Radar: Pole or Mast Mount?

[neelie]

I'm sure this has been discussed ad nauseum in the past, however, the search function does not reveal anything.

Apart from a reduced line of sight range of say 4 miles with a 10 ft high antennae instead of say 8 miles for a 30 ft high antennae why else would one choose to mount the scanner halfway up the mast?

I'm thinking that I can live with a reduced range of 4 miles to a low atoll - worst case! An oil tanker would still appear at 20 miles.

I am seriously contemplating changing from my mast mount to a pole mount.

Should I or shouldn't I?

[tryrsh]

Mines on a pole but I never turn it on... Good chart plotter with up to date maps and a couple iPads running Garmin Blue Carts and an AIS linked to all three, I have no use for or reason to turn my radar on... Well, I have in fog near shore but that's rare in my type of cruising. Anybody else feel this way or is it just me?

[Delancey]

Arch? Mount yer solar panels up there as well?

[Charliemciver]

I'm new to it all, but I think the same - AIS is amazing. Radar I'll be using for fog/night and close in small stuff without AIS. And due to the power consumption I'll likely power it up manually only every few mins.

[Randyonr3]

Have had both types.. the mast mount showed a large "dead" spot to the rear of the boat where the pole mount gives you a pretty clear shot 360 degrees.. don't have an AIS, and not sure I'm putting one on befor we leave this time..

[seacap]

What about the vessels who don't have AIS. I can't believe someone said that. I held an all oceans license which required radar certification. If I only had one electronic aid to navigation it would be radar. The question from the OP was wether mast or dedicated mount was best for radar.
Mounting on the mast gives more weight aloft. Not good. But it also increases the range. Good. But how much range do you need. Basically not much more than a dedicated mount. Motor yachts have to use a dedicated mount and do fine. As far as other vessels go you should be able to see them 10 miles out. Plenty of time for collision avoidance. Islands are good for a much longer range if you use topographic maps, or charts with topography and make appropriate calculations.

[bobconnie]

No matter which you choose, pole or mast mount, you will have one of the best tools you can have on a vessel! I know all of the new stuff available today, AIS and such ! But when ya get caught in the REAL fog! nothing will give ya that comfy feeling like a good radar!! Im sure that haveing AIS is nice but if I could only have one extra piece of navagation gear besides a compass, I would want to have a working radar !But then Im Old and learned my sailing In the PNW, and as some of yall know it gets foggy up there sometimes ! ( it also helps down here in the Gulf with all the metal out there!!LOL) Just my 2 cents

[gamayun]

Are you sure the range of radar on a 10-ft pole is 4 miles? I don't remember the formula but thought it was a little more, like 6 miles on an 8-foot pole, which is what I have. Also, why are you thinking of changing the setup you already have? Is there a problem with it on the mast? Having been in fog with 1/4 mile visibility right outside the Golden Gate Bridge, I was happy to have my radar. The pole was the only consideration for me because I have a carbon fiber mast and can't drill into it for the mounting holes. The radar is 3G, so it doesn't have the same radiation and power concerns as the other type, but I still don't keep it on when visibility is good. How close the radar is to your head is something to consider.

[neelie]

Originally Posted by gamayun

Are you sure the range of radar on a 10-ft pole is 4 miles?

Pretty sure (+/- 0.5nm) and that's to target of zero height. Of course if your target is a Walmart container vessel from China stacked 200 ft high with Christmas goodies then your radar will pick it up at 24 miles or so.

I don't remember the formula but thought it was a little more, like 6 miles on an 8-foot pole, which is what I have. Also, why are you thinking of changing the setup you already have?

Since I am changing the radar to a B&G 4G plus installing wind generator - I was thinking that mounting it on a pole would have more advantages than disadvantages. (Kato Marine do a wind gennie / radar combo pole.)

Also, the attraction of the 4G is its ultra short range capability - hence a scanner mounted high up is not an advantage.

Is there a problem with it on the mast? Not really - apart from weight high up and more difficult to access.

Having been in fog with 1/4 mile visibility right outside the Golden Gate Bridge, I was happy to have my radar. The pole was the only consideration for me because I have a carbon fiber mast and can't drill into it for the mounting holes. The radar is 3G, so it doesn't have the same radiation and power concerns as the other type, but I still don't keep it on when visibility is good. How close the radar is to your head is something to consider.

I read somewhere that the new generation radars don't transmit a lot of energy - having said that I wont be placing my testicles in front of the scanner to prove my point.

Answers in green....

[WindLove]

I think installation on a mast is preferable. Why have an additional structure with a lower line of sight. Radar and AIS are not things to compare and choose your favorite. They are two very different tools for two very different needs. You should try to have both.

[markpierce]

I don't like the idea of my eyes/body scanned by low-mounted radar. Mine is on the mast.

