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Filter Selection Approach

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Ed G-2

Filter Selection Approach

Hello,
I am getting ready to order a K3 with subreceiver soon, and have been
thinking about which filters to order. From most of what I read, folks seem
to order duplicates for the subreceiver of what they have ordered for the
main receiver, or perhaps just go with just a couple narrower ones for the
subreceiver. Since I work mostly CW, and am not too interested in diversity
reception (don't have the antennas either), I was thinking of the following:

Main Rx: 2.8 - 1.8 - 1 - 400 - 200
Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400

I know that's a lot of filters, but other than going broke, are there any
drawbacks to this? Has anyone else tried to essentially give themselves all
the filter options by populating both receivers with different filters?

--Ed--

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Don Wilhelm-4

Re: Filter Selection Approach

Ed,

The DSP filtering is quite effective all by itself - I have only the 2.7
kHz filter installed and fine it quite effective *except* for heavy
QRM/pileup situations - like contesting or serious DXing, and when the
'going gets tough', I go do something other than hamming.

Caution - I am going to present my own opinions here - YMMV.

If I were ordering a bunch of filters, I would have the 13 kHz in the
main for FM transmit (and receive), and the 6 kHz also in the main for
AM transmit. I do not see much sense in having both the 13 and the 6
kHz in the sub since either can be used for AM receive. Besides, why
would you want FM and AM receive only capability (by putting them in the
sub) if you have no transmit capability in those modes.

If you do SSB contesting or serious DXing, the 2.1 or even the 1.8
filters may be beneficial, and I would select one width of those two and
put one of those in the sub and one in the main to allow diversity
reception (if and when you get a separate receive antenna) for SSB
operation.

Similarly, I would pair up the narrow CW filters for CW use, and I would
choose the 400 and the 200 Hz filters. At 1 kHz CW width, I would use
the 2.1 (or 1.8) filter and narrow it down with the DSP. I just cannot
foresee conditions where I would want to listen to a wide CW bandpass
under conditions when the DSP could not handle the dynamic range. My
normal CW tuning is done with a 500 to 700 Hz bandwidth, so I would
likely choose a 500 Hz filter for normal CW work and if I were
interested in CW contesting, I would likely choose the 200 Hz width.

So, my 'ideal' filter setup would be.
Main (with no AM or ESSB transmit capability) - 13kHz - 2.8 kHz, 2.1 (or
1.8) kHz, 500 Hz and 200 Hz.
OR - Main (with no FM transmit or receive capability) - 6 kHz - 2.8kHz,
2.1 (or 1.8) kHz, 500 Hz and 200 Hz.
Sub - 2.8kHz, 2.1 (or 1.8) kHz, 500 Hz and 200 Hz.

If I wanted both FM and AM/ESSB transmit/receive capability, I would
bump out the 500 Hz filters and install both the 13kHz and the 6 kHz in
the main, and the choice of 2.1 or 1.8 kHz would tend toward the 1.8
because I would use that roofing filter along with the DSP for normal CW
operation and switch in the 200 Hz filter when the 'going gets tough'.

So my choice for all possible modes would be:
Main -- 13 kHz, 6 kHz, 2.8 kHz, 1.8 kHz and 200 Hz.
Sub --- 2.8 kHz, 1.8 kHz, 200 Hz.

That combination would allow future diversity reception for all modes
except FM and AM/ESSB where I do not believe diversity would offer me
much advantage (I would not regularly use those modes), but preserve the
possibility for diversity reception in SSB, DATA and CW modes.

As you can see, the choice will depend on your operating aspirations.
Consider the reasons for *my* choices, and then match *your* filter
selections to your anticipated operation requirements.

I might emphasize that at present, my K3 does not have the subRX and has
only the stock 2.7 kHz filter installed. I can always add filters later
when (and if) I find a need for them.

