# Why does the LimeSDR USB Rx have so many spur?

**URL:** https://discourse.myriadrf.org/t/why-does-the-limesdr-usb-rx-have-so-many-spur/5292
**Category:** LimeSDR
**Created:** [24 October 2019 08:33 UTC](https://discourse.myriadrf.org/t/why-does-the-limesdr-usb-rx-have-so-many-spur/5292 "2019-10-24T08:33:07Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Dynamix\_yang](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/dynamix_yang/32/2891_2.png) [@Dynamix\_yang](https://discourse.myriadrf.org/u/Dynamix_yang)
#### Post date: [24 October 2019 08:33 UTC](https://discourse.myriadrf.org/t/why-does-the-limesdr-usb-rx-have-so-many-spur/5292/1 "2019-10-24T08:33:07Z")

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Hi,  
I load the default setting in LimeSuite GUI and try to receive a single tone from a SMU200A RF Gen. I use default settings and tune the default clk rate and 1200MHz Rx freq. I input a -10dBm 1200.4MHz single tone signal and use the min gain by changing the lna gain and pga gain to min. I get the waveform from fft viewer but found many spurs. How do these spurs come form? I tried to cal the rx channel but things didn’t become better.

 ![Snipaste_2019-10-24_16-32-40](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/2/282b292d7f3cee7966eaed4d1385b00b56752639.png)  
Thanks!

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### Author: ![N0YKG](https://avatars.discourse-cdn.com/v4/letter/n/3bc359/32.png) [@N0YKG](https://discourse.myriadrf.org/u/N0YKG)
#### Post date: [24 October 2019 11:21 UTC](https://discourse.myriadrf.org/t/why-does-the-limesdr-usb-rx-have-so-many-spur/5292/2 "2019-10-24T11:21:45Z")

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A directly connected -10dBm signal may still be a bit hot. If you lower your input 3 dB, do the spurs go down 3dB, 6dB, or 9dB? That will tell you if these are real spurs on your signal, or are compression/3rd order effects.