Forum: GNU Radio DBSRX filter efficiency?

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
Andreas Bogk (Guest)
on 2009-05-18 14:09
(Received via mailing list)
Dear Gnuradio hackers,

I have problems with the DBSRX module of the USRP: I see GSM on all
frequencies.   I hope somebody can answer my questions: Is there an
antialiasing filter somewhere in the design?  If so, what is its nominal
efficiency? Where can I find data sheets for the MAX211x chips?

Thanks in advance,
Andreas
Eric B. (Guest)
on 2009-05-18 21:02
(Received via mailing list)
On Mon, May 18, 2009 at 12:08:01PM +0200, Andreas Bogk wrote:
> Dear Gnuradio hackers,
>
> I have problems with the DBSRX module of the USRP: I see GSM on all
> frequencies.   I hope somebody can answer my questions: Is there an
> antialiasing filter somewhere in the design?  If so, what is its nominal
> efficiency? Where can I find data sheets for the MAX211x chips?
>
> Thanks in advance,
> Andreas

Hi Andreas!  Welcome!

Try turning the Rx gain down.

The datasheets should be on Maxim's site, though I think they're
discontinuing the part.  If you can't locate them, let me know and
I'll see if I can't find one for you.

Eric
Andreas Bogk (Guest)
on 2009-05-18 21:13
(Received via mailing list)
Eric B. wrote:
> Hi Andreas!  Welcome!
>

Thanks! :)

> Try turning the Rx gain down.
>

Been there, done that.  It doesn't get rid of the images.

> The datasheets should be on Maxim's site, though I think they're
> discontinuing the part.  If you can't locate them, let me know and
> I'll see if I can't find one for you.
>

I can't find them, and googling for MAX211x only brings me to Gnuradio
related information.  Is there a magic part number I need to know? I'd
appreciate the datasheets, or alternatively the information that the
filters are indeed in the chip and not tunable.

Cheers,
Andreas
Eric B. (Guest)
on 2009-05-18 21:29
(Received via mailing list)
On Mon, May 18, 2009 at 07:11:43PM +0200, Andreas Bogk wrote:
>
>> The datasheets should be on Maxim's site, though I think they're
>> discontinuing the part.  If you can't locate them, let me know and
>> I'll see if I can't find one for you.
>>
> I can't find them, and googling for MAX211x only brings me to Gnuradio
> related information.  Is there a magic part number I need to know? I'd
> appreciate the datasheets,

OK, I'll look for them later on today.

> or alternatively the information that the
> filters are indeed in the chip and not tunable.

The chip has a controllable IF-filter bandwidth.  It can be controlled
using the set_bw method on the daugherboard subdevice.  Pass it the
desired bandwith in Hz.  The DBSRX code will accept a value between 1e6
and
33e6, though the chip's only spec'd down to 4e6.  By default we're
running it wide open (33e6).

Eric
Andreas Bogk (Guest)
on 2009-05-18 21:49
(Received via mailing list)
Eric B. wrote:
> [datasheets]
> OK, I'll look for them later on today.
>

Matt sent me the correct part number (MAX2118), and I've found the data
sheet.

> The chip has a controllable IF-filter bandwidth.  It can be controlled
> using the set_bw method on the daugherboard subdevice.  Pass it the
> desired bandwith in Hz.  The DBSRX code will accept a value between 1e6 and
> 33e6, though the chip's only spec'd down to 4e6.  By default we're
> running it wide open (33e6).
>

I'm going to play with this, thanks for the info!

Andreas
Marcus D. Leech (Guest)
on 2009-05-18 22:34
(Received via mailing list)
Eric B. wrote:
>
>
Arggggh!   I knew it had to happen some day.  What happens to DBS_RX
when MAX2118s aren't
  available any more?


--
Marcus L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
Matt E. (Guest)
on 2009-05-18 22:54
(Received via mailing list)
Marcus D. Leech wrote:
>>
>>
>>
> Arggggh!   I knew it had to happen some day.  What happens to DBS_RX
> when MAX2118s aren't
>   available any more?
>
>


We have plenty of chips and boards for the near future.  They make a
replacement chip (MAX2112), which will require a board spin.

Matt
This topic is locked and can not be replied to.