Ships Nostalgia - View Single Post - 500 Khz
Thread: 500 Khz
View Single Post
Old 3rd April 2011, 10:07
Ron Stringer's Avatar
Ron Stringer Ron Stringer is offline
Senior Member
Organisation: Merchant Navy
Department: Radio Officer
Active: 1960 - 1966
Join Date: Mar 2005
My location
Posts: 6,102
Originally Posted by trotterdotpom View Post
" was the failure by a few R/Os to copy Safety (TTT) nav warnings after the old silence periods that led to the famous 1970s disasters when ships ran full speed into wrecks in the English Channel that led to the introduction of Navtex."

Huh? I never hear that one before.
Well they say that all life is a learning experience, John

Originally Posted by trotterdotpom View Post
As far as I'm aware, Navtex didn't come out even experimentally until about 1990, so it was a pretty slow response.
Slow is the normal operating mode for international organisations such as the ITU and IMO - it is one of the downsides of democracy. If you ask a couple of hundred countries (or people) to agree on the best way to do something, it takes time before there is agreement and consensus on how to proceed.

However the Scandinavian countries (led by Sweden) had a system up and running in the late 1970s and the UK (not always an early-adopter) ran an "experimental" station at Cullercoats at the beginning of the 1980s. This was declared permanent in 1983 and the service was expanded adding stations at Portpatrick and Lands End (later moved to Niton to improve coverage).

During the 1980s, Navtex was adopted by IMO as part of the FGMDSS and the service was introduced in countries outside Western Europe. The first NAVTEX Manual was issued by IMO in 1988 (and has been reissued at intervals of 5-7 years since - it is currently in its 4th Edition) and the carriage of NAVTEX receivers was made mandatory for ships over 300 tons from 1993. Which is probably when you first came across it on FOC vessels.

Originally Posted by trotterdotpom View Post
My only experience of Navtex had reems of paper being spewed out giving warnings for the Atlantic to ships in the Pacific. It all ended up in the rosie.Hope they sorted that out! John T.
As always the tool is only as good as its user. All the NAVTEX receivers that I encountered had a facility (demanded by the IMO and CCIR recommendations/ specifications) to exclude messages - other than distress-related messages - from any stations. So if you were in the Baltic and had no interest in broadcasts from Iceland, you simply selected Iceland as a station to be ignored. Of course if no one bothered to do that, you got a lot of unwanted bumf, especially at night when the range of 518 kHz can be significant.

Initially there were problems because many of the early stations transmitted at far higher powers than were necessary to provide the coverage area that they were serving. They were established by coast station engineers who were familiar with the power used by their morse or R/T transmitters and who did not at first appreciate that on a dedicated (interference-free) frequency using SITOR they could cover their area with low-power transmissions. Iceland was one such atation whose coastal nav warnings could be received over almost the entire North Atlantic until they could be persuaded to reduce power.

Democracy and international independence played a part too. Although IMO agreements affected what happened aboard ships, there was (is) no such vehicle for what happens at the shore end. So if, for example, Gadaffi wanted to put a station up that enabled broadcasts to be made (at any time he chose) from Libya and which could be received across the entire Med, into the Baltic and along the West African coast, there was nothing to stop him. Eventually a NAVTEX co-ordinating panel was established and by negotiation and persuasion, countries with overlapping transmissions arranged such things as transmitter powers and times of broadcasts so that they complemented each other to provide a sensible service.

But it took time and there is still no requirement that countries must provde continuous coverage along their coastlines - oh for a benign dicator on occasions.

NAVTEX was a creation of its time. When it was started in the mid-1970s, there was no maritime satellite service and no other means of putting safety information aboard ships outside the 8 hours a day that there was an R/O on watch. Today a far better equivalent is available via satellite but such resources did not exist almost 40 years ago. SITOR was available and in use at sea for commercial communications - a little lateral thinking within the Swedish PTT saw it as a means of putting safety information aboard Swedish ships (which were provided with automated radiotelex facilities - Maritex). And NAVTEX was born. Like the rest of us it may now be a little past its sell-by date but when introduced, there was nothing better available.

Had there not been so much opposition to INMARSAT from certain IMO member countries, the SafetyNET service might have replaced NAVTEX within the GMDSS. But there we go again - democracy and politics.

Never regret growing older. It is a privilege denied to many. Don't worry about old age - it doesn't last.

Last edited by Ron Stringer; 3rd April 2011 at 10:20..
Reply With Quote