This is a high Impedance Balanced Line test fixture to allow a 50 ohm unbalanced VNA to make good high Impedance balanced line measurements. This is particularly relevant to measuring LoE and other traveling wave antennas such as the Bevarage.

The fixtured VNA is calibrated with an Open,Short and Reference Impedance Load in a conventional one-port measurement manner.  Reference impedance of measurements then become reference to the reference resistor. Choosing 750 ohms is particularly useful since it is twice the impedance of free space and useful for measuring dual SWTL lines such as are on a simpole dipole.