Open moko GPS pin connection
Dr. H. Nikolaus Schaller
hns at goldelico.com
Wed Nov 9 19:17:23 CET 2011
Am 09.11.2011 um 19:03 schrieb Alexander Lehner:
> On Wed, 9 Nov 2011, RANJAN wrote:
>> Does any one know about the OpenMoko GPS chipset pin connection. After I
>> opened it I could find only one grey wire which appears to be the antenna.
>> Where are the Vcc,Gnd and Rx-Tx pins?
> I guess you mean this part:
> The grey cable is a 2-wire coaxial cable. I once ripped it off and tried to re-solder it without success. It is too tiny to handle it with fingers.
Yes, they are very tiny. If someone is looking for a replacement,
you can cut this 10cm into two halves:
> The actual antenna is (from my understanding) the big light-brown piece of plastic in the top of the phone, while the GPS chip is soldered on the board itself. I think this is so because there is also a second external GPS antenna connector on the side of the phone. Also, plenty of shielding metal next to the GPS antenna connector lets me assume, that there is some high-frequencey electronics working under ;)
> I guess it works similair to a TV satelite receiver (LNB) which is also powered and data-exchanged with a 2-line coax cable.
> No idead how they do this technically.
> Roughly, there is power and some commands to justify the satelite receiver to a certain frequency. But IMHO the actual logic to interpret GPS data is not inside 'that brown plastic piece'.
The brown "plastic" piece is the ceramic antenna patch.
Under the metal shield on the green PCB is just
a single transistor amplifier.
So it is a active antenna with pre-amplifier that is DC powered
through the line and sends back the amplified 1500 MHz GPS signals.
The real GPS receiver (with RX, TX etc.) and an
antenna switch (internal/external antenna) is on
You can find the schematics here:
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