antenna spacing on a sternrail

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yimkin

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I am about to install the following 3 antenna on the pushpit of my Victoria 800.
a whip antenna [Metz] for a NASA receive only AIS
an ECHOMAX X band Radar target enhancer
a 'mushroom' antenna for a FURUNO GP-32 GPS
How close together can I mount them and which one should be mounted in the middle of the three?
I realize placing them on the rail and in a group will almost certainly compromise their individual performances . However in practice if the Echomax and AIS function to a range of 10 - 12miles that will be sufficient for my needs.
 
The problem with having them close together on the pushpit is that one plonker rafted outside of you, rigging a shoreline, will wipe them all out.
RF point of view, they won't interact much if 100mm apart. Probably. None is transmitting high power. They are well separated in frequency.
I would suggest mounting them on a pole if possible. It's rarely a bad idea to put antennas nearer the sky.
 
Personally, I'd want the ECHOMAX as high as I could place it. Sea clutter could wipe out any advantage of having it.
 
Only the Echomax is actually transmitting (and then hardly at all) the other two are only receivers, and the GPS is looking straight up, so you don't really have to worry.
 
Thanks for the replies they make a deal more sense than the manufacturer's handbooks
I can now proceed with confidence
 
lw395 said:
GPS wants to see satellites in all directions, right down to the horizon for best precision, but as a minimum 3 or 4 satellites, which are not all going to be 'straight up'.
Click to expand...
I have a raystar 125 on the lower tube of the stern rail ( for some protection ) and a GPS dongle bobbed on the window below deck for the laptop. Both work equally well. 1 cost a £250 the other £20.
Agree that the echomax would be better mounted as high as possible.
 
YIMKIN said:
I am about to install the following 3 antenna on the pushpit of my Victoria 800.
a whip antenna [Metz] for a NASA receive only AIS
an ECHOMAX X band Radar target enhancer
a 'mushroom' antenna for a FURUNO GP-32 GPS
How close together can I mount them and which one should be mounted in the middle of the three?
I realize placing them on the rail and in a group will almost certainly compromise their individual performances . However in practice if the Echomax and AIS function to a range of 10 - 12miles that will be sufficient for my needs.
Click to expand...

As others have said, the Echomax would be best fitted as high as possible. The GPS almost certainly does not need to be externally mounted, try connecting it to the display whilst it's in the saloon. My Garmin GPS receiver is fixed to the underside of the deck, in one of the aft cabin wardrobes and works perfectly.
 
It might be appropriate to fit a pole with a Tbar to accommodate the aerials. It wouldn't have to be very stout or high, but would keep them out of the way.
 
lw395 said:
GPS wants to see satellites in all directions, right down to the horizon for best precision, but as a minimum 3 or 4 satellites, which are not all going to be 'straight up'.
Click to expand...

In Ye Olde Days, when GPS receivers could only track a few satellites, systems for land or sea use used to look for satellites widely spaced around the horizon, to get the best 2D fix, while aviation systems used to look for a high up one to get a reasonable 3D fix (better altitude at the expense of lat./long). Now we have fifty-channel receievers they all track everything.
 
JumbleDuck said:
In Ye Olde Days, when GPS receivers could only track a few satellites, systems for land or sea use used to look for satellites widely spaced around the horizon, to get the best 2D fix, while aviation systems used to look for a high up one to get a reasonable 3D fix (better altitude at the expense of lat./long). Now we have fifty-channel receievers they all track everything.
Click to expand...

Indeed.
But they will still acquire faster, be more accurate, and have more in hand for rain and other signal losses, if they've got a better view of the sky.
It's all very well having GPS that works really nicely with the aerial indoors on a sunny day, but will it work as well when there's green lumps of sea coming over the deck?
If you must mount it under the deck, choose a bit of deck where no fat passengers will sit......
:-)
 
lw395 said:
Indeed.
But they will still acquire faster, be more accurate, and have more in hand for rain and other signal losses, if they've got a better view of the sky.
It's all very well having GPS that works really nicely with the aerial indoors on a sunny day, but will it work as well when there's green lumps of sea coming over the deck?
If you must mount it under the deck, choose a bit of deck where no fat passengers will sit......
:-)
Click to expand...
My GPS comes from my plotter at the chart table. It may not be ideal, but works faultlessly. We are not fat; maybe that helps.
 
lw395 said:
It's all very well having GPS that works really nicely with the aerial indoors on a sunny day, but will it work as well when there's green lumps of sea coming over the deck?
If you must mount it under the deck, choose a bit of deck where no fat passengers will sit......
:-)
Click to expand...

