Weather Fax Service Providers

A weather fax set only earns its place if the charts come in clean, and that depends less on the receiver than on the antenna, the tuning, and the way the signal is decoded. Weather fax services cover that side of the work: installation and antenna setup, tuning the set to the right broadcast frequencies and schedules, setting up and calibrating the decoding, repair, and the functional check that proves a chart actually prints or displays.

Installation and Antenna

Reception is an antenna job first. The set needs a good high-frequency antenna, clear of interference from the ship's other electronics, with its coupler tuned so the fax signal comes through without noise breaking up the chart. On an install or a move, the antenna siting and the earth are what decide whether the picture is usable, and getting them right on a steel ship among a crowded mast is the part that takes experience rather than a manual. A weather fax receiver also listens on single sideband, so it has to be set to receive the fax carrier correctly, and a set sharing an antenna with the ship's SSB or NAVTEX has to be arranged so the sets do not fight each other.

Frequencies, Schedules, and Propagation

Once the antenna is right, the set has to be programmed with the frequencies and times of the meteorological stations covering the ship's area, since a receiver tuned to the wrong schedule sits silent while the charts go out. Stations such as the US services, Hamburg, Tokyo, and Northwood each broadcast to a fixed timetable on several frequencies at once, and which of those frequencies actually reaches the ship changes with the time of day and the state of the ionosphere. Part of the service, and part of what a crew is shown, is how to pick the frequency that is propagating rather than staying on one that faded at dusk.

Decoding, Repair, and Test

On a modern installation the chart is not printed but decoded by software from an HF or SSB receiver, and that chain has to be set up: the audio fed cleanly into the computer, the fax standard matched at 120 lines per minute and the correct index of cooperation, and the slant corrected so the image does not tear off diagonally when the sampling clock is a fraction out. Where the fault is in a printing set, an engineer traces it to the board, the print head, or the power supply rather than swapping blind, and where a part is needed it comes through weather fax spare parts. Because it is a radio receiver, weather fax is often looked at in the same visit as the ship's other bridge radio equipment, alongside a radio survey and bridge navigation check.

A set that prints noise, or nothing, is usually an antenna, a tuning, or a decode problem before it is a broken receiver, so it is worth having looked at properly rather than written off. Weigh the weather fax services below by service area and by whether they can attend where the ship trades, and where a set is past repair a replacement from weather fax suppliers is fitted, tuned, and tested by the same team.