December 19, 2010
about 3 years ago
I struggled getting this to work reliably (with GPS-00177). I verified that the VBatt pad was soldered to 3.3 on the board. I verified that the high power search jumper was set. I touched up the solder on the center pin. I force fed it ASCII messages to use high power search and to be a pedestrian (not a car) for stationary applications. I confirmed that 1PPS was not floating high during boot. I measured 3.3V on Vcc and on the center pin of the SMA going out to the antenna. I shut down all computations and SD Card writes on my board to reduce possible EMI. Still the unit hardly ever got a fix.
I tried singing: “Venus, goddess of love that you are. Surely the things I ask. Can’t be too great a task.” No dice.
What worked was getting a ground plane behind the antenna. A 4x4" copper square (I used 3M1181 tape) works great. I tape the four sides of the metal antenna base to the center of the square, since the backing adhesive sticker is probably an insulator. I now get fixes in less than 60 seconds, SNRs ranging from 25 - 55, 8-10 satellites within 5 minutes. I can even get fixes aiming out a window of the house. This is in a heavily wooded lot on the eastern slope of a ridge.
No public wish lists :(
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