Can GPS "see" through GRP?

Re: Can GPS \"see\" through GRP?

I too thought I would have to mount the aerial outside until I gave it a try under the coachroof, it worked fine, GPS was a furuno gp32, so I just mounted the aerial on a bulkhead beside the nav station with a very short run it worked perfectly.
I should give it a try if I were you there's only one way to find out.
 
Re: Can GPS \"see\" through GRP?

My handheld Magellan works fine inside the cabin of our boat which has a balsa core deck/cabin top so thicker than usual.

It wouldnt work very well inside the wheelhouse of an aluminium motor boat.

Rig it up temporarilly give it a go.
 
Re: Can GPS \"see\" through GRP?

Trial and error isnt too difficult, if you have sufficient cable.

If you can find the indicators for satellite reception, you should see their signal levels going up and down as you move about.

also, if you are connecting it into a PC, it is possible to see the raw data coming in on Hyperterminal or similar. Then you can see if the data is garbled or clean with the antenna in different places.

I have been doing all this recently because I bought an EverMore SA320 receiver which was cheap (about £80) but is a bit tempramental.
 
Re: Can GPS \"see\" through GRP?

Clues??!! That takes all the fun out of it!!!

It is just a receiver pod, nothing more (no maker names on the GPS itself but it part of a larger system from Volvo QL Marine).

It is the GPS signal provider for my trim tabs. Basically the trim tabs have an automatic feature to level you out using a gyro-type affair.

However, as you turn it induces heel, which the gyro senses as not being level and tries to correct it using excess trim.

The GPS is used to sense turns (i.e. significant changes in heading) and disables the automatic trim correction until you straighten up again.

As such the GPS unit is very simple...just 3 wires (12v +ve/-ve and data)...with all the clever stuff being done in the trim tab black box.

Sounds sexy, eh!? Just can't be arsed to run yet another cable up the radar arch and have another aerial sticking out, ready to be damaged.

I have asked the manufacturers if I can use simple NMEA from existing aerial(s), they say no - it must be a "clean" signal with minimal data in the string because the unit is only listening for speed and heading and it must react quickly when you turn. This might be their paranoia...or that they havn't tested it outside their integrated system and as such won't warrant it...or they just want you to use it as it was intended.

So, just one meaningful cable, and it would be interesting to see the data too - not just to check whether it's garbled but if the GPS provides lat/long I would rather use it for my DSC as it is a completely standalone GPS and thus very reliable.

Thanks for your help!!

Stef
 
Re: Can GPS \"see\" through GRP?

Can GPS "see" through GRP? Most decidely "yes" - GRP is the material of choice for airborne radomes (radar being the same kinda frequency as GPS).

Both of my Lowrance/Eagles get max strength (S9) fixes in the lounge - signal through plasterboard, glassfibre insulation and concrete tiles. (Better than the Garmin and Magellans I used to own.) Boat grp is near enough invisible in comparison. Colin
 
Re: Can GPS \"see\" through GRP?

I have a Lowrance 3600 plotter with integral aerial. It works fine outside under the spay hood (with stainlass frame).
I do my passage planning/ routing in the cabin. Reception there is marginal with the signal dropping out with audible warnings from time to time. I think this is mainly due to movement of the crew and lowere signal strength. Mine is an old boat with two layers of fibreglass and encapsulated foam; probably thicker than modern boats. I wouldnt trust this instrument for real use below decks. In your case "suck it and see" is the obvious action.
 
Re: Can GPS \"see\" through GRP?

I was looking for a site for the plotter GPS antenna that did not require threading the cable through to the pushpit. So I set up the plotter and tried the antenna in several different locations adjacent to the instrument panel above the companionway. I tried it inside the GRP instrument housing and then mounted on top of it. The result was a significant difference in signal strength and satellites detected. Whilst the antenna did work inside I felt that the reduction in sensitivity was too great and gave it a permanent home on top of the housing.
 
Re: Can GPS \"see\" through GRP?

My Nauticat saloon top is quite thick. My Navman 5500i works fine inside unless it is heavily overcast or overcast and raining. I assume that the cloud cover attenuates the signal as does a damp deck. I usually run it on the external Raymarine GPS at sea, for that reason.
 
Re: Can GPS \"see\" through GRP?

[ QUOTE ]
Tomtoms work even inside an iron car! Not sure how!

[/ QUOTE ]

They, 'see' through the windscreen. Except certain continental winscreens shield them if they have some sort of sun protection built in.
 
Re: Can GPS \"see\" through GRP?

There may be a lot less signal strength when the deck is covered in heavy salt spray, plus rain. So the worst reception could be when you really want it most? GPS satellites also genarally transmit above the guaranteed (?) minimum, and may get turned down a bit. If you want to be sure, get a proper outdoor aerial! Or two! The better cars often have external gps aerials now, to get more uniform coverage as much as anything. (And because they have heated windscreen options which complete stuffs gps!).
Certainly on my old GPS120, there is a lot more margin with the aerial outside on the pushpit than under the deck. In my opinion you should give it the best antenna you can, it might only make a difference for a few minutes a few times a year, but unless your boat is too precious to drill holes in, why mess about? Or why not move the whole GPS out by the wheel?
But of course we 'proper navigators' don't rely on it any way!
 
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