There are a number of things to consider when installing VHF radio on a boat.
Mounting of the antenna is the first consideration. Rule one – the higher the antenna the greater the range.
On a yacht, there are generally two locations, the pushpit or the masthead. Mounting the antenna on the pushpit usually results in some degree of directivity. The mast and rigging often ‘block’ the signal resulting in fading while swinging at anchor.
Because of the height, a masthead installation offers greater range and omni-directional coverage, but remember, ‘if you lose the mast, you lose the radio’ probably at a time you most need it!
If you participate in competitive yacht racing it is advisable to install an emergency antenna on the pushpit. On a ketch the mizzen mast can be used.
On cruisers, the general rule is – mount the antenna as high as possible and at least a metre away from other antennas, while on trailer boats, a swing down antenna, mounted as high as possible, is usually the answer.
On runabouts and halfcabs, it is a good idea to mount the antenna on the driver’s side where it is more visible when coming alongside jetties or other boats and is therefore less likely to sustain damage.
Most VHF antennas these days are ‘pre-tuned and ground independent’ and therefore do not require a technician to install them.
Ideally the antenna coaxial cable should be one continuous length of good quality RG58C/U or RG213 cable.
The use of ‘antenna combiners’, allowing the same antenna to be used by an AM/FM broadcast receiver, should be avoided.
The more connections in an antenna cable, the greater likelihood of trouble.
For long coax runs, in excess of six metres, low loss coax such as Benelec RG58 foam/foil or RG213 should be used.
External antenna connections should be first taped over with insulation tape, then self amalgamating tape applied over the tape, and then insulation tape applied over the whole joint. (By taping over the connector first, the self amalgamating tape won’t stick to the connector if it has to be undone in future.)
If a coax plug needs to be fitted to the end of the coax make sure that no fine wires from the braid are accidentally ‘shorted’ to the inner conductor of the coax and that the inner conductor is ‘tinned’ with solder.
On masthead installations, the coax should be firmly clamped at intervals so that there is no strain on the plug. A ‘crimp’ type plug should be used at the antenna end for greater reliability.
If a proper coax crimping tool is not available make sure the outer braid is soldered to the outer section, or the cable adaptor, of the plug. Always solder the inner conductor to the centre pin of the coax plug.
Careful consideration should be given as to where to mount the radio. Whilst it may look nice mounted just above the chart table down below, ideally it should be able to be operated by the helmsman.
It must be mounted in a dry location, clear of rain and saltwater spray and free from engine vibration.
The microphone holder should be mounted where the microphone is easily accessible at all times.
An extension horn speaker can be mounted externally if required. Some manufactures offer ‘remote heads’ for flybridge or cockpit installations.
Because the radio has its own inline fuse, power for the radio should be taken from the nearest reliable source of power, preferably from the heavy cables at the INPUT to the accessory fuse / power board.
All power cables should be ‘tinned’ to ensure good connections. The radio should be the last thing onboard left operating after all other equipment and wiring has failed.
A spare fuse or two should be taped to the radio fuse holder as spares. Note that unlike HF radio installations, VHF radios do NOT require an ‘earth plate’ through the hull.
by Barry McCann – Tas Maritime Radio