To calculate the insertion loss for a two-port network, follow these instructions:
Measure the power delivered to the load before inserting the two-port network.
Measure the power delivered to the load after inserting the two-port network.
Divide the value from step 1 by that from 2 and take the logarithm of the result.
Multiply the result from step 3 by 10 to get the insertion loss.
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