Hearing CW - Fundamental Keying Waveform?

[Ron D'Eau Claire-2]

Yes, 47CFR97.307 (Mike quoted below) is the regulation that is usually
referenced by an ARRL Official Observer (OO) reporting chirp.

Of course, the regulations do NOT provide specific parameters nor have I
heard of the US Federal Communications Commission (FCC) ever issuing a
citation for clicks or chirp as long as the emissions remained within the
Amateur band. It all comes down to a matter of personal opinion about what
constitutes good Amateur or engineering practice.

I got an OO card some years back that said he could definitely hear "...just
detectable chirp" on my signal. In the QSO he cited I was chatting with
another station about the vintage rig I was testing and how they *all*
chirped a bit. It was inherent in the design. Had that OO been 'reading the
mail' he'd have realized he need not waste his time advising me he could
hear what we were talking about <G>.

I'm not denigrating the OO service. The technically-competent OO's provide a
real service to the Amateur community to alert Hams when their rigs are
mis-behaving in some manner that is observable on the air.

On the other hand, I've known a number of new hams to be really upset when
they got an OO card, thinking they had been "cited" for some infraction of
the rules, especially when the OO quotes an FCC regulation like the one
below as if the operator had violated it when, in fact, it was all a matter
of opinion. And, as the level of technical knowledge required to get an
Amateur license continues to drop coupled with more and more Hams focusing
on specific modes and on-air activities, we'll probably see a greater and
greater range of "opinion" in the future.

One of the very important concessions us Hams have managed to maintain over
the years is a minimum of rules that restrict us. In the USA at least, the
FCC is very lenient, allowing and encouraging Hams to tinker and experiment
and just have fun with a variety of equipment and technologies. What we get
is a freedom no other radio service enjoys, but it requires us Hams to be
very tolerant of each other and what we think is "good practice" considering
what we are doing at the time.

There's no rule that says that every rig has to sound as good as an Elecraft
rig. Besides, as I observed earlier, I can read a very weak slightly chirpy
signal much more easily than one that doesn't chirp, therefore a little
chirp is essential to meet the standards of good Amateur or Engineering
practice in that case, Hi!  

Ron AC7AC



-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Mike S
Sent: Wednesday, September 20, 2006 7:04 AM
To: Martin Gillen
Cc: elecraft
Subject: RE: [Elecraft] Hearing CW - Fundamental Keying Waveform?


At 09:13 AM 9/20/2006, Martin Gillen wrote...

>Which FCC or ARRL guideline mentions chirp, or otherwise attempts to
>regulate the keying waveform?

97.307(a) No amateur station transmission shall occupy more bandwidth than
necessary for the information rate and emission type being transmitted, in
accordance with good amateur practice.

(b) Emissions resulting from modulation must be confined to the band or
segment available to the control operator. Emissions outside the necessary
bandwidth must not cause splatter or keyclick interference to operations on
adjacent frequencies.

(c) All spurious emissions from a station transmitter must be reduced to the
greatest extent practicable. If any spurious emission, including chassis or
power line radiation, causes harmful interference to the reception of
another radio station, the licensee of the interfering amateur station is
required to take steps to eliminate the interference, in accordance with
good engineering practice.

And it continues on with regard to specific standards and measurements of
spurious emissions.

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[Masleid, Michael A.-2]

Hi Bob,

>As long as we are discussing hearing cw I'd like to ask a question that has
>been bothering me for many years.  I am very sensitive to chirp, and that is
>not what I am referring to.  When I listen to a good cw signal in the range
>of about 20-35 wpm I heard the dots and dashes as at slightly different
>frequencies. This may simply be some sort of psychological quirk unique to
>me.  I am not even sure "slightly different frequencies" or tones is correct
>way to describe it.  Realizing that I am not listening to a sinusoidal tone
>but sequences of short and long symbols and that long strings of dots will
>have wider sidebands than long strings of dashes, I wonder if this is
>relevant in any way.  Most likely it is some sort of personal quirk.  But I
>wonder if anyone on this reflector by any chance notices anything similar or
>has an explanation?

Let's say the dots are 40 msec long - that's 12.5 dots per second.
The fundamental frequency is 12.5 Hz of course, with all the odd harmonics (37.5, 62.5 ...)
So if you tune to hear this as 600 Hz, your actually hearing 600Hz+12.5Hz, 600Hz-12.5Hz,
and 600Hz+37.5Hz, 600Hz-37.5Hz and so on depending on keying waveshape and receiver filter
setting.

So, dashes must then be 120 msec long, but with only 40 msec space between.
That comes out to 6.25Hz.  So what you hear is 600Hz+6.25Hz, 600Hz-6.25Hz, and
the odd harmonics 600Hz+18.75, 600Hz-18.75, and so on, and certain even harmonics,
since this isn't really a square wave.

How much power is in each harmonic depends on the waveshape....

