# LimeSDR EMI compatibility issues and radiated interference

**URL:** <https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230>\
**Category:** General Discussion\
**Created:** [1 July 2021 09:50 UTC](https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230 "2021-07-01T09:50:45Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jarribas](https://avatars.discourse-cdn.com/v4/letter/j/7cd45c/32.png) [@jarribas](https://discourse.myriadrf.org/u/jarribas)\
**Post date:** [1 July 2021 09:50 UTC](https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230/1 "2021-07-01T09:50:45Z")

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Hi folks,  
We are designing a GNSS receiver using the LimeSDR as the front-end and we faced a serious problem with the radiated interferences coming from the LimeSDR PCB.  
The LimeSDR PCB is radiating a lot of electromagnetic noise specially between 1 GHz to 2 GHz. This interference prevents the placement of GNSS antennas nearby the LimeSDR PCB, and thus, they can not be integrated in a small device.

Please check the three videos I have recorded showing the problem:

```
https://youtu.be/2h7TVVrfxLs

https://youtu.be/pIsLOmMKQ2Y

https://youtu.be/JGieg1Mjds8

```

It is curious that the LimeSDR is not actually being used by the host computer, the interference appears just plugging the USB. I have tested it with two different LimeSDR boards just to discard a defective component, but I obtained the same result.

Any ideas of how to minimize the radiated interference? As far as I know there is no official or unofficial metal cage to solder in the LimeSDR board…  
Any ideas which is the signal / component that is radiating such amount of RF noise??

Thank you and best regards,

## Javier.

## Dr. Javier Arribas Lázaro Senior Researcher - Communications Systems Division Statistical Inference for Communications and Positioning Centre Tecnològic de Telecomunicacions de Catalunya (CTTC) Parc Mediterrani de la Tecnologia (PMT) Av. Carl Friedrich Gauss, 7 Box 08860 - Castelldefels - Barcelona Voice: +34 93 645 29 00 Fax: +34 93.645.29.01 E-mail: javier.arribas@cttc.es [http://www.cttc.es/people/jarribas/](http://www.cttc.es/people/jarribas/)

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**Author:** ![andrewback](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@andrewback](https://discourse.myriadrf.org/u/andrewback)\
**Post date:** [1 July 2021 14:46 UTC](https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230/2 "2021-07-01T14:46:52Z")

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@Zack, do you have any suggestions?

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**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [1 July 2021 15:35 UTC](https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230/3 "2021-07-01T15:35:34Z")

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Hi @jarribas,

> [@jarribas](#):
>
> It is curious that the LimeSDR is not actually being used by the host computer, the interference appears just plugging the USB.

This suggests that there is no configuration loaded. Hence PLLs will be un-locked, RF outputs are on.

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<div class="post-metadata">

**Author:** ![jarribas](https://avatars.discourse-cdn.com/v4/letter/j/7cd45c/32.png) [@jarribas](https://discourse.myriadrf.org/u/jarribas)\
**Post date:** [1 July 2021 16:35 UTC](https://discourse.myriadrf.org/t/limesdr-emi-compatibility-issues-and-radiated-interference/7230/4 "2021-07-01T16:35:35Z")

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Thank you Zack for the suggestion. I already checked this condition. The radiated interference does not change at all if I configure the LimeSDR. It also does not change even if I start the sample stream with GNURadio companion. I can record a video if required.

My thought is that it should come from a clock signal either from the FX3 chip or from the FPGA. What is curious is that it is apparently not a narrow band interference coming from , let say, harmonics from the 30.72 MHz clock… it appear as a wideband noise.

I measured it with a hackRF (shown in the video) and also with a shielded RTLSDR (nooelec one with metallic case and 0.5 ppm TCXO) with similar results = wideband interference present at least in between 1 GHz to 2 GHz