Thanks James, nice article. (I had not seen the TLA "PDN" before but now I know you mean "Power Distribution Network".) VNAs have become remarkably cheap; her

Thanks James, nice article. (I had not seen the TLA "PDN" before but now I know you mean "Power Distribution Network".) VNAs have become remarkably cheap; here's one that < $ 60 https://www.amazon.com/50KHz-900MHz-Analyzer-Measuring-Parameters-Standing/dp/B07Y53RCKW/ https://www.amazon.com/50KHz-900MHz-Analyzer-Measuring-Param... I have one of these, it works very well. Fancier ones are of course available. This one goes to 6.3 GHz https://www.amazon.com/LiteVNA-64-Analyzer-50KHz-6-3GHz-Portable-Vector/dp/B09T2LYY65 https://www.amazon.com/LiteVNA-64-Analyzer-50KHz-6-3GHz-Port... and is $ 180. I have this 'fancy' one: https://www.tindie.com/products/hcxqsgroup/nanorfe-vna6000/ https://www.tindie.com/products/hcxqsgroup/nanorfe-vna6000/ One trick I learned from the RF guys is: put two same value capacitors in parallel; it doubles the capacitance, and also reduces by about half the ESL (inductors in parallel rule). Clever.