GPS

[Yorick Moko]

two small questions:
1) is there ANYBODY who has a freerunner with a "normal" functioning GPS?
2) We must presume openmoko tested the GPS before starting the mass
production. The GPS of those devices must have worked, no?


On Mon, Jul 14, 2008 at 3:05 PM, thomasg <thomas at gstaedtner.net> wrote:
> On Mon, Jul 14, 2008 at 10:45 AM, Kalle Kärkkäinen
> <kalle.karkkainen at intstream.fi> wrote:
>>
>> In my past life I developed a fleet management device that had GPS and
>> GSM in it, able to send the fix data to server in intervals. we even
>> implemented some location alerts (around the vicinity of, or near
>> customer..).
>>
>> Based on that experience, we used on of falcoms devices for it, it most
>> probably did not have much of a cache for gps data (black box, tough to
>> tell), but it needed a strong antenna for gps. For a GSM antenna you
>> could use a hairpin, anything that had 10-15 cm of length was totally
>> enough for good quality gsm connection. GPS required much more, in our
>> case we supplied all the devices with external antennas.
>>
>> My knowledge is based solely on this work experience, I'm no radio-geek
>> so I cant really tell much about antennas and signal catching. What kind
>> of GPS-antenna is there in FR? Embedded for sure, but could that be the
>> problem?
>>
>> I guess your TomTom comes with an external windshield antenna?
>>
>> --
>> Kalle.
>
> No, it has no external antenna, only a window-mount with antenna connector
> but without one connected.
> That GSM works better is sure, because mobile GSM devices can receive at
> -110 dBm (usually ~ -70 to -90) while GPS chips receive at up to -160 dBm
> (usually between -130 and -150 at the antenna).
> I think the antenna in the freerunner is not that bad, it even has a preamp.
> Ublox can receive at -158 dBm (according to the datasheet), what is pretty
> good (and definitely not worse than every good navigation device), and
> should get at least -130 dB (good enough for a cold boot fix) _after_ the
> antenna (preamplified) I guess. It even has it's own additional amp on chip.
> So the problem is imho only bad build quality (QA) at least in some of the
> devices (might be a defect connector by 3rd party, don't know).
> Short version: antenna good (I bet it's better than the antennas in most
> other smartphones with GPS), chip very good -> bug.
>
> And btw. - SIRF Star III are damn good chips and used in many navigation
> devices and bluetooth gps devices, but the antaris is almost at the same
> level.
>
> It surely is no software issue, theoretically it could be a firmware issue
> of the u-blox, but I don't think it is.
>
> _______________________________________________
> Openmoko community mailing list
> community at lists.openmoko.org
> http://lists.openmoko.org/mailman/listinfo/community
>
>