[rgleason]

Written some time ago


Our backstay mount radar is on a gimbal 12' above water. The maximum range for a similar height object is
1.22nm x sq root height of radar + 1.2nm x sq root ht of target
1.22nm x sq root of 12' + 1.2nm x sq root of 12'
1.22nm x 3.464 + [/FONT]1.22nm x 3.464
4.22nm + 4.22nm = 8.4nm
Therefore we will only be able to see about 8 nm Miles over the curvature of the earth!
PURCHASING a 24nm or 36 nm RADAR and suffering the added weight (aloft or on the stern), windage due to size, and battery depletion is pure insanity.


I wrote some time ago, the following:

Our backstay mount radar is on a gimbal 12' above water. The maximum range for a similar height object is
1.22nm x sq root height of radar + 1.2nm x sq root ht of target
1.22nm x sq root of 12' + 1.2nm x sq root of 12'
1.22nm x 3.464 + [FONT=Arial]1.22nm x 3.464
4.22nm + 4.22nm = 8.4nm
Therefore we will only be able to see about 8 nm Miles over the curvature of the earth!
PURCHASING a 24nm or 36 nm RADAR and suffering the added weight (aloft or on the stern), windage due to size, and battery depletion is pure insanity.


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[rgleason]

Long thread here http://www.cruisersforum.com/forums/....php?p=1013621
B&G Zeus MFD - Has Anyone Tried it ? Sorry for double post. On cell

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[gamayun]

Originally Posted by rgleason

Long thread here B&G Zeus MFD - Has Anyone Tried it ? - Page 2 - Cruisers & Sailing Forums
B&G Zeus MFD - Has Anyone Tried it ? Sorry for double post. On cell

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I have the B&G Zeus 7" display. I'm very happy with it, but have had some "manufacturing warranty" defect with it interfacing with the radar. Not sure if the trouble getting it fixed is the manufacturer's or Johnson Marine in Santa Cruz. The people at Johnson Marine seem genuine in addressing the problem, but there hasn't been much progress. To get the most out of the MFD, which has some great sailing features, it needs to have the speed-depth-wind combo hooked up, which I haven't done yet. I also have the 3G dome because of that line of sight calculation -- no need to buy more than it would ever be able to function at.

[ka4wja]

Neelie,
Merry Christmas!!

1) Really???

Originally Posted by neelie

the search function does not reveal anything.

My search using radar and mast mounting, turned up quite a bit...including the definitive answers you were seeking, from just a few months ago!!

Please read this posting / thread for all the detailed answers to your questions....
"Radar dome location??"
http://www.cruisersforum.com/forums/...ml#post1325050





2) Brief / specific answers:

Originally Posted by neelie

Apart from a reduced line of sight range of say 4 miles with a 10 ft high antennae instead of say 8 miles for a 30 ft high antennae why else would one choose to mount the scanner halfway up the mast?
As detailed in the above linked thread, the 1st / primary advantage is NOT increased range, but rather the ability of the radar to actually work when at sea, in a heavy sea....a low-mounted radar is prone to having its beam blocked by the waves/sea!!!
(and fyi, there's no need to mount it "halfway up the mast", as typically 1/3 the way up a 65' mast is plenty...also, while your "4 nm" figure is accurate, the radar horizon from a 30' height is only approx. 6.9nm, not 8nm...)

Secondarily, the increased scanner height (of "mast-mounted radars") can provide some advantage in target acquisition, especially when looking for smaller targets that are either low to the water and/or when in heavy seas....

Another advantage is that it keeps the radar scanner from shading solar panels, etc. and/or cluttering-up the aft-end/transom....




I'm thinking that I can live with a reduced range of 4 miles to a low atoll - worst case! An oil tanker would still appear at 20 miles.....
......Since I am changing the radar to a B&G 4G plus installing wind generator. Also, the attraction of the 4G is its ultra short range capability - hence a scanner mounted high up is not an advantage.
----Not sure your B&G 4G radar is really going to detect much shipping at 20 miles....but even if it can, I doubt it'll be an oil tanker (typical superstructure radar cross-section is NOT 200' high, but closer to 100' high), so don't expect to see "oil tankers" too much beyond 16 nm or so, from a 10' high radar scanner (especially one that isn't designed for long-range..)
But....this is a pretty moot point as detecting shipping at ~20 miles is really not a requirement for most cruisers...

----And, unless you'll be doing "zero-visibility" docking, and require perfect target resolution at distances of 50', having the scanner mast-mounted (at say, 25' or so) shouldn't be an issue/disadvantage...




apart from weight high up and more difficult to access.
---- most modern radar scanners are very reliable.....and the reduction of a few pounds of weight aloft on a Valiant 50, would be unnoticeable...




I am seriously contemplating changing from my mast mount to a pole mount.
Should I or shouldn't I?
I would NOT....and depending on where you're sailing/cruising, I'd not recommend this for you either...
Just my opinion here...but you did ask!!

neelie, I do hope this helped...
Fair winds...

John
s/v Annie Laurie