I’ve changed the title and content of the original post, which was about my LimeSDR mini not receiving below 31mhz when the temperature of the LimeSDR mini as measured on Lime Suite was above 45C.
After more experimentation, it appears that the temperature readout of LimeSuite doesn’t really make sense to me. At a measured temperature of 45C in LimeSuite, a FLIR infrared camera measuring the temperature of the FT601 and Altera FPGA chips puts the surface temperature of the IC’s at approximately 158 F (70C). I have a heatsink over the can on the LMS7002M, so I can’t really accurately measure the LMS7002M surface temp.
Therefore, I can only imagine that when my LimeSDR mini was having low-freq receive issues, the board temp was well over 70C.
So maybe I need to ask a better question - which ICs need to be cooled on the limesdr mini, and what is the recommended surface temp?
Indeed and I’m guessing the SDR and its host is just heating up the air in the box. Depending on ambient temperature and workload/throughput, this could become an issue.
I found that I need to cool both my LimeSDR-mini and LimeSDR-USB in order to keep the gain stable and at a reasonable value as I work 1420MHz for radio astronomy work. Heatsinks won’t do it. I use an mineral oil bath at 10 degrees (0 for the mini) for that. It’s important not to get too low in temp else the clocks stop working properly.
We have systematically tested ten brand new LimeSDR-USB because we were observing self-test failures.
Each PCB was tested unboxed at an ambient temperature of 22 Degrees C, no heatsinking, no moving air.
Results:
9 of the 10 units failed the self test on the high-band Rx sensitivity (the on-chip temperature sensor indicated 58 - 60 Degrees on all units at the time of failure).
One unit passed the self test when the on-chip temperature exceeded 60 Degrees.
Remedial Action:
We have glued a variety of heatsinks to the various failed units and will run further tests.
Comment:
In my opinion, this exercise is indicative of an inherent thermal design flaw in the chip/PCB. Temperature is clearly an issue for the device. Given the existence of other SDRs on the market using the same LMS chip (e.g. Fairwaves) which are rated over an industrial temerature range, it seems the PCB needs a makeover from a thermal design perspective.
We LOVE the LimeSDR features and price point, but this issue makes it untenable as the basis for a commercial product for us.
Some feedback from Lime would be appreciated here
We have the same conclusion on the subject.
Regarding the cooling you need to have at last two heatsinks on the top of LMS & FPGA or
one with two levels and whole bottom of the USB board on the solid oversized heatsink
or metal case. Good luck.
