OsmocomBB

== Motorola filter replacement ==

In order to use the phone as a passive uplink sniffer, you will have to remove and replace the RX filters.

To replace filters on Motorola phones you will need:

 * [http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=HHM1526 HHM1526]

 * [http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=HHM1523C1 HHM1523C1]

 * [http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=04025A150JAT2A 04025A150JAT2A]

 * [http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=04025A220JAT2A 04025A220JAT2A]

As the shipping cost for such a small-quantity order is relatively high, a complete component kit is

 available for online order from http://shop.sysmocom.de/products/osmocombb-filter-kit

=== Remove existing baluns ===

First you will need to remove existing balun:

[[Image(motorola_filter_replacement_step_1_low.jpg, 250px)]]

[[Image(motorola_filter_replacement_step_2_low.jpg, 250px)]]

=== Solder new baluns ===

Clean up the phone and solder HHM1526 and HHM1523C1 on the right places (the black dot goes up):

[[Image(motorola_filter_replacement_step_3_low.jpg, 250px)]]

[[Image(motorola_filter_replacement_step_4_low.jpg, 250px)]]

[[Image(motorola_filter_replacement_step_5_low.jpg, 250px)]]

=== Solder ceramic capacitors ===

Last step is to solder ceramic capacitors 04025A150JAT2A and 04025A220JAT2A:

[[Image(motorola_filter_replacement_step_6_low.jpg, 250px)]]

[[Image(motorola_filter_replacement_step_7_low.jpg, 250px)]]

=== Credits ===

Thanks to [http://246tnt.com/gsm/rx_filter.html Sylvain] and Peter who made this possible.