[C38] Radar installation advice

[Les]

On Fri, 2008-04-11 at 10:03 -0400, Charles wrote:
> I am installing radar on the Mighty Quinn in preparation for my trip 
> through the Great Lakes this summer which will include wandering among 
> giant steel battering rams (commercial shipping), who don't wish to 
> debate navigation rules.  Tonnage rules is the byword and my personal 
> experience crewing on a 600' ore boat back in the 1960's supports this 
> as part of my night watch responsibilities was to make sure the pilot 
> was awake.... and yes I often had to wake him!
> I have purchased the Furuno 1715 during the Defender spring sale.  It 
> comes with 30 meters of cable to connect the masthead unit to the panel. 
> 1. Is this enough and
> 2. where did folks mount the control unit and run the cable?
> 
Hi, Charles,
	First of all congratulations on your radar purchase.  
	Are you sure you mean 30meters of cable?  That is 270 feet.  A bit
overkill for our boats ;-)  I think you mistyped, and probably got 30
feet of cable.  
	First of all, the radar must be well overhead.  Typically the beam
width will be about +/-15 degrees in the vertical (total of 30 degrees
of beam).  The horizontal beam width will be dependent on the size of
the antenna.  Generally the smallest antennas (about 1' diameter) will
give about 3 degrees of beam width down to about 1.2 degrees for the
large open arrays.  There is one out there that says they have 0.72
degrees, I think, but that would be an enormous antenna.  The Effective
Radiated power goes up as the beam width shrinks, so the larger arrays
have greater effective power.

	So the reason I talk about this is to give some background.  The
antenna beam should not sweep your head when you do normal things on the
boat.  Typically this means putting the antenna at least 8-9' above the
deck.  That is the minimum height.  As you increase the height of the
antenna off the deck you increase heeling moment, and generally the
effect is such that somewhere about 3x beam is the high end to keep that
effect from becoming pronounced.  So on our boats that means putting the
antenna somewhere between 9' off the deck and 35' or so.  therefore most
folks mount them on the mast at about the 20-25 foot height.  This will
give you about a 12 mile radar horizon to something 20' high (most radar
reflectors).  Some folks mount them on the backstay.  If the cable you
have won't reach, then you can buy another cable.  Do not splice the
cable.  The base frequency is not too high, but the bandwidth of the
returns is VHF, so go buy a cable long enough to reach.

	I mounted my antenna on a homemade pole on the stern 9' above the top
of the coamings.  One thing that I will say is that a radar you cannot
see from the control point (wheel) is not too useful.  Also use the
radar often.  Become familiar with its controls and also to keep the
calibration current (radars are sensitive to moisture, and frequent
operation keeps them working well).  The modern small boat radar is very
reliable.  Be aware also that it will draw considerable power, if you
have the LCD display, it will draw about 2.5 amps RMS when running, and
about .4 amps on standby.  Check your specs.  It is not usually a
problem, but be sure you have sufficient battery power.  When the radar
is needed, the solar panels will not be working, and mostlikely if you
have a wind generator it will not be turning either (fog generally comes
with still or near still air), so you will be depleting your batteries
continuously.

	To get the display at the cockpit companionway on a hinge  from the
mast will take about the height above deck+10' to get to the starboard
side+16' to get aft to the companion way+hinged support lenght.  Maybe a
bit more.  Running it down inside the mast while the mast is in the boat
is tough.  You MUST be sure the cable is not allowed to rub against the
halyards or it will be destroyed.  Also it should be supported well.
The manual will tell you most of this.  

	Once the radar is in, you will have to tune it and align it to your
boat.  The instructions are included.  Go though the steps several times
to get the best results.

Regards,
Les H