# Re: GNURadio Run with USRP2 Hangs on Execution

**URL:** <https://www.ruby-forum.com/t/re-gnuradio-run-with-usrp2-hangs-on-execution/237099>\
**Category:** GNU Radio\
**Created:** [October 24, 2013, 1:45am UTC](https://www.ruby-forum.com/t/re-gnuradio-run-with-usrp2-hangs-on-execution/237099 "2013-10-24T01:45:32Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [October 24, 2013, 1:45am UTC](https://www.ruby-forum.com/t/re-gnuradio-run-with-usrp2-hangs-on-execution/237099/1 "2013-10-24T01:45:32Z")

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Ian:

Thank you for your detailed response. If I stick with eight bits and  
increase to 50Msps, will that solve the decimation rate problem? I  
realize this would result in a decimation rate of two, which would not  
be ideal. I may decide to only grab 25MHz, not the full 30, to keep  
the decimation rate at four.

Thank you, again.

Paul B. Huter

Ian B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

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

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**Author:** ![Paul\_BSHuter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e8c25b/32.png) [@Paul\_BSHuter](https://www.ruby-forum.com/u/Paul_BSHuter)\
**Post date:** [October 24, 2013, 2:00am UTC](https://www.ruby-forum.com/t/re-gnuradio-run-with-usrp2-hangs-on-execution/237099/2 "2013-10-24T02:00:44Z")

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On 10/23/2013 07:44 PM, Paul B. Huter wrote:

> Paul B. Huter  
> Keep firmly in mind that your computer will need enough “grunt” to deal  
> with the resulting torrent of samples from the USRP.

Even if you’re only recording them, you’ll need a minimum of  
100Mbyte/second sustained write speed to your disks.

If you’re actually _doing something_ with the samples, in the  
mathematical sense, you’ll need lots of aggregate GFLOPS to keep up.

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<div class="post-metadata">

**Author:** ![Paul\_BSHuter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e8c25b/32.png) [@Paul\_BSHuter](https://www.ruby-forum.com/u/Paul_BSHuter)\
**Post date:** [October 24, 2013, 2:07am UTC](https://www.ruby-forum.com/t/re-gnuradio-run-with-usrp2-hangs-on-execution/237099/3 "2013-10-24T02:07:45Z")

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Thanks, Marcus. I am just saving the data into a data file for later  
analysis. I only plan to save about a minute of data at a time. I intend  
to  
start small, though, and work my way up to see if my computer can handle  
things.