73,
Don W3FPR

Ed G wrote:

> Hello,
> I am getting ready to order a K3 with subreceiver soon, and have been
> thinking about which filters to order. From most of what I read, folks seem
> to order duplicates for the subreceiver of what they have ordered for the
> main receiver, or perhaps just go with just a couple narrower ones for the
> subreceiver. Since I work mostly CW, and am not too interested in diversity
> reception (don't have the antennas either), I was thinking of the following:
>
> Main Rx: 2.8 - 1.8 - 1 - 400 - 200
> Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400
>
> I know that's a lot of filters, but other than going broke, are there any
> drawbacks to this? Has anyone else tried to essentially give themselves all
> the filter options by populating both receivers with different filters?
>
> --Ed--
>
>

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Svend Spanget

Re: Filter Selection Approach

Very well put, Don. I have almost the setup you suggest.
Last night I heard some weak but perfectly readable PY and YV stations on
20m. I am i Denmark (Europe). They were calling CQ and there was no
pile-up. But my 100W from the K3 didn't make a contact!
So why would I invest in a second receiver?

73,
Svend OZ7UV

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Bill W4ZV

Re: Filter Selection Approach

In reply to this post by Ed G-2

Ed G wrote

Since I work mostly CW, and am not too interested in diversity
reception (don't have the antennas either), I was thinking of the following:

Main Rx: 2.8 - 1.8 - 1 - 400 - 200
Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400

I know that's a lot of filters, but other than going broke

Wow, that's over $1200 on filters alone! You haven't said much about how you plan to operate (other than mostly CW), but 6 of your 10 filters are for voice modes (i.e. all above 1.0 kHz). Are you sure you wouldn't rather use that $750 for something more aligned with your main interest?

Just to complicate your choices even more, Inrad has 2 additional filters besides what can be ordered from Elecraft:

http://www.inrad.net/product.php?productid=299&cat=140&page=1
http://www.inrad.net/product.php?productid=316&cat=140&page=1

It may also benefit you to order your filters directly from Inrad rather than Elecraft since they offer quantity discounts (up to 20% for 10 filters...see page 16 of their catalog). That could save you about $120 but perhaps you're ordering your unit assembled.

73, Bill

P.S. Don't forget Elecraft will *someday* offer variable bandwidth filters!

Joe Subich, W4TV-4

Re: Filter Selection Approach

In reply to this post by Ed G-2

That is a lot of filters ...

1) The DSP is quite effective and there is not much difference
(if any) in the performance of the 2.8 KHz 8-pole filter vs.
the 2.7 KHz 5-pole filters. Even if one pays the extra $30
for a matched pair of 2.7 KHz filters, the added cost of the
2.8 KHz pair is $180.00

2) Unless you are in very heavy QRM/pile-up situations the
roofing filter does not provide a lot of "value added"
since the final bandwidth is determined by the DSP. The
1 KHz filters add little benefit vs. the 1.8 KHz or 1.5
KHz filters.

3) The 13 KHz filter can be used for AM receive - there is
no benefit in having both the 13 and 6 KHz filters in the
sub RX. It is a shame that Elecraft still do not permit
use of the 13 KHz for AM and ESSB transmit (even if it
were offset 3 KHz in transmit for additional image rejection).

A less expensive line-up that seems to provide maximum
(IMO) flexibility/performance is:
Main: 13 - 2.7 - 1.8 (1.5) - 400 - 200
Sub: 13 - 2.7 - 400

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Ed G
> Sent: Monday, April 13, 2009 7:24 PM
> To: [hidden email]
> Subject: [Elecraft] Filter Selection Approach
>
>
> Hello,
> I am getting ready to order a K3 with subreceiver soon,
> and have been thinking about which filters to order. From
> most of what I read, folks seem to order duplicates for the
> subreceiver of what they have ordered for the main receiver,
> or perhaps just go with just a couple narrower ones for the
> subreceiver. Since I work mostly CW, and am not too
> interested in diversity reception (don't have the antennas
> either), I was thinking of the following:
>
> Main Rx: 2.8 - 1.8 - 1 - 400 - 200
> Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400
>
> I know that's a lot of filters, but other than going broke,
> are there any drawbacks to this? Has anyone else tried to
> essentially give themselves all the filter options by
> populating both receivers with different filters?
>
> --Ed--
>

Matt Zilmer

Re: Filter Selection Approach

In reply to this post by Ed G-2

Eric Swartz - WA6HHQ

Re: Filter Selection Approach

Administrator

In reply to this post by Bill W4ZV

Bill, to my knowledge INRAD is not shipping quantities of our filters at
this time. They have had enough trouble meeting our demand on time.
Eric

Bill W4ZV wrote:

