K3 Filter Ring with Noise?

[Edwin Johnson]

I've had my K3, which I assembled, about a month, outfitted with 13kHz, 6kHz,
2.8kHz, and 400Hz filters. Thus far I've been exceptionally pleased with all
aspects of the rig. I've read with interest the audio discussions of this
group. There is one area in which I'm not totally satisfied, but this may be
due, partially, with my expectations of the rig.

When using CW on noisy bands, meaning the sort of atmospheric noise we often
are having now (NOT static crashes from storms), there appears to be an audio
product as the bandwidth is narrowed which is annoying to my ears, which
occurs both in speakers and phones. This is basically like a ringing of the
filters and especially evident as the passband is narrowed to 50-150Hz. This
phenomenon is not a problem in quiet conditions nor if the station is
especially strong, but can overpower a very weak station. (I'm using a pitch
of 600Hz for CW.)

(I've tried eliminating the 400Hz filter to make certain there isn't a
problem there, and all is well with that filter, apparently.)

I've been reducing RF gain and sometimes widening the passband to help
aleviate the problem, as well as using the NR. I've also modified the RX
equalizer from flat to settings of: #1=0, #2=3, #3=3, #4=-1, #5=-4, #6=-5,
#7=-8, #8=-10. Admittedly, part of these settings accomodate SSB to give,
what I hear, as a very pleasant sound for that mode. The primary ranges of
this noise are affected mostly by filters #4 and #5.

If the RX equalizer settings remain flat, hence 0, the sound is even more
annoying. But remember this is really only in noisy conditions, so my
hypothesis is that the chaotic sounds in the noise are mixing to produce
what sounds like a ringing of the filters. (So not necessarily the filters
actually ringing, as we think of it.) But this makes working very weak
signals very difficult without widening the passband quite a bit.

So, guess I would like to hear comments regarding this, as well as settings
and techniques people use to combat this phenomenon.

73 ...Edwin, KD5ZLB
____________________________________________________________
"Once you have flown, you will walk the earth with your eyes
turned skyward, for there you have been, there you long to
return."-da Vinci http://bellsouthpwp2.net/e/d/edwinljohnson
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[KK7P]

The K3 offers IIR and FIR filters for the narrowest bandwidths (100 Hz
and 50 Hz).

IIR may have some amount ringing.  The disable IIR, go to CONFIG:FLx ON
(or any other filter menu) and tap "7" on the keypad until you see IIR OFF.

The K3 uses fairly aggressive skirts on its filters.  We have talked
about implementing a "soft slope" which would make heavily filtered
noise a bit broader, but that has implications on dynamic range and
other issues that keep it from getting near the top of the list.

73,

Lyle KK7P

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[Steve Ellington]

Edwin
You did a wonderful job explaining exactly what I've noticed. To me, it
seems as if the noise mixes or blends with the cw and at times blips out cw
characters. This only happens when signals are weak and the band is noisy. I
recently came across an older TenTec Jupiter which has very wide skirts and
virtually no roofing filter (15kHz). The same noise has no effect on it. I
have done dozens of A/B test and the Jupiter always comes out the winner
until someone with an S9+30 signal gets within the roofing filter's
bandpass, like 6kHz away, and pumps the hardware AGC violently. Then it's
all over and I either switch back to the K3 and suffer poor copy or just
QRT.
I've tried all the EQ settings, NR (which helps) and AGC settings to no
avail. I don't consider this "ringing" since that's not what I'm hearing.

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "Edwin Johnson" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, August 08, 2009 3:34 PM
Subject: [Elecraft] K3 Filter Ring with Noise?

> I've had my K3, which I assembled, about a month, outfitted with 13kHz,
> 6kHz,
> 2.8kHz, and 400Hz filters. Thus far I've been exceptionally pleased with
> all
> aspects of the rig. I've read with interest the audio discussions of this
> group. There is one area in which I'm not totally satisfied, but this may
> be
> due, partially, with my expectations of the rig.
>
> When using CW on noisy bands, meaning the sort of atmospheric noise we
> often
> are having now (NOT static crashes from storms), there appears to be an
> audio
> product as the bandwidth is narrowed which is annoying to my ears, which
> occurs both in speakers and phones. This is basically like a ringing of
> the
> filters and especially evident as the passband is narrowed to 50-150Hz.
> This
> phenomenon is not a problem in quiet conditions nor if the station is
> especially strong, but can overpower a very weak station. (I'm using a
> pitch
> of 600Hz for CW.)
>
> (I've tried eliminating the 400Hz filter to make certain there isn't a
> problem there, and all is well with that filter, apparently.)
>
> I've been reducing RF gain and sometimes widening the passband to help
> aleviate the problem, as well as using the NR. I've also modified the RX
> equalizer from flat to settings of: #1=0, #2=3, #3=3, #4=-1, #5=-4, #6=-5,
> #7=-8, #8=-10. Admittedly, part of these settings accomodate SSB to give,
> what I hear, as a very pleasant sound for that mode. The primary ranges of
> this noise are affected mostly by filters #4 and #5.
>
> If the RX equalizer settings remain flat, hence 0, the sound is even more
> annoying. But remember this is really only in noisy conditions, so my
> hypothesis is that the chaotic sounds in the noise are mixing to produce
> what sounds like a ringing of the filters. (So not necessarily the filters
> actually ringing, as we think of it.) But this makes working very weak
> signals very difficult without widening the passband quite a bit.
>
> So, guess I would like to hear comments regarding this, as well as
> settings
> and techniques people use to combat this phenomenon.
>
> 73 ...Edwin, KD5ZLB
> ____________________________________________________________
> "Once you have flown, you will walk the earth with your eyes
> turned skyward, for there you have been, there you long to
> return."-da Vinci http://bellsouthpwp2.net/e/d/edwinljohnson
> ______________________________________________________________
> 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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[Joe Subich, W4TV-4]

> You did a wonderful job explaining exactly what I've noticed.
> To me, it seems as if the noise mixes or blends with the cw
> and at times blips out cw characters. This only happens when
> signals are weak and the band is noisy.

What you are describing is not true filter 'ringing' but the
effect of band limited noise.  Even though the noise is fairly
"random" it is confined in a narrow range and is close to the
desired signal.  

Keeping the filter wider may be somewhat counterintuitive in
noisy conditions but it helps in a couple ways ... first it
spreads the noise power out and allows the desired signal to
appear somewhat stronger than the "random" noise.  Second if
you use a lower center frequency the noise is spread over a
wider percentage bandwidth and a larger portion of the noise
is 'far enough' away from the desired signal to allow the
ear-brain DSP system to work more effectively.

> I've tried all the EQ settings, NR (which helps) and AGC
> settings to no avail. I don't consider this "ringing" since
> that's not what I'm hearing.

Try a lower FC and slightly wider filters.  Also give the
Dual PB filter a try.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Steve Ellington
> Sent: Saturday, August 08, 2009 9:32 PM
> To: Edwin Johnson; [hidden email]
> Subject: Re: [Elecraft] K3 Filter Ring with Noise?
>
>
> Edwin
> You did a wonderful job explaining exactly what I've noticed.
> To me, it
> seems as if the noise mixes or blends with the cw and at
> times blips out cw
> characters. This only happens when signals are weak and the
> band is noisy. I
> recently came across an older TenTec Jupiter which has very
> wide skirts and
> virtually no roofing filter (15kHz). The same noise has no
> effect on it. I
> have done dozens of A/B test and the Jupiter always comes out
> the winner
> until someone with an S9+30 signal gets within the roofing filter's
> bandpass, like 6kHz away, and pumps the hardware AGC
> violently. Then it's
> all over and I either switch back to the K3 and suffer poor
> copy or just
> QRT.
> I've tried all the EQ settings, NR (which helps) and AGC
> settings to no
> avail. I don't consider this "ringing" since that's not what
> I'm hearing.
>
> Steve
> N4LQ
> [hidden email]
> ----- Original Message -----
> From: "Edwin Johnson" <[hidden email]>
> To: <[hidden email]>
> Sent: Saturday, August 08, 2009 3:34 PM
> Subject: [Elecraft] K3 Filter Ring with Noise?
>
>
> > I've had my K3, which I assembled, about a month, outfitted with
> > 13kHz,
> > 6kHz,
> > 2.8kHz, and 400Hz filters. Thus far I've been exceptionally
> pleased with
> > all
> > aspects of the rig. I've read with interest the audio
> discussions of this
> > group. There is one area in which I'm not totally
> satisfied, but this may
> > be
> > due, partially, with my expectations of the rig.
> >
> > When using CW on noisy bands, meaning the sort of
> atmospheric noise we
> > often
> > are having now (NOT static crashes from storms), there
> appears to be an
> > audio
> > product as the bandwidth is narrowed which is annoying to
> my ears, which
> > occurs both in speakers and phones. This is basically like
> a ringing of
> > the
> > filters and especially evident as the passband is narrowed
> to 50-150Hz.
> > This
> > phenomenon is not a problem in quiet conditions nor if the
> station is
> > especially strong, but can overpower a very weak station.
> (I'm using a
> > pitch
> > of 600Hz for CW.)
> >
> > (I've tried eliminating the 400Hz filter to make certain
> there isn't a
> > problem there, and all is well with that filter, apparently.)
> >
> > I've been reducing RF gain and sometimes widening the
> passband to help
> > aleviate the problem, as well as using the NR. I've also
> modified the
> > RX equalizer from flat to settings of: #1=0, #2=3, #3=3,
> #4=-1, #5=-4,
> > #6=-5, #7=-8, #8=-10. Admittedly, part of these settings accomodate
> > SSB to give, what I hear, as a very pleasant sound for that
> mode. The
> > primary ranges of this noise are affected mostly by filters
> #4 and #5.
> >
> > If the RX equalizer settings remain flat, hence 0, the
> sound is even
> > more annoying. But remember this is really only in noisy
> conditions,
> > so my hypothesis is that the chaotic sounds in the noise
> are mixing to
> > produce what sounds like a ringing of the filters. (So not
> necessarily
> > the filters actually ringing, as we think of it.) But this makes
> > working very weak signals very difficult without widening
> the passband
> > quite a bit.
> >
> > So, guess I would like to hear comments regarding this, as well as
> > settings
> > and techniques people use to combat this phenomenon.
> >
> > 73 ...Edwin, KD5ZLB
> > ____________________________________________________________
> > "Once you have flown, you will walk the earth with your eyes turned
> > skyward, for there you have been, there you long to
> return."-da Vinci
> > http://bellsouthpwp2.net/e/d/edwinljohnson
> > ______________________________________________________________
> > 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
>
> ______________________________________________________________
> 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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[Brett Howard]

I'd never had a rig capable of going lower than 500Hz till I got the K3
and really found myself quite annoyed at times when the noise was high
and I really necked the filter down.  Its taken me time to figure all
these things out but Joe really has some great tips here and has done an
excellent job explaining why these things work.  I also find that use of
a lower FC makes the noise sit a little better with me as the noise is
more subdued and not as piercing.  

One thing to try is to turn the bandwidth down to around 200Hz and find
a quiet spot on the band then adjust your pitch up and down and listen
to the band noise in a few places to see what you prefer based on the
noise rather than the pitch.  Then see if you can live w/ that pitch.

I liked Joe's comment about it being spaced over more bandwidth.  Thats
an interesting thought but based on the whole logarithmic scaling stuff
it does make sense.

I find the dualPB filter is nice but I kinda wish I could adjust the
size of my focus filter as well as the outer skirts.  I'd even be ok if
it was just a menu setting for the size of my focus filter.  That would
be something I'd be sticking on a PF button and I'd then use the dualPB
more often.

~Brett

On Sat, 2009-08-08 at 23:42 -0400, Joe Subich, W4TV wrote:

>
> > You did a wonderful job explaining exactly what I've noticed.
> > To me, it seems as if the noise mixes or blends with the cw
> > and at times blips out cw characters. This only happens when
> > signals are weak and the band is noisy.
>
> What you are describing is not true filter 'ringing' but the
> effect of band limited noise.  Even though the noise is fairly
> "random" it is confined in a narrow range and is close to the
> desired signal.  
>
> Keeping the filter wider may be somewhat counterintuitive in
> noisy conditions but it helps in a couple ways ... first it
> spreads the noise power out and allows the desired signal to
> appear somewhat stronger than the "random" noise.  Second if
> you use a lower center frequency the noise is spread over a
> wider percentage bandwidth and a larger portion of the noise
> is 'far enough' away from the desired signal to allow the
> ear-brain DSP system to work more effectively.
>
> > I've tried all the EQ settings, NR (which helps) and AGC
> > settings to no avail. I don't consider this "ringing" since
> > that's not what I'm hearing.
>
> Try a lower FC and slightly wider filters.  Also give the
> Dual PB filter a try.
>
> 73,
>
>    ... Joe, W4TV
>  
>
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Steve Ellington
> > Sent: Saturday, August 08, 2009 9:32 PM
> > To: Edwin Johnson; [hidden email]
> > Subject: Re: [Elecraft] K3 Filter Ring with Noise?
> >
> >
> > Edwin
> > You did a wonderful job explaining exactly what I've noticed.
> > To me, it
> > seems as if the noise mixes or blends with the cw and at
> > times blips out cw
> > characters. This only happens when signals are weak and the
> > band is noisy. I
> > recently came across an older TenTec Jupiter which has very
> > wide skirts and
> > virtually no roofing filter (15kHz). The same noise has no
> > effect on it. I
> > have done dozens of A/B test and the Jupiter always comes out
> > the winner
> > until someone with an S9+30 signal gets within the roofing filter's
> > bandpass, like 6kHz away, and pumps the hardware AGC
> > violently. Then it's
> > all over and I either switch back to the K3 and suffer poor
> > copy or just
> > QRT.
> > I've tried all the EQ settings, NR (which helps) and AGC
> > settings to no
> > avail. I don't consider this "ringing" since that's not what
> > I'm hearing.
> >
> > Steve
> > N4LQ
> > [hidden email]
> > ----- Original Message -----
> > From: "Edwin Johnson" <[hidden email]>
> > To: <[hidden email]>
> > Sent: Saturday, August 08, 2009 3:34 PM
> > Subject: [Elecraft] K3 Filter Ring with Noise?
> >
> >
> > > I've had my K3, which I assembled, about a month, outfitted with
> > > 13kHz,
> > > 6kHz,
> > > 2.8kHz, and 400Hz filters. Thus far I've been exceptionally
> > pleased with
> > > all
> > > aspects of the rig. I've read with interest the audio
> > discussions of this
> > > group. There is one area in which I'm not totally
> > satisfied, but this may
> > > be
> > > due, partially, with my expectations of the rig.
> > >
> > > When using CW on noisy bands, meaning the sort of
> > atmospheric noise we
> > > often
> > > are having now (NOT static crashes from storms), there
> > appears to be an
> > > audio
> > > product as the bandwidth is narrowed which is annoying to
> > my ears, which
> > > occurs both in speakers and phones. This is basically like
> > a ringing of
> > > the
> > > filters and especially evident as the passband is narrowed
> > to 50-150Hz.
> > > This
> > > phenomenon is not a problem in quiet conditions nor if the
> > station is
> > > especially strong, but can overpower a very weak station.
> > (I'm using a
> > > pitch
> > > of 600Hz for CW.)
> > >
> > > (I've tried eliminating the 400Hz filter to make certain
> > there isn't a
> > > problem there, and all is well with that filter, apparently.)
> > >
> > > I've been reducing RF gain and sometimes widening the
> > passband to help
> > > aleviate the problem, as well as using the NR. I've also
> > modified the
> > > RX equalizer from flat to settings of: #1=0, #2=3, #3=3,
> > #4=-1, #5=-4,
> > > #6=-5, #7=-8, #8=-10. Admittedly, part of these settings accomodate
> > > SSB to give, what I hear, as a very pleasant sound for that
> > mode. The
> > > primary ranges of this noise are affected mostly by filters
> > #4 and #5.
> > >
> > > If the RX equalizer settings remain flat, hence 0, the
> > sound is even
> > > more annoying. But remember this is really only in noisy
> > conditions,
> > > so my hypothesis is that the chaotic sounds in the noise
> > are mixing to
> > > produce what sounds like a ringing of the filters. (So not
> > necessarily
> > > the filters actually ringing, as we think of it.) But this makes
> > > working very weak signals very difficult without widening
> > the passband
> > > quite a bit.
> > >
> > > So, guess I would like to hear comments regarding this, as well as
> > > settings
> > > and techniques people use to combat this phenomenon.
> > >
> > > 73 ...Edwin, KD5ZLB
> > > ____________________________________________________________
> > > "Once you have flown, you will walk the earth with your eyes turned
> > > skyward, for there you have been, there you long to
> > return."-da Vinci
> > > http://bellsouthpwp2.net/e/d/edwinljohnson
> > > ______________________________________________________________
> > > 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
> >
> > ______________________________________________________________
> > 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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[Steve Ellington]

Normally I would agree with all these suggestions that help us hear CW under
noisy conditions however I'm convinced that there is simply nothing there to
hear. Let's say we are listening to a weak CW signal on a noisy band and the
station sends the word T H E. What I hear is T S E because just at the wrong
instant, the noise "blipped the dit". (new techy term). I'm not talking
about huge QRN peaks of S9+30 or anything....Just a bit of atmospheric noise
that's producing some S meter fluctuation and just enough noise to be
annoying to listen to through a narrow CW filter but almost soothing when
heard through a wide SSB filter.
Listening to the same noise on the Jupiter is much less grating to the ears
even when using the 150Hz filter setting. BTW: Edwin, who originally posted
this question, tells me that his friend also has a Jupiter and although the
receiver isn't quiet as good, it handles that type of noise aspect better.
What's the deal with Jupiters? You can't even turn the AGC off!
Typically I blame AGC for such things but I can turn AGC off and still get
that blipping effect. The worst receiver I ever saw for this phenomena was
the TS-570. That thing would blip out entire letters as if it were punching
holes in the transmitted text. Nice little rig but not for copying CW in
noise!
I believe I'll play around with some audio software and try to see what I'm
hearing or what I'm not hearing. It could be some kind of mental weakness!

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "Brett Howard" <[hidden email]>
To: <[hidden email]>
Cc: "'Steve Ellington'" <[hidden email]>; "'Edwin Johnson'"
<[hidden email]>; <[hidden email]>
Sent: Sunday, August 09, 2009 1:35 AM
Subject: Re: [Elecraft] K3 Filter Ring with Noise?

