K3 in WPX SSB with 2.7 roofer

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K3 in WPX SSB with 2.7 roofer

Dave Hachadorian-2
I was in the WPX SSB contest this weekend, and wanted to try
using just the 2.7 roofing filter, using only DSP to narrow the
response below that.  I previously have had the feeling that the
1.8 roofer was degrading speech intelligibility.  The WPX is a
QRM-fest of the first order.  Everybody can work everybody, so
the whole world is doing their own thing all the time.  15 meters
was particularly bad, with almost nobody having a clear channel.

Using only the 2.7 filter, I never experienced a case of
adjacent-signal AGC pumping, or any other negative issue during
the contest.  I think if an SSB signal is so close to you that it
is pumping your agc through the 2.7 filter, the frequency is
hopelessly splattered anyway, and you'd best be moving on.  I did
narrow the DSP down by using HI CUT, and usually ran it at
LOW=0.15 and HIGH=2.25.

I could be persuaded to part with my pair of 1.8 filters, if
someone is interested in them.

Dave Hachadorian, K6LL
Yuma, AZ


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Re: K3 in WPX SSB with 2.7 roofer

k6dgw
That's been my experience too, Dave.  SSB is not my forte ... severely
compromised hearing ... but I do get into a small handful of phone
contests [not WPX SSB, for the reasons you mentioned].  I had a borrowed
1.8 filter for awhile, and found that it really did degrade the audio.
Conversely, I've never had a problem with strong adjacent signals using
the 2.7 even though I've got a couple of close neighbor hams.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 3/30/2014 1:30 PM, Dave Hachadorian wrote:

> Using only the 2.7 filter, I never experienced a case of adjacent-signal
> AGC pumping, or any other negative issue during the contest.  I think if
> an SSB signal is so close to you that it is pumping your agc through the
> 2.7 filter, the frequency is hopelessly splattered anyway, and you'd
> best be moving on.  I did narrow the DSP down by using HI CUT, and
> usually ran it at LOW=0.15 and HIGH=2.25.


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Re: K3 in WPX SSB with 2.7 roofer

Bill Coleman-2
In reply to this post by Dave Hachadorian-2

On Mar 30, 2014, at 4:30 PM, Dave Hachadorian <[hidden email]> wrote:
> Using only the 2.7 filter, I never experienced a case of adjacent-signal AGC pumping, or any other negative issue during the contest.  I think if an SSB signal is so close to you that it is pumping your agc through the 2.7 filter, the frequency is hopelessly splattered anyway, and you'd best be moving on.  I did narrow the DSP down by using HI CUT, and usually ran it at LOW=0.15 and HIGH=2.25.

I’ll echo this experience. I find the DSP filters to be stupendous. All I have for SSB roofing filter is the stock 2.7 kHz 5-pole filter. The heavy lifting is done in the DSP.

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
           -- Wilbur Wright, 1901

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K3 in WPX SSB with 2.7 roofer

Johnny Siu
In reply to this post by Dave Hachadorian-2
Hello Dave,

I did have the same experience with 1.8Khz filter in the past.  However, upon the guidance of my contest elmer, I played around the IF shift.  By moving the centre position of the IF passband, you will find a sweet spot where you can hear the speech with minimal degrade but excellent selectivity.

73 Johnny VR2XMC
 

________________________________
 寄件人︰ Dave Hachadorian <[hidden email]>
收件人︰ Reflector Elecraft <[hidden email]>
傳送日期︰ 2014年03月31日 (週一) 4:30 AM
主題︰ [Elecraft] K3 in WPX SSB with 2.7 roofer
 

I was in the WPX SSB contest this weekend, and wanted to try
using just the 2.7 roofing filter, using only DSP to narrow the
response below that.  I previously have had the feeling that the
1.8 roofer was degrading speech intelligibility.  The WPX is a
QRM-fest of the first order.  Everybody can work everybody, so
the whole world is doing their own thing all the time.  15 meters
was particularly bad, with almost nobody having a clear channel.

