Venus GPS no-longer getting a satellite fix

GPS/GNSS Development Boards
1

I’ve got a Venus module (GPS-09133) with antenna (GPS-00177). This used to work great, I was able to get a satellite fix both on my window sill inside, and obviously outside. Used it with a 3.3v Arduino Pro and directly with my laptop (via a 3.3v FTDI).

As I said it all worked great a few months ago. I pulled it off the shelf last week and now it won’t get a fix. I connected it up with my laptop again with the FTDI and took it outside, and it never gets a fix. I get the NMEA strings correctly, but never with any valid data. A few sample lines:

$GPRMC,115954.700,V,0000.0000,N,00000.0000,E,000.0,000.0,280N*76
$GPRMC,115954.800,V,0000.0000,N,00000.0000,E,000.0,000.0,280N*79
$GPRMC,115954.900,V,0000.0000,N,00000.0000,E,000.0,000.0,280,N*78

I was able to change the configuration on the Venus (update rate, NMEA config, etc). So I believe the Venus unit is functioning correctly, just no longer getting a fix. So I suppose the antenna has gone bad? Anyone have a similar problem?

2

Make sure it has clean 3.3V power and check your antenna isn’t upside down. The ceramic part with the dot on it should be pointing up. What you place the antenna on will also affect how well this module performs (i.e. if you are working on a metal desk, try moving it off of that or putting a piece of cardboard between the desk and the module.

Any window tint can block GPS signals.

I would look at $GPGGA string for the number of satellites it can pickup, to tell if the signal is weak or just not there.

Otherwise, the antenna or coax might be bad.

3

update its AGPS status (if its enabled) this should help it find the sats.

if yours is not AGPS enabled, then just leave it outside for atleast 15 minutes. Some people who has similar problems found out that when its been started afresh its sensitivity is lower and needs a good signal for a long time to get “kick started”

4

To troubleshoot, check how many satellites are in sight in $GPGGA. I have poor results on window ledges, the building blocks 1/2 the sky and I rarely get enough satellites, one or two. After a cold boot, the card needs several minutes to get a fix on 4+ satellites and build its almanac, download ephemeris data. It’s one thing to get a couple satellites and a fuzzy position but things can get starved until the initial position fix is done.

If you don’t have a backup battery connected, that gets lost during power down. With Trimble GPS cards, I have seen them scramble their almanac and I had to clear SRAM to fix.

So it sounds like poor signal quality or the card gets mixed up?

5

When you first get a lock, chances are it will be a 2D lock and that will be less accurate than when you get a 3d lock. That should explain your 60ft results.

Also, with Sparkfun’s Venus module, I’m pretty sure VBAT and 3.3V are tied together… at least that is what the schematic says. I don’t see that in the product photo and I don’t have mine in front of me to check. At any rate, you should double check that they actually are connected and if not, you should power both pins.

6

Just to follow up, I replaced my previous antenna with a new GPS-00464 and it works perfectly now. Was able to get a fix in less than 30 seconds.

7

5A6163:
Just to follow up, I replaced my previous antenna with a new GPS-00464 and it works perfectly now. Was able to get a fix in less than 30 seconds.

indoors or outdoors?

i’m currently in my university lab and it doesn’t seem to be getting any fix no many how long i waited, for both gps00464 and the vtorch antenna