Re: [Discuss-gnuradio] bladeRF - gr-osmosdr - gqrx - bandwidth?

[Alexandru Csete]

On Fri, Sep 13, 2013 at 3:53 PM, Brian Padalino <address@hidden> wrote:
> On Fri, Sep 13, 2013 at 2:19 AM, Ralph A. Schmid, dk5ras
> <address@hidden> wrote:
>> Hi,
>>
>> I am using bladeRF with gr-osmosdr, gnuradio 3.7 and gqrx, so far a fine
>> radio. One thing, when using gqrx...I am limited to USB2.0 at the moment, so
>> I use a sampling rate of 8 Ms/s, and in this mode I have big problems with
>> images from the neighbour frequencies that are still within the 26 MHz
>> bandwidth, or whatever the maximum BW is.
>>
>> Is there some command to set this bandwidth to a smaller value? I assume
>> that this would improve my RX experience a lot :) A quick look at osmocom
>> showed me nothing, but maybe I missed smth.
>
> The gr-osmosdr interface allows for a bandwidth setting to be changed here:
>
>   http://cgit.osmocom.org/gr-osmosdr/tree/lib/bladerf/bladerf_source_c.cc#n581
>
> The driver will figure out which bandwidth is closest to what you want
> with a minimum of 1.5MHz and a maximum of 28MHz for the low-pass
> filters.
>
> It will definitely make a world of difference by actually applying the
> LPF and removing the aliasing.
>
> As for official support for gqrx, it's next on our list.  We need to
> get on the gqrx mailing list and figure out what code we need to
> write.
>

Actually, it was a deliberate choice not to have explicit support for
that API call since it seemed unnecessary. Wouldn't one always want to
use the narrowest analog bandwidth corresponding to a given sample
rate? If yes, the setting may as well happen as part of the sample
rate configuration and best handled at a layer that knows about the
specific device. Am I wrong?

Alex