FURUNO or B&G

[Simi 60]

Originally Posted by Paul L

What size is the JMC antenna?
In recreational radar they are typically 18in or 24in antennas. The 24in is far better at small target discrimination. The number to look at in the specs is the horizontal beam width in degrees. The smaller the number the better in practice. A Furuno 19in antenna is 5.2*, a 24in (which costs very little more) is 4.0* and far better. An open array 3.5ft antenna is 2.3* and a 6 ft is 1.4*.

This..

[Paul L]

Originally Posted by Simi 60

This..

That should be decent discrimination. A larger, open array would probably do you better instead of swapping out to new generation, but small antenna. Your boat isn't restricted to a small, enclosed dome antenna like small sailboats.

I believe you are headed through Indonesia, right? If so, you will be motoring much of your time in very low wind, low seas conditions. You will be looking to pickup FADs of radically different size and construction in thousands of feet of water. You will most likely try real hard to minimize night passages. At night you are often exposed to an excessive congregation of small fishing vessels with random lights going on for 10s of miles. A radar with functioning MARPA can be very helpful in trying to figure out what direction, if any, the more threatening targets are going.
The ships, ferries and tugs tend to have AIS. Most of the large tugs with bulk tows are using class B and often don't show up untill you are close enough to have to deal with it quickly.

[Simi 60]

Originally Posted by Paul L

That should be decent discrimination. A larger, open array would probably do you better instead of swapping out to new generation, but small antenna. Your boat isn't restricted to a small, enclosed dome antenna like small sailboats.

Like I said, all good on flat water and no rain but throw waves and rain in and even with adjustment it gets a bit naff , was that something or was it a wave?

Open array is an option but the $$ for one $5k+++ is more than I am interested in spending for something I have lived my life thus far without.

I believe you are headed through Indonesia, right? If so, you will be motoring much of your time in very low wind, low seas conditions. You will be looking to pickup FADs of radically different size and construction in thousands of feet of water. You will most likely try real hard to minimize night passages. At night you are often exposed to an excessive congregation of small fishing vessels with random lights going on for 10s of miles

Planing to head up later in the year
And yes, in those conditions it'll work fine as it does here

A radar with functioning MARPA can be very helpful in trying to figure out what direction, if any, the more threatening targets are going

.
Seems the mark II version of what we have has it
And it was one of the reasons for looking at 4G
That and instant on, low power use so would leave it on continually under way and the belief that it actually picks up targets better (so the vested interest YouTube videos say)
Oh and the ability to use it on our larger monitors, at least then a larger range view might actually mean something.

The ships, ferries and tugs tend to have AIS. Most of the large tugs with bulk tows are using class B and often don't show up untill you are close enough to have to deal with it quickly.

We fitted AIS last month.
How close is close? We are getting class B pings today 9.4nm out and class A at 18.3nm

In theory a tug doing around 8knots and us same should give around 30 minutes.

[carstenb]

We picked up a tug at 35nm two days ago

[s/v Jedi]

Originally Posted by carstenb

We picked up a tug at 35nm two days ago

In Panama we picked up 140 targets from both sides of the canal (!)

[Simi 60]

Originally Posted by carstenb

We picked up a tug at 35nm two days ago

How high off the deck is the antenna?

[Paul L]

Originally Posted by Simi 60

.........


We fitted AIS last month.
How close is close? We are getting class B pings today 9.4nm out and class A at 18.3nm

In theory a tug doing around 8knots and us same should give around 30 minutes.

The Indonesian tugs are modern looking medium to small sized tugs. Anywhere else they would have Class A AIS. These tugs are fitted with Class B AIS and I believe many of the installations are poor. At times we only picked them up on our AIS at under 1.5nm. They are towing very large and stacked high ore barges. The tugs tend to have proper long tow lighting. The barges tend to have the smallest candle available.
These tug and tows can't make much SOG and have very little maneuverability. You will often see them moving at 2.5 to 4kts. Gets worse when there is current. Occasionally they will call on the VHF. Given the language issues it can be a bit difficult to figure who they are and what their intentions are. You know its a tug because they call out their name with Tango Bravo name. TB for tug boat.
At night they will run along lines of 100's of squid boats that have random, bright lights. In some areas the bright lights are green, and overpower any real green nav light. So using nav lights to determine what the tug is doing is pretty tough.

It makes for long night watches.

[simonhantler]

Wow lots of replies to my post. Thanks for help guys. Being on a steep learning curve, do any cruising sailing yachts install open array radar antennas? It seems like they work much better for picking things in the water up. If protected surely it would be something for me to look into.
If I understand correctly the higher the better correct? If I installed an open array off an arch at back of boat would the mast etc get in the way of its transmitting signal and it not being high enough off the water?

[mdsilvers]

Originally Posted by Paul L

The Indonesian tugs are modern looking medium to small sized tugs. Anywhere else they would have Class A AIS. These tugs are fitted with Class B AIS and I believe many of the installations are poor. At times we only picked them up on our AIS at under 1.5nm. They are towing very large and stacked high ore barges. The tugs tend to have proper long tow lighting. The barges tend to have the smallest candle available.
These tug and tows can't make much SOG and have very little maneuverability. You will often see them moving at 2.5 to 4kts. Gets worse when there is current. Occasionally they will call on the VHF. Given the language issues it can be a bit difficult to figure who they are and what their intentions are. You know its a tug because they call out their name with Tango Bravo name. TB for tug boat.
At night they will run along lines of 100's of squid boats that have random, bright lights. In some areas the bright lights are green, and overpower any real green nav light. So using nav lights to determine what the tug is doing is pretty tough.

It makes for long night watches.

I agree with Paul. We've spent almost three years - fulltime - sailing in Solomons, PNG, & SE Asia. I can assure you that the majority of large vessels do not have working AIS. It's a fact based on our experience. This includes some of the large barges pulling massive loads 50m+ behind them. It's naive to believe otherwise, and radar is your best friend in these waters.