Using only the 2.7 filter, I never experienced a case of
adjacent-signal AGC pumping, or any other negative issue during
the contest.  I think if an SSB signal is so close to you that it
is pumping your agc through the 2.7 filter, the frequency is
hopelessly splattered anyway, and you'd best be moving on.  I did

narrow the DSP down by using HI CUT, and usually ran it at
LOW=0.15 and HIGH=2.25.

I could be persuaded to part with my pair of 1.8 filters, if
someone is interested in them.

Dave Hachadorian, K6LL
Yuma, AZ


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Re: K3 in WPX SSB with 2.7 roofer

Dave Hachadorian-2
I’ve done all that.  On some voices, distortion is minimal.  On others, it is serious.

Dave Hachadorian, K6LL
Yuma, AZ



From: Johnny Siu
Sent: Sunday, March 30, 2014 5:29 PM
To: Dave Hachadorian ; Reflector Elecraft
Subject: K3 in WPX SSB with 2.7 roofer

Hello Dave,

I did have the same experience with 1.8Khz filter in the past.  However, upon the guidance of my contest elmer, I played around the IF shift.  By moving the centre position of the IF passband, you will find a sweet spot where you can hear the speech with minimal degrade but excellent selectivity.

73 Johnny VR2XMC

寄件人︰ Dave Hachadorian <[hidden email]>
收件人︰ Reflector Elecraft <[hidden email]>
傳送日期︰ 2014年03月31日 (週一) 4:30 AM
主題︰ [Elecraft] K3 in WPX SSB with 2.7 roofer


I was in the WPX SSB contest this weekend, and wanted to try
using just the 2.7 roofing filter, using only DSP to narrow the
response below that.  I previously have had the feeling that the
1.8 roofer was degrading speech intelligibility.  The WPX is a
QRM-fest of the first order.  Everybody can work everybody, so
the whole world is doing their own thing all the time.  15 meters
was particularly bad, with almost nobody having a clear channel.

Using only the 2.7 filter, I never experienced a case of
adjacent-signal AGC pumping, or any other negative issue during
the contest.  I think if an SSB signal is so close to you that it
is pumping your agc through the 2.7 filter, the frequency is
hopelessly splattered anyway, and you'd best be moving on.  I did

narrow the DSP down by using HI CUT, and usually ran it at
LOW=0.15 and HIGH=2.25.

I could be persuaded to part with my pair of 1.8 filters, if
someone is interested in them.

Dave Hachadorian, K6LL
Yuma, AZ


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Re: K3 in WPX SSB with 2.7 roofer

Phil Wheeler-2
In reply to this post by Dave Hachadorian-2
I have the 2.0 and 2.8 filters installed; I seldom
get below 2.2-2.4 though but I'm not a contester.

Was watching 20 SSB on my P3 a while ago. You
could sure tell something changed at around
midnight Zulu!

73, Phil w7ox

On 3/30/14, 1:30 PM, Dave Hachadorian wrote:

> I was in the WPX SSB contest this weekend, and
> wanted to try using just the 2.7 roofing filter,
> using only DSP to narrow the response below
> that.  I previously have had the feeling that
> the 1.8 roofer was degrading speech
> intelligibility.  The WPX is a QRM-fest of the
> first order.  Everybody can work everybody, so
> the whole world is doing their own thing all the
> time.  15 meters was particularly bad, with
> almost nobody having a clear channel.
>
> Using only the 2.7 filter, I never experienced a
> case of adjacent-signal AGC pumping, or any
> other negative issue during the contest.  I
> think if an SSB signal is so close to you that
> it is pumping your agc through the 2.7 filter,
> the frequency is hopelessly splattered anyway,
> and you'd best be moving on.  I did narrow the
> DSP down by using HI CUT, and usually ran it at
> LOW=0.15 and HIGH=2.25.
>
> I could be persuaded to part with my pair of 1.8
> filters, if someone is interested in them.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
>

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Re: K3 in WPX SSB with 2.7 roofer

alorona
In reply to this post by Dave Hachadorian-2
Dave, I have had pretty much the same experience. I think I would have placed the 2.1 kHz passband that you settled on a bit higher, say, LO=0.30 and HI=2.40, or even LO=0.40 and HI=2.50, which is probably better matched to the majority of contesters' transmitted signals out there. But I realize that not everybody's ear is the same, and my settings could even result in a listener's fatigue in you.