>
>
> Since I work mostly CW, and am not too interested in diversity
> reception (don't have the antennas either), I was thinking of the following:
>
> Main Rx: 2.8 - 1.8 - 1 - 400 - 200
> Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400
>
> I know that's a lot of filters, but other than going broke
>
>
> Wow, that's over $1200 on filters alone! You haven't said much about how you plan to operate (other than mostly CW), but 6 of your 10 filters are for voice modes (i.e. all above 1.0 kHz). Are you sure you wouldn't rather use that $750 for something more aligned with your main interest?
>
> Just to complicate your choices even more, Inrad has 2 additional filters besides what can be ordered from Elecraft:
>
> http://www.inrad.net/product.php?productid=299&cat=140&page=1
> http://www.inrad.net/product.php?productid=316&cat=140&page=1
>
> It may also benefit you to order your filters directly from Inrad rather than Elecraft since they offer quantity discounts (up to 20% for 10 filters...see page 16 of their catalog). That could save you about $120 but perhaps you're ordering your unit assembled.
>
> 73, Bill
>
> P.S. Don't forget Elecraft will *someday* offer variable bandwidth filters!
>

K2QI

Re: Filter Selection Approach

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

I agree with Joe,

Save your money where you can.

Here's what I have configured:

Main: 13 - 6 - 2.7 - 400
Sub: 13 - 2.7 - 400

The 6k in the main is used for AM or ESSB. The 13K on the main is for FM
transmissions, while the 13k in the sub is used for AM receive. I use the
400 for all other modes like CW or data, and if needed will use the DSP to
taper down.

73,
James K3JPS

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Joe Subich, W4TV
Sent: Tuesday, April 14, 2009 9:41 AM
To: 'Ed G'; [hidden email]
Subject: Re: [Elecraft] Filter Selection Approach

That is a lot of filters ...

1) The DSP is quite effective and there is not much difference
(if any) in the performance of the 2.8 KHz 8-pole filter vs.
the 2.7 KHz 5-pole filters. Even if one pays the extra $30
for a matched pair of 2.7 KHz filters, the added cost of the
2.8 KHz pair is $180.00

2) Unless you are in very heavy QRM/pile-up situations the
roofing filter does not provide a lot of "value added"
since the final bandwidth is determined by the DSP. The
1 KHz filters add little benefit vs. the 1.8 KHz or 1.5
KHz filters.

3) The 13 KHz filter can be used for AM receive - there is
no benefit in having both the 13 and 6 KHz filters in the
sub RX. It is a shame that Elecraft still do not permit
use of the 13 KHz for AM and ESSB transmit (even if it
were offset 3 KHz in transmit for additional image rejection).

A less expensive line-up that seems to provide maximum
(IMO) flexibility/performance is:
Main: 13 - 2.7 - 1.8 (1.5) - 400 - 200
Sub: 13 - 2.7 - 400

73,

... Joe, W4TV

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--... ...-- -.. . .--- .- -- . ...

.hank.

Re: Filter Selection Approach

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

Joe Subich, W4TV-4 wrote

That is a lot of filters ...

2) Unless you are in very heavy QRM/pile-up situations the
roofing filter does not provide a lot of "value added"
since the final bandwidth is determined by the DSP. The
1 KHz filters add little benefit vs. the 1.8 KHz or 1.5
KHz filters.

I would disagree regarding the value or benefit of the 1 KHz filter.
Originally I had, for CW, 1800, 500 & 200 filters. Since I normally set the width to 700 Hz for normal non contest CW operating, it seemed that I was having problems with loud signals within about 900 to 1800 HZ hitting the AGC. So when a 1000 HZ filter became available to trade for my 1800 HZ filter I jumped on it and have not looked back!
Last year in CQ WW CW I have had a chance to sit down on 20 meters with a K3 with 400 & 250 HZ filters. I was very happy to switch radios back to my K3 with 1000, 500 and 200 HZ filters.
To my ears the 500 & 200 filters were a definite advantage sorting out the weaker European signals in between the loud east coast U.S. stations.
This was not at all a scientific test - just how it sounded to me!
Both K3s were using the same firmware.
And I really think if I had purchased a K3 with no roofing filters, like I've seen suggested, I would have most likely sold the K3 and gone back to a K2!
Just my thoughts.
73 Hank K8DD

Bill W4ZV

Re: Filter Selection Approach

.k8dd. wrote

Joe Subich, W4TV-4 wrote

That is a lot of filters ...

