# OSParam Error

**URL:** <https://www.ruby-forum.com/t/osparam-error/237527>\
**Category:** GNU Radio\
**Created:** [November 17, 2013, 11:57pm UTC](https://www.ruby-forum.com/t/osparam-error/237527 "2013-11-17T23:57:03Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [November 17, 2013, 11:57pm UTC](https://www.ruby-forum.com/t/osparam-error/237527/1 "2013-11-17T23:57:03Z")

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I am running a USRP source through a throttle to an FFT sink and a file  
sink. Last time I ran it, I got an “OSParam error”, followed by a bunch  
of  
"D"s and the FFT was lagging and jumping. Any ideas as to what this is?  
My  
sample rate is 50M.

Paul B. Huter

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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:** [November 18, 2013, 12:42am UTC](https://www.ruby-forum.com/t/osparam-error/237527/2 "2013-11-18T00:42:36Z")

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> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)  
> You only ever need a “throttle” when you don’t have hardware in the  
> flow-graph pacing things.

AT 50Msps, whatever your flow-graph is doing will be working _really,  
really_ hard.

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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:** [November 18, 2013, 12:50am UTC](https://www.ruby-forum.com/t/osparam-error/237527/3 "2013-11-18T00:50:12Z")

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As always, thank you, Marcus.

I am thinking about getting rid of the graph (and throttle, now), and  
making another setup to run the output file from the original (through a  
throttle?) to the graph to look at smaller pieces. I want to be able to  
look at (say) 5MHz-10MHz, so my plan is to set the FFT to be 5MHz  
centered  
on 7.5MHz. However, I am not sure if that is correct. But - first step  
is  
to get my data.

Thanks, again, Marcus.

Paul B. Huter

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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:** [November 18, 2013, 8:49am UTC](https://www.ruby-forum.com/t/osparam-error/237527/4 "2013-11-18T08:49:21Z")

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Don’t use a throttle in a flow graph with a hardware source. A throttle  
block is software-limiting the number of samples that pass your  
flowgraph on average in a given time. You have an USRP that produces  
samples at a constant rate: Either this rate is significantly lower than  
your throttle rate, in which case throttle is superflous, or you’ll run  
into problems because throttle is trying to throttle what it shouldn’t  
throttle because the hardware defines how fast your samples must flow.

For your file-sourced flowgraph, however, throttle is the right way to  
go – but honestly, with 50Ms/s your PC will most likely get into such  
heavy work that it can’t process everything in real-time (otherwise it  
could do it with live data, too) and your throttle doesn’t do anything.

I don’t know your osparam error. But the D errors are likely caused by  
your computer being to busy to process the samples.  
Reduce the sample rate at the usrp, if you want to look at 10MHz of  
bandwidth, anyway.