> I'd never had a rig capable of going lower than 500Hz till I got the K3
> and really found myself quite annoyed at times when the noise was high
> and I really necked the filter down.  Its taken me time to figure all
> these things out but Joe really has some great tips here and has done an
> excellent job explaining why these things work.  I also find that use of
> a lower FC makes the noise sit a little better with me as the noise is
> more subdued and not as piercing.
>
> One thing to try is to turn the bandwidth down to around 200Hz and find
> a quiet spot on the band then adjust your pitch up and down and listen
> to the band noise in a few places to see what you prefer based on the
> noise rather than the pitch.  Then see if you can live w/ that pitch.
>
> I liked Joe's comment about it being spaced over more bandwidth.  Thats
> an interesting thought but based on the whole logarithmic scaling stuff
> it does make sense.
>
> I find the dualPB filter is nice but I kinda wish I could adjust the
> size of my focus filter as well as the outer skirts.  I'd even be ok if
> it was just a menu setting for the size of my focus filter.  That would
> be something I'd be sticking on a PF button and I'd then use the dualPB
> more often.
>
> ~Brett
>
> On Sat, 2009-08-08 at 23:42 -0400, Joe Subich, W4TV wrote:
>>
>> > You did a wonderful job explaining exactly what I've noticed.
>> > To me, it seems as if the noise mixes or blends with the cw
>> > and at times blips out cw characters. This only happens when
>> > signals are weak and the band is noisy.
>>
>> What you are describing is not true filter 'ringing' but the
>> effect of band limited noise.  Even though the noise is fairly
>> "random" it is confined in a narrow range and is close to the
>> desired signal.
>>
>> Keeping the filter wider may be somewhat counterintuitive in
>> noisy conditions but it helps in a couple ways ... first it
>> spreads the noise power out and allows the desired signal to
>> appear somewhat stronger than the "random" noise.  Second if
>> you use a lower center frequency the noise is spread over a
>> wider percentage bandwidth and a larger portion of the noise
>> is 'far enough' away from the desired signal to allow the
>> ear-brain DSP system to work more effectively.
>>
>> > I've tried all the EQ settings, NR (which helps) and AGC
>> > settings to no avail. I don't consider this "ringing" since
>> > that's not what I'm hearing.
>>
>> Try a lower FC and slightly wider filters.  Also give the
>> Dual PB filter a try.
>>
>> 73,
>>
>>    ... Joe, W4TV
>>
>>
>>
>> > -----Original Message-----
>> > From: [hidden email]
>> > [mailto:[hidden email]] On Behalf Of Steve Ellington
>> > Sent: Saturday, August 08, 2009 9:32 PM
>> > To: Edwin Johnson; [hidden email]
>> > Subject: Re: [Elecraft] K3 Filter Ring with Noise?
>> >
>> >
>> > Edwin
>> > You did a wonderful job explaining exactly what I've noticed.
>> > To me, it
>> > seems as if the noise mixes or blends with the cw and at
>> > times blips out cw
>> > characters. This only happens when signals are weak and the
>> > band is noisy. I
>> > recently came across an older TenTec Jupiter which has very
>> > wide skirts and
>> > virtually no roofing filter (15kHz). The same noise has no
>> > effect on it. I
>> > have done dozens of A/B test and the Jupiter always comes out
>> > the winner
>> > until someone with an S9+30 signal gets within the roofing filter's
>> > bandpass, like 6kHz away, and pumps the hardware AGC
>> > violently. Then it's
>> > all over and I either switch back to the K3 and suffer poor
>> > copy or just
>> > QRT.
>> > I've tried all the EQ settings, NR (which helps) and AGC
>> > settings to no
>> > avail. I don't consider this "ringing" since that's not what
>> > I'm hearing.
>> >
>> > Steve
>> > N4LQ
>> > [hidden email]
>> > ----- Original Message -----
>> > From: "Edwin Johnson" <[hidden email]>
>> > To: <[hidden email]>
>> > Sent: Saturday, August 08, 2009 3:34 PM
>> > Subject: [Elecraft] K3 Filter Ring with Noise?
>> >
>> >
>> > > I've had my K3, which I assembled, about a month, outfitted with
>> > > 13kHz,
>> > > 6kHz,
>> > > 2.8kHz, and 400Hz filters. Thus far I've been exceptionally
>> > pleased with
>> > > all
>> > > aspects of the rig. I've read with interest the audio
>> > discussions of this
>> > > group. There is one area in which I'm not totally
>> > satisfied, but this may
>> > > be
>> > > due, partially, with my expectations of the rig.
>> > >
>> > > When using CW on noisy bands, meaning the sort of
>> > atmospheric noise we
>> > > often
>> > > are having now (NOT static crashes from storms), there
>> > appears to be an
>> > > audio
>> > > product as the bandwidth is narrowed which is annoying to
>> > my ears, which
>> > > occurs both in speakers and phones. This is basically like
>> > a ringing of
>> > > the
>> > > filters and especially evident as the passband is narrowed
>> > to 50-150Hz.
>> > > This
>> > > phenomenon is not a problem in quiet conditions nor if the
>> > station is
>> > > especially strong, but can overpower a very weak station.
>> > (I'm using a
>> > > pitch
>> > > of 600Hz for CW.)
>> > >
>> > > (I've tried eliminating the 400Hz filter to make certain
>> > there isn't a
>> > > problem there, and all is well with that filter, apparently.)
>> > >
>> > > I've been reducing RF gain and sometimes widening the
>> > passband to help
>> > > aleviate the problem, as well as using the NR. I've also
>> > modified the
>> > > RX equalizer from flat to settings of: #1=0, #2=3, #3=3,
>> > #4=-1, #5=-4,
>> > > #6=-5, #7=-8, #8=-10. Admittedly, part of these settings accomodate
>> > > SSB to give, what I hear, as a very pleasant sound for that
>> > mode. The
>> > > primary ranges of this noise are affected mostly by filters
>> > #4 and #5.
>> > >
>> > > If the RX equalizer settings remain flat, hence 0, the
>> > sound is even
>> > > more annoying. But remember this is really only in noisy
>> > conditions,
>> > > so my hypothesis is that the chaotic sounds in the noise
>> > are mixing to
>> > > produce what sounds like a ringing of the filters. (So not
>> > necessarily
>> > > the filters actually ringing, as we think of it.) But this makes
>> > > working very weak signals very difficult without widening
>> > the passband
>> > > quite a bit.
>> > >
>> > > So, guess I would like to hear comments regarding this, as well as
>> > > settings
>> > > and techniques people use to combat this phenomenon.
>> > >
>> > > 73 ...Edwin, KD5ZLB
>> > > ____________________________________________________________
>> > > "Once you have flown, you will walk the earth with your eyes turned
>> > > skyward, for there you have been, there you long to
>> > return."-da Vinci
>> > > http://bellsouthpwp2.net/e/d/edwinljohnson
>> > > ______________________________________________________________
>> > > 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
>> >
>> > ______________________________________________________________
>> > 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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>