2) Unless you are in very heavy QRM/pile-up situations the
roofing filter does not provide a lot of "value added"
since the final bandwidth is determined by the DSP. The
1 KHz filters add little benefit vs. the 1.8 KHz or 1.5
KHz filters.

I would disagree regarding the value or benefit of the 1 KHz filter.
Originally I had, for CW, 1800, 500 & 200 filters. Since I normally set the width to 700 Hz for normal non contest CW operating, it seemed that I was having problems with loud signals within about 900 to 1800 HZ hitting the AGC. So when a 1000 HZ filter became available to trade for my 1800 HZ filter I jumped on it and have not looked back!

I was the one who traded my 1.0 for Hank's 1.8. The reason I didn't like the 1.0 is the following, which depends on the PITCH you normally like to use. If you use a high pitch, this may not apply, but I like a low pitch of 300-350 for weak signal DX-ing (and 400-450 for contesting).

The way the K3 works is that XFILs are normally centered about the selected PITCH, **UNLESS** the lower end of that passband falls below 200 Hz. In that case, the firmware shifts the XFIL such that the lower end is 200 Hz (to prevent negative IF response). If I set my PITCH to 300, my passband is actually 200-1200, or 900 Hz above my zero beat pitch. This means my AGC would still be pumped by a signal ~1 kHz away (actual 6 dB BW is 1063 Hz per the Elecraft/Inrad plot). In most rigs (e.g. Orion) with a 1 kHz filter centered on the desired PITCH, you would only be susceptible to AGC pumping ~500 Hz away. Practically speaking, for my desired low pitch of 300 Hz, the 1.0 filter in the K3 acts more like a much wider filter in another rig since it's passing signals ~1 kHz above my 300 Hz PITCH.

For casual use a 1.0 may be OK, but where I live in the land of Elephants and Fleas (160m), the 1.0 is practically worthless if there is much activity on the band. I swapped my 1.0 because of this and because I felt the 1.8 might be useful for SSB contesting (when and if 10m ever comes back).

73, Bill

P.S. I've still never understood why Orion worked with its XFILs centered at low pitches...yet the K3 apparently has a problem.

Joe Subich, W4TV-4

Re: Filter Selection Approach

In reply to this post by .hank.

> I would disagree regarding the value or benefit of the 1 KHz
> filter. Originally I had, for CW, 1800, 500 & 200 filters.
> Since I normally set the width to 700 Hz for normal non
> contest CW operating, it seemed that I was having problems
> with loud signals within about 900 to 1800 HZ hitting the
> AGC. So when a 1000 HZ filter became available to trade for
> my 1800 HZ filter I jumped on it and have not looked back!

As I responded to someone who raised this same point privately,
the wider filters are not centered on the desired signal. Thus,
if you favor a pitch of 500 Hz the 1000 Hz filter provides a
"window" that runs from approximately 600 Hz BELOW the desired
signal to about 400 Hz ABOVE the desired signal. The 1500 or
1800 Hz filter simply extends the window DOWN.

With the asymmetric "window," if one is receiving QRM on the
"wide" side changing to CW REV is just as effective in eliminating
that QRM as switching to a narrower filter. If switching to the
opposite sideband results in QRM from other signals, one would
need to use a still narrower filter - e.g., 500 Hz - to eliminate
the QRM from both sides in any case.

Because of the asymmetric window, there is little performance
difference among the 1000, 1500, 1800 and 2100 Hz filters in
CW. Nobody has bothered to report the fact that 2 KHz IMD
with the 2.7 or 2.8 KHz roofing filters is DIFFERENT if you
measure above and below the interfering tones ... this is due
entirely to the asymmetric window. The same differences will
be observed with 1 KHz or 500 Hz IMD DR in CW with any filter
wider than 500 Hz.

There is no doubt that an 800 Hz filter would be a good option
for "wide" CW or that the 1000/1500/1800 Hz filters might have
some benefit if the IF DSP were modified for "single signal"
operation and the filters "centered" on the desired CW signal.

> Last year in CQ WW CW I have had a chance to sit down on 20
> meters with a K3 with 400 & 250 HZ filters. I was very happy
> to switch radios back to my K3 with 1000, 500 and 200 HZ filters.

