Cannot Run TX Flowgraph More Than One time

Hi,

I thing there is a bug (defect) in gnuradio core. Checked with svn
revisions
7311 and 9036, on CoreDue system with Ubuntu 8.04, and USRP + RFX900,
it
seems that we cannot run TX flow graph properly more than one time. If
we
started it more than one time, we will have a very distorted TX signal
(observed on spectrum analyzer). The following python code was used to
check
this strange behaviour:


#!/usr/bin/env python

from gnuradio import usrp
from gnuradio import gr
import time

tb = gr.top_block()
tb.u = usrp.sink_s(0)
tb.u.set_interp_rate(512)
tb.src = gr.noise_source_s(gr.GR_UNIFORM,10000,0)
tb.subdev= usrp.selected_subdev(tb.u,(1,0))
tb.u.tune(tb.subdev._which,tb.subdev,915000000)
tb.subdev.set_enable(1)
tb.subdev.set_auto_tr(False)
tb.u.set_mux(usrp.determine_tx_mux_value(tb.u, (1,0)))
tb.connect(tb.src,tb.u)
i = 1
while i < 4:
print "running = ",i
tb.start()
time.sleep(5)
tb.stop()
tb.wait()
time.sleep(1)
i +=1


Regards,

Firas

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Mason wrote:
What kind of distortion is it? Also, does it exist for lower
interp_rates or just 512? (I ask because the rectangular QAM
constellation bending seemed to go away by switching to a faster tx
rate for me.)

Mason

Hi,

For interpolation rate of 512, I should get a signal with say 250KHz
spectrum wide. But actually, I got 32MHz wide, unknown (noisy) spectrum.
This phenomena, appears for all interpolation rates.

Firas

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