Strange sensitivity LNA_L vs. LNA_H on ~100MHz

#1

I recently received LimeSdr 1.4s and am very pleased.
But I noticed that for me, for example, FM Radio Broadcast (~ 100mhz) works better at the LNA_H input than at the LNA_L input, although according to the LNA_L specifications it is more suitable, LNA_W works approximately at the LNA_L level, i.e. just as bad.
I checked on both channels Ch0 and Ch1, the situations are the same.
How can this be? Why does the port calculated to a lower frequency give me a weaker signal? Is this normal? :slight_smile:
Is there a way to check that everything works exactly as it should?
Lime Quick Test runs fine. But sometimes it gives an error, apparently, when the temperature on the sensor begins to show higher than 52 degrees Celsius.

RF loopback test looks like this:
[RF Loopback Test]
-> Configure LMS
-> Run Tests (TX_2-> LNA_L):
CH0 (SXR = 800.0MHz, SXT = 805.0MHz): Result: (- 15.3 dBFS, 5.00 MHz) - PASSED
CH1 (SXR = 800.0MHz, SXT = 805.0MHz): Result: (- 16.2 dBFS, 5.00 MHz) - PASSED
-> Run Tests (TX_1 -> LNA_W):
CH0 (SXR = 1800.0 MHz, SXT = 1805.0 MHz): Result: (- 19.7 dBFS, 5.00 MHz) - PASSED
CH1 (SXR = 1800.0 MHz, SXT = 1805.0 MHz): Result: (- 18.4 dBFS, 5.00 MHz) - PASSED
-> Run Tests (TX_2-> LNA_H):
CH0 (SXR = 2500.0MHz, SXT = 2505.0MHz): Result: (- 17.6 dBFS, 5.00 MHz) - PASSED
CH1 (SXR = 2500.0MHz, SXT = 2505.0MHz): Result: (- 15.0 dBFS, 5.00 MHz) - PASSED
-> RF Loopback Test PASSED

#2

Hi @netdog,

Glad to hear! :slight_smile:

Check https://myriadrf.org/news/optimising-limesdr-matching-hf/ for more information, please.
You should remove MN18 inductor as per EasyFix1 in Table A.

#3

I already read this article, but I did not dare to perform this operation, because there it was all about more than frequencies below 100 MHz. But now I removed this coil, and it really improved the sensitivity in the ~ 100 MHz segment several times.
Thank you :slight_smile: