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K3 and preamp

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alsopb

K3 and preamp

Quite some time ago there was a discussion that adding a preamp at the
K3 antenna terminals couldn't possibly help. The argument is that it
can't improve S/N

Perhaps here is the reason it does help from somebody versed in
ear/brain signal processing.

73 de Brian/K3KO
--------------------
On 8/28/2014 17:45, David McClain [hidden email]
[FMT-nuts] wrote:
> Some weeks ago I was musing about the way we all listen to the weak
ones on the HF bands.... And then it struck me, based on what I know
about our hearing:
>
> While we all dislike the constant rush of noise in the headphones, it
actually turns out to be helpful, and that's why we instinctively turn
up the volume and just live with the noise. When you do that, you are
imposing strong ambient noise on your hearing. That in turn affects the
way your hearing works. It produces a much steeper response to weak
signals riding in the noise. So a very small change in signal level
causes a much larger change in apparent loudness in your brain. It makes
it easier to read the weak signals.
>
> Coupled with that, we also need that noise to produce something
called "stochastic resonance", which is the basis for dithered noise
added to recordings. It lets you hear things that are solidly below the
noise floor.
>
> - 73 de Dave, N7AIG
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k6dgw

Re: K3 and preamp

Uhmmm ... Given the domain of David's email address, he's probably
right. However ... between doing other things while in SE Asia in the
mid-60's, my team and I occasionally made it onto one of the larger
bases for a week or so. I usually made a trip to the MARS station to
get a long-overdue "radio fix," and ran a few phone patches for the troops.

At most of the stations, there were a couple of homebrew sound-deadened
phone booths with a telephone just outside the radio room. Even when
conditions were really good, it was fairly common for a wife to not
understand her husband, sitting about 3 meters from me, however, she had
no problem understanding me. They had run a number of tests locally and
the telephone input to the KWM-2A's sounded just like the mic on the air.

I finally concluded that there were two factors at work: First off, he
didn't sound like her husband, but she had never heard me except on the
radio so I was understandable. Second, and maybe more important, even
with good conditions, there was inevitable HF noise, and she was
listening to the noise instead of the weird voice purporting to be her
husband.

As a result of the "other things," I came home quite deaf and I run the
AF gain right at the distortion point in the headphones [my hearing aids
don't work under the phones]. T-storm static crashes cover weak CW
signals for me, possibly because they drive the cans into distortion.
Steady noise -- grass on the P3 baseline -- causes me no problems. I've
never managed to get much benefit out of the K3 APF, likely due to pilot
error.

I do know that our hearing mechanism is very complex.

73,

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

On 9/5/2014 5:14 AM, Brian wrote:

> Quite some time ago there was a discussion that adding a preamp at the
> K3 antenna terminals couldn't possibly help. The argument is that it
> can't improve S/N
>
> Perhaps here is the reason it does help from somebody versed in
> ear/brain signal processing.
>
> 73 de Brian/K3KO
> --------------------
> On 8/28/2014 17:45, David McClain [hidden email]
> [FMT-nuts] wrote:
> > Some weeks ago I was musing about the way we all listen to the weak
> ones on the HF bands.... And then it struck me, based on what I know
> about our hearing:
> >
> > While we all dislike the constant rush of noise in the headphones, it
> actually turns out to be helpful, and that's why we instinctively turn
> up the volume and just live with the noise. When you do that, you are
> imposing strong ambient noise on your hearing. That in turn affects the
> way your hearing works. It produces a much steeper response to weak
> signals riding in the noise. So a very small change in signal level
> causes a much larger change in apparent loudness in your brain. It makes
> it easier to read the weak signals.
> >
> > Coupled with that, we also need that noise to produce something
> called "stochastic resonance", which is the basis for dithered noise
> added to recordings. It lets you hear things that are solidly below the
> noise floor.
> >
> > - 73 de Dave, N7AIG

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Iain MacDonnell - N6ML-2

Re: K3 and preamp

In reply to this post by alsopb

That doesn't justify a pre-amp. If you want more acoustic noise, just
turn up the AF gain. The only reason (I can see) to use a preamp is if
the receiver internal noise level is higher than the atmospheric noise
(coming from the antenna). If the noise level perceptibly drops when
you disconnect the antenna, a preamp isn't going to do much for
you....

73,

~iain / N6ML

On Fri, Sep 5, 2014 at 5:14 AM, Brian <[hidden email]> wrote:

> Quite some time ago there was a discussion that adding a preamp at the K3
> antenna terminals couldn't possibly help. The argument is that it can't
> improve S/N
>
> Perhaps here is the reason it does help from somebody versed in ear/brain
> signal processing.
>
> 73 de Brian/K3KO
> --------------------
> On 8/28/2014 17:45, David McClain [hidden email]
> [FMT-nuts] wrote:
>> Some weeks ago I was musing about the way we all listen to the weak ones
>> on the HF bands.... And then it struck me, based on what I know about our
>> hearing:
>>
>> While we all dislike the constant rush of noise in the headphones, it
>> actually turns out to be helpful, and that's why we instinctively turn up
>> the volume and just live with the noise. When you do that, you are imposing
>> strong ambient noise on your hearing. That in turn affects the way your
>> hearing works. It produces a much steeper response to weak signals riding in
>> the noise. So a very small change in signal level causes a much larger
>> change in apparent loudness in your brain. It makes it easier to read the
>> weak signals.
>>
>> Coupled with that, we also need that noise to produce something called
>> "stochastic resonance", which is the basis for dithered noise added to
>> recordings. It lets you hear things that are solidly below the noise floor.
>>
>> - 73 de Dave, N7AIG
> ______________________________________________________________
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Jim Brown-10

Re: K3 and preamp

On Fri,9/5/2014 9:59 AM, iain macdonnell - N6ML wrote:
> That doesn't justify a pre-amp. If you want more acoustic noise, just
> turn up the AF gain. The only reason (I can see) to use a preamp is if
> the receiver internal noise level is higher than the atmospheric noise
> (coming from the antenna).

Right.

> If the noise level perceptibly drops when
> you disconnect the antenna, a preamp isn't going to do much for
> you....

Perceptibly is not the right word if you care about weak signal work.
The difference should be at least "twice as loud" when the antenna is
added, which corresponds to about 10 dB. Use the K3's internal audio
voltmeter to determine this. Turn off AGC, with the antenna connected,
calibrate the dB readout to zero following the instructions in the
manual, then remove the antenna.

73, Jim K9YC
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Phil Hystad-3

Re: K3 and preamp

> ...<cut>... Use the K3's internal audio voltmeter to determine this. Turn off AGC, with the antenna connected, calibrate the dB readout to zero following the instructions in the manual, then remove the antenna.
>
> 73, Jim K9YC

Here I have been a K3 owner for several years and I never knew that there was an internal audio voltmeter. I admit to maybe having missed this in reading the documentation but every time Jim (K9YC) speaks, I learn something.

73, phil, K7PEH

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Edward A. Dauer

K3 and Preamp

In reply to this post by alsopb

Aware as I am that the word ³data² is not the plural of the word
³anecdote,² I can offer a subjective anecdote to the contrary: With the
PR6-10 in the RX Ant line of my K3, there are CW signals I can copy
(barely) which I cannot hear at all with the preamp out of the circuit,
regardless of the RF and AF gain settings. I can¹t explain it and I don¹t
have the equipment to do any objective measurements; but it is the case.
I have found the pre-amp to be worth the money.

Ted, KN1CBR

>------------------------------
>
>Message: 25
>Date: Fri, 05 Sep 2014 10:34:17 -0700
>From: Jim Brown <[hidden email]>
>To: [hidden email]
>Subject: Re: [Elecraft] K3 and preamp
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=windows-1252; format=flowed
>
>On Fri,9/5/2014 9:59 AM, iain macdonnell - N6ML wrote:
>> That doesn't justify a pre-amp. If you want more acoustic noise, just
>> turn up the AF gain. The only reason (I can see) to use a preamp is if
>> the receiver internal noise level is higher than the atmospheric noise
>> (coming from the antenna).
>
>Right.
>
>> If the noise level perceptibly drops when
>> you disconnect the antenna, a preamp isn't going to do much for
>> you....
>
>Perceptibly is not the right word if you care about weak signal work.
>The difference should be at least "twice as loud" when the antenna is
>added, which corresponds to about 10 dB. Use the K3's internal audio
>voltmeter to determine this. Turn off AGC, with the antenna connected,
>calibrate the dB readout to zero following the instructions in the
>manual, then remove the antenna.
>
>73, Jim K9YC
>
>

Iain MacDonnell - N6ML-2

Re: K3 and Preamp

Hi Ted,

I didn't say that the pre-amp isn't worth the money - I just said that
supplying more noise to the ears isn't a good justification for it.
It's well known that the K3 needs a pre-amp for effective weak-signal
work on the higher bands, but it's not (primarily) because it makes
the noise louder - it's because it raises the signals (from the
antenna) above the receiver's internal noise.

73,

~iain / N6ML

On Fri, Sep 5, 2014 at 1:54 PM, Dauer, Edward <[hidden email]> wrote:

> Aware as I am that the word ³data² is not the plural of the word
> ³anecdote,² I can offer a subjective anecdote to the contrary: With the
> PR6-10 in the RX Ant line of my K3, there are CW signals I can copy
> (barely) which I cannot hear at all with the preamp out of the circuit,
> regardless of the RF and AF gain settings. I can¹t explain it and I don¹t
> have the equipment to do any objective measurements; but it is the case.
> I have found the pre-amp to be worth the money.
>
> Ted, KN1CBR
>
>
>
>>------------------------------
>>
>>Message: 25
>>Date: Fri, 05 Sep 2014 10:34:17 -0700
>>From: Jim Brown <[hidden email]>
>>To: [hidden email]
>>Subject: Re: [Elecraft] K3 and preamp
>>Message-ID: <[hidden email]>
>>Content-Type: text/plain; charset=windows-1252; format=flowed
>>
>>On Fri,9/5/2014 9:59 AM, iain macdonnell - N6ML wrote:
>>> That doesn't justify a pre-amp. If you want more acoustic noise, just
>>> turn up the AF gain. The only reason (I can see) to use a preamp is if
>>> the receiver internal noise level is higher than the atmospheric noise
>>> (coming from the antenna).
>>
>>Right.
>>
>>> If the noise level perceptibly drops when
>>> you disconnect the antenna, a preamp isn't going to do much for
>>> you....
>>
>>Perceptibly is not the right word if you care about weak signal work.
>>The difference should be at least "twice as loud" when the antenna is
>>added, which corresponds to about 10 dB. Use the K3's internal audio
>>voltmeter to determine this. Turn off AGC, with the antenna connected,
>>calibrate the dB readout to zero following the instructions in the
>>manual, then remove the antenna.
>>
>>73, Jim K9YC
>>
>>
>
> ______________________________________________________________
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Jim Brown-10

Re: K3 and Preamp

On Fri,9/5/2014 2:08 PM, iain macdonnell - N6ML wrote:
> I didn't say that the pre-amp isn't worth the money - I just said that
> supplying more noise to the ears isn't a good justification for it.
> It's well known that the K3 needs a pre-amp for effective weak-signal
> work on the higher bands, but it's not (primarily) because it makes
> the noise louder - it's because it raises the signals (from the
> antenna) above the receiver's internal noise.

Exactly.

73, Jim K9YC
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James Rogers

Re: K3 and preamp

In reply to this post by Phil Hystad-3

Well, I missed it too. Where do we find this internal audio voltmeter.
It isn't is my manual's index. ??

73s Jim, W4ATK

On 9/5/2014 1:04 PM, Phil Hystad wrote:

>> ...<cut>... Use the K3's internal audio voltmeter to determine this. Turn off AGC, with the antenna connected, calibrate the dB readout to zero following the instructions in the manual, then remove the antenna.
>>
>> 73, Jim K9YC
> Here I have been a K3 owner for several years and I never knew that there was an internal audio voltmeter. I admit to maybe having missed this in reading the documentation but every time Jim (K9YC) speaks, I learn something.
>
> 73, phil, K7PEH
>
>
> ______________________________________________________________
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James Rogers

Re: K3 and preamp

Well, do I feel stupid! Geez, my second K3 and I either ignored this or
forgot it. I choose to say "forgot" because at my advanced age, I have
an excuse. :-)) Thanks Walter.
73s Jim W4ATK
On 9/5/2014 5:29 PM, Walter Underwood wrote:

> See “VFO B Alternate Displays” on page 36. The displays are “AFV” and “dbV”.
>
> http://www.elecraft.com/manual/E740107%20K3%20Owner's%20man%20D10sm.pdf
>
> wunder
> K6WRU
> CM87wj
> http://observer.wunderwood.org/
>
> On Sep 5, 2014, at 3:25 PM, Jim Rogers <[hidden email]> wrote:
>
>> Well, I missed it too. Where do we find this internal audio voltmeter. It isn't is my manual's index. ??
>>
>> 73s Jim, W4ATK
>>
>> On 9/5/2014 1:04 PM, Phil Hystad wrote:
>>>> ...<cut>... Use the K3's internal audio voltmeter to determine this. Turn off AGC, with the antenna connected, calibrate the dB readout to zero following the instructions in the manual, then remove the antenna.
>>>>
>>>> 73, Jim K9YC
>>> Here I have been a K3 owner for several years and I never knew that there was an internal audio voltmeter. I admit to maybe having missed this in reading the documentation but every time Jim (K9YC) speaks, I learn something.
>>>
>>> 73, phil, K7PEH
>>>
>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>>
>> ______________________________________________________________
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>>
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> ______________________________________________________________
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Edward A. Dauer

K3 and Preamp

In reply to this post by alsopb

No argument with the theory here, though my personal experience is not
consistent with the earlier observation that a preamp won¹t do much if the
noise level drops perceptibly when the antenna is disconnected. On my K3
on 10M the noise level drops when no antenna is connected (by 10dB? Maybe
not); AND the PR6-10 preamp improves the readability of very weak signals
when it is in the circuit compared to when it is not. If that¹s just a
placebo effect, I¹ll take it.

I received a couple of off-list comments that might be of interest to
those who are following this thread. One was that narrowing the BW also
improves the S/N. That is quite true - indeed, BW narrowing in the K3 is
generally better, in my circumstances, than the K3¹s on-board NB and NR
facilities are (though I confess I have much to learn about those.)
Another comment was that I must have a very RF-quiet location. Perhaps
so: The station QTH is in a part of Teller County with single family / 35
acre zoning, which puts the nearest neighbor some 1,500¹ away; and my
power line is buried under 8¹ of decomposed granite on its final 200¹ to
the house. That, to be fair, is consistent with Jim¹s and Iain¹s
observations that the preamp works by raising the signal AND noise above
the receiver¹s internal noise.

Ted, KN1CBR

. .

>Message: 6
>Date: Fri, 05 Sep 2014 14:25:27 -0700
>From: Jim Brown <[hidden email]>
>To: [hidden email]
>Subject: Re: [Elecraft] K3 and Preamp
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>On Fri,9/5/2014 2:08 PM, iain macdonnell - N6ML wrote:
>> I didn't say that the pre-amp isn't worth the money - I just said that
>> supplying more noise to the ears isn't a good justification for it.
>> It's well known that the K3 needs a pre-amp for effective weak-signal
>> work on the higher bands, but it's not (primarily) because it makes
>> the noise louder - it's because it raises the signals (from the
>> antenna) above the receiver's internal noise.
>
>Exactly.
>
>73, Jim K9YC

Edward R Cole

Re: K3 and Preamp

In reply to this post by alsopb

Maybe most of you already know this, but...

It has been accepted that the K3 receiver needs a little help of a
preamp on 10m and 6m (especially 6m). That is why Elecraft came out
with the PR6 and later the PR6-10 preamps.

At lower frequencies the level of sky noise is much higher which
overwhelms any noise generated internally by the receiver, thus a
preamp would only contribute gain making both noise and signal
louder. But around 30-MHz sky noise starts dropping so that it is
necessary for the first stage of a receiver to be "quieter"
(technically that is called a low noise figure). If the noise
generated in the receiver is significantly equal to sky noise the
receiver sensitivity is not optimum (meaning you can't copy weak
signals). This trend continues downward with increase of frequency
up to 1.2 GHz where sky noise is minimum (on earth). One cannot
receive "weaker" signals without a low-noise preamp close to the antenna at mw.

So, use of the internal preamp is generally not needed below 20m as
all it will do is increase noise volume and not improve receiver
sensitivity. But at 15m it often helps. At 10m the internal preamp
is inadequate to obtain maximum sensitivity and an external low-noise
(figure) preamp can really help.

Like I said at the beginning, maybe you already knew this...

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Don Wilhelm-4

Re: K3 and Preamp

There is also a converse on preamp use that needs to be stated IMHO -
and mostly pertains to bands below 15 meters.

If there is a significant (3 to 6 dB) increase in noise heard in the
receiver when the antenna is connected (tuned where there are no signals
present) then the receiver gain is sufficient and the addition of a
preamp (or turning the internal preamp on) will only reduce the dynamic
range of the receiver.
For those who are not familiar with dynamic range, it is the difference
between the weakest signal that can be heard and the strongest signal
that will not cause overload.

What this means to normal operating is that when the band consists of
very strong signals as well as the weak ones you would like to copy, you
will be better off turning the preamp off and perhaps even inserting
some attenuation or turning down the RF Gain.

Now, if all stations within the bandpass of the receiver front end are
weak, adding preamplification will not create receiver front end
overload, and can be safely added.

So whether or not a preamp will help depends on the band, the antenna,
propagation conditions and many other factors. No blanket statements
can be made, particularly on the lower HF bands.
For 10 meters and above, band noise drops drastically with frequency and
what Ed has stated is certainly true.

73,
Don W3FPR

On 9/6/2014 4:36 PM, Edward R Cole wrote:

> Maybe most of you already know this, but...
>
> It has been accepted that the K3 receiver needs a little help of a
> preamp on 10m and 6m (especially 6m). That is why Elecraft came out
> with the PR6 and later the PR6-10 preamps.
>
> At lower frequencies the level of sky noise is much higher which
> overwhelms any noise generated internally by the receiver, thus a
> preamp would only contribute gain making both noise and signal
> louder. But around 30-MHz sky noise starts dropping so that it is
> necessary for the first stage of a receiver to be "quieter"
> (technically that is called a low noise figure). If the noise
> generated in the receiver is significantly equal to sky noise the
> receiver sensitivity is not optimum (meaning you can't copy weak
> signals). This trend continues downward with increase of frequency up
> to 1.2 GHz where sky noise is minimum (on earth). One cannot receive
> "weaker" signals without a low-noise preamp close to the antenna at mw.
>
> So, use of the internal preamp is generally not needed below 20m as
> all it will do is increase noise volume and not improve receiver
> sensitivity. But at 15m it often helps. At 10m the internal preamp
> is inadequate to obtain maximum sensitivity and an external low-noise
> (figure) preamp can really help.
>
> Like I said at the beginning, maybe you already knew this...
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> "Kits made by KL7UW"
> Dubus Mag business:
> [hidden email]
>
> ______________________________________________________________
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>

W2RU - Bud Hippisley

Re: K3 and Preamp

In reply to this post by Edward A. Dauer

On Sep 6, 2014, at 2:34 17PM, Dauer, Edward <[hidden email]> wrote:

> I received a couple of off-list comments that might be of interest to
> those who are following this thread. One was that narrowing the BW also
> improves the S/N.

Maybe. Maybe not. Or, maybe up to a point.

I believe that whether one observes monotonic improvement in ability to decipher the intelligence carried in a very weak signal as one reduces receiver BW will be a function of _how_ the BW is narrowed in the various electronic circuits and/or digital algorithms, as well as a function of our own individual hearing characteristics.

Perhaps I am not on the main part of the normalcy distribution curve (my close friends will assure me I’m _not_!) but I know for a fact that many, many times I have been best able to pull intelligible information out of a very weak CW signal on the low bands by using a receiver BW somewhat _wider_ than that provided by my narrowest filtering options. I have used primarily Kenwoods and (more recently) the K3 for most of my serious low-band DXing efforts, but I can’t tell you if this effect is more or less apparent in one model vs. any other.

I am also a strong believer in what I have been told is “stochastic resonance” as an aid to hearing and copying the intelligence carried in weak signals. I have found repeatedly, for instance, that I am more apt to hear certain “unusual” vehicle sounds from the engine compartment or underbody when I have the car radio playing music within a certain range of amplitudes. Of course, that might also depend on my choice of music genre … :-)

Bud, W2RU
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Don Wilhelm-4

Re: K3 and Preamp

Bud,

I think a lot has to do with the 'material between the ears'. Some have
developed the ability to hear signals that to my ears are buried in the
noise. Those chasing Low Band DX are examples of folks with that
ability. Some report using a wide bandwidth while others report good
results with a narrow bandwidth. I believe it all depends on the "brain
training". The human brain can provide a wonderful filter if you know
what to pay attention to (and ignore things that can distract). Some
have it while others do not. It may be something that can be learned,
but I have not accomplished that feat.

73,
Don W3FPR

On 9/6/2014 5:28 PM, W2RU - Bud Hippisley wrote:

> On Sep 6, 2014, at 2:34 17PM, Dauer, Edward <[hidden email]> wrote:
>
>> I received a couple of off-list comments that might be of interest to
>> those who are following this thread. One was that narrowing the BW also
>> improves the S/N.
> Maybe. Maybe not. Or, maybe up to a point.
>
> I believe that whether one observes monotonic improvement in ability to decipher the intelligence carried in a very weak signal as one reduces receiver BW will be a function of _how_ the BW is narrowed in the various electronic circuits and/or digital algorithms, as well as a function of our own individual hearing characteristics.
>
> Perhaps I am not on the main part of the normalcy distribution curve (my close friends will assure me I’m _not_!) but I know for a fact that many, many times I have been best able to pull intelligible information out of a very weak CW signal on the low bands by using a receiver BW somewhat _wider_ than that provided by my narrowest filtering options. I have used primarily Kenwoods and (more recently) the K3 for most of my serious low-band DXing efforts, but I can’t tell you if this effect is more or less apparent in one model vs. any other.
>
> I am also a strong believer in what I have been told is “stochastic resonance” as an aid to hearing and copying the intelligence carried in weak signals. I have found repeatedly, for instance, that I am more apt to hear certain “unusual” vehicle sounds from the engine compartment or underbody when I have the car radio playing music within a certain range of amplitudes. Of course, that might also depend on my choice of music genre … :-)
>
>

k6dgw

Re: K3 and Preamp

In reply to this post by W2RU - Bud Hippisley

On 9/6/2014 2:28 PM, W2RU - Bud Hippisley wrote:
> On Sep 6, 2014, at 2:34 17PM, Dauer, Edward <[hidden email]>
> wrote:
>
>> I received a couple of off-list comments that might be of interest
>> to those who are following this thread. One was that narrowing the
>> BW also improves the S/N.
>
> Maybe. Maybe not. Or, maybe up to a point.

Agreed, and it depends on the character of the noise for me. The 51J4's
we used in coastal marine service so long ago had the crystal filters of
the day, and it took some acquired skill to operate it effectively.
They weren't terribly good at weak signals, but then, weak signals and
QRM weren't usually a problem ... except on 500 KCs.

A dozen years later, I had a 2B with the 2BQ along with an S3-line in
Houston TX. The 2B/2BQ offered very precise tailoring of the passband
and I could copy signals on it that I couldn't hear [or could barely
discern] of the 75S3. It would be fun to compare my K3 with the 2B.

I've never had much luck with the K3 APF, I know others do and its
probably pilot error for me, but I wonder what it would take to make it
adjustable both in BW and frequency? DSP Q-Multiplier? :-)

73,

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

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Jim Brown-10

Re: K3 and Preamp

In reply to this post by W2RU - Bud Hippisley

On Sat,9/6/2014 2:28 PM, W2RU - Bud Hippisley wrote:
> I believe that whether one observes monotonic improvement in ability to decipher the intelligence carried in a very weak signal as one reduces receiver BW will be a function of_how_ the BW is narrowed in the various electronic circuits and/or digital algorithms, as well as a function of our own individual hearing characteristics.

Yes. Especially if the noise is impulse noise, ringing in the filter
skirts can make copy more difficult for me if I set the bandwidth too
narrow. This is, of course, strongly dependent on the shaping of the
filter.

From Psychoacoustics (the science of how the human ear-brain
combination works), we know that we process sound in narrow chunks of
bandwidth called "critical bands." The ear tends to process sounds
within that band together, so when the filter gets too narrow, the
filter skirts fall with the critical band and ringing begins to obscure
the desired signal. The width a critical band varies with the sound
spectrum, and is in the range a 1/3 octave to 1/6 octave. An octave is a
2:1 ratio of frequency.

73, Jim K9YC
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Alan Bloom

Psychoacoustics (Was: K3 and Preamp)

On 09/06/2014 04:26 PM, Jim Brown wrote:
> ...
> From Psychoacoustics (the science of how the human ear-brain
> combination works), we know that we process sound in narrow chunks of
> bandwidth called "critical bands." The ear tends to process sounds
> within that band together, so when the filter gets too narrow, the
> filter skirts fall with the critical band and ringing begins to
> obscure the desired signal. The width a critical band varies with the
> sound spectrum, and is in the range a 1/3 octave to 1/6 octave. An
> octave is a 2:1 ratio of frequency.

That corresponds with my intuition. I long ago figured out that when
using a very narrow-bandwidth filter, I can copy a lot better if I lower
the filter center frequency. For example, with a 50 Hz bandwidth I can
copy better if I tune the filter from the standard 800 Hz down to 300 Hz
or so. That's about 1/5 octave.

Alan N1AL

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Guy Olinger K2AV

Re: K3 and Preamp

In reply to this post by k6dgw

On Sat, Sep 6, 2014 at 6:24 PM, Fred Jensen <[hidden email]> wrote:

> I've never had much luck with the K3 APF, I know others do and its
> probably pilot error for me, but I wonder what it would take to make it
> adjustable both in BW and frequency? DSP Q-Multiplier? :-)
>

There is something I remember from the old radios and some really "bad"
headsets that were peaky in their response, and that was a moderate rolloff
above and below that allowed one to hear up there and down there but did
not allow it to dominate. I've asked for a config menu adjustment on the
APF but that never had enough support from others to move it up on the K3
do list.

The audio shaping could do that, but I can't put in a menu selection of
favorite settings, there is only the one. It would need to be easily
accessible for switching in/out on a QSO by QSO basis.

73, Guy.
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Pierfrancesco Caci

Re: K3 and Preamp

>>>>> "Guy" == Guy Olinger K2AV <[hidden email]> writes:

Guy> There is something I remember from the old radios and some really "bad"
Guy> headsets that were peaky in their response, and that was a
Guy> moderate rolloff
Guy> above and below that allowed one to hear up there and down
Guy> there but did
Guy> not allow it to dominate. I've asked for a config menu
Guy> adjustment on the
Guy> APF but that never had enough support from others to move it up
Guy> on the K3
Guy> do list.

isn't this sort of what DUAL PB does ?

--
Pierfrancesco Caci, ik5pvx
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