[CW] Re: CW in Emergency HF Comms System...

[George, W5YR]

I wonder if the planners are taking into account that PSK31 has zero error
correction and that there is no assurance whatsoever that the copy received
is the copy sent.

For casual plain-language conversation, this poses little problem. But  if
the traffic were a list of emergency medical supplies, for example, the
inherent errors in PSK31 operation could have serious consequences.
Especially if the text were forwarded a few times with new errors being
added each time.

I would think that a much less error-prone protocol would have to be used
instead of PSK31, however attractive are its other features.

CW is prone to the same errors, of course, and at each end. But with a human
transcribing the copy each time, it is more likely that many errors would be
caught and corrected or at least flagged.

RTTY at least offers the merits, doubtful as they may be, of character
parity checking while Packet operation does the full score but is too slow
to be useful or reliable at HF.

In the end, I suspect that the limiting factor that will decide the means
for emergency comms in any given situation will be the availability of
equipment and people with the talent to use it. As CW operators continue to
fade in number, that mode becomes less of an option.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr@att.net>





----- Original Message -----
From: "Alan W." <n5lf@qsl.net>
To: <cw@mailman.qth.net>
Sent: Saturday, June 21, 2003 11:10 PM
Subject: [CW] Re: CW in Emergency HF Comms System...


> kburrows (VE1DS) wrote: "...the newer digital modes would be better than
> manual CW ..." [in an EOC].
>
> Well, CW & other digital modes are complementary; not interchangeable -
it's
> apples & oranges.
>
> CW is well-suited for for short messages, and low levels of formal
traffic,
> logistical communications, etc.  In other words the same situations where
a
> voice net is used on HF.  That is its most common use on ham radio in
> real-life emergencies -- CW supplements the limitations of SSB when
> conditions are poor.  So, two stations on a traffic or tactical/logistics
HF
> net can switch to CW if the receiving station was having trouble copying.
> It works every time!
>
> PSK31, on the other hand - and other new digital modes - are the only way
to
> go if you have to send a long list, or books of messages.  The originating
> station must type it in - not much faster than CW, and due to typos it can
> be LESS accurate.  But you see the big speed difference only when stations
> relay the traffic - since that is mostly automated.  If there are no
relays,
> then station to station speed isn't much different.  By the way, PSK31 is
50
> wpm - again, not much faster than a fast CW op, but 2x or 3x faster than
> most causal CW ops.
>
> There are conditions where CW shines - CW has full break-in operation for
> example - even between characters or even between dits.  SSB is only
between
> words at best, and PSK31 - hasn't got break-in capability.  In AMTOR &
> PacTOR the rcvr stn can break-in between packets, so they do to some
extent.
>
> PSK31 falls apart with multipath, auroral flutter, and other condx that
> affect a signal's phase.  Other modes handle phase shifts, but in exchange
> for other weaknesses.  CW ops can use the wetware between their ears to
> overcome this.
>
> The difference in equipment and power required to run a CW station vs. a
> soundcard-digital system has been expounded elsewhere.
>
> Bottom line:  On HF nets, CW supplements SSB.  CW has its own strengths &
> weaknesses (mainly requiring that we have CW ops!).  PSK31 & other new
digi
> modes are complementary to SSB & CW - not an "either-or".
>
> AlanW N5LF
>
>
>
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