The 500/400/250/200 Hz filters have been discussed at length.
With real bandwidths of 480 Hz (measured in four filters in my
K3s) for the 500 Hz 5-pole filter, 450 Hz for the 400 Hz filter
(Inrad web site), 350 Hz for the "250 Hz" filter (Elecraft web
site) and 205 Hz for the 200 Hz filter, my choice will be to
move from the 500/200 Hz combination to the 400/200 Hz pairing.
The added skirts will improve performance where the wider filter
is useful (particularly RTTY) without being significantly more
narrow than the current 500 Hz 5-pole filters and the 200 Hz
filter is the best truly narrow option.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of .k8dd.
> Sent: Wednesday, April 15, 2009 12:10 AM
> To: [hidden email]
> Subject: Re: [Elecraft] Filter Selection Approach
>
>
>
>
>
>
> That is a lot of filters ...
>
> 2) Unless you are in very heavy QRM/pile-up situations the
> roofing filter does not provide a lot of "value added"
> since the final bandwidth is determined by the DSP. The
> 1 KHz filters add little benefit vs. the 1.8 KHz or 1.5
> KHz filters.
>
>
>
> I would disagree regarding the value or benefit of the 1 KHz
> filter. Originally I had, for CW, 1800, 500 & 200 filters.
> Since I normally set the width to 700 Hz for normal non
> contest CW operating, it seemed that I was having problems
> with loud signals within about 900 to 1800 HZ hitting the
> AGC. So when a 1000 HZ filter became available to trade for
> my 1800 HZ filter I jumped on it and have not looked back!
> Last year in CQ WW CW I have had a chance to sit down on 20
> meters with a K3 with 400 & 250 HZ filters. I was very happy
> to switch radios back to my K3 with 1000, 500 and 200 HZ filters.
> To my ears the 500 & 200 filters were a definite advantage
> sorting out the weaker European signals in between the loud
> east coast U.S. stations. This was not at all a scientific
> test - just how it sounded to me!
> Both K3s were using the same firmware.
> And I really think if I had purchased a K3 with no roofing
> filters, like I've seen suggested, I would have most likely
> sold the K3 and gone back to a K2! Just my thoughts.
> 73 Hank K8DD
> --
> View this message in context:
> http://n2.nabble.com/Filter-Selection-Approach-tp2630347p2636834.html
> Sent from the Elecraft mailing list archive at Nabble.com.
>
> ______________________________________________________________
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Guy, K2AV

Re: Filter Selection Approach

In reply to this post by Bill W4ZV

Casual operation has rarely strained my radios, and my MP and my K2 are quite adequate for that. When we get to contesting, all facilities are strained. I prefer the K2 audio to the K3, and sometime soon I will get to the bottom of that. The quickest, sharpest, deepest skirts on selectivity still belong to my MP with matched 8 pole INRAD filters in 8 Mhz and 455 kHz IF's. (I know that's heresy, but so be it...)

On receiver front-end, overload immunity and SDR-driven DSP magic (like blanking key clicks), with more to come, the K3 leaves everything else in the dust. But I pick roofing filters to get as close as I can to the MP+INRAD+INRAD skirt performance.

BOTH K3 selectivities (roofing and DSP) need to be matched to produce optimal rejection of signals just outside of the desired listening window. I have the "400" and "250" 8 poles in my K3 and list them as 450 and 350 in the filter setup. The bulk of my operation in a contest is RUNNING, not search and pounce, for DX tests mostly using a very large 40m antenna fixed on Europe, and with huge differentials (80+ db) between desired weak signals and undesired strong signals just above and below. I also specifically use the [sometimes complained about] "mild" difference between the two to advantage, as I use BOTH for running, and use 350/300 when I need it just a bit tighter.

While I could narrow down with a 5 pole 200 on a weak station, 1/3 or more of the stations calling are off my frequency, often because the current packet spot is up or down. And I'm not allowed to spot myself to fix it. I have to keep a window to hear them or someone else gets the top score.

The next CW station can be up/down only 350 Hz, meaning that outside the listening window, the skirt needs to dive for ultimate rejection as fast as possible. Being flat at +/- 175 is not the issue when setting at 350 width, it's how far down the combination of skirts has gone at +/- 225. The most important thing is where are the skirts halfway down and how much more do they drop with another 10 Hz, NOT the 3 db or 6 db points. The 8 pole roofers are part of making those skirts dive more in 10 Hz halfway down.

I set up my filters at the +/- 50 dB points, and eagerly await the day when CW widths and shifts are in 10 Hz increments.

