SAFETY
MAYDAY, MAYDAY Marine radio installations and troubleshooting By Markus Fourie
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NE of the most vital pieces of equipment on your ski-boat is the radio — your lifeline in times of trouble. In this article we will be discussing the marine radio, antenna and RF ground plane for use on ski-boats and how you can test your equipment. For operating a VHF radio in a marine environment, it is highly recommended that you purchase a proper “marine radio”. Many owners look for the least expensive way out and try to modify radios for marine applications. Bad decision! Marine radios are designed and manufactured to be able to withstand saltwater and sea air conditions. Marine radios meet the requirements of frequency stability and RF radiation. Only marine radios have the facility to do DSC calling. All marine radios have the ability to switch between high power (25 watt) and low power (1 watt). There is however one aspect where the radio manufacturers have “missed the boat”. There is no indication (or very little indication) of transmitting power or signal strength or reflected power indication on most of the marine radios. This feature would solve many 16 • SKI-BOAT March/April 2020
Very important: Please do not use Channel 16 for any radio testing — this is the emergency call channel. common problems. When installing the power and fusing circuits to the radios, make sure you use the new plastic blade fuses (shown below) that are specifically made for the auto industry. Not only are they
designed for 12-volt use, but they are also sealed to protect them from harsh environmental conditions. Glass fuses start to rust and corrode and that will cause problems. TRANSMIT MODE (TX) The radio consists of two parts — TX (transmitting) and RX (receiving). Let’s start with the transmit mode (TX) part of the radio ... Remember to measure the distance from the radio to the battery source. The further away the radio is from the power source (batteries), the thicker your cables need to be. Often when radios have low power output it’s because the wire is too thin which is preventing proper supply of 12 volt and current to the radio. To accurately measure the voltage do it as close as possible to the radio. Switch the radio to transmit at high power and press the “PTT”. The radio is now in transmitting mode. Now measure the voltage that the radio is getting. This test is extremely important. The voltage should not drop below 12 volt. If your radio panel goes dim when operating on high power (25 watt), it means that your supply wires are too thin. Never transmit if there is no anten-
