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Old 10-03-2013, 12:24 PM   #1
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Radar-36 vs 48 mile units

Hi All, I have a Garmin 740s gps w/ sonar. I want to add radar. I was told by one installer that the 48 mile unit vs 36 mile, would give better clarity ie. 2 bouys would show rather than one blip. I thought it would be best to get the 48 mile, even though the cost is almost double $1,100 vs $1999, because by 7 inch screen is rather small, so the added clarity would be needed. I have a 36' single engine boat, and plan on only icw costal crusing.This is all new to me, so any input would be appreciated. Thanks
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Old 10-03-2013, 12:52 PM   #2
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not true...

it's all about beam width which is usually a factor of dome or scanner width more so than power...just so happens that the more power...many times the scanner gets wider...thus better discrimination.

you have to check the specs carefully...and broadband is a whole nuther ballgame in some respects...

if the beam width isn't great the clarity won't be that great either and as far as the smaller screen...one pixel vesus two if the scanner can discriminate is all that matters...so don't get hung up the the scanner determines clarity...it doesn't...screen does that...the scanner does however determine discrimination between targets...
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Old 10-03-2013, 01:08 PM   #3
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I agree with the above post about clarity and discrimination. Of course, you would not be able to pick up a low level ground target at 24 or 36 miles, but you would be able to pick up thunderstorms. I have a 72 mile radar just to give me warning when in the out islands. It also gives good close in discrimination. I say buy the best radar you can afford.
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Old 10-03-2013, 02:06 PM   #4
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(gar-- Sent Private Message re your question)
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Old 10-03-2013, 02:43 PM   #5
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>plan on only icw costal crusing.<

The smallest , cheapest Quality unit you can find will be just fine.

In the ditch, sometimes only feet wide the question is where is the next buoy ., or are you about to run over some dummy anchored in the fairway in heavy rain or fog.?

Usually a totally MOOT question as in poor weather most ICW boats stay in place.

A radar for nav in open water , Am I 3 miles off the shore or 10, is usually well within the least expensive models.

Quality of the mfg is far more important than useless range specs.
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Old 10-03-2013, 03:35 PM   #6
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(gar-- Sent Private Message re your question)
Marin, old friend, you do realize just how "ridiculous" these PM announcements look, don't you? (I say that with all due respect.)
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Old 10-03-2013, 03:42 PM   #7
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Greetings,
Mr. SH. I didn't send you a Private Message re your comment.


I'll admit, pretty poor composition but you understand the message.
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Old 10-03-2013, 03:46 PM   #8
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I'll admit, pretty poor composition but you understand the message.
That's funny! (And I do understand the message.)
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Old 10-03-2013, 05:38 PM   #9
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not true...

it's all about beam width which is usually a factor of dome or scanner width more so than power...just so happens that the more power...many times the scanner gets wider...thus better discrimination.

you have to check the specs carefully...and broadband is a whole nuther ballgame in some respects...

if the beam width isn't great the clarity won't be that great either and as far as the smaller screen...one pixel vesus two if the scanner can discriminate is all that matters...so don't get hung up the the scanner determines clarity...it doesn't...screen does that...the scanner does however determine discrimination between targets...
We might be talking semantics here again, but the better radar has a NARROW beam width...not wider...and not greater. You want the energy to be concentrated in a narrower beam so therefore less energy is lost.

But just to reiterate....the narrower the beam width, the better. And usually the more powerful the radar, the narrower the beam width. In this case, the longer range radar likely has more power and a narrower beam width. I am generalizing here so check the specs. Narrow beam width is what we want!!!!
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Old 10-03-2013, 08:54 PM   #10
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I just added radar this year & have used it enough in clear conditions that in fog I think I would be comfortable if I got caught out or at night. I've found that it'll pick up channel markers 3/4 to a mile out, mine is a 4kw 5' Si-Tex open array and I believe it's 48 mile. The most useful distance is about 3/4 mile on the river & 1/4 mile in the harbor, I have ais to know where the tows are when their farther out. Small Fiberglas runabouts show up but you have to keep a sharp eye on the display, a larger display may make that easier. I would guess any 2 to 4 kW scanner should do what you want. Good luck
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Old 10-03-2013, 09:45 PM   #11
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Correct...narrow beam width ...wider array/scanner usually...means better discrimination.

More expensive and more power doesn't always mean better...when Raymarine first came out with their Pathfinder series, it blew everything else in it's category away back in the late 90's early 2000....mainly because I think it was the first smaller, less powerful radar that had more pulse widths to for various ranges.

