrote:
>> Bill W4ZV wrote:
>>>
>>>
>>> Gary Hvizdak wrote:
>>>>
>>>> If instead you think that there might be a greater demand for some other
>>>> bandwidth 8-pole INRAD roofing filter, please email me (off-Reflector) to
>>>> let me know that width and include your reasoning for desiring that other
>>>> width.
>>>>
>>>
>>> I'd be interested in a **true** 6 dB BW 8-pole for 200-250 Hz (Inrad's "250"
>>> is actually 370 Hz BW and I don't want that).
>>
>> Yes, the real gap in the available range of roofing filters is an 8-pole
>> with a *true* 6dB BW of 250Hz.
>>
>> As for the choice between 250Hz and 200Hz, I have tried both bandwidths
>> by modifying a stock 200Hz 5-pole filter (with design help from Wayne).
>>
>> In real-life contest QRM there is no noticeable difference between the
>> two bandwidths on CW, but there is a huge difference for RTTY.  With
>> 170Hz shift, a 250Hz filter is very close to the lower limit of usable
>> bandwidth, but definitely on the right side of the line - in heavy RTTY
>> QRM, a 250Hz filter can be a game changer. But 200Hz is below that
>> limit, not usable at all.
>>
>> For those reasons I would support 250Hz because it would meet the needs
>> of more users, but would vote against 200Hz (and in this, I do literally
>> mean "vote with my pocketbook").
>>
>>

--


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[Jim Brown-10]

On Thu, 15 Jul 2010 14:53:10 +0100, Ian White GM3SEK wrote:

>Agreed. 250-270Hz would be the "sweet spot" for an 8-pole filter, to
>guarantee good sales for the manufacturer *and* good performance for a
>range of users in heavy QRM.

>Now let's see if Inrad or Elecraft take the bait :-)

Hang on a minute, guys. Inrad builds a nominal 250 Hz filter, Elecraft
tests and re-sells it, and we buy it, because we've agreed that it's a
sweet spot operationally.

The issue is that it's wider than than at the -3dB points. So the
problem appears to be that it's pretty difficult to build an 8-pole 250
Hz filter at 8.8 MHz, and that Inrad has given up on doing better.

73, Jim K9YC


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