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[AC7AC]

CONTENTS DELETED

The author has deleted this message.

[Guy, K2AV]

The answer to so-called K3 "ringing" at 50 Hz is called 100 Hz.

Aggressive skirts are what allows me to hear what I want to instead of what
is just a little off my frequency.  You're not going to get me to say "yea,
rah" for any lessening of aggressive skirts.

As best as I can tell, the softening of CW signals using IIR at 50 Hz is due
to normal keying artifacts being peeled off by the skirts.  Yea, rah to
that.  While it's peeling off the artifacts that make CW sound sharp, it's
more so peeling off the interference just a little bit farther away and
significantly increasing my wanted to unwanted signal ratio.

** Please tell me you are not going to throw that away because someone wants
their received CW to sound "broad" even though their selectivity is set to
extreme sharp. **

I would characterize the FIR as 70 and 115 Hz, and the mild increase in
"sharpness" of a CW signal as simply allowing just a bit more of the
make-break artifacts getting through due to what amounts to increased
bandwidth by the choice of shape at the top.

I can make *real* ringing on an old RX with too high a Q in the analog
crystal filter circuit. The kind that takes entire dit lengths to
decay. Those who think the K3 is ringing have obviously never heard that or
it would never occur to them to call hearing only 50 Hz of background as
ringing. Ringing is basically an analog issue unless the digital processing
unwittingly duplicates it. I use the K3's 50 Hz IIR all the time and I don't
think it rings.

If you think that the audio from the 50 Hz width sounds "pinched" then
everything is working, including your ears.  50 Hz is the DEFINITION of
pinched bandwidth.

Some folks do better at deciphering CW with wider bandwidth.  That is not a
receiver issue, just a particular ham's personal arrangement of brain cells.


73, Guy.

On Sat, Aug 8, 2009 at 8:24 PM, Lyle Johnson <[hidden email]> wrote:

> The K3 offers IIR and FIR filters for the narrowest bandwidths (100 Hz
> and 50 Hz).
>
> IIR may have some amount ringing.  The disable IIR, go to CONFIG:FLx ON
> (or any other filter menu) and tap "7" on the keypad until you see IIR OFF.
>
> The K3 uses fairly aggressive skirts on its filters.  We have talked
> about implementing a "soft slope" which would make heavily filtered
> noise a bit broader, but that has implications on dynamic range and
> other issues that keep it from getting near the top of the list.
>
> 73,
>
> Lyle KK7P
>
> ______________________________________________________________
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--
73, Guy  K2AV
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[Jim Brown-10]

On Sat, 08 Aug 2009 22:35:42 -0700, Brett Howard wrote:

>I liked Joe's comment about it being spaced over more bandwidth.  Thats
>an interesting thought but based on the whole logarithmic scaling stuff
>it does make sense.

While Joe is rarely wrong, he is wrong about this, and Lyle is right. In
nature (that is, at the input of your K3) the noise voltage is spread out
over frequency. When you narrow down the IF, you receive less of that noise.
As you widen the filter, the noise rises in direct proportion to the
bandwidth. So when you narrow the filters, you are improving the signal to
noise ratio.

The fundamental problem of narrowing the filter is a psychoacoustic one --
that is, the ability of the human ear/brain being able to separate signal
from noise. When you narrow the filters, the only noise you hear has the same
frequency components as the signal, so the brain is trying to separate signal
and noise that are very close to the same pitch.

BUT -- human hearing is logarithmic, both in pitch and amplitude. Our ability
to separate frequencies is based on proportional differences in frequency, so
setting the CW pitch to a lower frequency gives the ear greater ability to
separate signals (or signal and noise) that are close together in frequency.
That is, if the pitch is set to 500 Hz, 100 Hz bandwidth is 20% of the signal
frequency, whereas at a pitch of 1 kHz, 100 Hz bandwidth is only 10%. I know
some really good CW operators (N6RO is one) who regularly work at pitches
below 500 Hz for this reason.

BTW -- I know exactly what the original poster of this thread is talking
about -- I really suffered from it when I lived in Chicago.

73,

Jim Brown K9YC


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[Joe Subich, W4TV-4]

Jim,

> While Joe is rarely wrong, he is wrong about this, and Lyle
> is right. In nature (that is, at the input of your K3) the
> noise voltage is spread out over frequency. When you narrow
> down the IF, you receive less of that noise.  As you widen
> the filter, the noise rises in direct proportion to the
> bandwidth. So when you narrow the filters, you are improving
> the signal to noise ratio.

You miss the point ... while there may be less noise power at
RF (or IF) as you narrow the filter, humans listen at AF.  

At AF and generally increase the audio gain - with a combination
of AF Gain, RF Gain and AGC - to maintain a constant "desired"
signal level in their ears.  When the lower noise power is
amplified more - and concentrated closer to the desired signal
- when the desired signal is at or even slightly below the
average noise level a narrow filter makes it MORE difficult
to copy the weak signal because the noise begins to become
coherent and sound more like a signal.  

Haven't you ever noticed it is sometimes easier to copy a weak
signal in the presence of noise if you turn down the AF gain
until the noise itself is barely at the threshold of hearing?
This is much the same thing ... it's a psychoacoustic phenomenon
that is difficult to explain until you've experienced it.

