How can I verify if my Lime SDR USB 3.0 is working correctly?

General Discussion
1

Hello,

I own a LimeSDR USB board. I’m a hobbyst not an expert, so my understanding of RF is somewhat basic, but I experience some issues, that seem very strange to me and can’t really tell if it’s due to the faulty hardware, or is it just as it’s supposed to be.

I can see and hear very clearly mirrors of broadcast FM radio stations (88MHz - 108MHz in Poland) on other bands, that they shouldn’t be present on. Is it normal, or is something strange happening in my hardware?

LimeQuickTest fails with one test:

[ RF Loopback Test ]
Note: The test should be run without anything connected to RF ports
->Configure LMS
->Run Tests (TX_2-> LNA_L):
CH0 (SXR=800.0MHz, SXT=805.0MHz): Result:(-16.1 dBFS, 5.00 MHz) - PASSED
CH1 (SXR=800.0MHz, SXT=805.0MHz): Result:(-18.4 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_1 -> LNA_W):
CH0 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-16.6 dBFS, 5.00 MHz) - PASSED
CH1 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-18.9 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_2-> LNA_H):
CH0 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-34.9 dBFS, 5.00 MHz) - FAILED
CH1 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-16.9 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test FAILED

I wrote 2 time to the email which I found on the internet, which was supposed to be LimeSDR support (enquiries@limemicro.com) but nobody have never answered me.

Could anyone help me verify if my hardware works properly?

Thank you.

2

This is normal if you don’t have any filtering in place and is caused by aliasing. Ideally you would have band pass filters for the bands of interest, but often just a band stop for e.g. FM broadcast will help a lot.

This is unrelated to the above, but not normal. Assuming that there is nothing connected to the RF ports — even SMA pigtails — and the board was cold when the test was run, this would suggest damage to an LNA input / Tx output.