Re: [Discuss-gnuradio] saturation with multi_fft.py

[Tarun Tiwari]

Thank you Eric. Your suggestions helped me a lot and I was able to see the two channels on my scope.
After looking at the scope, I see that the second channel does not have equal recieved power as that of first channel. Is it because of 4 channel deinterleaver or something else? Please see the line 76 of multi_fft.py which follows:

# deinterleave two channels from FPGA
di = gr.deinterleave(gr.sizeof_gr_complex)

I am using the command ./multi_fft.py -
f2.43G -d128 -g50

Any suggestion on this? My presumption was to get almost equal power in both channels, as both the antennas are not far away from each other. Please see the snapshot of scope at 
http://www.utdallas.edu/~tarunmani/gnuradio/multi_fft_result.jpg

One more question :) On line 46 in multi_fft.py,
why do we use sw_decim as 4 rather than 1 after we enable channel filter? Does it have to do anything with the refresh rate of scope?

Thanks again.

Regards,
Tarun Mani Tiwari
MSEE Student,
Research Assistant,
Multimedia Comm Lab,
UT Dallas

On 10/15/07, Eric Blossom <address@hidden> wrote:

On Thu, Oct 11, 2007 at 02:11:38PM -0500, Tarun Tiwari wrote:
> Hi,
> Thanks everybody, this thread helped me a lot to understand the multi
> antenna cabability of gnuradio.
> I tried to run the multi_scope.py on a cingle USRP having two rfx2400
> daughterboards with following changes in current multi_scope.py:
>
> 1) On line 44: nchan changed to 2 from 4
> 2) On Line 67: "len(self.subdev) != 4)"  changed to "len(self.subdev) != 2)"
> 3) On line 68 and 69: usrp_dbid.BASIC_RX changed to
> usrp_dbid.FLEX_2400_RX_MIMO_B
>
> I generate sinusoid of 2.43G on a different machine/gnuradio and then run
> the command ./multi_scope.py -f2.43G -d128 -g0 on another machine with above
> changes, but i dont see anything other than noise on my scope. I tried
> different rbf files std_2rxhb_2tx.rbf, multi_2rxhb_2tx.rbf and got nothing,
> but the noise.
>
> Next I changed the fpga_filename to multi_4rx_0tx.rbf, but i got following
> error:
> Can't find fpga bitstream: multi_4rx_0tx.rbf
> and program stoped with runtime error of "Can't open USRP"
>
> Any suggestion?

If you're using only two channels, stick with the default rbf "std_2rxhb_2tx.rbf".

The RFX boards are quadrature.  The Rx mux setting should be:

  self.u.set_mux(gru.hexint(0x00003210))

Not

  self.u.set_mux(gru.hexint(0xf3f2f1f0))


Try turning the gain up.

Eric