However, the ear-brain system is relatively good at finding
a coherent signal in a mass of incoherent noise but once
the noise begins to become coherent (band limited and narrow)
it is like adding discrete interfering signals.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Sunday, August 09, 2009 1:33 PM
> To: Elecraft List
> Subject: Re: [Elecraft] K3 Filter Ring with Noise?
>
>
> On Sat, 08 Aug 2009 22:35:42 -0700, Brett Howard wrote:
>
> >I liked Joe's comment about it being spaced over more
> bandwidth.  Thats
> >an interesting thought but based on the whole logarithmic
> scaling stuff
> >it does make sense.
>
> While Joe is rarely wrong, he is wrong about this, and Lyle
> is right. In
> nature (that is, at the input of your K3) the noise voltage
> is spread out
> over frequency. When you narrow down the IF, you receive less
> of that noise.
> As you widen the filter, the noise rises in direct proportion to the
> bandwidth. So when you narrow the filters, you are improving
> the signal to
> noise ratio.
>
> The fundamental problem of narrowing the filter is a
> psychoacoustic one --
> that is, the ability of the human ear/brain being able to
> separate signal
> from noise. When you narrow the filters, the only noise you
> hear has the same
> frequency components as the signal, so the brain is trying to
> separate signal
> and noise that are very close to the same pitch.
>
> BUT -- human hearing is logarithmic, both in pitch and
> amplitude. Our ability
> to separate frequencies is based on proportional differences
> in frequency, so
> setting the CW pitch to a lower frequency gives the ear
> greater ability to
> separate signals (or signal and noise) that are close
> together in frequency.
> That is, if the pitch is set to 500 Hz, 100 Hz bandwidth is
> 20% of the signal
> frequency, whereas at a pitch of 1 kHz, 100 Hz bandwidth is
> only 10%. I know
> some really good CW operators (N6RO is one) who regularly
> work at pitches
> below 500 Hz for this reason.
>
> BTW -- I know exactly what the original poster of this thread
> is talking
> about -- I really suffered from it when I lived in Chicago.
>
> 73,
>
> Jim Brown K9YC
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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[Brett Howard]

I find that placing a low pass filter in the audio really softens things
up and fixes the issues that you're talking about here.

~Brett


On Sun, 2009-08-09 at 09:04 -0400, Steve Ellington wrote:

