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To : HDDIG@EU
Date: Sun, 02 Jul 00 14:23:06 MET
Message-Id: <hd_2000_177A>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
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Ham-Digital Digest Sun, 2 Jul 2000 Volume 2000 : Issue 177
Today's Topics:
CW versus hi speed digital etc. (5 msgs)
Digipan Software for PSK-31 (3 msgs)
Field day review (MixW rocks)
Field day review (MixW rocks)(TrueTTY OK too!)
how does PSK31 really work?
Live SSTV webcams on the net
need 9k6 mods
NEW AMATEUR RADIO WEBSITE!
Study finds most CW operators are homosexual (2 msgs)
WinPSK source question
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(by FTP only) from ftp.UCSD.Edu in directory "mailarchives/ham-digital".
We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party. Your mileage may vary. So there.
Loop-Detect: Ham-Digital:2000/177
----------------------------------------------------------------------
Date: Sat, 1 Jul 2000 10:47:21 -0400
From: "Bob Lewis" <aa4pb@erols.com>
Subject: CW versus hi speed digital etc.
The trade-off for CW is "technical simplicity" for "operator skill".
The equipment doesn't require much in the the way of frequency
stability or processing power. How well CW works depends mostly on how
skilled the operator is rather than on equipment complexity. Minimum
equipment requirements is the primary advantage to CW today (plus the
fact that some enjoy using their CW skill just like some enjoy
sailing).
The newer digital modes (pactor, PSK31, etc) don't require the
operator to decode in his head, but the equipment technical
requirements are much more involved. The result is bigger, heavier,
and more power consumption to get the job done but the throughput is
normally much higher than the vast majority of CW operators can
handle.
If you want to compare the newer digital modes to computer decoded CW
then CW looses hands down. On/Off keying is the least reliable way to
transfer data between computers. Computer decoded CW gives you all the
disadvantages of both systems.
Since CW has two states I suppose you can claim it's digital - but
then so is the light switch on my wall. When you mention "digital" few
will immediately think of my light switch or CW.
CW, like most modes, has its advantages and disadvantages. I don't get
the competition between modes - use the mode that best suits what you
want to do at the time or that you enjoy operating. The mode that does
everything the best has yet to be invented.
------------------------------
Date: Sat, 1 Jul 2000 10:25:03 -0500
From: "Peter O. Brackett" <ab4bc@ix.netcom.com>
Subject: CW versus hi speed digital etc.
Hamish:
All FEC systems make use of memory!
What?
Peter K1PO
"Hamish Moffatt VK3SB" <hamish@cloud.net.au> wrote in message
news:Moh75.311$I43.1819@news1.eburwd1.vic.optushome.com.au...
> Peter O. Brackett <ab4bc@ix.netcom.com> wrote:
> > How do you think high speed CW operators can copy way ahead of their
paper
> > copy [pencil or keyboard] in their heads?
>
> > It's called FEC...
>
> I wouldn't call that FEC at all. It sounds just like having a good
> memory to me!
>
>
> Hamish
> --
> Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
------------------------------
Date: Sun, 02 Jul 2000 01:01:11 GMT
From: hamish@cloud.net.au (Hamish Moffatt VK3SB)
Subject: CW versus hi speed digital etc.
Peter O. Brackett <ab4bc@ix.netcom.com> wrote:
> All FEC systems make use of memory!
FEC usually means encoding extra information into the transmission
to correct possible errors (rather than to correct the errors after
transmission). Again I ask, how have you used FEC with CW?
73
Hamish
--
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
------------------------------
Date: Sun, 2 Jul 2000 02:57:53 -0500
From: "Peter O. Brackett" <ab4bc@ix.netcom.com>
Subject: CW versus hi speed digital etc.
Hamish:
My friend you are Dead Wrong!
Forward Error Correction (FEC).
There are two basic approaches to accomplishing FEC, and a myriad of subsets
of algorithms within those two basic approaches...
As you suggest, both methods encode extra information into the transmissions
to enable "correction" of errors at the receiver without ARQ.
For decades, the FEC "Gods" professed and believed that FEC could not be
used without expanding the bandwidth of the transmission. For decades, FEC
was said to be useless for the bandwidth limited channel. It was in fact
only used on the power limited channel (Read long range space missions.).
Today there are two methods of FEC in wide use. In fact the newer,
bandwidth efficient methods of FEC applied to bandwidth limited channels are
now far more widely used than the power limited channel bandwidth expanding
methods.
The oldest approach to FEC, is bandwidth in-efficient and expands the
bandwidth of the transmission. The proponents of this bandwidth expanding
approach believed that Shannon had said that coding and modulation had to be
separated. (He said no such thing, but indicated that it was a good way to
conceptualize communications systems.)
These bandwidth expanding methods were the only methods of FEC known up
until about 1980 when Gordon Lang in Canada invented lattice coded
modulation and in 1982 when Gottfreid Ungerboeck in Switzerland invented
trellis coded modulation. The breakthrough made by these two great
"inventors" was to combine coding and modulation in one integral
operation/algorithm.
Hamish clearly as you, or someone else, pointed out up the thread
"conventional" CW uses simple on off keying (OOK) of a single carrier as the
conventional method of modulation.
And so... clearly CW operators cannot and have not done bandwidth
efficient (integrated coding and modulation) FEC...
Now on the other hand for the much older and traditional approach to FEC,
where coding and modulation are separate, many skilled CW operators and
their communications administrators have in the past, and can easily add the
first method of FEC to their transmissions.
In fact many commercial CW operators and certainly most military CW
operators use FEC. This usage of FEC over CW began in WWII, "the big one"
and has been in use continuously since then.
Of course you won't have heard it on the air in "plain language", but I can
send you to several HF frequencies where you may copy on air CW FEC,
generally in the format of "five letter code groups".
In fact, unlike for amateur radio examinations where the testing for CW
prowress is done in plain language, for commercial and military sending and
receiving CW tests, the tests invariably include/included code groups, many
of which are/were FEC encoded.
Now it should be noted that if a modulation more complex than OOK is
allowed, and it is, then CW systems could easily be devised to accomplish
bandwidth efficient FEC as well.
So there!
FEC is not only possible over CW, but has in fact quite been commonly been
used.
As I stated further up the thread, mosr of you so-called "digital"
communications "experts" who post on this NG, know not whereof you speak
To be continued in digest: hd_2000_177B
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