RTL-SDR: E4000 IF bandwidth (& Slashdot!)

Michał Rogala michal.rogala at gmail.com
Sun Apr 1 12:21:50 UTC 2012


Hi!

Thanks, would be great if it turns out that those changes improve
reception :). What I've seen in source code FC0013  also has regulated
IF bandwidth filter, although in very limited steps - 8 MHz, 7 MHz, 6
MHz.

best regards and thank you for great work :)

Michal Rogala

W dniu 1 kwietnia 2012 04:53 użytkownik Balint Seeber
<balint256 at gmail.com> napisał:
> Hi Michal,
> Thank you for asking the question - I was thinking about this too last night
> (actually this morning) while I was trying to catch up on some sleep, but my
> brain wouldn't stop ticking over :)
>
> Can't be sure of the effect as datasheets aren't public, but I will
> experiment with narrowing the bandwidth. The 'IFfilter' function in the
> E4000 tuner code is made up of a massive if/else block that sets various
> register values by checking the input IF-BW values from <= 2150 to > 5500,
> so it appears to support a wide range (despite the convenience
> 'E4000_BANDWIDTH_HZ' enum in the header).
>
> Will post findings a little later, unless someone beats me to it :)
>
> Kind regards,
> Balint
>
> PS: "Software-Defined Radio For $11" on Slashdot!
> http://hardware.slashdot.org/story/12/03/31/1914217/software-defined-radio-f
> or-11
>
> PPS: I've been working to improve the GNU Radio Source block and Windows
> plugin with generous feedback from the community. Grab them here if you
> wish:
> http://wiki.spench.net/wiki/gr-baz#rtl_source_c
> http://wiki.spench.net/wiki/USRP_Interfaces
>
>> -----Original Message-----
>> From: Michał Rogala [mailto:michal.rogala at gmail.com]
>> Sent: Sunday, 1 April 2012 4:36 AM
>> To: balint256 at gmail.com; osmocom-sdr at lists.osmocom.org
>> Subject: RTL-SDR: E4000 IF bandwidth
>>
>> Hi!
>>
>> I've just noticed one issue about E4000 driver that bothers me - IF
>> bandwidth at the chip is set to 8 MHz, where maximum bandwidth of RTL2832U
>> sampling is 3.2 MHz.
>>
>> Wouldn't reducing IF bandwidth at tuner chip improve overall sensitivity
>> (and maybe noise level)?
>>
>> best regards
>>
>> Michal Rogala
>




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