july 2012
11
practical sailor
being able to add
multiple stations.
However, hav-
ing multiple mics
should not be con-
fused with having sys-
tem redundancy since the mics depend
on a single transceiver. The redundancy
provided by a second VHF radio might
be a more prudent approach than relying
only on remote mics for long-distance
cruisers.
Performance-wise, the VHF 300 held
its own. Power and audio output was the
lowest of the test group, but it did have
the best receiver sensitivity. Transmit
power stability was Excellent, while fre-
quency stability was Very Good. Audio
quality was also rated Good.
The 300 carries the same limited two-
year warranty as the Garmin 200.
Bottom line: The 300, the most ex-
pensive VHF in the group, is well-built
and offers a lot of options from both op-
erational and installation standpoints,
but its limited
warranty kept
it out of the
winner’s circle
in this close
evaluation.
icom ic-m424
Icom bills the IC-M424 as the world’s
first fixed-mount VHF with Class D
DSC and active noise canceling, a fea-
ture that our test setup unfortunately
didn’t allow us to try out.
The IC-M424 also features Icom’s
new soft-key user interface, which is in-
tuitive, easy to use, and provides quick
access to radio functions with fewer
button pushes than a typical menu-
driven interface. The radio
is compatible with the new
Icom CommandMicIV
(HM-195) microphone,
which shares the
same soft-key user
interface.
The IC-M424 has a built-in 10-watt
amplifier that increases audio output
for functions such as the PA and fog-
horn with the addition of an external
speaker. When connected to an external
GPS receiver, it displays time and cur-
rent position. When receiving position
information from another vessel, the IC-
M424 can also transfer it to a compatible
chartplotter.
Other features include priority and
normal scan, dual/tri-watch monitoring
function, and weather channels (with
alert function). When coupled with
an Icom MA-500TR Class B AIS tran-
sponder, the IC-M424 can make calls to
an AIS-equipped target boat using the
transponder with a few button pushes
and without entering the tar-
get’s MMSI number. Users
simply select the AIS target
from the display screen, se-
lect the VHF channel you
want to use, then push
the DSC call button.
F e a t u r e s 4 1 1
AquaQuake: A draining function specific to Icom radios; a
vibrating "buzz" clears water from the speaker grill.
Noise-canceling: Reduces background noise, so you can be
heard and can hear more clearly.
PA/hailer and foghorn: Public address function allows
users to make announcements from the mic like a loud
speaker when an optional external speaker is installed. The
foghorn emits horn sounds from the external speaker.
Waterproof ratings: IPX7 means the VHF can handle sub-
mersion to 3 feet deep for up to 30 minutes. An IPX8 rating
means the unit can handle continuous underwater use.
Dual-watch scan: A channel scan mode that monitors chan-
nel 16 and another selected channel every few seconds.
Tri-watch scan: Monitors both channel 16 and two other
selected channels while scanning.
Priority scan: Channel 16 is checked between every other
channel during scan.
Memory scan: All VHF channels in the VHF memory are
scanned from lowest to highest.
Normal scan: VHF channels are scanned in numeric order.
MMSI: Maritime Mobile Service Identity number. Boats are
assigned one nine-digit MMSI for all onboard equipment ca-
pable of transmitting and receiving digital signals—EPIRBs,
AIS devices, DSC-capable VHFs, INMARSAT satellite terminals,
etc.—and that number serves as an identifier for the boat.
The boat’s emergency contact info is linked to the MMSI, so
when a distress call is broadcast, the info is included in the
message, giving rescue and emergency personnel accurate
details of the boat.
DSC: Digital Selective Calling; primarily a distress-alerting
function. Users can send a pre-configured digital distress
message (over channel 70) to emergency personnel and oth-
er DSC-equipped boats in their area. The message contains
information about the boat and its owner, its MMSI number,
the nature of the distress, and priority of the call. When a
DSC radio is connected to a GPS, the Mayday includes the
boat’s location. The transmission takes about one-third of a
second and is automatically repeated until a rescue author-
ity answers.
Class D DSC: Class D radios have two separate receivers, one
for voice communications and the second for continuously
monitoring channel 70 for any DSC calls.
a rundown on common vHf features and functions
Icom IC-M424
Icom IC-M504A
