I did not want to run that kind of test for a couple of reasons, but I’m glad I did.
It revealed a concern and then further testing led to more concerns about LimeSuite.
I connected one of the TX ports to an inexpensive, but excellent analyzer and signal generator. (the picture shows the devices, but for a test using signal generation to LimeSDR RX)
Without explicitly turning on TX elements, I measured -26 dBm (red line in picture below). This could be a problem for radio astronomy environments, but also is consuming extra power and generating extra heat as measured by the board controls temperature and other means. Turning off the TX elements is shown in the picture where the measured output drops to the measurement threshold of the TPI device (-55 dBm / yellow line).
What is also problematic is that the Quick Test(s) do not tell you that just loading one of the .ini files in LimeSuite turns on the TX elements. You don’t have to click GUI->Chip for TX to become active. Nor does closing/stopping the application turn off the TX elements. I’m hoping Lime @Zack @andrewback can update their documentation for these concerns, if I’m correct, and address the FFT viewer issues identified in my first posting.
There are at least three ways to turn off TX elements that I have discovered:
- From the TRF tab, uncheck Enable TRF module in the Power down controls section.
(yes this is semantically confusing as are other “power down / enable” combinations). - From the TBB tab, uncheck the Enable TBB module in the Power down controls section.
- From the TBB tab, reduce the Frontend gain to 0. (the gain value may be affected by calibration, so the scale for positive numbers is not fixed.)
LimeSDR v1.4s and LimeSuite 17.01.1 Windows 10
Tony