On 7/21/02 6:58, Bill Tippett at btippett@alum.mit.edu wrote:
>Neither CW nor SSB is obsolete; in fact, both are far superior to any of
>the new digital modes at rapidly communicating information between
>many different stations under extreme conditions. In fact, PSK31 has
>NOT been proven to be superior to CW in weak signal environments IMHO.
>PSK31, WSJT, QRSS, etc are superior ONLY if you know the exact frequency
>to tune your receiver to the signal buried in noise. Without this
>critical information (either from a prearranged schedule or via the
>Internet), they cannot magically extract signals from noise. Can you
>imagine a contest where you tune your receiver but cannot hear the
>signals? I don't think so.
Bill, I though think that anyone who is an MIT alumni would be able to
acknowledge that modes like PSK31 could easily be superior to CW.
On a theoretical grounds, PSK has a signal/noise advantage of about 4 dB
over OOK (on-off-keying -- eg CW) in the presence of Gaussian noise.
Granted, the signal impairment of typical HF channels isn't purely
Gaussian, but the theory is there none the less.
As a pratical matter, PSK31 has demonstrated that solid copy is possible
with signal levels that are INAUDIBLE to the human ear. Read that again.
Inaudible -- as in you cannot hear it. Since CW is typically decoded by
ear, this clearly indicates the superiority of the mode in weak signal
environments.
As for tuning PSK31 signals, it's pretty obvious to anyone who is
familiar with current PSK31 applications -- you do not tune in signals by
ear. It would be impractical to do so. Instead, you tune according to a
visual display, typically an FFT waterfall. Signals are clearly evident
on this display and easily tunable. Many applications don't require
precise tuning -- just click on the visible stream in the waterfall
display.
>What I said was "I personally do not think a
>computer-to-computer 'QSO' means much". I specifically meant when
>neither station can hear the other station (with their own ears),
>and I'll stand by my statement.
By that logic, e-mail doesn't mean anything, either.
To me, though, it's just a means of person-to-person communication.
>To me, a QSO like this is just like
>nets where the Netmeister tells each side of the QSO "Good Contact"
>when in fact neither station can hear the other. The only difference
>is our computers have replaced the Netmeister!
It still takes considerable radio skill and communications acumen to hold
a PSK31 QSO.
Do you hold the same opinion of Baudot RTTY?
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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