For years I have heard folks state that 1.8 kHz is mandatory for SSB contesting... but I have never understood how one could put up with this narrow bandwidth for long. I need more information hitting my ears and am perfectly happy with letting the famous 'ear-brain' filter extract the maximum from that information.

This illustrates what I have just stated in another post: receiver settings are very specific to each operator. One size doesn't fit all. That's why, thank goodness, our rigs have so many wonderful controls that can be tweaked to sound 'just right'.

Al  W6LX
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Re: K3 in WPX SSB with 2.7 roofer

Clive Lorton

On 31 Mar 2014, at 06:47, Al Lorona <[hidden email]> wrote:

> For years I have heard folks state that 1.8 kHz is mandatory for SSB contesting... but I have never understood how one could put up with this narrow bandwidth for long. I need more information hitting my ears and am perfectly happy with letting the famous 'ear-brain' filter extract the maximum from that information.

Morning all, First post here from a new K3 owner.

I have used a Inrad 1.8 kHz filter in my old Icom 756 and just loved it.  I’ve just built K3 8098 and find the 1.8kHz filter much more uncomfortable to listen to in normal use.  It is different beast.  But I expect it will come into its own when digging that weak signal out of the QRM!

At the moment I’m just enjoying learning to drive it…...

Clive G8POC

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Re: K3 in WPX SSB with 2.7 roofer

Clive Lorton
In reply to this post by Dave Hachadorian-2
Was my post that awful?

Clive G8POC
On 31 Mar 2014, at 13:27, Tony McClenny <[hidden email]> wrote:

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> Subject: Re: [Elecraft] K3 in WPX SSB with 2.7 roofer
> From: Clive Lorton <[hidden email]>
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Re: K3 in WPX SSB with 2.7 roofer

gm3sek
In reply to this post by Clive Lorton
Hi Clive

I had the same good experience with the 1.8kHz Inrad filter in the old
FT-1000MP, so I moved that filter across to the K3 (with a change in
mounting board)... and have not regretted it.

Because the filter has such a restricted bandwidth, I configured the
filter to switch in at a WIDTH setting of 1.9kHz to avoid the bandwidth
being further narrowed by the DSP as well. The SHIFT setting is also
very critical for the best voice intelligibility. My particular filter
requires a fc setting of either 1.25 or 1.30kHz, and anything outside of
that range sounds very noticeably worse.

Once the 1.8kHz filter has been carefully set up, and its settings
stored in the NORM II SSB memory for easy recall, the SHIFT and WIDTH
controls hardly ever need to be touched... which is exactly what the SSB
contester requires.


73 from Ian GM3SEK


>-----Original Message-----
>From: [hidden email] [mailto:elecraft-
>[hidden email]] On Behalf Of Clive Lorton
>Sent: 31 March 2014 10:58
>To: [hidden email]
>Subject: Re: [Elecraft] K3 in WPX SSB with 2.7 roofer
>
>
>On 31 Mar 2014, at 06:47, Al Lorona <[hidden email]> wrote:
>
>> For years I have heard folks state that 1.8 kHz is mandatory for SSB
>contesting... but I have never understood how one could put up with
this
>narrow bandwidth for long. I need more information hitting my ears and
am
>perfectly happy with letting the famous 'ear-brain' filter extract the
>maximum from that information.
>
>Morning all, First post here from a new K3 owner.
>
>I have used a Inrad 1.8 kHz filter in my old Icom 756 and just loved
it.  I've
>just built K3 8098 and find the 1.8kHz filter much more uncomfortable
to
>listen to in normal use.  It is different beast.  But I expect it will
come into its

>own when digging that weak signal out of the QRM!
>
>At the moment I'm just enjoying learning to drive it....
>
>Clive G8POC
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
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K3 in WPX SSB with 2.7 roofer

Johnny Siu
I fully concur with Ian's observation and have done the same for mine.

