Martin, thanks for responding. See my follow ups below:

— On Thu, 1/13/11, Marcus D. Leech [email protected] wrote:

- What are good values for “Audio Pass” and "Audio

produces at leastsomenoise, the detected version

of that noise results in a small residual DC offset. You can

null it out with an

an “ADD” block.

I’ve tried an ADD block, but I noticed that if my decimation is not a

power of 2, the offset changes.

move to the correct position. Any thoughts?

The FFT sink isn’t psychic. It needs to be told what

the current sample rate is, so if you change decimation on

the fly, you’ll need to

arrange for the FFT sink to know about the new

sample rate.

I believe the code is already doing this. Here are code segments for 2

fft guis. The first shows the fft of the raw output of the USRP2. This

gui responds correctly. Notice the line:

“sample_rate=100e6/usrp2_decim”, so I assume that as I dynamically

adjust usrp2_decim, this value is being updated. However, with the

second fft, while there is a similar line:

“sample_rate=100e6/usrp2_decim/sw_decim” that includes the software

decimation value, this fft gui does not correct the position of the fft

when I dynamically change sw_decim. The x-axis DOES change, but the

peaks in the spectrum just stay fixed in their relative positions. Any

thoughts?

1st FFT: self.wxgui_fftsink2_0 = fftsink2.fft_sink_c(

self.notebook_0.GetPage(1).GetWin(),

baseband_freq=0,

y_per_div=20,

y_divs=10,

ref_level=10,

ref_scale=2.0,

sample_rate=100e6/usrp2_decim,

fft_size=1024,

fft_rate=10,

average=False,

avg_alpha=None,

title=“Total Signal FFT”,

peak_hold=False,

)

2nd FFT: self.wxgui_fftsink2_1 = fftsink2.fft_sink_f(

self.notebook_0.GetPage(3).GetWin(),

baseband_freq=0,

y_per_div=20,

y_divs=10,

ref_level=10,

ref_scale=2.0,

sample_rate=100e6/usrp2_decim/sw_decim,

fft_size=1024,

fft_rate=10,

average=False,

avg_alpha=None,

title=“Demodulated FFT Plot”,

peak_hold=False,