On Sat, Jul 24, 2010 at 01:26:31AM +0100, Cal Leeming [Simplicity Media Ltd] wrote:
> Besides, you gotta remember, that the USRP is a very expensive piece of kit, > and just having one might not be enough depending on what you need it for. > See Sylvain's earlier post reply for a good explaination about this. > > Personally, I think it would be a really cool idea to start up work shops > which would look primarily at extracting the transceivers out of > cheap/unwanted handsets, and putting them to a good use. It would certainly > be a lot more fun than just paying for the hardware :) Well, you can try to look at the work that we've been doing as part of OsmocomBB (http://bb.osmocom.org/). We've done all the code you need to drive the transceiver of the TI Calypso chipset (TRF6151 / Rita), the analog baseband (TWL3025 / Iota) and the digital baseband (Calypso / HERCROM400G2). Next problem is: If you ever want to tune into the uplink, you need custom hardware as the filters for the frequencies are reversed. Plus, it is impossible to find any SAW filters for the reverse bands in the same or similar mechanical dimensions - not even speaking of the same impedance and balanced/unbalanced-ness as needed. Thus, it is impossible to simply replace the filters on existing hardware. More modern GSM phone designs use a 'frontend module', i.e. an integrated component that contains the RF transceiver, the filters and often also the PA. In such a module, you simply cannot change the filter characteristics anymore. Also, I would not waste time at developing your own hardware based on an old / end-of-life RF transceiver. Don't underestimate the time you will have to spend on doing analog RF design at frequencies that come close to 2GHz. Without the proper skills/experience and particularly measurement equipment, you will not be able to design something that will be close to the performance of a commercial handset. I've analyzed this long enough and I think it's simply not worth putting so much time and effort into something that inevitably only very few people will show an interest in. Regards, Harald. -- - Harald Welte <lafo...@gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6) _______________________________________________ A51 mailing list A51@lists.reflextor.com http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
