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Thread: What Tone?

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AuthorText


Posted: 2017-06-12 16:42
What is the best Tone for learning CW?


Posted: 2017-06-12 19:07

You must work out the best audio tone for learning morse yourself
and
in my view it can be a critical factor in the speed with which you accomplish it,
so
unless you got to 25wpm in two weeks, I think it is worth some effort . . .

Depending on your hearing response, you may find moving one of two hundred Hz makes a big difference to read-ability.

If you can't hear it properly you can't learn it quickly.

If you think it might be worth trying out a few frequencies you could try making up some test mp3 files at various frequencies
and
just listening to see what sounds like dits and dahs and what sounds like a funny noise.

cb


Posted: 2017-06-12 22:59
Tone does not matter so much. General 600 to 800 Hz is used.

When you tune a receiver, you change the tone by tuning. That is an advantage because you can often omit QRM (sound of undesired stations) by choosing another pitch of the desired signal.

Important is that you keep loudness low. Strong audio makes copy more difficult and is fatiquing.

US-army used 641 Hz, as you can hear on
https://www.youtube.com/watch?v=Li8Hiwbc664

On https://www.youtube.com/watch?v=eTizFjjVXh0
you can hear different tones on a record dated 1942
The purpose in the army was to learn the servicemen Morse code as fast as possible.



Posted: 2017-06-15 00:09

Tone doesn't matter so much to a few 00Hz for people with a talent for morse and no hearing response issues,
who have been ok at 40wpm through the middle of a pile-up for the past 40 years . . . . .

For the rest of us . . .


Posted: 2017-06-26 18:20
800 hz. When you are right on top of a transmitting stations frequency that is about the tone you hear. If it sounds lower than or higher than that you are probably not transmitting where he is or are listening on one frequency and transmitting on another. This will really knock down your signal that he hears, or he will have to retune to get to your frequency. Some will not agree, but I have found it to hold true on all my qso's. I have proved this on a spectrum analyzer. Most stations are at least 200 hz off from each other when they are talking. Not a big deal if you and he are 20 over s-9, but if either weak it is. Back in the days of crystals and not vfo's (recieve and transmit) this was not a problem, but today it is. I hope this made some sense to you, and helped. Bob


Posted: 2017-06-26 20:27
Hi Bob,

I am not that experienced like you, and at technician ham level not educated the way you demonstrate that you are; however possibly you want to correct me please on the next statements:

1. CW has less bandwidth than SSB so with a CW filter you gain abt 12 dB in SN ratio because you eliminate noise at other than the CW audio frequency including its bandwidth.

2. However in an QRM free band, as nowadays usable, you can't copy a CW signal better in a 250 Hz filter then in a 4 kHz bandwidth, because your BRAIN is a natural adaptive bandfilter automatically adjusted to the desired pitch, with a bandwidth of about one octave. So the lower the pitch the smaller the bandwidth. In the case of 800 Hz pitch it is 1600Hz wide, and in the case of 200 Hz it is 200 Hz wide, about the bandwidth of CW.

3. I suppose that commercial transceivers have an fixed build in offset between received pitch and transmitted frequency, Only when you QSO at that pitch the receiving and the transmitting frequency are the same. May be a RIT control can change that, that is something I never have understood. I suppose that when you tune ur rx to a 600 Hz pitch your transmitter is shifted 200 Hz, but when you use the RIT to change the pitch, your transmitter is at the same frequency. This under the condition that when you receive a pitch of 800 Hz your transmitter frequency is zero beat with the tx of the QSO partner.






Posted: 2017-06-27 17:53
Very good point. I should have mentioned the RIT control in my post. It is a great option, and you are right it does not, or should not change your transmit frequency. IF shift is also pretty neat, because it will actually move a lot slower than RIT to fine tune the QRM further away from the station you are trying to receive. I recently bought a 500 hz filter for my Icom and am well pleased..I did a lot of research on it, because I was confused about which filter to buy. The majority opinion (and everyone has one) was that the 250 hz filter was too narrow for most cw. It was mostly for contesters in a big pileup..like fielday was. just too narrow. Lea, I will tell you that I don't know even close to everything, and will have to hit the books about the pitch ver bandwith matter. I have just never thought of it like that. Thanks for your post...and hope you get your general soon. There is a website out there called hamexam.org that really helped me. Take care..Bob


Posted: 2017-06-27 22:22
O yes, a 500 Hz CW filter triggers at me the next story:

Last time I was in in the local radio club, some time ago, they had invited an extreme old guy, ham for over 70 years or such already, who presented a lecture about CW. He regretfully passed away in the mean time I read.