73  Johnny VR2XMC
 

________________________________
 寄件人︰ Ian White <[hidden email]>
收件人︰ 'Clive Lorton' <[hidden email]>; [hidden email]
傳送日期︰ 2014年03月31日 (週一) 9:42 PM
主題︰ Re: [Elecraft] K3 in WPX SSB with 2.7 roofer
 

Hi Clive

I had the same good experience with the 1.8kHz Inrad filter in the old
FT-1000MP, so I moved that filter across to the K3 (with a change in
mounting board)... and have not regretted it.

Because the filter has such a restricted bandwidth, I configured the
filter to switch in at a WIDTH setting of 1.9kHz to avoid the bandwidth
being further narrowed by the DSP as well. The SHIFT setting is also
very critical for the best voice intelligibility. My particular filter
requires a fc setting of either 1.25 or 1.30kHz, and anything outside of
that range sounds very noticeably worse.

Once the 1.8kHz filter has been carefully set up, and its settings
stored in the NORM II SSB memory for easy recall, the SHIFT and WIDTH
controls hardly ever need to be touched... which is exactly what the SSB
contester requires.


73 from Ian GM3SEK


>-----Original Message-----
>From: [hidden email] [mailto:elecraft-
>[hidden email]] On Behalf Of Clive Lorton
>Sent: 31 March 2014 10:58
>To: [hidden email]
>Subject: Re: [Elecraft] K3 in WPX SSB with 2.7 roofer
>
>
>On 31 Mar 2014, at 06:47, Al Lorona <[hidden email]> wrote:
>
>> For years I have heard folks state that 1.8 kHz is mandatory for SSB
>contesting... but I have never understood how one could put up with
this
>narrow bandwidth for long. I need more information hitting my ears and
am
>perfectly happy with letting the famous 'ear-brain' filter extract the
>maximum from that information.
>
>Morning all, First post here from a new K3 owner.
>
>I have used a Inrad 1.8 kHz filter in my old Icom 756 and just loved
it.  I've
>just built K3 8098 and find the 1.8kHz filter much more uncomfortable
to
>listen to in normal use.  It is different beast.  But I expect it will
come into its
>own when digging that weak signal out of the QRM!
>
>At the moment I'm just enjoying learning to drive it....
>
>Clive G8POC
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Re: K3 in WPX SSB with 2.7 roofer

George Danner
In reply to this post by alorona
One of the things that Bell Labs found in adding loading coils to phone
lines (to reduce the high frequencies) was that in an audio system if you
reduce the high frequencies then you needed to also reduce the low
frequencies to keep the intelligibility constant. Since a phone system
needed intelligibility above fidelity; Bell Labs just decreased the coupling
capacitors to reduce the low end while using the line loading coils to
reduce the high frequencies.

I tend to use lo-cut to improve "listen ability" when I cut the high end.
I use a 1.8 kHz filter for a morning SSB net that has other nets 3 kHz away
usually on both sides. Some of the transmitters on the adjacent frequencies
can't fit in 5 kHz much less being 3 kHz away. The 1.8 kHz filter is the
best solution - the filter skirts along with the DSP skirts help the most I
can expect.

I would recommend adjusting Hi-Cut for the interference and Lo-Cut for the
best compromise on fidelity & intelligibility; if that switches in a tighter
filter, then that might be needed.

My 2 cents!
73
George  AI4VZ

-----Original Message-----
From: Al
For years I have heard folks state that 1.8 kHz is mandatory for SSB
contesting... but I have never understood how one could put up with this
narrow bandwidth for long. I need more information hitting my ears and am
perfectly happy with letting the famous 'ear-brain' filter extract the
maximum from that information.

