Cruising Helmsman – June 2017

reverted to using a VHF radio mounted
in the cabin for routine monitoring
of channel 16. The extension cockpit
speaker for this radio had already failed
so, apart from the inconvenience of
having to go below to use the radio, it
needed to be turned up fairly loud to
be audible in the cockpit and tended to
disturb whoever was off watch.
I investigated buying a remote VHF,
thinking I could mount just its speaker/
mike behind the cockpit chartplotter but,
as I wanted DSC, a stand-alone unit was
cheaper. VHF radios are often mounted
under a bimini which can also support
the whip antenna, but our equivalent, a
steerable solar panel array, was not really
suitable so Mk.3 is just a slightly extended
version of Mk.2; allowing the new DSC
VHF transceiver to be mounted on the
same overhead pivot.
Back to back mounting was less
obstructive than side by side. Although
the radio points the opposite way to the
chartplotter, it can of course be heard and

the microphone used, or pivoted around to

adjust a control.

The radio is within its declared 450

millimetres 'safe' distance from the

steering compass but, even during

transmit, I have not noticed any deviation.

To avoid interference issues, after passing

through the hollow pivot, the radio’s

power and antenna cables are routed

via the opposite side of the dodger to the

chartplotter/sounder’s cables.

Plugs in the cabin allow this radio to

use either the masthead or one of the davit

mounted antennae. The original remote

mike/speaker socket is now also on the

Mk.3 frame.

NMEA COMPLICATION

The radio was supposed to get its GPS

input, necessary for DSC operation,

from the chartplotter via an NMEA

link. However, when set to receive AIS

at the standard rate of 38,400 baud

the chartplotter seemed unable to

simultaneously output its own GPS data

at the slow 4800 required by the VHF.

To get around this I purchased a default

4800 baud 48 channel GPS puck from

Taiwan ($50) and mounted it on top of the

doghouse, inside the waterproof housing of

the now redundant external GPS antenna

for the old chartplotter. This internal GPS

works fine under the aluminium dodger,

but can also get GPS from the AIS data.

The puck draws just 60 milliamps and is

powered via a fuse and switch from the

VHF’s supply.

POSSIBLE DRAWBACKS

Apart from perhaps intruding into

headspace, the main drawbacks are that the

connections are exposed and the wiring is

not as neat or protected as f lush mounting

and, perhaps, that the equipment is easily

removed/stolen.

Flush mounting makes theft more

difficult, but does not prevent it if the boat

is unattended in an insecure location.

55

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