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GPS Repeater for indoor GPS

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jayamohan

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Hi all,

I like to build a GPS repeater. can some one share the details or schematic for the same please.

Thanks in advance.

Regards
Mohan.
 

E Kafeman

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You can build a repeater, but why? Your GPS receiver will freeze at the position your repeater have even if you move around the receiver.
 

jayamohan

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I need to check many GPS receiver units parallel inside the office and i don't want to keep many antenna's outside. Instead one repeater outside and all the GPS antenna's inside the office.
 

E Kafeman

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A repeater can be done in many ways, a simple proposal:
A 3 element cross-yagi pointing at sky, -> LNA+20 dB -> bandpass filter-> 5 meter coax cable -> Yagi pointing at your receivers.
As GPS signals are real weak must a good low noise LNA be used. A full size RX antenna improves total snr. If needed, additional gain is possible to insert in the end of coax cable if isolation is good enough between the both RX/TX antenna radiation patterns. 5 meter coaxial cable adds distance between the both antennas, which also helps to reduce unwanted self-oscillating.
If the GPS receivers can receive both direct and indirect signal from same satellite, is it possible that that satellite becomes blocked or results in unstable readings.
 

RCinFLA

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Buy a amplifed antenna like Gilsson. Try to find a model with higher gain (30 db).

You have to aquire or build a bias T to apply 5 vdc up the coax to power antenna/amp and coupling cap to output of bias T.

Build a radiator by stripping back shield to expose 1.6 inches of center conductor. Make a sheeth of 1.6 inches of brad and slip it over the outside of coax. Solder the sheeth to the shield of coax at point where it was peeled back to expose the center conductor of coax.

I have built many of these to re-radiate inside building. Just have to have enough separation between outside antenna/amp and re-radiator to avoid feedback. I use one in the car for my Samsung Galaxy S smartphone with re-radiator mounted on a phone mount stand hanging from windshield and magnetic mount antenna/amp on top of car.

For the antenna/amp, you need at least 4" of ground plane under antenna/amp module.
You can use a more expensive outside antenna/amp like a marine unit that includes its own ground plane if you want. It is intended to have GPS receiver within 6"to 12" from re-radiator. If you want to flood an inside area you can put an additional amp and better antenna for re-radiator. You will need sufficient isolation distant to outside signal for this.
 

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jayamohan

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Thanks for the feedback. I will try the same and let you know the results please...
 

Nubiee

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Thanks for the feedback. I will try the same and let you know the results please...
Hi Jayamohan, I'm also thinking of building one for testing purposes. Can you share if your attempt was successful?

Thanks!
 

davenn

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You can build a repeater, but why? Your GPS receiver will freeze at the position your repeater have even if you move around the receiver.
Ohhh its wonderful how old threads get rejuvinated ;)

when this thread was originally posted June 2011. I didnt know much about this stuff, but in August 2011 had a change in profession and am now a service technician for the primary Trimble GPS systems for heavy industry and surveying agent. We use reradiators indoors to be able to test all the equip. The fact that the actual location fixed is the receiver location outside on the mast is pretty irrelevent. I just want to see that my piece of gear I'm servicing on my workbench is receiving satellites and how many etc

I havent discovered much about the reradiator itself --- they are supplied from Trimble

Dave
 

tony_lth

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Trimble is a famous vendor on GPS, and Leica also.
 

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