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Re: [Discuss-gnuradio] GNURadio Run with USRP2 Hangs on Execution
From: |
Ian Buckley |
Subject: |
Re: [Discuss-gnuradio] GNURadio Run with USRP2 Hangs on Execution |
Date: |
Wed, 23 Oct 2013 16:35:38 -0700 |
Paul,
With (the default) 16bit complex sample format the maximum sample rate
supported on USRP2 is 25Msps, simply because that is pretty much as much data
as you can get over 1G Ethernet in one direction.
50Msps is supported if you use 8bit complex samples and loose some dynamic
range.
The decimation rate must be an integer, thus 25Msps is a decimation rate of 4
from the raw ADC converter clock of 100MHz. Also, since the receive DSP chain
cascades 2 Halfband FIR filters (each with fixed decimation of 2) before a CIC
filter (With arbitrary integer decimation), it is preferable to always use
decimation rates that factor by 4 so that both half band filters are active
which results in the flattest passband. UHD will automatically use the half
band filters in preference to the CIC when possible with the specified
decimation.
-Ian
On Oct 23, 2013, at 3:39 PM, Paul B. Huter <address@hidden> wrote:
> I finally got my GNURadio Python script running, but after I execute the
> script, I get a UHD Warning about requested decimation (a few lines of text),
> then a single 0 on a newline, and nothing. I let it run for about five
> minutes, and my output file didn't change from 0 bytes.
>
> I am trying to capture the entire shortwave frequency spectrum to analyze
> later (hence the output file). I am using a sample I found online, modified
> for GNURadio 3.7. I have set the following parameters
>
> samp_rate = 30000000 (for 30MHz)
> tune_request = 15000000 (for the middle frequency)
> self._head = blocks.head(8, int(1000000)) (that is what the example stated to
> use for number of samples, but I will likely change that once I verify
> everything is working correctly)
>
> I am not getting any errors, like I was initially before converting it all to
> 3.7, except not doing anything for five minutes and the output file size not
> growing.
>
> Links to similar projects are welcome, and any feedback/help is appreciated.
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