GPS antenna under deck?

[PaulRainbow]

I need to move the GPS antenna from its current perch on the radar pole (scanner incoming, we bought the boat with a pole clearly designed to take more than a small antenna).
And will be adding an AIS transceiver ere long, so two GPS antennae to place.

If it's not a bad idea, and noting that Garmin state you can put the GPS antenna under a fibreglass deck, I was wondering about doing that and preventing clutter from the pushpit.
It must attenuate the signal a bit, but is it viable in practice? Or is it better to put up with the blighters being at eye height, photobombing a lovely anchorage view?
Function overrides form here, but if it doesn't matter, I'll take form!

I have two possible locations in mind - under the aft side deck beside the (quite high) coaming, or for more effort, in the hanging locker.

Anyone got any experience with any of this?
Many thanks.

I have used a few of those Garmin under deck mounts, no problems.
I have fitted dozens of Emtrak AIS, most commonly behind the switch panels, under the side deck, never had an issue.
Fitted scores of chart plotters in all sorts of locations, no problems.

I have two plotter, VHFs and AIS on the flybridge, the VHF and AIS are under some pretty thick GRP, all work fine.

At the lower helm are two Android tablets, mounted in the main dash pod, with thick GRP directly above them, above that, a vinyl covered housing, about that is the saloon ceiling and finally, above that the flybridge floor. They work fine.

Also in the saloon, another tablet, a PC with a USB GPS puck (tucked in the bottom of the curtain track, beside a stainless window frame) and two phones.

I think you might be OK.

 

[BobnLesley]

We had the antenna die on our Garmin 128 and as a stop-gap bought a cheap £10 puck antenna off an American yacht in St Lucia, which I temporarily stuck (with blue tack) onto the fibreglass above the chart table (it was close to a window). When we sold the boat in NZ seven years later, the only alterations I'd made to that set-up were to buy another cheap puck as a spare, in case it ever happened again (it didn't, it was still sat in the spares locker) and I eventually replaced the blue-tack with a blob of araldite.
Edit: When we subsequently bought an AIS transceiver, we fitted the mushroom antenna for that on the goalposts where the GPS one used to live; we didn't see any noticeable difference between the performance of our AIS and those of friends who went to the significant effort of locating their antennas at the mast head.

 

[Shaz77]

Having a look online most chart plotters have an internal ariel. My mushroom ariel is still on my pushpit from a previous model and has not been used in years but is a good holder for coiled rope.

 

[Refueler]

I just hang mine from the curtain rail .....

As I said earlier - only time it may not work is if we moor against a high wall ....

 

[Channel Sailor]

I have a very recently installed AIS with internal antenna and an option for an external. It is installed on a vertical surface under the deck, approximately 300-350 below the underside of the deck. The deck is foam cored grp. I think it would be a better gps signal if it had been installed horizontally, as indicated in the manual. Yesterday in the diagnostics I observed 21 satellites seen with well over half of them approximately 35% and no problem with a GPS fix.

As an experiment I connected an old “external “ GPS antenna that I left installed very close under the cockpit coating (still under the deck). The satellite signal strengths recorded were about 10- 18% better compared to just the internal antenna. All ok for me.