But - let's say your hearing or filter settings don't have a perfect flat response
around 600 Hz.  To exagerate, lets just cut off everything below 600 Hz.  You might
then hear dashes as 606.25 Hz, and dots as 612.5 Hz.  That's a difference of 1% or
so, and about 17 percent of the difference between two notes on a piano.  The
effect would get bigger as you move the center frequency down.  You would be able
to hear the change.

73, Michael, AB9GV
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[Matt Osborn]

On Wed, 20 Sep 2006 10:57:15 -0400, "Stephen W. Kercel"
<[hidden email]> wrote:

>In cognitive processing of sensory data, the brain functions a
>differencing engine. Each brain has a capability of distinguishing
>audible spectra, but some are more sensitive to particular nuances of
>difference than others.

That's interesting.  I've spent over 150 hours listening to CW at
various speeds, but I have developed no ability to comprehend what I'm
hearing.

My conscious brain only reports differences, not absolutes.  The
result is that 'dash dash dot dash' is heard as 'something something
change something'.  That's exactly the same as 'dot dot dash dot' is
heard.

I think I now know why the church choir wasn't eager to have me
participate.
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[N2EY]

In a message dated 9/20/06 6:29:25 PM Eastern Daylight Time,
[hidden email] writes:


> My conscious brain only reports differences, not absolutes.

How can that be, assuming you were able to learn to read and write, speak and
understand speech?


 The
>
> result is that 'dash dash dot dash' is heard as 'something something
> change something'.  That's exactly the same as 'dot dot dash dot' is
> heard.
>

I see a clue.

If you are hearing individual dots and dashes as separate elements, you're
probably listening to code charaters that are too slow for you.

We don't teach babies to talk and understand speech by speaking v-e-r-y
s-l-ow-ly. We don't expect them to hear "cat" as 'consonant k sound'......'short
vowel a sound'.....'consonant t sound'. Instead they hear "cat" as a unit, even
though it has three parts.

What we *do* when teaching speech is to separate the words clearly.
"The......cat........is.......on.....the.......mat'. So there's lots of
recognition/process time and the words are clearly separated. And we start with a very small
vocabulary, then build on it.

The same principle applies to learning Morse Code via the Koch/Farnsworth
method.

Consider the following thought-experiment:

Suppose you had the task of listening to a series of common words spoken
clearly and distinctly. And after each word, you were expected to write down the
last letter of the word.  Would that be difficult?

Receiving Morse Code is basically the same thing except that the words are
replaced by a series of short and long sounds.

73 de Jim, N2EY
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[Matt Osborn]

On Wed, 20 Sep 2006 21:07:48 EDT, [hidden email] wrote:

>In a message dated 9/20/06 6:29:25 PM Eastern Daylight Time,
>[hidden email] writes:
>
>
>> My conscious brain only reports differences, not absolutes.
>
>How can that be, assuming you were able to learn to read and write, speak and
>understand speech?
>
>
> The
>>
>> result is that 'dash dash dot dash' is heard as 'something something
>> change something'.  That's exactly the same as 'dot dot dash dot' is
>> heard.
>>
>
>I see a clue.
>
>If you are hearing individual dots and dashes as separate elements, you're
>probably listening to code charaters that are too slow for you.
>
>We don't teach babies to talk and understand speech by speaking v-e-r-y
>s-l-ow-ly. We don't expect them to hear "cat" as 'consonant k sound'......'short
>vowel a sound'.....'consonant t sound'. Instead they hear "cat" as a unit, even
>though it has three parts.
>
>What we *do* when teaching speech is to separate the words clearly.
>"The......cat........is.......on.....the.......mat'. So there's lots of
>recognition/process time and the words are clearly separated. And we start with a very small
>vocabulary, then build on it.
>
>The same principle applies to learning Morse Code via the Koch/Farnsworth
>method.
>
>Consider the following thought-experiment:
>
>Suppose you had the task of listening to a series of common words spoken
>clearly and distinctly. And after each word, you were expected to write down the
>last letter of the word.  Would that be difficult?
>
>Receiving Morse Code is basically the same thing except that the words are
>replaced by a series of short and long sounds.

I listen primarily to Chuck Adams' K7QO CD. I'm not sure at what speed
the code is being sent but believe it to be 13 to 15 words per minute.
I've also used the G4FON Koch method trainer at speeds of up to 25
characters per second

I do hear the rhythm of the characters, but the rhythm of opposite
sequences sounds the same.  That is, 'dit dah' and 'dah dit' has the
same rhythm.  Likewise 'dit dit dit' and 'dah dah dah' .  I can't tell
them apart.

Short word sequences (2 to 3 characters) come through somewhat better,
as the rhythm of words tend to be unique and can be memorized and duly
recognized (as is spoken language). Long word sequences are almost
impossible due to memory limitations.  Random character sequences lack
any intelligibility at all.

