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Tips and questions relating to the GPS modules from SFE
By GekoCH
#124776
Hy,

Right now I'm using the Copernicus DIP from Sparkfun.
After browsing the page I saw that there exists a Logic Level converter.
I only use the TX pin from the GPS so connected to the RX of the
5v Arduino. I get every second the Serial data from the GPS without
problem. The only thing is that it almost never gets a GPS lock....
Although with my mobile phone I get easily a GPS lock...
Is this because I don't use a Logic Level converter?

PS: The Antenna is the one Sparkfun sells the ceramic one (GPS-00177).

Thx
Andy
By MichaelN
#124782
How are you powering the GPS module? What voltage, filtering etc? It doesn't sound like the lack of level converter is causing your problem, and the antenna looks like a suitable match...
By GekoCH
#124786
first i directly connected it to the 3.3v pin of the arduino.
However the pin does only support 50mA Current and
the GPS does need a bit more so I tried to connect a
3.3v regulator with filtering caps but still the problem
stayed the same.

The very special thing is that when i touch a Metal part of the antenna
or the connector to the GPS it does find GPS satellites within seconds...

Very strange....
By bls
#124872
The GPS-00177 antenna works as good as any. And 5V parts will usually accept 3.3V levels with no problem (at least I've never seen a case where they wouldn't) so I highly doubt you need a level converter which is more to protect a 3.3V input from a 5V part if the 3.3V input isn't 5V tolerant.
At first, by 'touch', I thought you meant when the metal antenna part or connector was touched (as in connected or shorted) to the GPS but I think what you meant was it works when you touch a metal part of the antenna or the connector with your finger. If so, it sounds like you may have an RFI problem (RF interferance from some wireless device, a PC or anything else close by with a processor or high freq clock signal) and that touching the antenna helps reduce the level of the RFI or at least helps prevent it from reaching the antenna. If you have a scope you should also check the output of your 3.3V reulator to ensure it's not oscillating or simply make sure there's an input and output capacitor close to the regulator to ensure it's stable. As a note, I've never had a problem with a Copernicus, but Lassen iQ GPS receivers will not work anywhere within about 15ft of my main PC due to RFI.
By GekoCH
#124875
Thx for the answer.

I just received a new package with the Globalsat Gps Antenna PDF.
When I hook this antenna to the Copernicus module I get a fix within 30sek with 8 Satellites!

When I do attach a GPS-00177 back it does loose completely the signal to 2-3 Satellites and
can't get a fix. When I do hover my finger over the connector it immediately gets 6 satellites...

Where is the magic???

Image
By bls
#124896
30-35 sec's is typical for a fix, but I have no idea as to the magic, other than it could be RFI. After my Lassen iQ experiance I'm always on the lookout for RFI problems as I use GPS to track and recover high altitude balloon payloads and can't afford to have a problem with a camera or some other equipment in the payload box generating RFI and affecting the GPS. Most active antennas include a filter to help reject frequencies close to the GPS signal freq. and all I can think of is perhapes the Globalsat Antenna has a better filter or at least a filter with a slightly different response that helps reduce some particular local RFI frequency. Do you have a different computer you could try using in case it's RFI from the computer?
By GekoCH
#124904
bls wrote:recover high altitude balloon payloads
I do the same since 2008 and now I can even sell some devices :)

I will now use the Globalsat Gps Antenna otherwise it will be to dangerous as you
said.
Are you using now the Lassen iQ or the Copernicus?

Andy