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Re: K3 in WPX SSB with 2.7 roofer

riese-k3djc
In reply to this post by Dave Hachadorian-2
actually loading coils were to reduce overall  loss
by helping to cancel the line capacity
before amplifiers 1000 cycles was the frequency passed with
best loss Characteristics,,,, the phones were designed to emphasise that
frequency
"whats that you say "
making phone calls werent for sissies

Bob K3DJC

On Mon, 31 Mar 2014 10:52:13 -0400 "George Danner"
<[hidden email]> writes:
> One of the things that Bell Labs found in adding loading coils to
> phone
> lines (to reduce the high frequencies) was that in an audio system
> if you
> reduce the high frequencies then you needed to also reduce the low
> frequencies to keep the intelligibility constant.
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Re: K3 in WPX SSB with 2.7 roofer

mikerodgerske5gbc
In reply to this post by Dave Hachadorian-2
Just a thought,

On SSB, you guys should try using LO & HI cut instead of shift and width. You won't look back and it will probally sound better.

You can probably leave lo cut pretty much alone and vary hi cut. Roofing filters will come in automatically.

Try it.

73
Mike R



RIP- Mr 500.  STP's Andy Granatelli from racing fans everywhere.
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Loading Coils For Audio Transmission Lines

Jim Brown-10
In reply to this post by George Danner
On 3/31/2014 7:52 AM, George Danner wrote:
> One of the things that Bell Labs found in adding loading coils to phone
> lines (to reduce the high frequencies) was that in an audio system if you
> reduce the high frequencies then you needed to also reduce the low
> frequencies to keep the intelligibility constant. Since a phone system
> needed intelligibility above fidelity; Bell Labs just decreased the coupling
> capacitors to reduce the low end while using the line loading coils to
> reduce the high frequencies.

Sorry George, but that's not quite right. The attenuation, velocity
factor, and characteristic impedance of ALL transmission lines vary
drastically through the audio spectrum. All transmission lines behave to
some extent as a low pass filter (because attenuation increases with
frequency), and the variation in Vf causes the higher frequencies to
arrive before the lower frequencies. Loading coils were added to phone
lines to compensate for those variations. The result was to "flatten"
both the amplitude response and the time response in the audio passband,
then allow it to drop sharply above audio.

There's a tutorial discussion of this on my website. It was an appendix
to the materials I prepared for a 3-day "Hum, Buzz, and RFI" workshop
for audio professionals in 2005.

http://k9yc.com/TransLines-LowFreq.pdf

73, Jim K9YC
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Re: Loading Coils For Audio Transmission Lines

Eric Swartz - WA6HHQ
Administrator
Folks,  we're drifting OT. Please wind this thread down and then take it to
direct email if needed.

73,

Eric
List Moderator etc.
elecraft.com

On 3/31/2014 11:15 AM, Jim Brown wrote:
>
> Sorry George, but that's not quite right. The attenuation, velocity factor,
> and characteristic impedance of ALL transmission lines vary drastically
> through the audio spectrum. All transmission lines behave to some extent as a
> low pass filter (because attenuation increases with frequency), and the
> variation in Vf causes the higher frequencies to arrive before the lower
> frequencies. Loading coils were added to phone lines to compensate for those
> variations. The result was to "flatten" both the amplitude response and the
> time response in the audio passband, then allow it to drop sharply above audio.

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Re: K3 in WPX SSB with 2.7 roofer

Buck - k4ia
In reply to this post by George Danner
I have found that if I shift the passband I can still understand SSB
even though the DSP filter says it is only 1.1 khz wide. Try it and the
signal will be very clear once you hit the sweet spot.  I think this is
because the intelligence carrying portion of the voice is not
necessarily in the center of the passband.


