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Calibrating the low output levelUsing one of the many calculators you can find on the internet the relation between dBm and Vp-p is quick to calculate. An example calculator can be found at https://www.random-science-tools.com/electronics/dBm-Watts-volts.htm Measurement setupThis calibration requires firmware 1.2-47 or later. Enable the tinySA CAL OUTPUT at 30MHz and set it to HIGH INPUT mode to avoid disturbances from the high connector. The cal output will provide an exact -25dBm signal. On the scope we will a somewhat distorted square wave with an amplitude of 35mVp-p. The small deviation can be explained by the harmonics present in the cal output. Calculating and setting the correctionUsing the calculator we convert 30mVp-p to dBm and find the output level to be -26.5dBm. To correct the output level (which is -1.5dB too low) we use connect to the tinySA over USB and issue the commands leveloffset low output -1.5 to change the output level calibration setting and store the data so it survives a reset. Verifying the correctionUsing the scope we measure again the Vp-p of the output and now we measure 35.6mVp-p which matches perfectly an output level of -25dBm. |