# 2RX Phase measurement issue -180 degree phase jump

**URL:** <https://discourse.myriadrf.org/t/2rx-phase-measurement-issue-180-degree-phase-jump/4087>\
**Category:** LimeSDR\
**Created:** [28 January 2019 23:04 UTC](https://discourse.myriadrf.org/t/2rx-phase-measurement-issue-180-degree-phase-jump/4087 "2019-01-28T23:04:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mauro](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@mauro](https://discourse.myriadrf.org/u/mauro)\
**Post date:** [28 January 2019 23:04 UTC](https://discourse.myriadrf.org/t/2rx-phase-measurement-issue-180-degree-phase-jump/4087/1 "2019-01-28T23:04:54Z")

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Hi!  
I want to use LimeSDR to measure the magnitude and phase of a signal connected to the 2 RX channels of the Lime.  
I am using one of the TX channels to generate a sinusoid, the Lime’s TX port is connected to the input of a power splitter. The outputs of the power splitter are connected to the RX channels of the Lime (as shown in the below picture). For the moment I am working in the 35-200 MHZ frequency range.

 ![LimePowersplitediagram1b](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/7/785a1b99a4bf3282c5f05e531e072e5ca7eed7d6.jpeg)

The first problem I run into is that the phase of both channels can be (approximately) 180 degree out of phase in a random way. The following screen shoots of the " I versus Q" plots of the Lime suite GUI (FFT viewer) shows the problem very well (All this graphics are taken at the same frequency=100MHZ, just by pressing the Start-Stop button the points in the constellation jumps from one position to the other).

 ![IQplots](https://canada1.discourse-cdn.com/flex034/uploads/myriadrf/original/2X/c/ceb01fa6c13242c47de291fd45bb42acab05a2de.png)

Is there any solution or a workaround for this problem?

Regards  
Mauro.