Measuring Low frequencies

When measuring signals below 1MHz some annoying artifacts can appear.\First a fairly clean 1MHz signal at -15dBm

attachment:low_1MHz.jpg

When we move the input signal to 0.3MHz at -15dBm we get a very different measurement

attachment:low_on.jpg

The artifacts are caused by the AGC that is misbehaving below 0.5MHz. That is why in default mode the AGC is disabled when below 0.5MHz. Setting the AGC and LNA to the default automatic settings gives some improvement.

attachment:low_auto.jpg

The menu shown is the second page of the EXPERT CONFIG showing everything is on default/automatic. As the signal is too strong for the LNA it is advised to also switch off the LNA

attachment:low_off.jpg


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TinySA-LowFrequencies (last edited 2020-10-16 14:10:21 by RudolfReuter)