Separate VHF aerial for AIS - location

[jwilson]

Thinking of fitting an AIS engine to feed a chartplotter at the helm. Do not want to disturb fixed VHF cabling (chart table radio to masthead antenna), instead want to fit a separate aerial. Originally I thought of a whip aerial on the pushpit, but it is a bit vulnerable to people passing lines, catching hold of it and bending it etc. (Seen too many plastic NASA Navtex aerials on pushpit snapped off).

I was wondering about fitting an approx one metre whip aerial inside the hollow GRP cockpit coamings, near horizontal. Easy to fit, access to space and cabling to plotter easy. I accept that it will not get ideal reception, but would it be good enough for AIS use for reasonably close quarters reception.

Anyone else done this? Did it work?

 

[prv]

On Kindred Spirit I used a Digital Yacht ANT200:

The rail mounting comes off leaving a flat bottom, and mine was mounted on the deck near the mast (due to the boat's deck layout it wasn't as vulnerable as it sounds).

My point is that this demonstrates that a short rubber-duck aerial mounted vertically at deck level is perfectly adequate for AIS reception. You could use a similar aerial (or even the whole AIS unit, if you don't have one yet) inside your coaming. I would worry that a conventional whip won't work very well horizontally, though I don't really know for sure.

Pete

 

[Pinnacle]

I am sure others will advise......but I am not sure horizontal mounting will be successful.

We too have a "stubby" aerial for AIS transmit/receive, which is mounted on the backstay about 4m above the waterline. Yes, I know we may lose it if the mast comes down, but hey, in those circumstances AIS may not be my biggest worry! In any event we also have an emergency vhf aerial we could use instead.

We get good reception from ships many miles away ( helped by the fact Class A units broadcasts are of a higher wattage than Class B and are usually mounted high up on top of the bridge, so can "see" quite a long way ). A friend mounted a similar aerial on the top of his lower spreaders ( job done when mast was down, so quite easy to do ) and he too gets good reception.

 

[nigelmercier]

aerial mounted vertically at deck level is perfectly adequate for AIS reception...

And provides a useful emergency VHF antenna.

 

[Daydream believer]

Could you put the whip aerial in a piece of plastic waste pipe & tape it to the backstay
Would it transmit through the plastic? may have to cut slots in the tube.
Fit a hook to the top of the tube ( as, say, a jib forestay hank) & slide it up the stay then fix the bottom as high as you can reach with tape to stop it sliding back down .A couple of hooks mid way as well . It may hook above the adjusting block if you have an adjustable stay to stop it sliding down
Run the wire down to the deck via the stay with an elastic tensioner for adjustable stays

 

[doug748]

I have used a simple stubby VHF aerial on the stern and atop a 6 ft pole. It seemed the same to me.

I also have a Plotter with built in AIS and this works, attached to the bridgedeck, with a simple 3 quid telescopic aerial plugged directly into the back. Before I had the telescopic job I used a homemade aerial (from instructions supplied by a kind forum member) and that worked equally well.

If I was going to experiment with an aerial hidden below deck, I would suggest this homemade job, as it is physically orientated in a handy manner - and it costs nothing.

To make an aerial, you strip about 3ft off the insulation of a piece of co-ax. Pull the central core through the braid and use the aerial in the splits position with the braid in one direction and the central core splayed in the other. I think the length is important, if you need to make one let me know and I will find the proper instructions.

 

[jwilson]

On Kindred Spirit I used a Digital Yacht ANT200:

The rail mounting comes off leaving a flat bottom, and mine was mounted on the deck near the mast (due to the boat's deck layout it wasn't as vulnerable as it sounds).

My point is that this demonstrates that a short rubber-duck aerial mounted vertically at deck level is perfectly adequate for AIS reception. You could use a similar aerial (or even the whole AIS unit, if you don't have one yet) inside your coaming. I would worry that a conventional whip won't work very well horizontally, though I don't really know for sure.

Pete

I could fit that whole thing inside the binnacle GRP housing - might be a good solution - the housing is here - http://www.yachtsnet.co.uk/boats/charter/ped.jpg

 

[Laundryman]

I could fit that whole thing inside the binnacle GRP housing - might be a good solution - the housing is here - http://www.yachtsnet.co.uk/boats/charter/ped.jpg

That's exactly what I have done. I use the Digital Yacht ais100 housed in the binnacle with the short stubby antenna attached to the back. No cables to run and I hate to see cables! Merry Christmas. Alan