AIS - two questions

[Wunja]

I've just bought a NASA AIS 'Radar' and whilst awaiting delivery I looked at the download of the manual - Its... limited!

Does anyone know what sort of antenna connector is on the back of it?

Secondly, the antenna is a one meter whip, I was going to mount it on the pushpit rail, but I'm wondering about mounting it on the top of the transom, inside the pushpit, so it doesn't get in the way so much. Any opinions on this?

Thanks.

 

[Salty John]

I believe the connection on the NASA is a BNC. If you intend to use the aerial as a backup for your masthead vhf aerial the best way is to fit the standard PL259 to the cable and then use an SO239/BNC adaptor to connect to the AIS engine. The radio will take the PL259 without the adapter, of course.

Fitting the aerial inside the pulpit has some risks to performance. Aerials don't like being alongside vertical metal members. On the rail would be better.
To guestimate range use 1.4 x root of the combined height of your aerial and the transmitting aerial. Heights in feet, answer in nm. A ship will have an aerial mast as high as 100', so even if yours is at 10' your theoretical range will be around 14nm. That's better than half an hours notice of ships moving at 25k.

 

[doug748]

I think I found that the usual aerial fitting did not go in the back of the Radar, so I had to sort it out, which is prob'bly what Salty John said, so no change there. A standard fitting would have been nice. So would an off switch, so if you want one in the system, you might think about it now.
I have a stubby aerial on the pushpit which gives me only 4 miles. This is a function of my set up, not the height of the aerial. It could be losses in the fittings I was forced to use because of that soddin plug. I hope you get better than 4 miles, but at least it stops me developing an unhealthy interest in far away things of which I know nothing.
Apart from that I am pretty happy with the thing. Let us know how you get on.

 

[LadyInBed]

your theoretical range will be around 14nm. That's better than half an hours notice of ships moving at 25k.

My AIS aerial is a couple of mtrs of wire strung horizontally round the boat! I pick up ships at about 5 - 6 Nm, just the right distance to look for them on the horizon

 

[Tranona]

I've just bought a NASA AIS 'Radar' and whilst awaiting delivery I looked at the download of the manual - Its... limited!

Does anyone know what sort of antenna connector is on the back of it?

Secondly, the antenna is a one meter whip, I was going to mount it on the pushpit rail, but I'm wondering about mounting it on the top of the transom, inside the pushpit, so it doesn't get in the way so much. Any opinions on this?

Thanks.

Think you will find that most people use a stubby VTronix antenna on the top rail. A whip is very vulnerable and inconvenient there. Reception should be fine _ get about 10 miles on both the installations I have done. You need the adaptor and then you can use the antenna as an emergency for your VHF.

 

[Salty John]

If you're going to use a whip antenna on the rail one option is to have a tool-less detachable rail mount. You can then swivel the antenna over so the whip points downward when not in use, or take it off completely for stowage in dock.
But, in most cases it's not a problem anyway.

 

[mcframe]

Think you will find that most people use a stubby VTronix antenna on the top rail. A whip is very vulnerable and inconvenient there. Reception should be fine _ get about 10 miles on both the installations I have done. You need the adaptor and then you can use the antenna as an emergency for your VHF.

I just went for:
http://www.digitalyacht.co.uk/product_info.php?products_id=11646
for ease of wiring into a Standard Horizon plotter.

(Separate emergency ariel carried +H/H)

 

[prv]

I just went for:
http://www.digitalyacht.co.uk/product_info.php?products_id=11646
for ease of wiring into a Standard Horizon plotter.

That's exactly what I plan to do if I ever decide to fit AIS. Is the plotter the CP180? Do the two work well together?

Pete

 

[Wunja]

I just went for:
http://www.digitalyacht.co.uk/product_info.php?products_id=11646
for ease of wiring into a Standard Horizon plotter.

(Separate emergency ariel carried +H/H)

That was my original plan, but not having a chart plotter, was looking quite expensive. Additionally, the power consumption of the two components is high.

 

[nmeyrick]

From what I understand a splitter is needed when sharing an aerial with VHF in order to stop the IAS being overload when TXing. Does this mean then if I have a separate aerial fitted for navtex that I could use this with no need for a splitter?

 

[prv]

Does this mean then if I have a separate aerial fitted for navtex that I could use this with no need for a splitter?

Highly unlikely, as while AIS and VHF both use, um, VHF frequencies, NavTex is somewhere else. I think of it as being more like Radio 4 long-wave, although I'm sure the many radio buffs will enlighten us

In addition, many (not all) Navtex aerials are actually active devices, with both aerial and part of the Navtex receiver built into the same box. They won't be sending VHF signals down the wire for the AIS receiver to use.

Pete

 

[mcframe]

That's exactly what I plan to do if I ever decide to fit AIS. Is the plotter the CP180? Do the two work well together?

Yes - a SH CP180 - external - the ANT200 is mounted on the pushpit rail, above the quarterdeck flush-mounted GPS mushroom, so they share the same cable run forward.

Check the downloadable manuals for both to work out which coloured cables you have to join, but it's pretty straightforward.

I had to update the firmware on my 2008 plotter for the AIS to work, and the human interface is, err, Standard Horizon, not Apple, so is slightly counter-intuiative initially - you get triangles on the display for acquired targets, but need to go (from memory) Menu->User points->AIS to get a list of targets sorted by distance.

Initially, I didn't see the raw NMEA data displayed on the plotter diagnostic menu, but after a couple of minutes, it picked up the traffic and showed it in the normal manner.

I know it's quite low-budget compared with other setups, but it works - around the Solent, I probably get 10-15 miles AIS range.

It's interesting (good practice) in Portsmouth listening to QHM, then seeing the Cap Finistère/Normandie Express & other big traffic on the plotter before crossing Camber/Gunwharf to Ballast.

For extra fun, if you've got a DSC radio (mine is an SH GX1500), then you can try a 'position request' DSC request to a friend and (assuming his kit is working - in this case it was another SH VHF, but being driven by a Garmin GPS) get the position of his anchored boat appear as a waypoint on the CP180 - ideal for meeting for breakfast in Priory Bay when your friend's has arrived too late to get into Bembridge the night before ;-)

 

[prv]

I know it's quite low-budget compared with other setups, but it works

Cheers. I don't have any need for AIS at present, but if I were planning a cross-Channel trip and feeling flush at the time, I might just add one to help out with weaving through the shipping. I might well make it demountable, as there's no really good place to install it, so it would only be fitted when I was likely to be tangling with ships.

For extra fun, if you've got a DSC radio (mine is an SH GX1500), then you can try a 'position request' DSC request to a friend

I have a DSC radio, but I don't think it can send that sort of thing to a plotter - it only has NMEA input, for position for the infamous red button. In fact I don't think it does routine position reporting or polling at all - there doesn't seem to be any mention in the manual. It's the NASA SX35 DSC, came with the boat.

Pete