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Electronics In Car Entertainment (ICE), Sat-Nav, lighting, wiring etc.

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post #6 of 12 (permalink) Old 26th June 2007
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I have a Tom Tom One V2 (regional) that uses the ultra sensitive SIRF III chipset (so the box says) and have no problems getting a signal in my car which has a heat reflecting windscreen. My tom tom does sometimes take up to 5 mins to lock onto a signal though, even when Im not in the car.

If you get an external antenna for it and place it on your windscreen on the black dotted areas either side of your rear view mirror, then you will be able to get a good signal as these areas are not coated with the athermic coating.

Hope this helps.
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Last edited by dave_mezza2006; 26th June 2007 at 01:28 PM.
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post #7 of 12 (permalink) Old 26th June 2007
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Originally Posted by mimo View Post

I have a Laguna 2002 and i also own a tomtom go 910, when i put the tomtom in my car it has trouble finding a signal, it eventually does, after about 5 mins or so...

But in aany other car i have tried it in, it finds a signal almost instantly... am i the only one this is happening to? isa there something that reppels the signal?

Please help...
Have you run the Sat location updates receintly ? .... I have a 910 in My Espace IV with a athermic windscreen, and it does take longer to lock on than in normal cars to the sats, but is generally quicker if you have up dated the sats location from TOMTOM Home.

hope it helps

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Last edited by Truckbusuk; 26th June 2007 at 01:15 PM. Reason: ytpo
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post #8 of 12 (permalink) Old 26th June 2007 Thread Starter
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thanks for that guys...

Your right, i sometimes even get a signal indoors and i even get it in the car but it just takes a bit longer to find me, which is a bit annoying when you just wanna get in and drive.... i'm looking into the external antena....
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post #9 of 12 (permalink) Old 26th June 2007
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I suppose the windscreen must be attenuating the signal to some degree. It's just that the theory goes that Sirfstar III is sensitive enough to be able to use the lower strength signal.

Having said that, the signal is still weakened, and maybe that means that even Sirfstar III loses some of the signal.

But aside from the signal strength, there are three things that can seriously lengthen the time it takes for a sat-nav to achieve a lock:
1) Out of date almanac data, possibly for satellites that are no longer in range. This shouldn't really be a problem if the unit's only been off for a few hours, but if it's a matter of days, then it can be an issue.
2) The unit has been switched on in a significantly different location to where it was switched off (the stored almanac data is incorrect for the new location, and it takes the unit a while to figure that out.
3) The unit is trying to acquire a GPS lock in a moving vehicle. (It's much harder for it to reconcile its position when that position is constantly changing.)

Combine any of the above with the attenuating effect of the windscreen, and I suppose lengthy lock times are to be expected. The more factors you combine, the longer it's likely to take to acquire a lock. It's an achievement that Sirfstar III works at all. My 700 with Sirfstar II rarely gets a lock in the Lag without the external aerial.
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Last edited by Horatio; 26th June 2007 at 01:32 PM.
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post #10 of 12 (permalink) Old 26th June 2007
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We had a pda and a blue tooth separate gps receiver - we always had to put the reciever directly under the sunroof or on the rear parcel shelf to get a signal.

PDA died, wasn't really used for much else other than gps so we got a good deal on a Tom Tom 910 - that works ok in the Laguna no problems - can take a few minutes sometimes to lock on but otherwise works fine with the athermic w/screen!

The Megane doesn't have an athermic w/screen and to be honest haven't noticed much difference. Although when the roof is down we get full signal no problem ( wonder why?)

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