GBS receiver (BT) - which way up?

[hornist]

Does it matter which way up a GPS receiver goes?



I have a TT Bluetooth GPS receiver. Because my windscreen is heat-reflecting I mount the receiver in the non-metallised 'window' up by the mirror. While I've been experimenting with the setup I've had the base of the 'docking station' (the small holder for the GPS recevier) blue-taked to the windscreen, and then I clip the receiver in as required. This effectively means that the base of the receiver is pointing up towards the sky (at an angle).



One of the instructions with the docking station talked about the edge of it being angled to suit the angle of most windscreens. This would imply that (if you go for windscreen mount) they expect you to stick the edge of the holder to the windscreen. If you've not seen the TT BT docking station you probably won't know what I mean, but the effect would be to create a horizontal tray on which the GPS receiver would mount right-way-up. It would then be pointing top upwards towards the sky.



My limited knowledge of GPS receivers (based on my Garmin GPS12) suggests they will work at any orientation.



Is there likely to be any difference at all between mounting the TT GPS BT receiver bottom-up and top-up? Does the fact that the base is magnetic make any difference?



I'm interested to know before I permanently bond the base unit to the windscreen.



Paul

[Dave]

The edge being angled is the downward slope I believe it talks about so you can push it right up to the base of the window. The GPS Receiver patch antenna is facing upwards, so for optimal settings it would be best to bluetack the top of the GPS to the windscreen. Although it really depends on what sort of signal you're getting. If you're getting 7 or 8 sats, then you should be fine as you are. You need to look at getting 4 or more sats.

[lbendlin]

The antenna on the Garmin units is mostly of the circular type. This means those kind s of receivers should be held upright with the antenna pointing into the sky (Up, so to speak). The BT based systems are all using a planar antenna which means they need to lay around as horizontally as possible.
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[hornist]

Let me now answer my own question!



Based on some real (but not particularly scientific tests) with the vehicle stationary, I tested the GPS signal for the following configurations. The results are all obtained after the unit has had 15 minutes to settle down, and percentages are an approximate judged average.



1. Receiver mounted horizontally on it's 'tray', face up, in the clear 'window' at the top of the screen.

8 red-bar satellites, strength 70-90%



2. receiver stuck directly to the screen, base up, in the clear 'window'.

8 red bar satellites, strength 70-90%



3. recevier mounted in holder and holder stuck to screen in the clear 'window', so receiver is oriented base-up but 'looking through' the holder.

8 red bar satellites, strength 40-80%



4. recevier stting face-up on dashboard (under athermic windscreen).

8 red bar satellites, strength 40-80%



It's interesting that 1 and 2 were the same, so the actual orientation doesn't seem to make much difference. Interesting also, though, that 3 was worse than 2, which implies that 'looking through' the base reduces the signal.



I have therefore now gone for option 1, which is shown in the instruction book anyway, sticking the sloping edge of the holder to the screen with the supplied adhesive pad to form a horizontal tray on wich the receiver sits.



Paul

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