I have had some extremely vociferous contradictions from some insisting that the 8 pole roofers are simply a waste, and a wide and narrow 5 pole are all needed, but my contest experience continues to suggest otherwise.

All of the above are in stark contrast to casual operation. Buy filters for how you use the radio. If you are into hard contesting, do it with 8 poles.

73, Guy
K2AV

Bill W4ZV

Re: Filter Selection Approach

Guy, K2AV wrote

The most important thing is where are the skirts halfway down and how much more do they drop with another 10 Hz, NOT the 3 db or 6 db points. The 8 pole roofers are part of making those skirts dive more in 10 Hz halfway down.

I set up my filters at the +/- 50 dB points, and eagerly await the day when CW widths and shifts are in 10 Hz increments.

I have had some extremely vociferous contradictions from some insisting that the 8 pole roofers are simply a waste, and a wide and narrow 5 pole are all needed, but my contest experience continues to suggest otherwise.

All of the above are in stark contrast to casual operation. Buy filters for how you use the radio. If you are into hard contesting, do it with 8 poles.

The DSP filter is the driving factor in making the skirts steep, especially when you're below the 435 Hz BW of the "400" or the 370 Hz BW of the "250", since there would be little cascading effect there. See K8ZOA's plot for the "500 Hz 5-pole CW/Data Filter" section about half way down this page:

http://tinyurl.com/dho6j6

You can see the shape of the XFIL itself when looking at the DSP = 4000 trace (i.e. when the DSP is >> in width than the XFIL). If DSP is about the same as the XFIL (i.e. WIDTH = ~430 for the "400" or WIDTH = ~370 for the "250"), then there is some help. If the DSP is inside the flat area of the XFIL, there is little contribution from the XFIL skirts.

73, Bill

Bill W4ZV

Re: Filter Selection Approach

Bill W4ZV wrote

See K8ZOA's plot for the "500 Hz 5-pole CW/Data Filter" section about half way down this page:

http://tinyurl.com/dho6j6

While looking at those plots, note that the slope of all the skirts is about the same once you're inside the roofing filter (i.e. beginning at 5-600 Hz). This is because the slope is determined mainly by the DSP. Lyle once told me exactly what that slope was but I've forgotten it. The reason apparent DSP shape factors increase at narrow BWs is because the DSP skirt slope is a constant in dB/Hz, and independent of DSP BW. Of course a wider shape factor is good because you don't want extremely narrow filters to ring, which could happen if you made a 100 Hz filter with an extremely narrow shape factor.

BTW, the FIR/IIR options for the 100/50 DSP filters is another area K8ZOA examined below:

http://tinyurl.com/d5skb8

73, Bill

Bill W4ZV

Re: Filter Selection Approach

In reply to this post by Bill W4ZV

For some strange reason Nabble is not attributing quotes correctly on posts sent to the main list...even though they appear correctly on the Nabble website. Just to make sure there's no confusion as to who said what...

K2AV wrote:

********************************************************************
The most important thing is where are the skirts halfway down and how much more do they drop with another 10 Hz, NOT the 3 db or 6 db points. The 8 pole roofers are part of making those skirts dive more in 10 Hz halfway down.

I set up my filters at the +/- 50 dB points, and eagerly await the day when CW widths and shifts are in 10 Hz increments.

I have had some extremely vociferous contradictions from some insisting that the 8 pole roofers are simply a waste, and a wide and narrow 5 pole are all needed, but my contest experience continues to suggest otherwise.

All of the above are in stark contrast to casual operation. Buy filters for how you use the radio. If you are into hard contesting, do it with 8 poles.
**********************************************************************

I responded:

The DSP filter is the driving factor in making the skirts steep, especially when you're below the 435 Hz BW of the "400" or the 370 Hz BW of the "250", since there would be little cascading effect there. See K8ZOA's plot for the "500 Hz 5-pole CW/Data Filter" section about half way down this page:

http://tinyurl.com/dho6j6

You can see the shape of the XFIL itself when looking at the DSP = 4000 trace (i.e. when the DSP is >> in width than the XFIL). If DSP is about the same as the XFIL (i.e. WIDTH = ~430 for the "400" or WIDTH = ~370 for the "250"), then there is some help. If the DSP is inside the flat area of the XFIL, there is little contribution from the XFIL skirts.

73, Bill