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Re: IMO SYNOPTIC was Re: LF: The Wideband Noise

To: <[email protected]>
Subject: Re: IMO SYNOPTIC was Re: LF: The Wideband Noise
From: "Graham" <[email protected]>
Date: Fri, 5 Nov 2010 19:38:32 -0000
Importance: Normal
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Looks like a  second ex RO   Dreamer band ,  4 Khz with EU hams getting  100 Hz data  mode ?
 
Firstly  all  the  coast is covered by  VHF  to  30  + miles out ,  linked aprs  and radar plots give position  and ship  date , gps has replaced console &  MF beacons , secondly, Imarsat and auto-hf  have replaced the  Radio operators , and nav-text relays   endless  data  on channel buoys with  lights out , rig moves , and  no go  areas  for  gunnery practice , with the  odd  gale warning oh and the  odd bit of  cargo  adrift , on its way  to  Cornwall   
 
So what  on earth  is the  system going to  relay, that  the  existing  system (systems) is/are not  doing   at the  moment , and at 300/400  miles range who  cares , the  ship  will more likely  be tied  up at the  destination  port  and the  crew  ashore in the  pub ..
 
And  2 slots  as well  simplex broadcast only  ...  what nonsense ...  Just a  'dead dog' data  system  with rigamortis  ...
 
G.

Sent: Friday, November 05, 2010 6:14 PM
Subject: RE: IMO SYNOPTIC was Re: LF: The Wideband Noise

"The estimated coverage area from shore is approximately 320 nautical miles with a radiated power of 1 kW and 400 nautical miles with a radiated power of 5 kW."

This seems a very conservative estimation to me.

I can hear the stronger G-stations (ERP 1-10W) day and night with solid copy at similar distances (with a partly land path).

 

73, Rik  ON7YD - OR7T

 

PS: the "bubbles" arround 500kHz are good copy here, but the signal seems to appear/disappear all the tile


________________________________________
Van: [email protected] [[email protected]] namens Terry GW0EZY [[email protected]]
Verzonden: vrijdag 5 november 2010 18:41
Aan: [email protected]
Onderwerp: RE: IMO SYNOPTIC was Re: LF: The Wideband Noise

I guess these tests relate to a proposed new system being discussed in ITU
Working Party 5B:

PROPOSED MODIFICATIONS TO PRELIMINARY DRAFT NEW
REPORT ITU-R M.[500 kHz]
Utilization of the 495-505 kHz band by the maritime mobile
service for the digital broadcasting (from shore-to-ships)
of information related to safety and security

The draft new report has contributions from France and USA. Some extracts
from the documents:

This preliminary draft Report provides information on a digital broadcasting
system working in the 500 kHz band. This system is intended to be used to
broadcast from shore to ships information related to navigational and
meteorological warnings, urgent information and other information related to
safety and security. The system will utilize the band 495-505 kHz and have
the same coverage area as the current NAVTEX system operating at 490 kHz and
518 kHz. New digital technology provides a greatly improved data throughput
from that provided by the current NAVTEX system. It also provides protection
to the incumbent NAVTEX system.

This system will operate in a manner similar to the current NAVTEX system.
The coast stations will be spaced along the coast approximately [500]
nautical miles apart. All the transmitters on a coast will share the 10 kHz
channel by transmitting in a specific time slot. An example of time slot
allocations for a network of 500 kHz broadcast transmitters for the Atlantic
coast of Europe is based on 3-minute slots of a 60 minute cycle. There is
also discussion on using 495-500 kHz and 500 - 505 kHz as two slots for a
"permanent mode"

The radiated power from the regional coast station transmitter should be
what is sufficient to cover the intended service area of that coast station.
The power would be decreased at night during periods of better r.f.
propagation. The estimated coverage area from shore is approximately 320
nautical miles with a radiated power of 1 kW and 400 nautical miles with a
radiated power of 5 kW. The modulation is of type OFDM with N-QAM. An
example of 64-QAM @ 47.4 kbps.system has a data rate of 100 bit/second with
a 300 Hz channel. This system would have a data rate of up to 47 400
bits/second with a 10 kHz channel.

A transmitter site in France is mentioned in the report: Pointe de Corsen
coordinates: 48.414444 N, 4.794444 W. Google Earth shows some sort of
installation there.

73 Terry GW0EZY



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