Buck
k4ia

On 3/31/2014 10:52 AM, George Danner wrote:

> One of the things that Bell Labs found in adding loading coils to phone
> lines (to reduce the high frequencies) was that in an audio system if you
> reduce the high frequencies then you needed to also reduce the low
> frequencies to keep the intelligibility constant. Since a phone system
> needed intelligibility above fidelity; Bell Labs just decreased the coupling
> capacitors to reduce the low end while using the line loading coils to
> reduce the high frequencies.
>
> I tend to use lo-cut to improve "listen ability" when I cut the high end.
> I use a 1.8 kHz filter for a morning SSB net that has other nets 3 kHz away
> usually on both sides. Some of the transmitters on the adjacent frequencies
> can't fit in 5 kHz much less being 3 kHz away. The 1.8 kHz filter is the
> best solution - the filter skirts along with the DSP skirts help the most I
> can expect.
>
> I would recommend adjusting Hi-Cut for the interference and Lo-Cut for the
> best compromise on fidelity & intelligibility; if that switches in a tighter
> filter, then that might be needed.
>
> My 2 cents!
> 73
> George  AI4VZ
>
> -----Original Message-----
> From: Al
> For years I have heard folks state that 1.8 kHz is mandatory for SSB
> contesting... but I have never understood how one could put up with this
> narrow bandwidth for long. I need more information hitting my ears and am
> perfectly happy with letting the famous 'ear-brain' filter extract the
> maximum from that information.
>
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Re: Loading Coils For Audio Transmission Lines

ab2tc
In reply to this post by Eric Swartz - WA6HHQ
Hi Eric,

Forgive me, Eric, for adding yet another post to this long thread. Jim was very justified in correcting the erroneous information about the reason for introducing loading coils on long distance phone lines. His information is right on the money; the purpose was to improve the flatness within the audio passband, not to make it worse.

AB2TC - Knut

Eric Swartz - WA6HHQ, Elecraft wrote
Folks,  we're drifting OT. Please wind this thread down and then take it to
direct email if needed.

73,

Eric
List Moderator etc.
elecraft.com

On 3/31/2014 11:15 AM, Jim Brown wrote:
>
> Sorry George, but that's not quite right. The attenuation, velocity factor,
> and characteristic impedance of ALL transmission lines vary drastically
<snip>
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[K3] Roofing filters are misunderstood

alorona
In reply to this post by gm3sek
What determines the bandwidth you hear at the loudspeaker? It's not your roofing filter, despite a continuing notion that it is.
 
Dave Hachadorian's point in a post a few weeks ago was that you don't need a 1.8 kHz filter to get a 1.8 kHz bandwidth. You're free to set whatever bandwidth you want with any filter.

Before rigs had DSP we got used to the idea that your crystal filter sets your bandwidth. That's not true any more. It sets your *maximum* bandwidth. You then have the freedom to narrow and position a bandwidth arbitrarily using the DSP controls [SHIFT and WIDTH or HI and LO].


Here's a true-false quiz:

 
1. I'm a contester, so I need a 1.8 kHz roofing filter in the K3.
 
2. I should purchase the 400 Hz filter if I like to operate CW with bandwidths of 300 - 400 Hz.
 
3. For SSB, the 2.7 and 2.8 kHz filters are 'too wide'.
 
4. I have the 2.7 kHz filter installed, so for best results I should set my WIDTH control for a passband of 2.7 kHz.
 
5. I can use my 2.7 kHz filter in CW mode with my LO=0.30 and HI=0.50 (that is, BW=0.20).
 
 
The answers are:
 
1. False. You do not need a 1.8 kHz filter just to set the BW=1.80. A 2.7 kHz filter can serve well during a contest with a much narrower DSP bandwidth. Refer to Dave's original post.
2. False. You can set the CW bandwidth to 400 using any filter whose bandwidth is equal to or greater than 400.
3. False. This was Dave's point. You're free to have a 2.7 or 2.8 installed, yet set the WIDTH to 1.8, 1.5 or anything else you wish.
4. False. You don't need to restrict yourself to only that bandwidth. You can set it to a narrower value if you wish.
5. True. And you'll probably suffer no ill effects under most conditions.
 
