Further developments in the Communications and Navigational Aids of a Modern Lifeboat By Cdr KEN WOLLAN QBE RN Staff Officer (Communications) RNLI MY PREDECESSOR, Lieutenant Ernest Gough, wrote an excellent article which appeared in the Spring edition of THE LIFEBOAT in 1976 which described the electronics equipment carried on board the second Arun class lifeboat (52-02) noting that she was fitted with the latest communications equipment and navigational aids.

The next Arun class lifeboat to join the offshore operations fleet will be number 36 (52-36) and except for the addition of a VHF direction finder and the removal of an autopilot, the amount of electronic equipment fitted is the same as that fitted in 52-02.

This underlines the comprehensive way in which the Arun class were originally equipped to carry out their task but it is interesting to note that because of the developments which have occurred in the field of electronics during the past 10 years, the performance of the equipment now being fitted to 52-36 has improved considerably.

As 52-36 will not be completed in time to include a photograph with this article, reference will be made to 47-15, the latest Tyne class lifeboat, which has similar electronics equipment but has some aerial differences due to the low profile of fast slipway lifeboats.

A succession of whip and dipole aerials have been tried out to improve the performance of the very high frequency (VHF) frequency modulated (FM) radio, which is the primary means of communications used by lifeboats, from the 4ft 6in whip originally shown, through folded dipoles mounted on the yardarm, to the 9ft VHF whip aerial mounted on a dummy 9ft base which is shown here on 47-15 as aerial FIG (1).

In another attempt to gain height and thereby improve the range of the VHF FM equipment we now fit a 4ft 6in whip aerial on the back of the platform which carries the blue flashing light on Aruns.

The six channel VHF FM sets @ have been superseded by multi-channel VHF FM sets to meet the increasing requirementto monitor more VHF channels are also compatible with digital selective calling systems which will be used for alert communications when the Global Maritime Distress and Safety System (GMDSS) is introduced during the next decade.

The small VHF amplitude modulated (AM) whip aerial is still fitted to selected offshore lifeboats which have a requirement to operate with civilian helicopters in the Channel Islands and in certain oilrig areas.

One of the two 18ft whip aerials was used for MF reception and as a sense aerial for the Bellini-Tosi medium frequency direction finding (MFDF) loop in the Arun class. This aerial is now used in Arun class lifeboats to provide the input to the Mk 21 or 53 Decca Navigator via a special filter in place of the cylindrical head amplifier previously fitted.

Although the round DF loops (2) resemble those originally fitted in early Aruns they now work on a different principle. These sets feed an automatic MFDF receiver which does not require a separate sense input.

The removal of the requirement for manual sensing of signals intercepted on the MFDF equipment has led to much greater confidence by lifeboat crew members in the use of MFDF.

The other 18ft whip aerial (3) is still used for the main MF tranceiver but here again there will be a major change in 52-36 which will be the first Arun to.