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

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...

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.

(gar-- Sent Private Message re your question)

>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.

Marin said:

(gar-- Sent Private Message re your question)

Click to expand...

Marin, old friend, you do realize just how "ridiculous" these PM announcements look, don't you? (I say that with all due respect.)

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.

RT Firefly said:

I'll admit, pretty poor composition but you understand the message.

Click to expand...

That's funny! (And I do understand the message.)

psneeld said:

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...

Click to expand...

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!!!!

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

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.

gar said:

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

Click to expand...

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.

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.

gar said:

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

Click to expand...

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.

Via iPad using Trawler

FF said:

>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.

Click to expand...

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.

A long range radar will be mostly wasted if you can't mount it high enough.

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.

Brooksie said:

A long range radar will be mostly wasted if you can't mount it high enough.

Click to expand...

true...but in thunderstorm areas...long range cell detection can be a lifesaver...

>.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 .

FF said:

>.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 .

Click to expand...

I get excellent weather radar & forecast on my iPad or iPhone or just using my eyes to watch what's blowing in.

One feature that I don't think has been stressed is the ability to overlay the radar image on the chart. This came in very handy for us in the Bahamas since the charts are not totally accurate. Using the radar overlay we were able to offset the various cays to match the radar image thereby making the chartplotter much more accurate. It seemed that the offset was slightly different for different areas.

Bob

I have had a 16 mile dome Furuno, great for collision avoidance and close navigation, and have 64 mile open array Furuno which is also great for collision avoidance and slightly better for distant navigation. The 64 is a lot more sensitive, picking up birds etc and distant thunder storms.

Given where chart plotters are today I feel a radar for collision avoidance is it’s predominate roll and like others have said with AIS you have a great complement of electronics. I don’t think you could go wrong with either unit.

Marlinmike:

What action do you take when you see a boat out at 64 miles that is on a collision course with you ;-).

Seriously, I have used 2 Kw/24 mi units and 4 kw/48 mi units. Offshore at night I set them on 6 NM range and occasionally go out to 12 NM and look around for traffic.

A 12 mile range works pretty good for painting thunderstorms during the day. That range gives plenty of time to reef down and prepare for the blow that may come.

The 4KW units have a 24" scanner diameter so they give slightly better resolution. With the new HD units you can get the same resolution in a 2KW/24 mi unit.

Near shore or entering a harbor I go down to about 1-1/2 to 3 mile range. Either the 2KW or the 4KW can pick up ocean buoys at that range. If I want to discriminate between the red and the green buoy at right angles to the channel, I just wait to get a little closer and range down.

For recreational use the 2KW HD units are the best bargain.

Something that the majority of posts here have missed regarding range is that higher range radars very often come with higher power transmitters.

A higher power transmitter will produce more reflected energy, making small target detection better at even close range.

The narrower beam of most long range units further helps small target detection.

So, while looking at something 64 miles away isnt all that realistic, the 64 mile radar will generally see smaller targets like little fiberglass fishing boats much better than lower distance units

"Marlinmike:

What action do you take when you see a boat out at 64 miles that is on a collision course with you ;-)."

Actually never on 64 mile range, as I'm sure you know that number is more a lab number. But I did get a unit sized based on my offshore fishing and I wanted 6kw power with a narrow HBW angle, I won't go into all the uses of a high powered radar here, just suffice it to say it's useful 100 miles offshore.

Interesting side note, when I first got the 64 mile unit I actually didn't like it compared to my 16 as it was too sensitive, with time you learn to adjust and adapt.

ksanders said:

Something that the majority of posts here have missed regarding range is that higher range radars very often come with higher power transmitters.

Click to expand...

<<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.>>

...said Baker...

Radar install on a 1982 mainship 34

I am working on installing 3g radar on a 1982 mainship 34. the mast is located on fht for deck. Has anyone found a way to pull wires from the bottom of the mount to the inside helm.

Thanks Walter