Furthermore, the "but extremely strong signals will pump my hardware AGC" arguments are probably a bit overrated. Most folks, even before a strong station gets close enough to do that, will give up and leave the frequency because of the QRM, especially in the presence of transmitted phase noise or key clicks as has come up in more recent posts.

So then why have narrow roofing filters to choose from? To maximize the close-in dynamic range, which is important if you have large antennas in high-RF environments.
 
The vast majority of hams does not absolutely need really narrow roofing filters. It's wonderful that the K3 allows this, but it's certainly not mandatory, especially for casual operating.
 
Finally, note that if you received good training as a Novice with a poor, unselective receiver, you'll be able to copy right through any AGC pumping! It's the operator, more than the filters.

 
Al  W6LX
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Re: [K3] Roofing filters are misunderstood

David Gilbert

I completely agree with all of that except for the very last sentence.  
Clearly you've never used a 756Pro (first version) in a major CW
contest.  I can remember very loud stations 10 or 15 KHz away completely
desensing my receiver to the point that the station I was trying to copy
simply disappeared.  When I switched to the K3 the difference was
astounding.

73,
Dave   AB7E


On 5/11/2014 2:03 PM, Al Lorona wrote:

> What determines the bandwidth you hear at the loudspeaker? It's not your roofing filter, despite a continuing notion that it is.
>  
> Dave Hachadorian's point in a post a few weeks ago was that you don't need a 1.8 kHz filter to get a 1.8 kHz bandwidth. You're free to set whatever bandwidth you want with any filter.
>
> Before rigs had DSP we got used to the idea that your crystal filter sets your bandwidth. That's not true any more. It sets your *maximum* bandwidth. You then have the freedom to narrow and position a bandwidth arbitrarily using the DSP controls [SHIFT and WIDTH or HI and LO].
>
>
> Here's a true-false quiz:
>
>  
> 1. I'm a contester, so I need a 1.8 kHz roofing filter in the K3.
>  
> 2. I should purchase the 400 Hz filter if I like to operate CW with bandwidths of 300 - 400 Hz.
>  
> 3. For SSB, the 2.7 and 2.8 kHz filters are 'too wide'.
>  
> 4. I have the 2.7 kHz filter installed, so for best results I should set my WIDTH control for a passband of 2.7 kHz.
>  
> 5. I can use my 2.7 kHz filter in CW mode with my LO=0.30 and HI=0.50 (that is, BW=0.20).
>  
>  
> The answers are:
>  
> 1. False. You do not need a 1.8 kHz filter just to set the BW=1.80. A 2.7 kHz filter can serve well during a contest with a much narrower DSP bandwidth. Refer to Dave's original post.
> 2. False. You can set the CW bandwidth to 400 using any filter whose bandwidth is equal to or greater than 400.
> 3. False. This was Dave's point. You're free to have a 2.7 or 2.8 installed, yet set the WIDTH to 1.8, 1.5 or anything else you wish.
> 4. False. You don't need to restrict yourself to only that bandwidth. You can set it to a narrower value if you wish.
> 5. True. And you'll probably suffer no ill effects under most conditions.
>  
> Furthermore, the "but extremely strong signals will pump my hardware AGC" arguments are probably a bit overrated. Most folks, even before a strong station gets close enough to do that, will give up and leave the frequency because of the QRM, especially in the presence of transmitted phase noise or key clicks as has come up in more recent posts.
>
> So then why have narrow roofing filters to choose from? To maximize the close-in dynamic range, which is important if you have large antennas in high-RF environments.
>  
> The vast majority of hams does not absolutely need really narrow roofing filters. It's wonderful that the K3 allows this, but it's certainly not mandatory, especially for casual operating.
>  
> Finally, note that if you received good training as a Novice with a poor, unselective receiver, you'll be able to copy right through any AGC pumping! It's the operator, more than the filters.
>
>  
> Al  W6LX
> ______________________________________________________________
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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