Thread: GPS repeater

I suppose it's time I posted some progress on the GPS repeater project.

The unit comes from E-bay with an external antenna and internal transmitter :


I put the external antenna to one side. Don't need it.

The concept is to split the NAV GPS and feed it to the transmitter. I did this with a Fakra splitter, and Fakra to SMA adapter cable :



The NAV unit supplies power to the GPS antenna, so does the repeater. So having them both poking volts down the line is likely to end in tears, thus the need for a DC block between the repeater and the remainder :

All up it looks something like this :



Having the DC block seemed like a good idea, but in theory if the repeater is pushing power down the line it can be modified not to :


Prying the back off saw a module with a GPS patch antenna on the front and soldered metal shield on the back. The shield is held in place with 2 joints, and a hot iron and tweezers saw those loose.

R8 is a 150 Ohm resistor that supplies 5V to the Antenna, and R7 is a 2K resistor that supplies power to the LED. The theory being if the antenna is shorted the led is out. I removed R8 and bodged R7 across to the 5V input to make the LED come on. I could have just removed both.

I soldered the shield back in place and used superglue to stick the back on, holding the module in place. Now I can (and have) remove the DC block.

None of the cables are long enough to allow me to conceal the unit, so initially I ordered a 1M SMA extension. Then I found a place that made me a custom cable. It's a Fakra splitter, with the Fakra->Fakra being 20cm, and a Fakra->SMA at 1.4M.

Fakra ”C“ Male to SMB Female 5005 SMA Male Y Splitter Combined Cable 20cm 140cm | eBay

That will allow me to thread the cable up under the console and put the repeater in top of the center console.

Results wise, it has solved all reception issues I've had with both dashcam and phones in the vehicle. I'm waiting on an additional GPS receiver to arrive to allow me to do quantitative signal surveys, but that's just "for info". The results so far are outstanding.

Ok, after months sitting on the dash I finally got around to setting this up properly with the new cable and all wired in.
The new custom GPS "Y" cable :

Running the cable up inside the center console under the passenger cup holder. Fiddly! :


Wiring connectors. The fig-8 taps off the 5V converter I mounted in the roof for the dash-cam. I used a 6 core cable to get the 12V up, so I had spare cores to get 5V back. The SMA connector is just straight to the end of the custom cable I had made :


The GPS repeater double-sided taped to a step in the console :


It has been sitting on the console shelf directly above its current location, so provided that plastic console doesn't have metalized paint it'll be ok. Time will tell.