So there's a few other things to consider but beam width and scammer size seem to be the primary factors...except for broadband which I haven't a clue how it works.
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Old 10-03-2013, 09:54 PM   #12
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Quote:
Originally Posted by gar View Post
Hi All, I have a Garmin 740s gps w/ sonar. I want to add radar. I was told by one installer that the 48 mile unit vs 36 mile, would give better clarity ie. 2 bouys would show rather than one blip. I thought it would be best to get the 48 mile, even though the cost is almost double $1,100 vs $1999, because by 7 inch screen is rather small, so the added clarity would be needed. I have a 36' single engine boat, and plan on only icw costal crusing.This is all new to me, so any input would be appreciated. Thanks
GAR, you may think that this contradicts what I have already said. For the ICW and close coastal cruising radar is not really necessary. I have done quite a bit of cruising on the ICW. Only a couple of times has fog enveloped me after leaving a harbor. Those times, of course, radar was extremely helpful. My radar will overlay my chart. I have had boats to line up behind to follow. One boat was so close that on the radar screen it looked as if my boat had a tail. If it is foggy I will not leave the harbor until the fog lifts. So, on the ICW it is not usually a problem.

I also have a short range radar with a 7" screen on my Blackfin. My regret there is that I didn't buy a better unit. It is of limited value.
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Old 10-03-2013, 11:11 PM   #13
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I'll add a little to this and repeat what others have said.

You want narrow beam width, which provides more horizontal resolution.

You want more power, which provides a stronger signal to recieve.

You want the radar reciever to have the lowest noise floor, or minimum detectable signal. This provides for the capability to detect a weaker return.

You want the best signal processing you can get. This can remove noise, improve low level target resolution, etc...

I wont argue the merits for or against "broadband" radar, except to say that no matter what the technology you use, the things indicated above are the basics of a Radar system, and they do not go away as technology changes.

And..... I do not get a chance to say this often, but here it goes.

I am a FCC licensed ships radar technician. License PG-17-635

Now if that does not date my old butt, nothing will.
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Old 10-04-2013, 12:45 AM   #14
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Hi All, I have a Garmin 740s gps w/ sonar. I want to add radar. I was told by one installer that the 48 mile unit vs 36 mile, would give better clarity ie. 2 bouys would show rather than one blip. I thought it would be best to get the 48 mile, even though the cost is almost double $1,100 vs $1999, because by 7 inch screen is rather small, so the added clarity would be needed. I have a 36' single engine boat, and plan on only icw costal crusing.This is all new to me, so any input would be appreciated. Thanks
Here are just a few numbers you might want to keep in mind when shopping for a new radar. The working range of the radar is controlled more often by the antennae height than the kW output. 1.22 times the square root of the antennae height will be the approximate horizontal distance to the radar's "lower limb" on the horizon. The vertical and horizontal beam angles will determine the minimum size target that can be differentiated at a particular distance. 1.047" at 100 yards equals 1 minute of arc or moa. That equates to 62.8" (or approximately 5ft) per degree per 100 yards. At 800 yds that's about 42' per degree or 168' plus for a 4 degree horizontal beam width. To sum it all up shop for the most kW per degree beam angle per dollar that will fit on your boat.

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Old 10-04-2013, 08:03 AM   #15
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>plan on only icw costal crusing.<

The smallest , cheapest Quality unit you can find will be just fine.

In the ditch, sometimes only feet wide the question is where is the next buoy ., or are you about to run over some dummy anchored in the fairway in heavy rain or fog.?

Usually a totally MOOT question as in poor weather most ICW boats stay in place.

A radar for nav in open water , Am I 3 miles off the shore or 10, is usually well within the least expensive models.

Quality of the mfg is far more important than useless range specs.
I have to agree with this theory. Been boating in fog prone Long Island Sound for 20 plus years on low power radars (all Furuno). Going slow and with a little practise they do what's necessary.
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Old 10-04-2013, 10:09 AM   #16
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A long range radar will be mostly wasted if you can't mount it high enough.
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Old 10-04-2013, 10:31 AM   #17
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A lot of good responses. We have a 64 mile Furuno that does great service. However, it is almost always set on 24 miles or less. I think discrimination and integration with a chart plotter are more important considerations than just distance. Chart plotter integration can really help with improving target location identification, especially when used together with AIS.
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Old 10-04-2013, 10:48 AM   #18
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A long range radar will be mostly wasted if you can't mount it high enough.
true...but in thunderstorm areas...long range cell detection can be a lifesaver...
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Old 10-04-2013, 03:58 PM   #19
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>.but in thunderstorm areas...long range cell detection can be a lifesaver...<

Where most folks cruise simply turning on the TV shows a far superior weather picture .
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Old 10-04-2013, 04:30 PM   #20
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>.but in thunderstorm areas...long range cell detection can be a lifesaver...< Where most folks cruise simply turning on the TV shows a far superior weather picture .
I get excellent weather radar & forecast on my iPad or iPhone or just using my eyes to watch what's blowing in.
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