Hi,
This may interest some, bore others, and remind others of the time when
*all* modem communication was slow:
http://www.winlink.org/WINMOR
Traditionally, digital communication over long distance radio has been
slow and expensive. Slow of necessity because the carrier radio waves
for the digital signal are typically in the 2MHz - 16MHz frequency range
and therefore don't carry significant amounts of digital information per
second (10 - 100 bytes per second are typical of the technology), and
expensive because of a proprietary protocol and product called PACTOR
that requires a specific make & model of HF modem to interface between
the PC and the HF radio set.
However for long distance communication between HAM radio enthusiasts
and vessels at sea, it's the only option. Other than satellite, which
for vessels at sea takes "expensive" to new levels of meaning (it's
difficult to arrange a fixed satellite dish on a ship that's moving and
pitching in all directions), there are no other means of communicating.
The higher frequency spectrums that carry digital signals to users of
mobile broadband just don't have that sort of propagation.
The PACTOR protocol is covered by several patents which make it
impossible for third party vendors to implement this protocol. So
everyone who wants to use this is stuck with the expensive and
proprietary PACTOR modems, along with their proprietary (and MS Windows
only) software to drive them.
There is a new protocol and software under test called WINMOR, developed
by the Winlink 2000 folks who traditionally provide an endpoint for
digital communications with amateur stations and vessels at sea.
Although the current software is available for Windows only, the
protocol and specification have been released to the public domain for
anyone to implement. Although the protocol and software are both under
development, the end product has been shown to be reasonably stable and
reliable. The only hardware required is a sound card, and of course an
HF or HAM radio (nearly all ships would have the latter as an essential
piece of safety equipment).
There are a number of WINMOR enabled HF stations worldwide, with more
popping up regularly, including 2 so far in Australia. Remember that HF
propagation, depending on the frequency chosen, time of day, solar
activity, number of sunspots, etc, can be anything from 200km to
planet-wide, so for global communications to be effective over this type
of network there is no significant need for large numbers of stations.
--
Del
Babel Com Australia
http://www.babel.com.au/
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