DAVID E. DOBBS, JOHN C. PETERSON, The Sign-Chart Method for Solving Inequalities, The Mathematics Teacher, Vol. 84, No. 8 (NOVEMBER 1991), pp. 657-664 ...

The Smith chart is a staple for analyzing complex impedance. [W2AEW] notes that a lot of inexpensive test gear like the MFJ-259B gives you complex readings, but fails to provide the sign of the ima… ...