Venus GPS with SMA - Very disappointing

GPS/GNSS Development Boards
1

I purchased the Venus GPS with SMA connector and a GPS00177 SMA antenna from Sparkfun.

I’ve connected it to an Arduino Mega and indeed have it talking very nicely and receiving NEMA messages at 9600 bps very well.

In fact, I can get a fix and get data.

So why am I disappointed? This GPS unit was a little oversold. 51 satellites, 14 channels, -161dbm and touted at the time as the best GPS unit they had found with excellent sensitivity.

I’m in my bedroom sitting in an enormous bay window with windows from knee high to the ceiling all around. If I stick the antenna out a window on a ledge, it will track. If I move it to my disk, 2.5 feet away, it loses it. I can reproduce this at will.

The device was to go in a car. I won’t bother. It will never receive anything.

If anyone has any ideas of other antennas or magic dust to make this thing a little better at picking up a fix, I’m all ears. For right now, it just goes on a pile of other electronic junk that was oversold and underdelivered. Very nearly useless it would appear unless you want to wear an Arduino on top of your head and walk around NOT lost in the rain.

Jack Rickard

http://EVTV.me

2

The venus modules are sensitive enough to get a track indoors… with the right antenna, usage, and environmental factors. I know this after building my own all-in-one module (which I hope to interest sparkfun in after testing the second revision! :D)

Here is what SkyTraq had to say when I asked them about the poor performance of the sparkfun module/sparkfun antenna combo:

The SparkFun evaluation board should get position fix around

30seconds with normal active antenna (as attached) under open sky.

The active patch antenna you are using from SparkFun, I’m not sure

what kind of environment it is particularly tuned for. Patch antenna

performance is highly susceptible to the particular application environment

it is tuned for. You can test if placing a large sheet of metal underneath

the antenna improves reception, or put the antenna on a cardboard box away

from the metal sheet improves signal reception.

So…you can try their suggestions, or try another antenna. Skytraq pointed this one out to me ( I have yet to try it):

http://www.inpaqgp.com/Specification/Sp … 090227.pdf

or another one that matches the requirements of the module better.

Before you do all of this too, lets make sure you are using the module right… while the sparkfun antenna does take a long time to get a fix, I found it pretty stable indoors afterwards. Are you sure you:

-Are powering it at the correct voltage?

-Are providing it with enough current?

-Do you have the antenna oriented correctly? The ceramic part with the dot should be facing UP towards space at all times.

-Do you have the module near any noisy circuitry/devices? (i.e. big motors)

Edit: I’m curious where you were planning on putting this in the car now too :smiley:

3

I get a signal in my house using the basic breakout and the magnetic mount antenna sold on SFE. I’m getting a couple cheap antenna’s and I’m going to play with them a bit to work on signal reception. This is for a data logging app for canoeing and going through the woods when portaging can be pretty tough on reception.

4

macpod:
The venus modules are sensitive enough to get a track indoors… with the right antenna, usage, and environmental factors. I know this after building my own all-in-one module (which I hope to interest sparkfun in after testing the second revision! :D)

Here is what SkyTraq had to say when I asked them about the poor performance of the sparkfun module/sparkfun antenna combo:

The SparkFun evaluation board should get position fix around

30seconds with normal active antenna (as attached) under open sky.

The active patch antenna you are using from SparkFun, I’m not sure

what kind of environment it is particularly tuned for. Patch antenna

performance is highly susceptible to the particular application environment

it is tuned for. You can test if placing a large sheet of metal underneath

the antenna improves reception, or put the antenna on a cardboard box away

from the metal sheet improves signal reception.

So…you can try their suggestions, or try another antenna. Skytraq pointed this one out to me ( I have yet to try it):

http://www.inpaqgp.com/Specification/Sp … 090227.pdf

or another one that matches the requirements of the module better.

Before you do all of this too, lets make sure you are using the module right… while the sparkfun antenna does take a long time to get a fix, I found it pretty stable indoors afterwards. Are you sure you:

-Are powering it at the correct voltage?

-Are providing it with enough current?

-Do you have the antenna oriented correctly? The ceramic part with the dot should be facing UP towards space at all times.

-Do you have the module near any noisy circuitry/devices? (i.e. big motors)

Edit: I’m curious where you were planning on putting this in the car now too :smiley:

I do have the dot facing up. The module appears to be working correctly. If I hang the little stub out the window, it gets a fix within a few seconds. If I move it 2 feet inside the window, it loses it. I mean, I can do this at will while watching the output scroll up the screen.

I’m using the basic 3.3 v output of an Arduino Mega. It appears to run it.

The Arduino is in reality part of a current measurement system for an electric car. The car is a replica of a 1957 Porsche Speedster and is mostly fiberglass. See http://EVTV.me. I’m using a couple of LEM HASS hall effect current sensors to measure current and integrate it over time to derive Amp hours out and amp hours in from regenerative braking to establish a State of Charge on the cells.

I want to derive Miles to Empty. My hope was to use the GPS to integrate speed over time to derive distance travelled. I can then use distance travelled with AH consumed to predict miles to empty. But if the GPS is going to be in and out, the whole plan rather fails.

The unit was to be placed under the hood in the forward part of the car. Lots of EMI from an electric motor in the rear of the car. But the hood of the boot is fiberglass. A normal stereo GPS works quite well with the antenna placed under this fiberglass hood.

The Venus module was described in rather glowing terms as the BEST module they had found. If it won’t work 2 feet inside a bay window area indoors, I can’t imagine it working reliably anywhere, unless I want to wear it on top of my head with the convertible top down.

Thanks for the antenna link. I will try it.

Jack RIckard

5

u-blox makes the best GPS modules, I think that SFE stocks them. They are used by the military and law-enforcement agencies because of their performance. I’ve used one in the past, and it worked very well indoors.

6

I have the same setup and it works just fine under the fiberglass hardtop of my miata. The only issue I’ve had is it drops out when going through tunnels, but I haven’t used any other GPS on that stretch of road so I don’t know if the tunnel is long enough to make them all drop.