Steve Lusardi said:
Marc,
Excellent advice, but I would also like to add that power is your freind and
it is not just for distance, as the radar mount will always be low in
height, but it is for small partially submerged objects that are close that
when struck could ruin your day. (like containers)
Power is automatically reduced in all radars for closer ranges. And with
the typical 50 microsecond pulse at short range a range of 15 metres
around your antenna is blind anyway.
The key issue is learning to adjust and read the radar, again and again,
under good conditions blocking the radar operator's sight.
There is an excellent simulator to train by the way from
http://www.lightmaster.co.uk/Radar/LightMaster_Radar_Simulator_Mk2
I found it when training for the Long Range Certificate, they have a
simulator too for GMDSS DSC VHF, very useful to train distress calls.
If had to start again, I'd first get the simulator, then go through a
course, and only then select and buy the radar. I had the luck to get
good advice from a trainer.
From own experience in training for the radar certificate (Rhine at
Basel, 200 meters wide, commercial ships up to 135 m long crossing at 30
m lateral distance, bridges with support towers, narrow ports etc...),
objects vary wildly in reflection, eg you may easily mistake a goose on
the water or a duck flying by for a small rigid bottom inflatable power
boat WITH a radar reflector (-> emergency stop of a 30 metre fire boat
when cruising under radar only - real time simulation of dense fog
or the next navigation mark with radar reflector at times. On the lake
of Zurich we have ferries for cars - they have two parallel faces in
their superstructure - this makes for a great multiple echo, even of
your own boat ... the same can happen with oil storage tanks, regularly
planted trees, a motorway bridge ... All this on a river quietly
streaming. We were trained for failures too, be it rudder broken, radar
failing or motor. It does give you confidence when you know what to do.
I learnt too that you must not have a radar without VHF to call
approaching vessels - on a river to call around bends, or negotiate
crossing port to port or starboard to starboard crossing. AIS goes one
step further as it broadcasts your position, heading, speed, size of the
vessel, destination continously and includes the MMSI, so you can
selectively call approaching vessels. Simrad has a unit for recreational
boats.
A narrow river is much more demanding than open waters in this respect.
Knowing the waters (or at least having a good chart, preferrably
overlaid) is key. A flat coast will be much closer as it seems because
the reflections do not come from the waterline but from the next tree,
house, boulders, ...
Another important fact
about 6' radiators is that the vertical fan is close to 20 degrees, as
opposed to a 4' radiator's 30 degree fan. If, as in my case, mounting the
antenna on an aft bridge, it means that a 6' radiator will not radiate the
center cockpit and a 4' will. Marc has advised anyone to witness the radar
you intend to buy before you buy it is imperitive. I helped install two
Kelvin Hughes commercial radars on a super yacht last summer. Both of these
drove 17" marine LCD screens at a very high resolution. They had 4'
radiators. The ability of these radars to discriminate targets at close
range was appalling.
You can get that on a small boat if you have the same 4' antenna.
(They might have some digital filters that help some more, but you get
most of it.)
Actually on a super yacht I'd get a larger open array (IF I had the
money for the yacht...) - at least 6', preferrably more.
I am not a radar expert, but I do know that everybody
that is anybody buys Furuno for a reason. It is not unusual to see 20,000
hours of transmit time without failure. That says a lot.
Steve
There are other choices, Furuno is not the only one. Swissradar has some
pretty nifty digital filters for example.
(Check eg
http://www.apple.com/downloads/dashboard/information/swissradar.html if
you have a Mac - 3 weather radars map the current rainfall for the whole
of Switzerland, 100 by 200 sm)
Koden (Sitex) might actually try hard and be successful at it.
On a small boat the combinations become important, as you might not have
the space for a separate echo, chart plotter, radar and AIS display.
A good balance of technical specs with space requirements and user
interface is what you are typically after.
My Simrad has a rather good auto setting on tuning/gain/etc, which for
me is a big advantage as I expect other people to operate it with even
less experience than myself. Along with the good chart overlay and a
very flat unit to mount this tipped the scale. It does not have a MARPA
on the other hand, but its trails work well as a substitute. The user
interface is clear but not as nice as Mac OS X or my TomTom GPS for the
street. (BTW their manual at
http://www.simrad-yachting.com/Products/Leisure/Navigation-Fishfinding/CX
44-NavStation/Downloads/
has a good explanation of radar operation and what sorts of displays can
be handy - off centre display is one of them, what is behind you is less
interesting than what's ahead).
And I knew Koden as an electronic engineer, so I did not have any doubts
there. Simrad's key expertise is actually echo sounders but their radars
have a good reputation for a reason too. In yachting they are well known
for their autopilots.
On my small boat I could install a 4' open array antenna, which still is
useful. I would not want anything less. Bear in mind also that larger
antennas often have a smaller vertical beam, which is NOT what you want
on a small boat, because it is rolling and you still want to see.
It might be worthwile to check some of the articles referenced in
http://marinedirectory.ybw.com/reprints/results1.jsp
a search for "radar chart" from 2005-2007 in Category Electronics turns
up this eg
Buying a radar plotter Practical Boat Owner Jul 2006 p76-79 (4.00
pages) etc
before testing and buying equipment.
The reprints are not free but most likely worth the money.
HTH
Marc
