DIY BTS

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Hans Witvliet hwit at a-domani.nl
Mon Nov 29 08:29:11 UTC 2010


On Sun, 2010-11-28 at 23:49 +0100, Sylvain Munaut wrote:
> Hi,
> 
> > My first reaction was one of sceptism, but according to the people of
> > huwei it is do-able, no hardware changes needed, just some (major)
> > software rewrite.
> 
> With a single dongle ? Sounds weird.
> 
> The "client"/MS side of GSM have no duplexer but a TX/RX switch and a
> BTS needs to be able to TX and RX at the same time.
> (to be easily detectable by phones. It could 'possibly' work without
> it and phone would stay camped onces they are there but it could take
> several try for them to 'see' the network).
> 

Indeed, i am still skeptic: seeing is believing.
Got my HF-licence since 1978, so i know that it is very hard to do tx
and rx on nearby frequencies. One needs extreme good (cavity) filters.
Without those, even separate transmitters and receivers will not be
sufficient, as your receiver input stage will be completely saturated.

Eventhough "normal" bts must be capable of handling multiple handhelds,
while these dongles needs only to communicate with just a single one, at
extreme low power, there is not enough space inside for decent filters.

Hans (PE1CXJ)






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