Side by side comparison of two LimeSDR Mini's

Hello Lime Guru’s
Today I received the two LimeSDR Minis, and did a quick test of them straight out of the box(s).
The procedure used so far:
Plug each of the LimeSDR Mini’s into a USB3 Extension cable one at a time, Windows 7 (32bit) went off and found drivers (It did this with both Lime’s in the same cable and port of the PC).
Fired up SDR Console V3 Beta 2, added definition for one LimeSDR Mini and successfully tuned to our local FM radio station.
Stopped the radio, unplugged it, plugged in second Mini, added its definition, once again tuned to the local station only to have a different looking spectrum. Checked over SDR Console, cant find any differences in the settings for each of the definitions or settings for each radio.
Here is the first LimeSDR Mini

And the second LimeSDR Mini

And for comparision, Airspy using same antenna and SDR Console settings

So as can be seen, the noise floor of one of the LimeSDR Mini’s is 30dBm or so higher than the other and 23dBm of the Airspy.
I have not used Limesuite on either of these LimeSDR Mini’s, All test done with the same antenna mounted externally to the workshop.
Any thoughts?

@martywittrock Hello Marty,
Can you do a test for me when you get a chance, can you see what the noise floor is on your Lime Mini at around 107 Mhz. I’m thinking one of the ones here is faulty, once I confirm this I guess it is back to crowd supply to get it sorted.


Looking at the waterfall for “first LimeSDR Mini”, I see lots of horizontal lines, which could be a symptom of dropped USB packets (which would manifest as a raised noise floor). So my question would be were all other USB devices disconnected, and was the same USB port also used for the “second LimeSDR Mini” image.

Hello Mzs,

Other than the wireless mouse and keyboard using a separate USB port, all LimeSDR tests (and resultant screen shots) were done with the same USB3 Port, same USB3 Extension one plugged in at a time. The Airspy was plugged into a different USB2 port with its own USB A to USB Mini cable.

I will look into the lost packet idea some more, as a test I have done today with a separate PC (Windows 10 64bit and SDR Console V3) gave some pretty poor results when testing the “Good” LimeSDR Mini, it looked so bad that I stopped the radio, and when I tried to restart I could not get the LimeSDR Mini to work on the Windows 10 PC, and think I need to reboot the machine to fix the issue, but the machine is currently busy with another task so the reboot will have to wait.

Thank you for the feedback, will give an update if I find anything.

@vk5bd - Bevan,

Will do - I’ll check that for you later this evening when I get back to the house - Stay tuned…!

73 de Marty, KN0CK

That is me out of ideas then. The only other things I can think of would be HDMI as a possible noise source, like if one of the USB cables was literally interwoven with a video cable (wrapped around it for several turns) or if the wireless mouse was much closer to one device than the other and injecting interference either directly or through the USB cable.

@vk5bd - Bevan,

I did a trial of my Lime Mini last night and had to use GQRXsince, for some reason, SDRConsole wasn’t working with it…I did my test At the FM band (88 to 108 MHz) and then again at 162.475 KHz WX band. In both instances, the noise floor was at -110dBm and signals were routinely 40 to 60dB above the noise…So for me, I’m not seeing the high noise like you were and was connected to USB 3.0 when I performed the testing.

Hope this helps - keep us advised on your progress, Bevan,

73 de Marty, KN0CK

Thank you Marty for doing that testing,

I have been doing a little testing tonight with my 64bit laptop and trying to use GQRX and initially found the opposite sensitivity issues to the 32Bit SDR Console findings. I have a lot more testing ahead of me I think, at one point in time both LimeSDR mini’s seemed to be working identically on the 32bit machine, but that was short lived, stopped the radio and it hasn’t worked properly since, several reboots of the machine, deleting the definitions etc have not proven successful and possibly even worse noise floor results than previous, and found that the tuning was offset ie what should have been 107.7 Mhz had to be tuned at 107.633 Mhz. I then swapped SDR’s, over and then back again and now it is working mostly okay, I think mzs may be onto something with his idea of lost data, one symptom I have observed tonight is that it will go from not able to resolve a signal with a -60dBm noise floor and then the noise floor drops to -110dBm for 400 to 500 ms (guestimation not measured) and signals appear before the noise floor shoots back up for random lengths of time. At one point the received audio sounded slowed down, had the voice and music frequency lower that expected.
Well that has been some of my observations tonight.
I will do some more testing, but just wanted to thank you for indulging me.

Hello All,
It has been a while since I started this topic, but another topic today reminded me that I had meant to post information about some testing.
While I still have issues with SDR Console, I have been getting good performance out of HDSDR with either of the two LimeSDR Mini’s, All tests done on the same PC, USB3 port and USB extension cable.
So this hasn’t identified the root cause of the problem it may give someone a clue as to what is going wrong, presumably with SDR Console (however it works fine with one Mini), the only obvious difference is the serial number but cant see how that would cause any issues.

Will keep plodding along :slight_smile: