Can't get a fix

GPS/GNSS Development Boards
1

I think I’m having antenna problems with my gps module because I can’t seem to get a fix. I’m using the wi2wi w2sg0006 ( http://www.wi2wi.com/navigation.php ) and a ceramic patch antenna connected by a U.FL coax connector. No, sparkfun doesn’t sell this particular model but they were sold out of anything similar when I made my order and it should be similar to the ones they carry. When I monitor the serial port with my bus pirate I get this as my GPMRC string: $GPRMC,001314.090,V,150209,N*4C

The “V” given means no fix and even after letting it sit running for 30 minutes in open sky I get the same result. My guess is that I maybe have the antenna hooked up wrong and it isn’t getting a signal. I connected the ANT_IN pin (22) to the center pole of the antenna and then the other connection on the antenna to ground. Everything else seems to be working right because it is spitting out data. Anybody know what I am doing wrong?

2

did you connect 3.3V to pin 19 and 21 if you were using active patch?

3

Yes, pins 19 and 21 are both connected to 3.3V. I read somewhere that with a cold fix you have to leave it running in an open sky for several hours so I left mine outside overnight and I still get the same result.

4

if you are using active antenna, then I guess that the only reason you are not getting GPS is due to bad reception.

The normal time for a good GPS to download the ephermirs is 18-50 seconds and almanac is 8-20 minutes max. So leaving it outside for longer will not help.

the only way to fix this is to change one item at a time to see where the fault lies. To do this you need several different kind of GPS antennas, a few GPS receivers and differnt power suppplies.

  1. Try changing the antenna to other kinds and see if any thing changes. Place antenna at differtn distances from GPS and see if it works.

if not

  1. Try chaning the GPS an see if the GPS may be broken. GPS chips are prone to static damage. Usually static damage does not complely kill a chip buy only distroyes some transistors. So overall it may look like functioning but may be working without a few (but important transistors). Always take care of static while dealing with GPS devices.

  2. If other GPS doesnt wirk, then try chaning your power supply to a battery or some other source. Your power supply may be noisy and GPS systems require a very clean power supply.

hope this helps