The brain is a powerful tool, but each is different in how it filters
input, calculates and generates output.  The brain of the barn owl,
for instance, so highly optimizes visual input for motion detection
that the owl is virtually blind if nothing is moving.  The owl has
move his head to create enough relative motion so it can orient itself
to its surroundings.  As a result, the owl can see a mouse creeping
along the floor in dark barn, but can't see the barn door 20 feet
away.

The human brain filters out CW from normal language processing, just
as it does the roar of a jet engine, a bird chirping, and even
background conversations.  If it didn't, it wouldn't be possible to
hold a conversation at a party, let alone in noisy bar.

I'm not sure what advantage, if any, my filtering offers me. Perhaps
it is rapid threat or food source identification, but the downside is
abundantly clear,  CW is most likely outside my reach.


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[Karl Larsen]

Don Wilhelm wrote:

> Darrell,
>
> That has ben dropped from the more recent handbook (does not appear in my
> 2005 edition).
> I am going 'out on a limb' here by saying that this stems from the concept
> that 'some keyclicks are good' philosophy.  Sidebands on a CW signal are the
> result of the keying shape, and there is more to it than just the rise and
> fall times - there is the rounding at the corners to consider too.
>
> I have heard many an operator state that 'hard keying' will get you through
> a pile-up better.  While that may be true, it certainly is not 'neighborly'.
>  

    Hi Don, I recall a lot of years ago a really good DXer used a
measured amount of chirp on his signal. It was not bad but it was
distinctive. He was a DX station often and you knew his signal in an
instant.

    It was back when a radio transmitter had a crystal holder and we
were all building a VFO with some degree of success. My VFO was about
the size of a K2 and it was mounted on rubber to eliminate mechanical
noise. Had to build a voltage regulater with a OB2 that made a sort of
regulated 150 volts for the vfo tube plate. It worked great.

73 Karl K5DI

> I am glad to see that this statement does not appear in the more recent
> handbooks.
>
> 73,
> Don W3FPR
>
>
>  
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]]On Behalf Of Darrell Bellerive
>> Sent: Tuesday, September 19, 2006 6:08 PM
>> To: Elecraft List
>> Subject: [Elecraft] Hearing CW - Fundamental Keying Waveform?
>>
>>
>> The recent thread on filter settings and hearing reminded me of a
>> question I
>> would like to get an answer to.
>>
>> In the ARRL 2001 Handbook on page 15.7 we find:
>>    "The dots and dashes of a CW signal must start and stop
>> abruptly enough so
>> we can clearly distinguish the carrier's presences and absences
>> from noise,
>> especially when fading prevails. The keying sidebands, which sound like
>> little more than thumps when listened to on their own, help our brains be
>> sure when the carrier tone starts and stops.
>>    It so happens that we always need to hear one or more harmonics of the
>> fundamental keying waveform for the code to sound sufficiently crisp."
>>
>> What is meant by "the fundamental keying waveform"?
>>
>> How do we take "the need to hear one or more harmonics of the fundamental
>> keying waveform" into account when setting up the IF and audio filters?
>>
>> 73,
>>
>> Darrell  VA7TO  K2 #5093
>>
>> --
>> Darrell Bellerive
>> Amateur Radio Stations VA7TO and VE7CLA
>> Grand Forks, British Columbia, Canada
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>>    
>
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[Darrell Bellerive]

And what about the effects of compression?

Wouldn't the AGC tend to reduce the dynamic range between the noise floor and
the CW elements? Would an audio expander help to make the CW stand out from
the noise better and therefore easier to hear?

73,

Darrell  VA7TO  K2 #5093

--
Darrell Bellerive
Amateur Radio Stations VA7TO and VE7CLA
Grand Forks, British Columbia, Canada
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[Ron D'Eau Claire-2]

Darrell, VA7TO wrote:

And what about the effects of compression?

Wouldn't the AGC tend to reduce the dynamic range between the noise floor
and
the CW elements? Would an audio expander help to make the CW stand out from
the noise better and therefore easier to hear?

---------------------------

Yes. Being a CW op, that's one of the things I hate about AGC. It pulls the
noise level up whenever the signal pauses.

Of course, you can use SLOW AGC while will help avoid that effect on if the
speeds are high enough.

Years ago "hang" AGC was popular. It actually used a timer that waited a
specific time - the "hang" time - after the signal last appeared before
ramping the gain up quickly. That way the AGC didn't "pump" at all as long
as the hang time exceed the maximum gaps in the signal.  

My preference is to turn the AGC off. Then, on all but the weakest signals
the receiver is quiet except for the signal beating out its CW. When the
signal stops, there blessed silence. Maybe a whisper of background noise,
but only a whisper...

On the K2, all you have to do is run the audio gain up and turn down the RF
gain, and use the RF gain as your "volume" control. The old "rule of thumb"
is to turn the RF gain all the way down, then run the audio gain up until
you just barely begin to hear the background noise of the receiver in the
speaker or phones. Leave it there, then turn the RF gain up as needed to
hear signals. Don't touch the Audio gain after that.

Ron AC7AC

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