Het spreaded a smell that I associated and remembered me of my grandfather and his home.

Not nice, absolutely not, it was quite hot and the chairman installed a big fan in order to dilute the smell of the old guy, but he friendly mentioned another reason. hi

I made some notes. I am absolutely not sure I understood everything so correct me when I am obviously wrong, but his story was:

CW has a smell sri small bandwidth he demonstrated that with a wav audio file on a PC that had CW 20 wpm and the off to on was 8 millisecond he said, with a coseinsquared slope, whatever that may be. Sounded pretty, ok.

Next he was talking about digital filters. Brick wall has an impulse response of sinc(x)= sin(x)/x. sin(x) is a sinewave and de x in the denominator makes it weaker and weaker in amplitude with growing x.

He showed the pass through, a FIR, finite impulse response filter block diagram, not very good, but he added a smoothing Blackman window and expanded the filter to 1025 stages of a shift register that is able to contain analog samples. The result was amazing, never seen such a good low pass filter and the phase was linear he said.

After that he inverted all the odd weighting factors of the filter, that was because he multiplied with a sinewave with frequency half the sampling frequency, and I can't understand but it turned out the low pass was transformed to a high pass.

Time for the break, really not nice to have a drink with that smell hanging around.

After resume, he added the weighting factors of the 1025 long low pass with the high pass and it turned out to be a band stop filter.
When that was done he was putting parallel a filter with only one weighing factor 1 and the rest 0, an all pass he said.

Adding this all pass or substracting, my notes are not clear at this point, he ended up with a small bandpass of 150 Hz wide, unbelievable steep, flat on the top and phase linear.

The 20 wpm morsesignal was passed through it and I only watched some very small difference at the start of each morse mark out of the speakers.

So the 20 wpm CW passed practically undistorted through a 150 Hz wide filter.

Next step was the sound of noise played. He put the filter over it and the noise sounded very band limited. After that the CW was at low amplitude added to the noise. I could not copy it. With the 150 Hz filter taken away and the noise back to wide band, I did copy abt 80% in the noise.

Unbelievable experience.



Posted: 2017-06-27 23:03
Too deep for me but I bet it was very interesting. See you are smart, because I would still be lost in the math. I have played around with a q-multiplier I built a few years ago, but it doesn't work near as well as the 500 hz filter. Also has no effect on ssb except for harmonic suppression. Would have liked to be there for that; except for the smell...lol Bob


Posted: 2017-06-28 03:32
Here is something to think about: the faster you send code the more bandwidth it uses!!!! The formula is Bw=wpm X 4 ie 13 wpm x4= 52 hz...now plug in another speed....28 wpm X4 = 112 hz. So these code racers are taking up more space than us 13 to 18 folks. Bet they didn't know that.


Posted: 2017-06-28 18:46
Bob,
That depends on the leading and trailing edge of your dits and dahs, The factor 4 is for a signal that transmits up to the 5-th harmonic of the base frequency.

When you look at a websdr such as
websdr.ewi.utwente.nl:8901 in a busy CW band, maximal zoomed in on the waterfall display, you will notice that with the same speed, the bandwidth vary a lot between stns, key-clicks. I suppose they are generated by linears after the transceiver on contest weekends, that are just switched on and off with uncontrolled edges


Posted: 2017-06-29 00:10
I know the book I read also goes into k factors relating to the shape of the keying envelop and baud rates. Which means nothing to me.


Posted: 2017-06-29 09:16
The shortest time in Morse code is the duration of a dit.

The number of shortest timeunits per second is the Baud rate by definition.

PARIS contains 50 dittime units

Hence 1 wpm is 50 dittimes in 60 second.

That is 5/6 dit/second = 5/6 Baud

Conclusion: 5/6 times wpm = baudrate.
Example: 24 wpm = 20 Baud, Each dit takes 1/20 s = 50 ms.


Posted: 2017-06-29 15:07
I have found as I get older it is easier to decode or listen to Morse code at a lower frequency than I used to listen to when I was young. 750 HZ in the old days but now down to 600 HZ and dropping rapidly, I guess this is because we lose the top frequencies as the ears grow less responsive. I totally agree about keeping the rf/af gains right down when copying CW it is less tiring. I always use headphones to copy as well as you don't get any reflections bouncing off the walls to confuse the operator. I was taught by an old radio operator to keep the phones well forward on the ears and not right over the ear but these days I use phones that cover right over the year,
VY 73 Rich G4FAD..


