Text 22003, 49 rader
Skriven 2006-10-05 13:03:34 av TOM WALKER (1:123/140)
     Kommentar till en text av GORDON HUFF
Ärende: PSK31
=============
PSK31 is the result of a belief that the present batch of "data" modes have
left a gap in amateur radio operating, the gap that was previously filled
by AMTOR or even traditional RTTY, in which two or more operators chat to
each other on an open channel. Modes such as packet radio, Pactor, and
others, are highly complex, are unsuited to multiway conversations, and in
particular, the long block lengths introduce an unacceptable delay in the
processing of text such that even normal conversation is unpleasant and
quick-break question/answer sessions are impossible. The move to automated
unattended message forwarding has left a gap in the person-to-person
communication field, and PSK31 is an attempt to remedy this situation with
a simple but efficient code structure coupled with the narrowest possible
bandwidth, and with only enough error-correction to match typical
typing-error rates, and with no time-consuming synchronisation, changeover,
and ARQ processes. 

The 31 baud BPSK modulation system used in PSK31 was introduced by SP9VRC
in his SLOWBPSK program written for the EVM. Instead of the traditional
frequency-shift keying, the information is transmitted by patterns of
polarity-reversals (sometimes called 180-degree phase shifts). This process
can be thought of as equivalent to sending information by swapping-over the
two wires to the antenna, although, of course, the keying is more usually
done back in the audio input into the transceiver. A well-designed PSK
system will give better results than the conventional FSK systems that
amateurs have been using for years, and is potentially capable of operation
in much narrower bandwidths than FSK. 

The 31 baud data rate was chosen so that the system will just handle
hand-sent typed text easily. 

 
->  TW>for hte Hams today is PSQ-31. Which is a 31 Baud protocal.
->  TW>Those bandwidth limitaions don't apply to the WiFi systems.
-> 
->  EV> 31 Baud sounds awful slow.
-> 
-> It is - it's the kind of thing that appeals to "DC band hams"
-> sorta like the appeal of "ancient modulation."
-> 
-> In those years I favored 4mbps DPSK because we used
-> it at work and I though specialized ICs would become 
-> available. Today, I'd favor the satellite TV standard
-> or the digital cable TV standard. Hams are cheap - the
-> wise man would place his money on IEEE 802 - like stuff.
-> 
-> Regards, Gordon
-> ... MultiMail, the new multi-platform, multi-format offline reader!
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