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Here's a very cool example of something you could do with the Raduino.
Imagine you are off on an island somewhere, a Bitx was dropped from the sky but doesn't quite work.
Would be nice to have a DC voltmeter, perhaps using a Raduino ADC.
We might want a diode+cap RF probe in the corner of the board somewhere.
Then we could do things like sweep that IF filter using the Si5351.
What other handy tools does the Raduino make possible?
What's the best way to measure inductance with a minimum of additional parts?
A bit beyond what I'd try with the Raduino, but I really like K5BCQ's AQRP Vector Impedance Analyzer. Two Si5351 channels kept exactly 2khz apart are routed to two SA612 mixers such that the two 2khz outputs can be sensed by two ADC's. One 2khz signal measures voltage, the other measures current, and the phase shift between the two is significant. Processed by some DSP algorithms on a uC. Using the Si5351's square waves, can reject harmonics since those would be separated by more than 2khz. Does a very nice job of measuring an inductor, graphically showing at what frequency the capacitance between windings starts to take over.