# Performance degradation at lower Frequencies

**URL:** <https://discourse.myriadrf.org/t/performance-degradation-at-lower-frequencies/4957>\
**Category:** LimeSDR\
**Created:** [18 July 2019 20:41 UTC](https://discourse.myriadrf.org/t/performance-degradation-at-lower-frequencies/4957 "2019-07-18T20:41:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![booth](https://avatars.discourse-cdn.com/v4/letter/b/848f3c/32.png) [@booth](https://discourse.myriadrf.org/u/booth)\
**Post date:** [18 July 2019 20:41 UTC](https://discourse.myriadrf.org/t/performance-degradation-at-lower-frequencies/4957/1 "2019-07-18T20:41:14Z")

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Dear All,  
We are using the Lime mini for TX and sending a sine wave (sampled at 2MS/s) using GNU RADIO and gr-limesdr.  
At the RX side we use the LIMESDR-USB and configure it using LimeSuite 19.04.  
We use the"Example.ini" file to configure the LIMESDR-USB.  
At 800 MHz the constellation looks like a thin Ring as shown in the attachment.  
At 200 MHz the constellation looks like a FAT Ring and there are fluctuations in amplitude as shown in the attachment.  
At 70 MHz the constellation looks like a exploding Ring and there are heavy fluctuations in amplitude .  
(we applied the EasyFIX1 but it didn’t help)  
We don’t know if its the fault of the Lime-mini gr-limesdr atTX or the LIMESDR-USB Limesuite combo’s fault.

 ![receive-800MHz](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/6/6f67b69bf0c27f7b561467e2d088065b6af3a392.png) ![receive-200MHz](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/8/89f22d9f75b69ac54bc9922fefedebec7fd2eebf.png)

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**Author:** ![mzs](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/mzs/32/2678_2.png) [@mzs](https://discourse.myriadrf.org/u/mzs)\
**Post date:** [22 July 2019 01:25 UTC](https://discourse.myriadrf.org/t/performance-degradation-at-lower-frequencies/4957/2 "2019-07-22T01:25:46Z")

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I think that the lowest LPF(Low Pass Filter) for TX is 5MHz, I’d probably start by increasing the IQ sample rate to 5MSPS and see if the problem persists.