Mounting an AIS aerial

[Joker]

I am intending to fit a Class B AIS transponder, and this needs its own, separate, dedicated GPS antenna. Garmin say it can be flushmounted.

There is a very convenient place in the cockpit, but the face is almost vertical instead of horizontal, so the antenna is pointing sideways. Is this a Bad Idea?

 

[RAI]

Probably a bad idea, most GPS antennas are of the patch type and are best mounted on horizontal surfaces, i.e. axis vertical. However, they often work below deck on fibre glass boats.

 

[Norman_E]

I think the GPS antenna should be mounted as near upright as possible. I have put one (not for AIS) under the headlining in a corner of the nav station, making sure that there was no metal above it, and it works well, and never loses signal. For AIS you also need a separate VHF aerial unless you buy an expensive splitter or get a unit with the splitter built in. I an thinking of adding AIS, and if I do so I will mount a dedicated AIS tuned antenna on the fixed frame of the bimini. A recent post about Metz VHF antennas led me to Salty John's website, where I noticed that Metz make a special antenna tuned to the AIS wavelength. I am not sure if that precludes using it as an emergency VHF antenna if dismasted.

 

[Salty John]

I am not sure if that precludes using it as an emergency VHF antenna if dismasted.

It will still work for radio. It's centred on 163 MHz and as you move away from this the performance declines but is still acceptable down at 154 MHz. Similarly, the VHF version is centred on 158 MHz where it performs best but it performs well across the whole band from 154 to 163 MHz.

 

[Joker]

I bought one of Salty John's antenna at the beginning of the season for my present receiver. It's mounted on the rail in the cockpit and picks up signals from >30 miles.

 

[ianfr]

I bought one of Salty John's antenna at the beginning of the season for my present receiver. It's mounted on the rail in the cockpit and picks up signals from >30 miles.

I have a Metz antenna from Salty John on the pushpit, and also get targets from over 30 miles away. Best one to date was a collection of ships around Ostende while we were in the Blackwater.

The other Metz is at the masthead, and that gives superb results as well.

Regards

Ian