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Ham-Digital Digest Sun, 16 Jul 2000 Volume 2000 : Issue 191
Today's Topics:
CW versus hi speed digital etc. (4 msgs)
Forget HF & CW - Think Digital (5 msgs)
WANTED KENW MC-45DM(E) MIC (2 msgs)
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Loop-Detect: Ham-Digital:2000/191
----------------------------------------------------------------------
Date: Sat, 15 Jul 2000 20:30:02 -0500
From: "Peter O. Brackett" <ab4bc@ix.netcom.com>
Subject: CW versus hi speed digital etc.
Klein:
Excellent analysis. No bias or emotion, just plain objective statements and
musings. I like it.
Other than my own feeble attempts to get folks to look at and understand the
merits of CW, your comments here on this thread are a very thoughtful
examination of the phenomena of which I wrote.
The situation of human operators beating out all forms of modern digital
communications using CW on real HF channels are real and not just idle
claims.
I believe that there is some justification in asking why, and trying to find
out why and how this happens.
I know there are sceptics. But this scepticism comes only because there are
[relatively] few really skillful except nois and interference on frequency
while two skillful CW operators were continuously passing 100% perfect copy
traffic on that frequency! One cannot expect them to know about the
existence of such capability when they are not skilled enough to observe and
hear what's going on.
Sort of like trying to explain the benefits of calculus to a grade 4
student, they just don't get it!
That does'nt mean it is not true!
There is something going on there in the human brain processing
[Psycho-acoustical phenomena and brain post processing, a full Baysian
receiver?] and other aspects of the CW system that could and should be
investigated for sources of new robust methods of digital signalling at even
higher speeds.
And... what other area by professional communications engineers?
Modern digital systems could be improved by emulating any such algorithmic
knowledge gained from a study of skillfull high speed CW operators operating
in a typical HF channel with noise and interference.
More, thoughts, comments,
Peter K1PO
"Klein Gilhousen" <kleing@NOSPAMqualcomm.com> wrote in message
news:396b90a7.344546802@news...
> This is a pretty interesting thread for me. I have been a ham since I
> was 13 and have spent most of my professional career in digital
> communications, most recently (the last 15 years) as a co-founder at
> Qualcomm.
>
> In principal, OOK (CW) ought to be poorer in performance than PSK in a
> Gaussian channel by a few dB. But we have anecdotes claiming that
> human operators can match the performance of some of the digital
> modes. How do we reconconcile this? One way is to consider that "in
> principal" didn't consider the whole system involved in human decoded
> Morse. In fact there IS an FEC system in Morse CW. It's called the
> English (or whatever you speak) language. There is considerable
> redundancy in the language and additional redundancy on the context.
> A skilled human "decoder" can take advantage of all this context and
> code and wring more out of a given situation than one might suspect.
> In addition to FEC coding, there is feedback coding available. CW
> traffic handlers developed methods for detecting errors and asking for
> "fils" to make corrections. A further aspect of the system is rate
> adaptation. The transmission speed can be adjusted to take advantage
> of or accommodation to temporary changes in channel conditions.
>
> I disagree with the notion that Morse CW is not or cannot be a digital
> system. The key idea in what makes a digital system is that the
> modulation system defines a number of discrete symbols that are sent.
> Morse CW certainly qualifies on this count. Additionally, I have no
> problem conceiving of a machine implemention of Morse CW that is every
> bit as digital as the other modes which we have no problem accepting
> as digital. Fully implementing all the implicit codes would be quite
> a challenge, however.
>
> Actually, we use FEC all the time in ham communications, i.e., the
> phonetic alphabet. If one wishes to have an explicit FEC code in
> Morse CW, it is a simple matter to encode the messages (mentally, it
> you like) into the phonetic alphabet and transmit them this way. And
> it is also a simple matter for the skilled human operator to mentally
> perform the error detection and correction function. Does this work
> as well as convolutional encoding/Viterbi decoding? Of course not.
> But it does function as a FEC system, and one that can be implemented
> by incredibly simple means.
>
> By the way, I think that Morse CW is a binary modulation system (not
> ternary or whatever). There are two signalling elements: transmission
> of a dot length pulse, and a dot length silence. Everything else can
> be described as a simple code combining sequences of these elements.
> The code has certain rules, such as that there are no two dot long
> pulses transmitted. This may sound pedantic but it is the way you
> begin to describe how you would build an optimum receiver for Morse
> CW. And yes, one can build a practical matched filter system for
> Morse CW. Just because people usually don't doesn't mean one can't do
> it.
>
> I'm not trying to start arguments here, just bringing another
> perspective.
>
> Klein Gilhousen
> Bozeman, MT
> WT6G
>
------------------------------
Date: Sat, 15 Jul 2000 20:47:13 -0500
From: "Peter O. Brackett" <ab4bc@ix.netcom.com>
Subject: CW versus hi speed digital etc.
Steve and Klein:
I respect your rights to your opinions and to your own classification or
phylogenic systems, but the "convention" has always been to at least
conceptually separate "channel coding" from "modulation".
Of course the ones who ignored this conceptual dictum [Gordon R. Lang in
Canada and Gottfried Ungerboeck in Switzerland] were the ones who invented
To be continued in digest: hd_2000_191B
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