# Problem to set RF filter on DBSRX board

**URL:** <https://www.ruby-forum.com/t/problem-to-set-rf-filter-on-dbsrx-board/188340>\
**Category:** GNU Radio\
**Created:** [May 10, 2010, 2:51pm UTC](https://www.ruby-forum.com/t/problem-to-set-rf-filter-on-dbsrx-board/188340 "2010-05-10T14:51:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![meco1982](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/9de0a6/32.png) [@meco1982](https://www.ruby-forum.com/u/meco1982)\
**Post date:** [May 10, 2010, 2:51pm UTC](https://www.ruby-forum.com/t/problem-to-set-rf-filter-on-dbsrx-board/188340/1 "2010-05-10T14:51:57Z")

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Hi,  
I’m a new user on this forum…  
I need some help and I hope someone can save me from the madness %-|%-|  
I used on USRP 1 the DBSRX daughterboard with discrete success to  
acquire  
DVB-T signal in 800 MHz band.  
Now i want to carry on my work on USRP2 to avoid problem with overrun  
but…after hardware changes at daughterboard it works very well to see  
the  
signal but I can’t set daughterboard RF filter bandwidth to select a  
particular DVB- T channel cause in USRP2 there is no method “set\_bw()”.  
Now…I can modify db\_dbsrx.c to add this method that modify registers  
to  
set RF frequency bw like the same “.cc” script for USRP1…but after  
that? I  
have to recompile something after that? how can I recall “my” new method  
in  
a python flow graph if the usrp2 class not contain this new method?

Please help me…and I’m deeply sorry if someone thinks I’m an ignorant  
😕

## Thanks, Domenico

View this message in context:  
[http://old.nabble.com/Problem-to-set-RF-filter-on-DBSRX-board-tp28509367p28509367.html](http://old.nabble.com/Problem-to-set-RF-filter-on-DBSRX-board-tp28509367p28509367.html)  
Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).

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<div class="post-metadata">

**Author:** ![meco1982](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/9de0a6/32.png) [@meco1982](https://www.ruby-forum.com/u/meco1982)\
**Post date:** [May 12, 2011, 5:26pm UTC](https://www.ruby-forum.com/t/problem-to-set-rf-filter-on-dbsrx-board/188340/2 "2011-05-12T17:26:21Z")

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Domenico,

Here’s the deal your daughter board is probably suffering from low  
impedance which is what is causing the DVB -T Channel to have the wrong  
radio frequency. if you really want it to work correctly then what you  
will have to do is replace the rf filter with one that works correctly  
you can see a list of rf filters here  
[http://www.oscilent.com/catalog/Category/rf\_saw\_filter.htm](http://www.oscilent.com/catalog/Category/rf_saw_filter.htm) let me know  
if this works properly for you. You also may want to check to see if the  
diagnostic tool is functioning properly.

> Now i want to carry on my work on USRP2 to avoid problem with overrun  
> but…after hardware changes at daughterboard it works very well to see  
> the  
> signal but I can’t set daughterboard RF filter bandwidth to select a  
> particular DVB- T channel cause in USRP2 there is no method “set\_bw()”.  
> Now…I can modify db\_dbsrx.c to add this method that modify registers  
> to  
> set RF frequency bw like the same “.cc” script for USRP1…but after  
> that?