# Minimum Sample rate limitation

**URL:** <https://discourse.myriadrf.org/t/minimum-sample-rate-limitation/1551>\
**Category:** LimeSDR\
**Created:** [2 August 2017 20:54 UTC](https://discourse.myriadrf.org/t/minimum-sample-rate-limitation/1551 "2017-08-02T20:54:10Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ChuckM](https://avatars.discourse-cdn.com/v4/letter/c/5f9b8f/32.png) [@ChuckM](https://discourse.myriadrf.org/u/ChuckM)\
**Post date:** [2 August 2017 20:54 UTC](https://discourse.myriadrf.org/t/minimum-sample-rate-limitation/1551/1 "2017-08-02T20:54:10Z")

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I’ve got a question on sample rate. I’ve been exploring it with gnuradio.

If I set the sample rate below 4Mhz I get an Rx: log of 2.043MB/second

If I set the sample rate to 4Mhz or above I get an Rx: log of reading 12MB/s or higher

is this the VCO just giving up?

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**Author:** ![F4EXB](https://avatars.discourse-cdn.com/v4/letter/f/f08c70/32.png) [@F4EXB](https://discourse.myriadrf.org/u/F4EXB)\
**Post date:** [4 August 2017 13:12 UTC](https://discourse.myriadrf.org/t/minimum-sample-rate-limitation/1551/2 "2017-08-04T13:12:04Z")

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Hello,

it looks like LimeSuite is packing 2 12bit samples into 3 bytes therefore the actual rate on the USB link reads as 3 times the Lime sample rate (on the host side before/after hardware interpolation/decimation).

Best regards, Edouard.

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**Author:** ![ChuckM](https://avatars.discourse-cdn.com/v4/letter/c/5f9b8f/32.png) [@ChuckM](https://discourse.myriadrf.org/u/ChuckM)\
**Post date:** [4 August 2017 15:48 UTC](https://discourse.myriadrf.org/t/minimum-sample-rate-limitation/1551/3 "2017-08-04T15:48:32Z")

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I agree with your analysis (three bytes per sample) and 4Mhz sample rate gives 12MB/sec data flow, but less than 4Mhz gives a fixed 2.043MB/s flow which, at three bytes per sample, would be 681kHz sampling rather than 3.9MHz sampling. That is the part that is curious.

–Chuck