Ham Radio Afloat

December 2004

We regard our Ham radio as one of the most important pieces of equipment aboard. Here's a few tips on how to instal one on a yacht and how we use ours.

HAM RADIO and MARINE SSB

Ham radio is a hobby that appeals to young and old alike from all around the world. It awakens in them a sense of excitement and wonder through the ability to communicate with friends around the world from your loungeroom at home of from the saloon of a small boat at sea. A license is needed to do this since operating a ham radio requires selection of a free, complying frequency as compared to a marine SSB radio which has a simpler to operate, channel-based system. Ham radio enthusiasts need both technical knowledge and an understanding of the regulations to pass the licensing exams. Plenty of help is available to learn these skills and the rewards, especially for a "maritime mobile" operator are invaluable.

A number of amateur radio (ham) maritime mobile networks operate around the world, designed to assist cruising yachts by providing check-in facilities, position tracking, weather and location data. In addition to this great service a ham can chat all day to other hams around the world (great if your family or friends at home are licensed) and he/she can send free email using the "winlink" system. SSB allows ship to ship and ship to shore facilities on a more or less commercial, per channel basis. Email over SSB using the commercial "Sailmail" system is also available at a reasonable price.
Both systems require similar installation and equipment and the notes that follow apply to both. Some marine SSB radios also offer limited ham functionality at a price - so you can have it both ways!

MARINE HF EQUIPMENT

The essential components are a radio (HF transceiver), antenna tuner , antenna and earth system. Modern mobile ham radios and some SSB, feature a control head separate from the radio as shown in the Icom 706MkIIG below. There are significant advantages in this arrangement, allowing a small panel footprint at the Navstation for the control head and an out-of-the-way location for the radio convenient for 12V power and antenna connections.

Illywhacker has an Icom 706mkIIG - the control head mounts easily on a flat surface at the Nav table and the radio proper at the rear of this photo is mounted in the copper box shown in the photo below

For a "long-wire" antenna, the antenna tuner should be directly below the backstay or whip antenna under the deck and as close as possible to the earth system

We have a locker lined with copper foil which houses the radio in an effort to reduce interference with sensitive marine instruments. The radio is mounted below the lower shelf out of sight in this photo. The black box shown on the upper level is not the radio but the autopilot control unit.

An Icom AH4 antenna tuner - water resistant design for under deck mounting, usually at the stern under the backstay. Illywhacker is a ketch and uses the triatic stay as an antenna.

ANTENNA and GROUNDING SYSTEMS

The aim of the installation is to ensure 99% of the power from the radio is radiated from the antenna. A boat floats on a perfect "rf ground", the sea so antenna systems are often designed in a 1/4 wavelength configuration. When such an antenna is tuned to the desired frequency (determined by its length and the ATU settings), the ground plane acts in concert to ensure all power is radiated from the wire - both are equally important.
Most yachts find it easiest to use the backstay as an antenna. This requires 2 insulators be inserted, the lower one a metre or 2 above the deck to avoid radiation burns if human contact is made during a transmission.

The insulated cable leaving the ATU is passed through a waterproof gland in the deck, run via standoffs up the backstay and connected with an anti-drip loop to prevent water finding its way down the cable core.
Grounding is often easiest using an external "dynaplate" but much literature suggests connection with the ship's earth system. This is our preferred arrangement although this also introduces issues such as electrolysis and interefrence - try, measure and see!

Loop the cable upwards before
connecting to the backstay

Standoffs are easily made with
1/2" conduit and a cable tie

A good installation in accordance with the sketch above will yield some amazing results - clear communications around the world sometimes - with few side effects to the performance of the yachts electrics/electronics. Adding more equipment such as a modem and computer for email, antenna switching, weather fax modems and so on are all part of the fun, especially when inadvertent coupling causes the auto-pilot to veer off course or the lights to flicker when transmitting! There are ways around all such problems and the ham and cruising community is always ready to help. I find this a fascinating topic and would be happy to share our experience with readers wishing to understand more.

73's Peter VK4EFC and Lyndall VK4JLY

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