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PA2AGA > HDDIG 04.07.00 00:00l 190 Lines 6933 Bytes #-9412 (0) @ EU
BID : HD_2000_178E
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Subj: HamDigitalDigest 2000/178E
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Sent: 000703/1831Z @:PI8HGL.#ZH1.NLD.EU #:58001 [Den Haag] FBB $:HD_2000_178E
From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Mon, 03 Jul 00 19:07:56 MET
Message-Id: <hd_2000_178E>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
"Peter O. Brackett" wrote:
> Gary:
>
> Heh, heh...
>
> Gary, this is unlike you! Usually you are right on point.
>
> But here you are WRONG.
No, he's not.
> There are some aspects of analog in hand sent CW, this would be interperted
> only as a timing "jitter" effect which all digital communications systems
> from SONET lightwave systems to ELF submarine data systems, have to various
> extents.
>
> In fact even this aspect of CW has been addressed by coherent CW enthusiasts
> who have addressed the timing and synchronous detection problems you alluded
> to.
>
> Also... from a channel coding and modulation viewpoint, CW can easily be
> transmitted using a variety of modulations from FSK to PSK, to whatever. It
> just then makes direct copy of the sound "by ear" less familiar to
> operators, a conversion device to convert back to a keyed tone would suffice
> for human readability.
Well, since "CW" in the amateur radio context specifically means "Morse
telegraphy
via bandwidth-limited on-off keyed AM", you can't easily transmit "CW" using a
variety of modulation techniques.
Once you start talking about PSK, for example, you're talking about something
totally different in terms of performance.
As for the rest of your Morse advocacy arguments, to each his own.
--
Dana K6JQ DoD #j
dana@source.net
------------------------------
Date: Sun, 2 Jul 2000 19:24:12 -0500
From: "Peter O. Brackett" <ab4bc@ix.netcom.com>
Subject: CW versus hi speed digital etc.
Gary:
You are waffling again...
Good human operators making use of their pscycho-acoustic abilities and with
appropriate filters and processing in front of them while copying CW can
usually always beat your vaunted "modern" digital modes over a congested and
noisy HF channel. [The comparison has to be calibrated at the same data
rates, of course humans can't operate at thousands of bits per second, but
that's not the point. The point is that humans can beat the modern digital
systems using CW at the same information rates! Period!]
The fact that no one has yet implemented a machine decoder that can do as
well, is simply a statement of the vast improvements still available in
digital signal processing.
Human beings are likely actually instinctively implementing a pure full
non-linear Bayseian receiver process and such a non-linear Bayseian receiver
has never yet been economically implemented to run in real time at the speed
and a price amateurs can afford.
I agree that most CW is conducted using simple OOK, but so what. To be
fair in a comparison then all other modes should use the same modulation.
If they can use more advanced modulation, then there is no reason why CW
cannot do so as well.
And so... if CW was sent and received by human operators over an "advanced"
modulation system, say generalized QAM, or DMT/QAM or whatever, then that
would be a fair comparison.
Even so, without that, CW the superior digital mode, when decoded in real
time by skilled humans invariably beats the new complex modulation schemes
in the new modes running on everyday HF channels.
Want to run some tests at the same data rates, the same bandwidths in some
typical HF channel conditions while varying the "interference"? I've done
it often... When the other modes have long faded... the CW guys are still
communicating. What, why?
The question is not about the fact that it is a superior mode, that is an
established fact!
The real interesting question is why?
Why should the trained human using an apparently simple external digital
system be able to out communicate modern digital systems over real HF
channels? What is going on inside the operator's head, ears, and hands?
What???
If you could answer that you would have a lead on how to efficiently
implement economical and robust machine based detection algorithms.
Sort of like the speech recognition problem, they still can't beat the
human ear and brain!!
Gary what is going on with this why does everyone trash CW instead of
investigate its' superiority?
Why? Are you not interested? Is it not an interesting digital
communications problem, challenge, etc....
What?
Why do you waste your time denying that the skilled human operating at
comparable data rates is still superior to the best digital modes in use
today? Why not find out why and then try to improve the machine based
modes?
Stop trashing CW and learn something!
Best Regards,
Peter K1PO
"Gary Coffman" <ke4zv@bellsouth.net> wrote in message
news:tmavlssbodb1k0pg732ue07uri0cclk0d2@4ax.com...
> On Fri, 30 Jun 2000 11:26:11 -0500, "Peter O. Brackett"
<ab4bc@ix.netcom.com> wrote:
> >CW is a digital mode, it can be high speed, it was the "first" mode as
well,
> >and it is both machine and human decodable.
>
> While the OOK modulation typically used is in a sense digital, ie an AM
modulation
> of on and off states of the baseband signal, Morse Code is not digital. It
is a timing
> code. All the coding information is in the timing edges, not in distinct
levels. While
> ideally that timing is derived from a fixed clock, in practice it
generally is not and
> must be considered more of an analog process.
>
> >Remarkable!
> >
> >Think about it, it is in fact the only digital mode that is decodable
both
> >by human operators and machines!
> >
> >Think about that! Try decoding Baudot RTTY by ear, or PacTor, or
Clover...
>
> Actually, some people can decode Baudot RTTY by ear (I can pick out
> my own call sign and the RYRYRY signal for example). Each character
> does have a distinctive sound if you train your ear to recognize it. Of
> course the fact that it is normally sent at 60 WPM or faster makes that
> a bit difficult, but slow it down to normal CW operating speeds and it is
> not difficult to decode by ear.
>
> In fact FSK is somewhat better (6 dB) than OOK because the ear is
> deciding between two distinct signal states and not between the presence
> and absence of a single signal against noise, which is a harder detection
> problem. In the old days, when using arc and alternator transmitters,
where
> it was technically difficult to generate OOK, operators used FSK to send
> Morse. It worked better than OOK then, and still does. Too bad most Morse
> operators got away from that type of moduation. Both machines and men
> could take better advantage of it than OOK.
>
> >Try high speed CW on HF with a keyboard program and high speed CW reader
> >program, it often works as well as, or better than, at the same speeds,
more
> >modern digital modes on the HF channel.
>
> But it almost always occupies a larger bandwidth. The sharp timing edges
> essential to Morse coding cause the occupied bandwidth to be larger than
To be continued in digest: hd_2000_178F
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