US triband vs EU triband
spaar at openmoko.org
Wed Jun 17 22:03:14 CEST 2009
Joerg Reisenweber wrote:
> I just confirmed basic functionality of 850/1800/1900 devices (US Freerunner)
> for 900MHz networks. RF sensitivity is poor, but sufficient for areas with
> good coverage.
> For Germany a US device (850/1800/1900) worked flawlessly with German operator
> T-Kom (in urban area), and rather poor with Vodafone. Both are 900MHz
> Please notice I didn't yet check for the actual band used, so *if* T-Kom *and*
> Vodafone both had 1800MHz BTS here in the tested area, then this report might
> be moot. Anyway the result meets expected behaviour and 1800MHz BTS are not
> known for either operator.
So this is what I suspected but could not be answered by anyone till now.
According to my investigation the only difference between the two
variants should be a different filter in the reception path, in one case a
bandpass filters GSM850, in the other it is GSM900. Transmitter path
should be the same. As a result the phones should work in all four bands,
however with about 30 dB less signal strength in the not supported band.
A different issue is calibration, its not sure if the transmitter path
four bands is calibrated properly.
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