UmTRX preselector

Andrey Sviyazov andreysviyaz at
Wed Aug 8 17:16:38 UTC 2012

2012/8/8 Sylvain Munaut <246tnt at>

Which spec is that exactly ?
Its about far-near problem (05.05 p.5.1), i.e. blocking by near mobile with
high signal at only 600kHz offset.
Therefore, calculated that LO noise at 600kHz offset should be around
-140dBc/Hz to keep nominal Rx sencitivity for wanted far mobile.

> > Regarding the GSM 1800 version of the selectivity board, it will not be a
> > problem to change the mixer and the filters. However, are you sure we
> will
> > be able to get the correct matching if we only change the passives ? Are
> you
> > sure we would not need to modify the PCB traces to get a good matching
> for a
> > 1800 MHz version of the board ? What do you think ?
> Unless I missed something fundamental, this board is only RX side right ?
Yes, it contain LNA, DivSwitch, down converter and IF filter for Rx path
Late I'll make band dependant boards with 1-2W TxPA and ceramic duplexer.
But, possible no reasons to do it, I don't sure yet.

To get any significant loss in RX due to mismatch, you need a very
> large mismatch.

Best regards,
Andrey Sviyazov.
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