Vectronics SWR-584B User Manual

Page 22

SWR-584B Instruction Manual

HF/VHF SWR Analyzer

4.) Press the “GATE” button again, and the display will indicate distance in feet.

Use the following procedure:

1.) Measure the physical length of the line in feet.

2.) Divide the display reading by the actual feedline length.

Example: 27 feet (physical length) divided by 33.7 feet (measured length) equals .80 . The velocity factor

is .80 or 80%.

7.3

Impedance of Transmission Lines or Beverage antennas

The impedance of transmission lines between a few ohms and 650 ohms can be directly measured with the SWR-
584B. Lines of higher impedance can be measured if a broadband transformer or resistance is used to extend the
SWR-584B’s range. Select any measurement mode that indicates resistance (R=) and reactance (X=).

If a balanced line is used, operate the SWR-584B only from internal batteries. Keep the SWR-584B a few feet
away from other conductors or earth, and do not attach any wires (other than the feedline) to the unit. Use the
ANTENNA connector’s shield for one lead and its center pin for the other. Two wire balanced lines must be
suspended in a fairly straight line a few feet away from metallic objects or ground.

Coaxial lines can lay in a pile or coil on the floor. Internal or external power can be used, and the SWR-584B
can be placed on or near large metallic objects with no ill effects. Coaxial lines connect normally, with the shield
grounded.

Beverage antennas must be directly connected to the SWR-584B.

Using fixed resistances:

1.) Terminate the line or antenna in a non-inductive resistance somewhere around the expected value.

2.) Connect the transmission line or antenna directly to the

SWR-584B

"ANTENNA" connector. Adjust the

frequency (near the expected operating frequency) until the lowest resistance and lowest reactance is
measured.

3.) Record the impedance value.

4.) Adjust the frequency until the highest resistance and lowest reactance is measured.
5.) Multiply the highest resistance by the lowest resistance, and find the square root of the result.