Posted: 2017-06-29 18:12
g4fad

When you use a 250 Hz filter, it passes sufficient sideband power to enable a sufficient steep signal edge after detection. As brushup showed at 30 wpm you need 120 Hz bandwidth, also according
to the formula KN8BTA presented, to include the fifth harmonic in order to ensure sufficient steep edges.

HOWEVER when the signal is detected to sound, the fifth harmonic of the 600 Hz sound is already 3000 Hz.

When the elderly (let) test their ears it often turns out they hear up to 1.5 or 2 kHz straight but above that frequency , 3 kHz turns out to be 60 or 80 dB down. (The "what did you say" stage of hearing loss)

So you are missing the fifth and probably partly the third harmonic, of the pitch, and that makes that above 400 to 600 Hz pitch you can't copy the code anymore especially not when it is faster.

What you can try is a direct hard contact with your skin, close to your ears of a metal plate
(actually the experiment was the head pushing to the vertical standings of an aluminum ladder), that increases the max frequency detected by the person with the head under test, enormously.


Posted: 2017-06-29 22:50


Poor DEBORAH . . . .

At least you now know what frequencies to use as you get older . . .



Posted: 2017-06-29 22:56

. . . actually, if you use a zero cross switch, you don't need a vertical edge with a huge number of harmonics . . .


Posted: 2017-06-29 23:59
Zero crossing switch want help ANYbody, when the signal to noise ratio is negative , -5 dB or so,
Your switch goes wild, actually one of the reasons CW decoders only work with strong signals.

And cb - Chris, some basic signaltheory: when you have hearing loss of 80 dB on 1,5 kHz I assure you that ANY form of signal with a base frequency above 750 Hz is just detected by the listener as sine wave. Block wave, saw tooth or whatever, makes no difference.


Posted: 2017-07-09 19:48
brushupCW:
Zero crossing switch want help ANYbody, when the signal to noise ratio is negative , -5 dB or so,
Your switch goes wild, actually one of the reasons CW decoders only work with strong signals.


I meant at xmit - not that it happens . . .




brushupCW:

And cb - Chris, some basic signaltheory: when you have hearing loss of 80 dB on 1,5 kHz I assure you that ANY form of signal with a base frequency above 750 Hz is just detected by the listener as sine wave. Block wave, saw tooth or whatever, makes no difference.


Hmmm, when you have severe hearing loss, you can't hear things properly; yup fairly basic.

I doubt any animal anywhere has ever heard a pure sine wave - considering the path the sound takes, including amplification via a lever and a diaphram tensioned by a muscle -
but
if you are just trying to tell me that any periodic waveform can be expressed as the sum of an infinite set of sine waves, the I take your point.

cb



Posted: 2017-07-09 21:58
OK cb-Chris

It is important not to put some theoretical on off switch in your final transmitting amplifier,

That is because that is a sure way to make tremendous key click on the band. Keep the slopes from zero power to PEP and back to zero each at least 5 ms.

When a constant tone has multipath propagation to your ears, you still hear the same tone but with another phase, which you can't detect with your ears.

However, when I listen to morse code and move away from the loudspeaker,it all smears out and I can't decode it anymore at speed 40 wpm. lower then 20 is still possible for greater distance between rooms in the house.





Posted: 2017-07-11 00:31
brushupCW:
OK cb-Chris

It is important not to put some theoretical on off switch in your final transmitting amplifier,

That is because that is a sure way to make tremendous key click on the band. Keep the slopes from zero power to PEP and back to zero each at least 5 ms.


Yup - well, if you switch "on" a sine wave at 45° for example, you get the best impression of a square wave click that your amp can produce . .

I meant wait until the wave voltage cycle is zero before swiching on - so you don't get a distorted sine wave . . .


I guess some people like the clicks - especially if the code is accurately timed enough.

They give me a headache . . .

brushupCW:

When a constant tone has multipath propagation to your ears, you still hear the same tone but with another phase, which you can't detect with your ears.


Your ears have multiple detectors for the same frequency . . .


brushupCW:

However, when I listen to morse code and move away from the loudspeaker,it all smears out and I can't decode it anymore at speed 40 wpm. lower then 20 is still possible for greater distance between rooms in the house.


I suppose so . .

The volume will drop away, but you will loose more of any "click" element due to the higher frequencies being more directional.

Have you tried a tube resonator round your speakers ??

Anyway, your mate Pierpont is an absolute proponent of headphones set out of phase ones, as they providing double the s/n of speakers ( see the last bit of chapter 14 ), so maybe it's not worth the effort . . .



