Hotbird reception at sea?


David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺
 

--- In MSG-1@yahoogroups.com, "Luca Bertagnolio" <lucaberta@y...>
wrote:
I always like the british term "overseas"... as if they are not
the ones living on an Island!!! ;-)
It always give me the idea of long sea journeys to far away lands!
But I digress. It triggered the question:

How do ships at sea pick up geostationary satellites, particularly
satellites like Hotbird needing alignment to within a degree? Do
the ships have very expensive stabilised or tracking antennas? What
about the smaller vessels or amateur sailors? Only receive when
stable in port?

Cheers,
David


Peter Benney <tugboat@...>
 

How do ships at sea pick up geostationary satellites, particularly
satellites like Hotbird needing alignment to within a degree?
David,

For HRPT/CHRPT and Meteosat/GOES

http://www.dartcom.co.uk/products/hrpt_chrpt/system_options/13m_active_stabilised/index.html

For satellite TV, one of a few for smaller vessels;-

http://www.simrad.com/PDF_Library/Simrad_sat_tv_spec.pdf

Many more systems for the larger cruise ships.

Peter


Guy Martin <agm@...>
 

A standard shoulder mounted broadcast camera (parrot) such as a Sony BVP70 was can be mounted on a gyro stabilised platform which is attached to the cameraman around the waist and hands and he can run down stairs without the camera exhibiting any shake at all. I suspect that kind of device could easily cope with ship movement.

Cheers, Guy

----- Original Message -----
From: David Taylor
To: MSG-1@yahoogroups.com
Sent: Wednesday, January 14, 2004 11:26 AM
Subject: [MSG-1] Hotbird reception at sea?


--- In MSG-1@yahoogroups.com, "Luca Bertagnolio" <lucaberta@y...>
wrote:
> I always like the british term "overseas"... as if they are not
the ones living on an Island!!! ;-)
>

It always give me the idea of long sea journeys to far away lands!
But I digress. It triggered the question:

How do ships at sea pick up geostationary satellites, particularly
satellites like Hotbird needing alignment to within a degree? Do
the ships have very expensive stabilised or tracking antennas? What
about the smaller vessels or amateur sailors? Only receive when
stable in port?

Cheers,
David



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Dave Martin <Dave.Martin@...>
 

David,

I think the answer to all your questions is "yes" .....

The first generation of satellite used widely for communications at sea were
the Inmarsat series which carried their analogue "Inmarsat-A" service -
those use tracking antennae - typically 1m dia dish in an enclosed radome.
Active tracking takes input from ship's gyro and position; and motive
elements were usually stepper motors - although as it is at 1500MHz the
beamwidth is more like that of Met-7 kit rather than Hotbird, so they are
somewhat more forgiving. Modern terminals have a commutator ring, but older
terminals were notorious in that when they reached end-of-arc you would have
a break in your phone/fax/data call whilst the terminal rewound. Modern
higher-speed digital Inmarsat fundamentally the same, but require better
pointing.

Inmarsat also had alternative strategies to exploit the bottom end of the
market - Inmarsat-M is a lower bandwidth / higher power system which gives
typically 2400 baud, but requires smaller (app. 30cm) antenna (still
steered, but sometimes dish and sometimes flat panel) and further reduced
pointing accuracy. Inmarsat also introduced a telex-only (i.e. "text only"
service) Inmarsat-C which uses relatively high transponder power at very low
bit rates & bandwidth, and uses an omni-directional antenna.

There is a growth now in deployment of VSAT (very small aperture terminals)
at sea - this started with such as our cruise vessels (where we even provide
Internet Cafes) and others requiring high data rates such as survey
vessels - again these are all stabilised and steered, terminals costing from
20kUSD+++ An even more critical requirement is onboard TV - where
systems can cost hundreds of K USD; although they are still subject to the
laws of propagation and I can remember a serious discussion - even to the
extent of whether we would need to re-route a vessel - so the pax could
enjoy a football final !

and, at the other end - yes, you can walk along a marina pontoon and see Sky
dishes mounted with a sandbag or old motor tyre on the quayside! (even in
harbour, most yachts move and range too much to keep a TV sat dish in
alignment)

Dave M

----- Original Message -----
From: David Taylor
To: MSG-1@yahoogroups.com
Sent: Wednesday, January 14, 2004 11:26 AM
Subject: [MSG-1] Hotbird reception at sea?

How do ships at sea pick up geostationary satellites, particularly
satellites like Hotbird needing alignment to within a degree? Do
the ships have very expensive stabilised or tracking antennas? What
about the smaller vessels or amateur sailors? Only receive when
stable in port?

Cheers,
David

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nigel heasman <nigel_heasman@...>
 

What about the smaller vessels or amateur sailors?
Only receive when stable in port?
That's my experience, David. Even then it can be a bit
tricky with floating pontoons and strong winds/waves!
Nigel



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Robert Moore
 

Unless you are good at applying calculus in spherical geometry do not try to
build a system at home!
Robert


Quoting Peter Benney <tugboat@gotadsl.co.uk>:


How do ships at sea pick up geostationary satellites, particularly
satellites like Hotbird needing alignment to within a degree?
David,

For HRPT/CHRPT and Meteosat/GOES

http://www.dartcom.co.uk/products/hrpt_chrpt/system_options/13m_active_stabilised/index.html

For satellite TV, one of a few for smaller vessels;-

http://www.simrad.com/PDF_Library/Simrad_sat_tv_spec.pdf

Many more systems for the larger cruise ships.

Peter







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------------------------------
Professor Robert Moore
Department of Sociology, Social Policy
and Social Work Studies
The University of Liverpool
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