# Soapy says "Rx calibration fail". What to do?

**URL:** <https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374>\
**Category:** LimeSDR\
**Created:** [25 September 2018 14:48 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374 "2018-09-25T14:48:10Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![ChrisLM](https://avatars.discourse-cdn.com/v4/letter/c/958977/32.png) [@ChrisLM](https://discourse.myriadrf.org/u/ChrisLM)\
**Post date:** [25 September 2018 14:48 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374/1 "2018-09-25T14:48:10Z")

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Hi,

I have a limesdr (v1.4) and use it via SoapySDR (latest version). With no connected antenna, my soapy app runs fine and I see in the log that Soapy calibrates the lime. But as soon as I connect my target antenna and start my app, I get the message: “ERROR: Rx calibration: MCU error 5 (Loopback signal weak: not connected/insufficient gain?)”.

Is that an issue? What am I supposed to do?  
Thank for your help

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**Author:** ![yindra](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/yindra/32/1901_2.png) [@yindra](https://discourse.myriadrf.org/u/yindra)\
**Post date:** [25 September 2018 15:20 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374/2 "2018-09-25T15:20:04Z")

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I’m assuming that you have a LimeSDR-USB  
what antenna is selected by software?  
what is the rf frequency?  
both of those are conditions of the calibrate function in gr-limesdr: [https://github.com/myriadrf/gr-limesdr/blob/master/lib/common/device\_handler.cc](https://github.com/myriadrf/gr-limesdr/blob/master/lib/common/device_handler.cc)

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**Author:** ![ChrisLM](https://avatars.discourse-cdn.com/v4/letter/c/958977/32.png) [@ChrisLM](https://discourse.myriadrf.org/u/ChrisLM)\
**Post date:** [25 September 2018 16:25 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374/3 "2018-09-25T16:25:14Z")

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Yes, it’s a limeSDR-USB. Antenna is LNAH on channel 0 (same result if using LNAL and/or using channel 0 + 1), RF freq is 2450 MHz, TIA / LNA / PGA gains are 0, 15, 0 (but playing with them didn’t change anything neither).

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**Author:** ![ChrisLM](https://avatars.discourse-cdn.com/v4/letter/c/958977/32.png) [@ChrisLM](https://discourse.myriadrf.org/u/ChrisLM)\
**Post date:** [25 September 2018 16:33 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374/4 "2018-09-25T16:33:20Z")

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Argh, I went too fast. I played on LNA and it hadn’t change. But setting either TIA high (to 12) or PGA relatively high (to 5) makes the message disappear.

Could anybody help me understand this? Also, on which gain should I play more (I’m not sure to understand PGA and TIA)?

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**Author:** ![yindra](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/yindra/32/1901_2.png) [@yindra](https://discourse.myriadrf.org/u/yindra)\
**Post date:** [25 September 2018 16:39 UTC](https://discourse.myriadrf.org/t/soapy-says-rx-calibration-fail-what-to-do/3374/5 "2018-09-25T16:39:37Z")

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I set the gain by calling LMS\_SetGaindB with a gain value in the range of 0 to 70.  
LimeSuite figures out the relative gain values from there.