general GPS advice required

A few months ago i purchased a pair of Rockwell micro tracker GPS receivers from ebay.
It's only now that i've had chance to play with one...

I have wired up a MAX232 and all is functioning correctly.
I wired in a single LiPOL as battery backup for the GPS unit as recommended in the datasheet...
the datasheet says that first fix can take upto 15 mins from a complete power down so i left it connected to a USB to serial cable on my laptop with realterm running.
When i come to go bed the only thing in realterm was the standard 'hello' NMEA string that it left upon power up.

Code:

---

$GPGGA,,,,,,0,00,,,,,,,*66
$GPGGA,,,,,,0,00,,,,,,,*66
$GPGGA,,,,,,0,00,,,,,,,*66
$GPGGA,,,,,,0,00,,,,,,,*66
$GPGGA,,,,,,0,00,,,,,,,*66

---

i left it over night and it still hasn't started spitting out NMEA strings...
The antenna is sat on my window ledge i'm guessing it can't find enough satellites???
Unfortunately, the manual is crap, but does anyone know a way of getting it to tell me what it is doing?

Thanks

I grabbed the Satnav from the car and it picks up it's location from inside the house.

i moved the unit to the garage and put the antenna on the garage roof. and still i get nothing but the start sequence...

Anyone got any suggestions?

My best guess is an incompatible antenna, somthing not made for the unit. What kind of antenna are you using, and where did you get it from? It can take a good hour or so when starting out completely from scratch (no backup battery) with the older units, with a little bad coverage. But it sounds like you have this covered.

I have purchassed a lot of stuff from ebay, and I have been pretty lucky with most of the things I buy. But once in a while, I get a dud. Hope that has not happened to you.

Walter

hi walter,
ok, i bought 2 gps receivers and two antenna's off ebay from the same seller.
The antenna's were separate sale from the receiver but it shows the antenna plugged into a receiver that looks like the one i got.
http://tbphoto.bababian.com/upload1/...DSC06643_m.JPG

The antenna is a Rockwell Jupiter TU30 GPS module 's 27db GPS antenna and my receiver is a Rockwell GPS TU00-D200-401

Datasheet for the antenna is http://www.inpaq.com.tw/en/RF_Antenn...ed20100224.pdf

I hope that helps. Thanks

Hi,

Maybe you could wire it according to the manufacturer for RS232
and communicate with this:

http://www.rfsolutions.co.uk/acatalo.../Celestron.rar

Hope it works

Well, I can't read the last attachment, but if you are reading the data out of the unit, I would say you have the serial communication part down.

After reading this: http://eshop1.chem.buffalo.edu/600M-GPS.html it seems to take amplified as well as non amplified antennas. So that's probably not it. How about power supply? Are you giving it enough juice?

This is supposed to be a similar model and pinout, but the board is different.
http://images.weirdstuff.com/thumb/rockwellGPS.pdf

You might try giving the pre-amp pin 5 volts, if you are not already. This is supposed to give the amplified antenna, its power source. Also, note the frozen start they refer to. They don't even tell you how long it will take out of the box, with old ephemeris data. So be prepared to wait a while to first fix.

Walter

The preamp has been tried powered and unpowered... according to the datasheet for the antenna's they require 3.3V or 5V...

The 5V supply is from a 5V regulator LM7805CV and that is fed from a 12V 16AH lead acid battery...
The unit is currently pulling ~250mA including charging a 3.6V LiPOL @ ~10mA (SRAM and RTC battery backup)

Comms to and from the unit seems ok.

The last attachment is a PDF datasheet for the antenna.

I've left the unit on over night ~ 8 hours but the manual says 15 mins...

I did notice the receiver is TU00 and the antenna's are for TU30 which i'll be surprised if it's incompatible...
I'm going to try the other board (i baught two identical) just to see if it's a board fault...
If that fails i'm going to see if i can make a passive antenna...

FWIW- I have the same type of unit. I hooked it up to an active antenna and while it powered the patch antenna it only output the GPGGA with all zeroes. It did see satellites but it refused to acquire a fix. Then I swapped the patch antenna for another one liberated from a USB GPS receiver (Navtech or something, lost the enclosure) and within 15 minutes, as promised, I had a fix with proper GPGGA and GPVTG data.

You may want to check the decrease in drawn current, these patch antennas need about 10 mA at 5 volts to work. Just unplug the MCX connector.

Good luck!