Vectronics SWR-584C - Manual (Page 9)

SWR-584C Instruction Manual HF/VHF/220MHz SWR Analyzer
9
[ ] Read Impedance Magnitude (Z) on the analog meter scale.
Ohms
40 50 70 100 400
0 10 20
[ ] Read Impedance Magnitude (Z) and Phase Angle ( ) presented numerically by pressing
and holding the
Gate button. The LCD display changes, as shown below:
[ ] Release Gate to revert back to R&X.
Note that Reactance readings (X) could be inductive (+ X
L
) or capacitive (- Xc) because the
processor can't calculate the sign. However, you can often find the sign by installing a small
capacitor across the feedline connector to add a few ohms of capacitive reactance. If your
capacitor increases X, the load is likely capacitive (-) because your reactance added to it. On
the other hand, if your capacitor caused X to decrease, the load is likely inductive (+
)
because
it cancelled out some of the X. To ensure accuracy, keep the amount of Xc you add as small
as possible.
Also, when measuring through a feedline, always remember the values for R, X, Z, and are
displaced values measured at the analyzer's calibration plane and do not represent the actual
impedance of the device connected at the far end.
To read the impedance of the device under
test accurately, you must connect directly to the DUT using the shortest leads possible (or use
an electrical half-wave of 50-Ohm cable) .
4.3 Measure Coax Loss (dB): This mode displays the Measured Loss in dB at the VFO
operating frequency for any length of 50-Ohm coax cable. It will also measure losses incurred
through 50-Ohm attenuators, transformers, or baluns. To measure Loss:
[ ] Turn on the analyzer and allow it to boot to the default mode (R&X).
[ ] Press Mode once to access Coax Loss and wait for the working screen.
[ ] Adjust the Frequency switches and Tune control to the desired test frequency (MHz).
[ ] Connect the feedine under test (or 50-Ohm device) to the Antenna jack.
[ ] Make sure the far end of the coax or the output port of the device is unterminated.
[ ] Read Coax Loss on the lower line of the LCD display:
10.120 MHz 1.5
Z= 75 = 5° SWR
10.120 MHz 1.5
R= 73 X=10
10.120 MHz
Coax Loss = 2.1 dB