Validation measurements were performed using Vector network analyzer (VNA) Rohde&Schwarz ZNB 8, 100kHz to 8.5GHz. This is my first VNA measurement so please be tolerant. Should I evaluate measurement validity and error sources my guess is that any measurement above 100MHz is invalid due to banana plugs being used. Actually I think that propper LISN manufacturers cheat their validations a bit by having SMA connectors directly in the units and connecting measurement equipment there. For test setups see simulation project log.

Output impedance measurement confirmed that LISN is compliant to CISPR-25 requirements. I’m fairly confident that impedance drop between 90-10MHz is caused by banana connectors. Matches the simulation nicely.

Measurement setup

Insertion losses measurement again looks very nice and flat. Measurement below 10MHz does not match the simulation and I have no clue why. I believe there is some issue with units VNA vs LTSpice. This is my homework to explain. Measurement above 90MHz again affected by banana plugs.

Inter channel isolation measurement explains why it is a bad idea to place two channels into same box and why all respected manufacturers don’t do it. There is quite a high amount of crosstalk below 10MHz. This is caused by magnetic coupling of inductors through thin internal wall separating the channels. CISPR-16 requires less than -40dB though, so I consider this unit as fine.

 

Long story short, after performance validation I consider this home-made CISPR-25 5uH LISN as success and based on measurement results, I release it for hobby use pre-compliance measurements 😊