Good news - support for advanced tuning with UHD devices

[Darren Long]

Hi all,

Some good news to share. After a little discussion in #gnuradio last
night, Marcus "PatchVonBraun" Leech lived up to his name by cooking up a
little patch to add support for UHD advanced tuning (i.e. LO offset
support) for UHD devices in the gr-osmosdr backend, as used in gqrx.

I tested it last night in gqrx and all seems good. I've been able to
move most spurii out of the spectrum of interest.

The patch currently lives at http://pastebin.com/wzw4jHPq although it
should make it into the upstream git repo sometime soon, you can keep an
eye on the commits here: http://cgit.osmocom.org/cgit/gr-osmosdr/log/

I applied the patch by creating a file called pvb-uhd.patch in the
gr-osmosdr source directory and pasting the content from the raw paste
data view on the pastebin page into it, then running:

git apply pvb-uhd.patch
sudo make install
sudo ldconfig

i think git complained about whitespace issues in the patch but I gave
that a good ignoring. I don't think you need to rebuild gqrx, but I did
for good measure.

The LO offset can be applied in the device string of the gqrx device
configuration dialog like so:

"label=wbx,type=b100,uhd,subdev=A:0,lo_offset=15.9e6"

I suppose the ideal offset will be daughter-board, sample-rate and local
spurii dependent.


Cheers,

Darren, G0HWW

[Darren Long]

It's in gr-osmosdr upstream now.

Darren, G0HWW

[Alexandru Csete]

Hi Darren,

Thanks for the good news and for contributing to making this happen.
I have updated my gr-osmosdr package yesterday and I hope soon to have
some time to play with my USRP.

Just to be sure I understand this LO concept correctly... When we set
an LO offset, does it mean that the oscillator of the daughterbord
will be tuned to this offset and the FPGA will the compensate for thew
offset again?

Alex

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[Darren Long]

Yes. Exactly that :) There's a couple of screenshots i posted as
testing evidence here:
http://www.g0hww.net/2012/11/advanced-tuning-for-uhd-in-gqrx.html

There is some info from ettus here:
http://files.ettus.com/uhd_docs/manual/html/general.html#two-stage-tuning-process

Darren, G0HWW

[Alexandru Csete]

Thanks for the info Darren.

I have started a wiki page for listing tips & tricks about device strings:
https://github.com/csete/gqrx/wiki/Device-strings

I will also update the front page in the coming days.
If anybody wants to write some documentation let me know - I hope in
time we can collect useful information this way.

Alex

[Alexandru Csete]

By the way, yesterday I pushed some changes which add command line
option for selecting a configuration file so you no longer need add
the changes you described earlier this year.

Alex

[Pawel Janowski]

the RTL_TCP will be supported ?

P.

[Alexandru Csete]

On Tue, Dec 4, 2012 at 8:29 PM, Pawel Janowski <pawel.j...@gmail.com> wrote:
> the RTL_TCP will be supported ?

Pavel,

rtl_tcp is part of the rtl_sdr driver so it has been supported since
rtl_sdr support has been added.
Not sure though what to enter into the device string. Please do let us
know if you find out :)

Alex