Posted: 2017-07-12 11:18
Ok cb chris, my error, excuse me, I understood you wrong while you formulated correct abt the 0-crossing. That was because I supposed you meant something else than you actually wrote, hi.

I suppose you start the RF sinewave always at zero when you push the key, because there was no sine wave and no energy in the final filter with key up. With Morse dit or dah leading edge of a few millisecond on 80 m it takes about 2000 RF sinewaves with increasing amplitude to reach full key down power. The first sinewave starting at 0 voltage has an amplitude nearly 0.

Concerning sound, AFAIK you do not hear phase difference of a constant tone between 2 ears, but on the start of the tone it is indicating the listener the direction of the sound source.

Interesting thought with the phase difference on the headphone of sigs in the noise.


Posted: 2017-07-16 01:11
brushupCW:


I suppose you start the RF sinewave always at zero when you push the key, because there was no sine wave and no energy in the final filter with key up. With Morse dit or dah leading edge of a few millisecond on 80 m it takes about 2000 RF sinewaves with increasing amplitude to reach full key down power. The first sinewave starting at 0 voltage has an amplitude nearly 0.



If you "key-down" to start the oscillator and radiate as the amplitude builds up then you won't be radiating a sine wave,
because
the increasing amplitude contains the feedback frequency of the oscillator - i.e. a distorted sign wave.

Mostly this will be on QRP tho, but then you will need the oscillator for BFO anyway,
so it will mostly be RIT shift and click.

Older VFOs used to get pulled by the load into the xmit amp leading to chicken chirp.

https://www.youtube.com/watch?v=GddwlOaGeCQ&ab_channel=burt2481

( one of my fave youtubes )


RRGITD - what do you think brushup OM ???


Posted: 2017-07-16 11:51
cb:


( one of my fave youtubes )




The youtube I can watch but not understand because, as a self educated man, I can read English but not get it with my ears (unless it is Morse) That is not because I am deaf but because the pronounciation is completely different with what is in my thoughts when I read a word or text.

Amplitude distortion of a master oscillator is completely of no importance at all. because in a final CW Power amplifier only the top half of positive part of the excitation is used for opening the valve or semiconductor, so that is pulsing (120 out of 360 degree) with a lot of harmonics the tank circuit, that obviously is not interested in harmonics and grows in amplitude the way I described, except my typing error that this all ought to happen in 2 ms and hence om 80 meter in 7000 RF cycles. (not 2000)
cb:


RRGITD - what do you think brushup OM ???


I am completely baffled, you must be an extra licensed ham, I am sure.


Posted: 2017-07-16 21:19
brushupCW:
The youtube I can watch but not understand because, as a self educated man, I can read English but not get it with my ears (unless it is Morse) That is not because I am deaf but because the pronounciation is completely different with what is in my thoughts when I read a word or text.


I'm sure you are very clever.

You could hear the chirp as the osc gets pulled ???


brushupCW:

in a final CW Power amplifier only the top half of positive part of the excitation is used for opening the valve or semiconductor, so that is pulsing (120 out of 360 degree)


Yup - it won't be much bandwidth, and only at key-click time - and there will be an ever so slight delay but no one will notice . .
but
I thought that those were some of the points you were discussing . .


brushupCW:
I am completely baffled, you must be an extra licensed ham, I am sure.


You are not baffled - you just didn't recognise it . .

"Real radios glow in the dark" - Burt is demoing his 55 year old rigs in the "youtube" vid . . .

. . he adds that people answer his CQ to tell him that his equipment is failing badly !!

We don't have "extra".

Really there should be several other courses to pursue, so on-going study is encouraged


Posted: 2017-07-17 00:19
Here Brushup,
I do not understand you. Chirp is FM modulation, due to supplyvoltage, and temperature change of the master oscillator, it has nothing to due with distortion of the produced sinewave. Should that sinewave be distortion-free then the power amplifier introduces it. Blockwaves in case of MOSFET.s and 120 degree pulsing current in the case of a class C tube amplifier.

So your story about keyclicks that should be very heavy when you switch the RF sinewave in on half amplitude, is of no value, because you actually do that because sine 30 degree is 0.5 when the tube opens on 30 degree and closes on 150 degree. Produces no keyclick as I tried to explain.

And keyclick is due to to fast growing amplitude of the output of the power amplifier. Takes thousands of sinewaves of growing amplitude in the tank circuit. Amplitude of the ENVELOPE has to take abt 5 ms in order to prevent keyclick.

That's all.

Antique equipment is nice for collectors, and
http://www.v-d-r.net/images/T1154.mp3
yields a recording of a chirpy T1154 signal.

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