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ProCos · 03-14-2004, 06:09 AM

Quote: Originally Posted by Falken

Hi, I sell a vehicle tracker which, as an option, comes with a high gain GPS. The manufacturers say this is for covert installations of the unit and GPS and works through metal skins but only updates every 15 seconds. I was rather surprised to see it's a Fortuna U2. No idea why it should be any more sensitive but that's what the tracker manufacturers say.

Doug

Your supplier could sell sand in the saharah dessert if he is able to convince buyers that his high gain antenna works through the metal skin.....

Come on wake up, the GPS signal link margin is very low (signal is only -130dBm) and therefore very sensitive to any attenuation. What he might mean is that his high gain antenna will help the gps receiver to receive multipathes/reflection and this way operate without clear skyview. This does not mean that you can put it in a place where it is totally surrounded by metal.

High gain antenna are normally used for application where in-door operation is wanted, but high gain antenna's are also more directive and therefore not necessary better for GPS since you need minimum 4 satellites for 3D or 3 satellites for 2D fix.

GPS modules that claims that their module works in-door normally means that you need the first fix outdoor or close to a window, and then you would be able to move "longer" away from a clear skyview. The reason that the GPS receiver needs to be outdoor or close to the windows initially is following: A gps good receiver normally needs C/No of 36-38 dBc/Hz for acqusition (initially) and only needs a C/No of 26-28 dBc/Hz for tracking.

BUT there is a price to pay, navigation on multipathes/reflections results in higher DOP (Dilution of precision) and thereby a worse position accuracy.

/ProCos.

03-14-2004, 06:09 AM	#5
ProCos Newbie Join Date: Nov 2003 Location: Denmark Posts: 33	Quote: Originally Posted by Falken Hi, I sell a vehicle tracker which, as an option, comes with a high gain GPS. The manufacturers say this is for covert installations of the unit and GPS and works through metal skins but only updates every 15 seconds. I was rather surprised to see it's a Fortuna U2. No idea why it should be any more sensitive but that's what the tracker manufacturers say. Doug Your supplier could sell sand in the saharah dessert if he is able to convince buyers that his high gain antenna works through the metal skin..... Come on wake up, the GPS signal link margin is very low (signal is only -130dBm) and therefore very sensitive to any attenuation. What he might mean is that his high gain antenna will help the gps receiver to receive multipathes/reflection and this way operate without clear skyview. This does not mean that you can put it in a place where it is totally surrounded by metal. High gain antenna are normally used for application where in-door operation is wanted, but high gain antenna's are also more directive and therefore not necessary better for GPS since you need minimum 4 satellites for 3D or 3 satellites for 2D fix. GPS modules that claims that their module works in-door normally means that you need the first fix outdoor or close to a window, and then you would be able to move "longer" away from a clear skyview. The reason that the GPS receiver needs to be outdoor or close to the windows initially is following: A gps good receiver normally needs C/No of 36-38 dBc/Hz for acqusition (initially) and only needs a C/No of 26-28 dBc/Hz for tracking. BUT there is a price to pay, navigation on multipathes/reflections results in higher DOP (Dilution of precision) and thereby a worse position accuracy. /ProCos. Last edited by ProCos; 03-14-2004 at 06:21 AM.