Better let all of the plotter manufacturers know this, considering they are all making plotters with built in GPS. Not to mention, they will sell you an under deck mount for a separate GPS receiver.

When i was testing my network, before installation, i had the GPS receiver in the battery compartment, under a saloon sofa, still worked fine.

My sat nav works inside of my car, a nice steel box.

Why would there be fat people sitting on my side decks when green water is coming over the boat ?
 
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YIMKIN said:
I am about to install the following 3 antenna on the pushpit of my Victoria 800.
a whip antenna [Metz] for a NASA receive only AIS
an ECHOMAX X band Radar target enhancer
a 'mushroom' antenna for a FURUNO GP-32 GPS
How close together can I mount them and which one should be mounted in the middle of the three?
I realize placing them on the rail and in a group will almost certainly compromise their individual performances . However in practice if the Echomax and AIS function to a range of 10 - 12miles that will be sufficient for my needs.
Click to expand...

The Furuno GPS will certainly work very well through a thin layer of GPS so try to put it under the deck somewhere, where it will not be damaged.

Tha NASA AIS will probably work ok on the pushpit, but the higher the better.

I think Echomax radar enhancers are the devilish work of a clever British entrepreneur who expertly marketed them to gullible British sailors who are all cultishly obsessed that they are a must-have on their boat. Oddly the rest of the world has never caught on, which is why British yachts can be recognised at great distance by their rugby ball half way up their mast. I stand by with asbestos blanket to be flamed by all the Echomax worshippers who defiantly believe that they are more useful than an AIS transmitter.
 
CCJ, I'd be interested in the details of your Laptop Dongle, please PM if it would break the advertising rules in an open forum. Cheers, CT.
 
Slightly off thread, but does anyone have an InReach SE? I'm trying to find out the contract cost (Monthly v Annually) and it's been very difficult to get an answer from Garmin.

Any advice would be greatly appreciated, I've done a search but couldn't find a thread on it.

Thanks in advance for any replies, CT.
 
PaulRainbow said:
Better let all of the plotter manufacturers know this, considering they are all making plotters with built in GPS.
Click to expand...

They're probably expecting the majority of those plotters to be mounted in cockpit binnacles or motorboat centre consoles, though. It's been quite a few years now since most boatbuilders cottoned on and stopped hiding plotters downstairs where you can't use them properly.

(Not disputing that GPS generally works pretty well inside a fibreglass boat, of course, and two of my sensors are mounted that way - but the manufacturers often do warn against it and advise that an external aerial might be needed if you insist on putting their plotters below decks.)

Pete
 
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prv said:
They're probably expecting the majority of those plotters to be mounted in cockpit binnacles or motorboat centre consoles, though. It's been quite a few years now since most boatbuilders cottoned on and stopped hiding plotters downstairs where you can't use them properly.

(Not disputing that GPS generally works pretty well inside a fibreglass boat, of course, and two of my sensors are mounted that way - but the manufacturers often do warn against it and advise that an external aerial might be needed if you insist on putting their plotters below decks.)

Pete
Click to expand...

Raymarine will sell you a GA150 GPS receiver, "Ideal for installations where the display is mounted below decks or under a hard top"

Garmin will sell you an under deck mount for their GPS receiver. "Mount your antenna under a fiberglass surface with this under deck mount"
 
In the same way that you can slap a TomTom on the dash of your car and it will mostly work, but the system on the Merc with an aerial on the roof works better when you drive under some trees or between lots of tall buildings.
You make a choice about going to a bit more effort for a system that has more margin for when conditions are poor.
 
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