> Normally I would agree with all these suggestions that help us hear CW under
> noisy conditions however I'm convinced that there is simply nothing there to
> hear. Let's say we are listening to a weak CW signal on a noisy band and the
> station sends the word T H E. What I hear is T S E because just at the wrong
> instant, the noise "blipped the dit". (new techy term). I'm not talking
> about huge QRN peaks of S9+30 or anything....Just a bit of atmospheric noise
> that's producing some S meter fluctuation and just enough noise to be
> annoying to listen to through a narrow CW filter but almost soothing when
> heard through a wide SSB filter.
> Listening to the same noise on the Jupiter is much less grating to the ears
> even when using the 150Hz filter setting. BTW: Edwin, who originally posted
> this question, tells me that his friend also has a Jupiter and although the
> receiver isn't quiet as good, it handles that type of noise aspect better.
> What's the deal with Jupiters? You can't even turn the AGC off!
> Typically I blame AGC for such things but I can turn AGC off and still get
> that blipping effect. The worst receiver I ever saw for this phenomena was
> the TS-570. That thing would blip out entire letters as if it were punching
> holes in the transmitted text. Nice little rig but not for copying CW in
> noise!
> I believe I'll play around with some audio software and try to see what I'm
> hearing or what I'm not hearing. It could be some kind of mental weakness!
>
> Steve
> N4LQ
> [hidden email]
> ----- Original Message -----
> From: "Brett Howard" <[hidden email]>
> To: <[hidden email]>
> Cc: "'Steve Ellington'" <[hidden email]>; "'Edwin Johnson'"
> <[hidden email]>; <[hidden email]>
> Sent: Sunday, August 09, 2009 1:35 AM
> Subject: Re: [Elecraft] K3 Filter Ring with Noise?
>
>
> > I'd never had a rig capable of going lower than 500Hz till I got the K3
> > and really found myself quite annoyed at times when the noise was high
> > and I really necked the filter down.  Its taken me time to figure all
> > these things out but Joe really has some great tips here and has done an
> > excellent job explaining why these things work.  I also find that use of
> > a lower FC makes the noise sit a little better with me as the noise is
> > more subdued and not as piercing.
> >
> > One thing to try is to turn the bandwidth down to around 200Hz and find
> > a quiet spot on the band then adjust your pitch up and down and listen
> > to the band noise in a few places to see what you prefer based on the
> > noise rather than the pitch.  Then see if you can live w/ that pitch.
> >
> > I liked Joe's comment about it being spaced over more bandwidth.  Thats
> > an interesting thought but based on the whole logarithmic scaling stuff
> > it does make sense.
> >
> > I find the dualPB filter is nice but I kinda wish I could adjust the
> > size of my focus filter as well as the outer skirts.  I'd even be ok if
> > it was just a menu setting for the size of my focus filter.  That would
> > be something I'd be sticking on a PF button and I'd then use the dualPB
> > more often.
> >
> > ~Brett
> >
> > On Sat, 2009-08-08 at 23:42 -0400, Joe Subich, W4TV wrote:
> >>
> >> > You did a wonderful job explaining exactly what I've noticed.
> >> > To me, it seems as if the noise mixes or blends with the cw
> >> > and at times blips out cw characters. This only happens when
> >> > signals are weak and the band is noisy.
> >>
> >> What you are describing is not true filter 'ringing' but the
> >> effect of band limited noise.  Even though the noise is fairly
> >> "random" it is confined in a narrow range and is close to the
> >> desired signal.
> >>
> >> Keeping the filter wider may be somewhat counterintuitive in
> >> noisy conditions but it helps in a couple ways ... first it
> >> spreads the noise power out and allows the desired signal to
> >> appear somewhat stronger than the "random" noise.  Second if
> >> you use a lower center frequency the noise is spread over a
> >> wider percentage bandwidth and a larger portion of the noise
> >> is 'far enough' away from the desired signal to allow the
> >> ear-brain DSP system to work more effectively.
> >>
> >> > I've tried all the EQ settings, NR (which helps) and AGC
> >> > settings to no avail. I don't consider this "ringing" since
> >> > that's not what I'm hearing.
> >>
> >> Try a lower FC and slightly wider filters.  Also give the
> >> Dual PB filter a try.
> >>
> >> 73,
> >>
> >>    ... Joe, W4TV
> >>
> >>
> >>
> >> > -----Original Message-----
> >> > From: [hidden email]
> >> > [mailto:[hidden email]] On Behalf Of Steve Ellington
> >> > Sent: Saturday, August 08, 2009 9:32 PM
> >> > To: Edwin Johnson; [hidden email]
> >> > Subject: Re: [Elecraft] K3 Filter Ring with Noise?
> >> >
> >> >
> >> > Edwin
> >> > You did a wonderful job explaining exactly what I've noticed.
> >> > To me, it
> >> > seems as if the noise mixes or blends with the cw and at
> >> > times blips out cw
> >> > characters. This only happens when signals are weak and the
> >> > band is noisy. I
> >> > recently came across an older TenTec Jupiter which has very
> >> > wide skirts and
> >> > virtually no roofing filter (15kHz). The same noise has no
> >> > effect on it. I
> >> > have done dozens of A/B test and the Jupiter always comes out
> >> > the winner
> >> > until someone with an S9+30 signal gets within the roofing filter's
> >> > bandpass, like 6kHz away, and pumps the hardware AGC
> >> > violently. Then it's
> >> > all over and I either switch back to the K3 and suffer poor
> >> > copy or just
> >> > QRT.
> >> > I've tried all the EQ settings, NR (which helps) and AGC
> >> > settings to no
> >> > avail. I don't consider this "ringing" since that's not what
> >> > I'm hearing.
> >> >
> >> > Steve
> >> > N4LQ
> >> > [hidden email]
> >> > ----- Original Message -----
> >> > From: "Edwin Johnson" <[hidden email]>
> >> > To: <[hidden email]>
> >> > Sent: Saturday, August 08, 2009 3:34 PM
> >> > Subject: [Elecraft] K3 Filter Ring with Noise?
> >> >
> >> >
> >> > > I've had my K3, which I assembled, about a month, outfitted with
> >> > > 13kHz,
> >> > > 6kHz,
> >> > > 2.8kHz, and 400Hz filters. Thus far I've been exceptionally
> >> > pleased with
> >> > > all
> >> > > aspects of the rig. I've read with interest the audio
> >> > discussions of this
> >> > > group. There is one area in which I'm not totally
> >> > satisfied, but this may
> >> > > be
> >> > > due, partially, with my expectations of the rig.
> >> > >
> >> > > When using CW on noisy bands, meaning the sort of
> >> > atmospheric noise we
> >> > > often
> >> > > are having now (NOT static crashes from storms), there
> >> > appears to be an
> >> > > audio
> >> > > product as the bandwidth is narrowed which is annoying to
> >> > my ears, which
> >> > > occurs both in speakers and phones. This is basically like
> >> > a ringing of
> >> > > the
> >> > > filters and especially evident as the passband is narrowed
> >> > to 50-150Hz.
> >> > > This
> >> > > phenomenon is not a problem in quiet conditions nor if the
> >> > station is
> >> > > especially strong, but can overpower a very weak station.
> >> > (I'm using a
> >> > > pitch
> >> > > of 600Hz for CW.)
> >> > >
> >> > > (I've tried eliminating the 400Hz filter to make certain
> >> > there isn't a
> >> > > problem there, and all is well with that filter, apparently.)
> >> > >
> >> > > I've been reducing RF gain and sometimes widening the
> >> > passband to help
> >> > > aleviate the problem, as well as using the NR. I've also
> >> > modified the
> >> > > RX equalizer from flat to settings of: #1=0, #2=3, #3=3,
> >> > #4=-1, #5=-4,
> >> > > #6=-5, #7=-8, #8=-10. Admittedly, part of these settings accomodate
> >> > > SSB to give, what I hear, as a very pleasant sound for that
> >> > mode. The
> >> > > primary ranges of this noise are affected mostly by filters
> >> > #4 and #5.
> >> > >
> >> > > If the RX equalizer settings remain flat, hence 0, the
> >> > sound is even
> >> > > more annoying. But remember this is really only in noisy
> >> > conditions,
> >> > > so my hypothesis is that the chaotic sounds in the noise
> >> > are mixing to
> >> > > produce what sounds like a ringing of the filters. (So not
> >> > necessarily
> >> > > the filters actually ringing, as we think of it.) But this makes
> >> > > working very weak signals very difficult without widening
> >> > the passband
> >> > > quite a bit.
> >> > >
> >> > > So, guess I would like to hear comments regarding this, as well as
> >> > > settings
> >> > > and techniques people use to combat this phenomenon.
> >> > >
> >> > > 73 ...Edwin, KD5ZLB
> >> > > ____________________________________________________________
> >> > > "Once you have flown, you will walk the earth with your eyes turned
> >> > > skyward, for there you have been, there you long to
> >> > return."-da Vinci
> >> > > http://bellsouthpwp2.net/e/d/edwinljohnson
> >> > > ______________________________________________________________
> >> > > 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
> >> >
> >> > ______________________________________________________________
> >> > Elecraft mailing list
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> >> > Post: mailto:[hidden email]
> >> >
> >> > This list hosted by: http://www.qsl.net
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> >>
> >> ______________________________________________________________
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>

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[Brett Howard]

At the moment I need things fairly quiet to be able to copy well so for
now narrow filters are the cats meow for me but maybe someday I'll
graduate to wider filters.  I prefer the sound of wider but... for me
narrow aids in copy for me.  

