Forum: GNU Radio IndexError: gr_firdes check failed: 0 < fa <= sampling_freq / 2

Hello everyone! I am getting another weird error here. i received my USB 
e4k tuner and it was working. On OP25 i was using the scopes trying to 
figure how to get the four lines of dots and with RTL_FM i was getting 
audio, although the quality was bad. So i shut it down and i went out 
try on high ground but the signal was still weak. So i shut it down 
again, put myself within line of sight of the tower, and started it up 
and now OP25 dies like this:

Traceback (most recent call last):
File "/home/matt/gr-baz/gr-baz-master/samples/op25_grc.py", line 595, in 
<module>
tb = op25_grc()
File "/home/matt/gr-baz/gr-baz-master/samples/op25_grc.py", line 339, in 
__init__
self.gr_freq_xlating_fir_filter_xxx_0 = 
gr.freq_xlating_fir_filter_ccc(decim, (firdes.low_pass(1, samp_rate, 
xlate_bandwidth/2, 1000)), 
xlate_offset+xlate_offset_fine-fine_click_freq-auto_tune_offset_freq, 
samp_rate)
File 
"/usr/local/lib/python2.7/dist-packages/gnuradio/gr/gnuradio_core_general.py", 
line 6871, in low_pass
return _gnuradio_core_general.firdes_low_pass(*args, **kwargs)
IndexError: gr_firdes check failed: 0 < fa <= sampling_freq / 2

I have no idea how OP25 (same for RTL_FM) goes from working to failing 
with this error. Anyone have any ideas about this error?

Cheers,
Matt

On Tue, Mar 12, 2013 at 5:20 PM,  <md123@nycap.rr.com> wrote:
>
> I have no idea how OP25 (same for RTL_FM) goes from working to failing with this 
error. Anyone have any ideas about this error?
>
> Cheers,
> Matt

That error message is pretty explicit in what it's telling you. Either
xlate_bandwidth/2 is less than 0 or greater than samp_rate/2. It
should be easy enough to print out the value you are passing it to see
what you are actually passing the filter constructor algorithm.

Tom