[C38] Radar installation advice

[Charles]

OUCH!  I meant 10 meters!

Les wrote:
> 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
>
>
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