Katech AIS Test and Analysis System

Support

Support Information 4

Choice of data terminal or software emulation

All KATAS receivers with in-built decoder (including OnBoard for AIS Engine) have human-readable display modes included that allow them to be used with a simple data terminal, without the need of a PC operating system, giving maximum system reliability. This facility is known as Multi-mode and is selectable by an internal jumper link. Receivers are delivered with multi-mode set but this can be disabled if desired. One of the sub-modes is Page mode and requires the terminal to be able to interpret VT100 escape codes or to have a so-called VT100 emulation. The page mode has been fully tested with Wyse data terminals type WY-60. A suitable, currently available, terminal is the Wyse 55 that can be specially supplied if required. Users wishing to use a personal computer for terminal emulation have several choices of software that can be used. Versions of 32-bit Windows operating systems can use the Hyperterminal program from the master disc as a starter but this version does not support the 42 lines that the page mode requires for full operation. The default setting for page mode on KATAS receivers is for 24 line operation so that the standard supplied version of Hyperterminal can be used. A simple command changes the receiver into 42 line operation which is saved for future use.

The suppliers of the free Hyperterminal program, Hilgraeve, have a more advanced version that is available for download here. This allows selection of 42 line mode as well as giving other features. The program is free for a single private user but business users must pay a small licensing fee. The 42 line mode may then easily be enabled with a simple software command. For PC users running Windows, there are many alternative programs that can be used for VT100 terminal emulation. Programs that have been tested are Telix and PowerVT. These programs are each licensable at low cost but there are also others that may be suitable. The KATAS AIS Starter Disc, supplied with the Portable Range receivers includes a copy of Tera Term for Windows which is recommended. Users of other operating systems also have a wide choice of 42 line VT100 terminal emulation software available. The KATAS OnBoard for AIS Engine product is not wired for hardware handshaking and users should be aware of this when selecting a data terminal for use with this unit.

Using a »SAILOR« Marine VHF transceiver to receive AIS transmissions

It is widely known that almost any marine VHF transceiver can be specially modified to be able to output an audio signal of extended lower bandwidth directly from the discriminator circuit in order to be fed into ShipPlotter. VHF transceivers from the »SAILOR« range from SP Radio A/S and latterly Eurocomm Industries (ECI) are very popular on European commercial ships and many of these units are finding their way onto smaller leisure vessels. There is one model from the »SAILOR« range, the RT2048, that is more suitable than the others for receiving AIS signals as it has an ideal dc-coupled output signal direct from the reciever's demodulator circuit presented on the rear handset socket. It is therefore able to be used to good effect without any modifications. Other »SAILOR« VHF units such as the RT144, RT145, RT146 and RT2047 are not suitable for receiving AIS transmissions in their standard form. Earlier units than the RT144 do not have a frequency synthesiser and so this is an additional problem as crystals would have to be specially obtained for the two AIS frequencies.

The ECI VHF 4000 units such as the »SAILOR« branded RT4800, RT4801, RT4722 and RT4822 are also suitable for the reception of AIS signals although their performance in this respect is not quite as good as the RT2048. There are also channel programming issues to contend with with these later radio sets and so the use of these units shall be discussed in a later memo.

The new »SAILOR« RT5022 transceiver from Thrane & Thrane has not yet been assessed for AIS reception capability.

The RT2048 has been in production for several years and there have been some minor revisions to both the circuitry and the system firmware. The vast majority of RT2048 units in use shall be suitable for use with ShipPlotter but there may be issues with the very earliest units and also the very latest units, ie. those manufactured after approximately August 2005. The few of the very earliest units did not have the connection from the demodulator IC to the handset socket and the very latest units have a firmware version that maps channels 87 and 88 into the low band, previously these channels were set to receive in the high band which is what is required. If either of these problems is encountered, please send an email as our experienced SAILOR^® repair engineers can, most likely, help.

There are two products within the KATAS range which allow the connection of an RT2048 to a personal computer for signal decoding via ShipPlotter. The first is a simple lead in various lengths which simply connects the radio to the computer. This is intended for temporary connections, perhaps for test purposes. The second device is an adapter, also available in various cable lengths, that allows the simultaneous connection of the AIS lead and the original handset. This is intended for permanent fitment and comes with the KATAS AIS Starter Disc. See the appropriate part numbers page for more details.

If the RT2048 is used on board a ship with the Rx output connected as described here, the following facts should be borne in mind. If the unit is used on land, there should be no problem. In common with other marine VHF radios, the RT2048 uses the battery negative rail as the common terminal for all signals internal to the set. This means that, if the direct Rx output is used into a computer running ShipPlotter, it must be remembered that the computer's ground return from its soundcard will adopt the voltage potential of the radio's battery negative supply lead which may be undesireable. Depending upon how the computer is powered and which peripherals are connected and how they also are powered, may result in the vessel's galvanic isolation between battery minus and earth being defeated. This may have adverse effects with other on board equipment and may be solved in several ways, not least by the fitment of a dc-dc converter to power either the computer or the radio. If in any doubt with these issues, consult a qualified marine electrical engineer for advice.

Previous | Next