~Brett

On Sun, 2009-08-09 at 07:31 -0700, Ron D'Eau Claire wrote:

> Brett wrote:
> I'd never had a rig capable of going lower than 500Hz till I got the K3
> and really found myself quite annoyed at times when the noise was high
> and I really necked the filter down.  
>
> ----------------------------------
>
> You've discovered exactly why many of us avoid narrow filters whenever
> possible. Our brains are much better at recognizing a CW signal in broadband
> noise than in narrow-band noise. The same is true for digital noise
> reduction.
>
> At very narrow bandwidths the filter also modifies the CW signal, softening
> the keying to make it sound more and more like noise rather than a keyed
> signal. Both the tx at the far end and your receiver must allow enough of
> the CW sidebands through to hear clean, sharp keying transitions. That takes
> some reasonable bandwidth. The faster the CW the more bandwidth is needed.
> Some people don't want to hear any keying transitions (what, when excessive,
> we call "clicks") at all only a few Hz from the carrier, but that really
> compromises readability. Our brains hear those sidebands and help us detect
> the signal from the noise, and the sidebands must be passed through your
> receive filter.
>
> The first step to using wider bandwidths is to learn to copy CW when other
> signals are present, just like learning to listen to one conversation in a
> crowded room even though you can hear others talking all around you.
>
> When another signal within the passband is sufficiently loud to be a serious
> distraction, sort of like trying to hear a quiet voice with someone else
> shouting in your ear, a notch filter is preferred over narrowing the
> bandwidth. All the notch need to is reduce the offendingly-loud signal
> enough to make it less troublesome. Poking a narrow 'hole' in the noise
> doesn't cause the problems a narrow filter does.
>
> Optionally, you can often tune the rx off frequency just a bit to push a
> 'loudmouth' off the edge of the filter bandpass while keeping the desired
> signal within the bandpass.
>
> It takes practice, but it's a skill worth having on a crowded band. Probably
> 90% of my brass pounding is done at a bandwidth of 1 kHz or wider.
>
> Ron AC7AC
>
>

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[w9cf]

Jim Brown wrote:
...
>BUT -- human hearing is logarithmic, both in pitch and amplitude. Our ability
>to separate frequencies is based on proportional differences in frequency, so
>setting the CW pitch to a lower frequency gives the ear greater ability to
>separate signals (or signal and noise) that are close together in frequency.
>That is, if the pitch is set to 500 Hz, 100 Hz bandwidth is 20% of the signal
>frequency, whereas at a pitch of 1 kHz, 100 Hz bandwidth is only 10%. I know
>some really good CW operators (N6RO is one) who regularly work at pitches
>below 500 Hz for this reason.
>
>BTW -- I know exactly what the original poster of this thread is talking
>about -- I really suffered from it when I lived in Chicago.
>
>73,
>
>Jim Brown K9YC

While this seems reasonable, when I took an online frequency
discrimination test a year or so ago (unfortunately I haven't been able
to find the link), I did not find this to be true for me.  This test
was, of course, not for separating two cw signals, but instead it sent
two tones sequentially, and you had to choose whether the second was
higher or lower pitch than the first. It repeated this with smaller and
larger intervals until it had a measurement within error bars. Obviously
different people have different results or there wouldn't be a need for
a test. My results were, for the 3 ranges that the test used:

250Hz tones 3.6Hz difference with standard deviation 2.1Hz                      
500Hz tones 1.9Hz difference with standard deviation 1.4Hz                      
1000Hz tones 3.4Hz difference with standard deviation 2.2Hz

Taking the fractions I get 1.4 percent at 250 Hz, 0.4 percent at 500 Hz,
and 0.3 percent at 1000Hz. Although the standard deviations cloud this
a bit. I know some ops like to run at low frequency as Jim says, but I
prefer higher frequencies, and this hearing test may help indicate why.

73 Kevin w9cf

[AC7AC]

CONTENTS DELETED

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[Jim Brown-10]

On Sun, 9 Aug 2009 14:26:21 -0400, Joe Subich, W4TV wrote:

>You miss the point ... while there may be less noise power at
>RF (or IF) as you narrow the filter, humans listen at AF.  

No, I don't miss the point at all. See the rest of my post.

73,

Jim K9YC


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[Jim Brown-10]

On Sun, 9 Aug 2009 16:34:56 -0500 (CDT), w9cf wrote:

>While this seems reasonable,

What I'm talking about is the ability of human listeners to
discriminate between (that is, mentally separate them from each
other) audio frequency signals that are close in frequency.

The science of psychoacoustics is extremely well developed, and the
principles I'm stating have long been well understood by those who
have studied them. Yes, there are differences from one person to
another, experience matters, and humans can learn lots of special
skills. But most of us are starting from the fundamental place I've
described.  

73,

Jim K9YC


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[Jim Brown-10]

On Sun, 9 Aug 2009 15:21:21 -0700, Ron D'Eau Claire wrote:

>I'm not expert on human hearing, but I suspect we can discriminate tones
>(and hear tones in noise) much better than we can discriminate subtle
>changes in amplitude

YES! And there are also several ways in which humans can hear VERY small
differences in arrival times of the same acoustic signal coming from two
directions. One of those ways is selective fading, which is primarily the
cancellation between two signals arriving via different paths that are
slightly different in length. The repetition rate of fading is inversely
proportional to wavelength, so is quite long on 160M (slow QSB) and quite
short on 2M (picket-fencing).

Another way is when the same electrical signal is fed in phase and in
polarity to two loudspeakers that are at different points in space. If you
use broadband noise as the test signal and walk a straight line parallel
to a pair of speakers about ten feet apart (that is, with one ear facing
them) about six-ten feet in front of them, you will hear coherent addition
at the point where you are precisely on centerline, and a strange sort of
"phasy" distortion that Lou Burroughs called "acoustic phase
cancellation" and modern sound engineers call "comb filtering."  

If with the same setup you FACE the loudspeakers and "crab walk" side to
side between them, you will hear the image be dead center in front of you
on centerline, and quickly shift to the closest loudspeaker as you move
only a few inches off centerline. A difference in travel time on the order
of a few tens of microseconds can be clearly heard as an image shift.

73,

Jim K9YC


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[drewko]

On Sat, 08 Aug 2009 22:35:42 -0700, ~Brett wrote:

>
>One thing to try is to turn the bandwidth down to around 200Hz and find
>a quiet spot on the band then adjust your pitch up and down and listen
>to the band noise in a few places to see what you prefer based on the
>noise rather than the pitch.  Then see if you can live w/ that pitch.
>

Yes, but that is very tedious. Much better would be the ability to
adjust the pitch of signals while you are listening to them.

Unfortunately, when PITCH is on, received signal audio is blocked,
even if you set the pitch volume to zero. It would be very nice to be
able to  interactively adjust a CW signal's pitch for optimum copy
under current conditions of QRM and QRN, without detuning the VFO or
RIT.

73,
Drew
AF2Z



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