MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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6.)
If SWR changes
with coaxial line length, line placement, or feedline or equipment
grounding, the feedline has one or more of the following shortfalls:
a.) The feedline is carrying common mode current and radiating.
b.) The feedline is not a 50 ohm line, or does not exactly match the impedance the analyzer is
programmed for.
c.) The feedline has significant loss.
4.2.2 Coax Loss
The second main (or opening) mode is
“Coax Loss”.
Access this mode by turning the MFJ-269 on and stepping
to the Coax Loss display with the
MODE
button. In this mode, the MFJ-269 LCD indicates frequency and coax
loss in dB. The
IMPEDANCE
meter is disabled. This mode was designed to measure 50 ohm cables, but
measures differential mode loss in many types of 50 ohm transmission line transformers and choke baluns, as
well as loss in 50 ohm attenuator pads.
Note: An additional coax loss function is available in Advanced 3. Advanced 3 allows user selection of
analyzer impedance, and measurement of loss non-50 ohm systems.
Caution:
Do not measure loss of conventional transformers, attenuators, or coaxial cables with impedances other
than 50 ohms in the
“MAIN”
menu. When making loss measurements, the opposite end of the device-under-test
must have an open circuit, a short circuit, or a pure reactance for termination. Any termination loss will make
attenuation appear worse than it actually is. The “
ADVANCED 3”
menu allows measurement of devices with
impedances other than 50 ohms.
a.) To measure loss, connect the MFJ-269 to the 50 ohm cable, attenuator, or the transmission line type balun or
transformer to be measured. Be sure the distant end of the component tested is not terminated in any resistance or
other lossy termination.
b.) Turn the MFJ-269 on. After the display reaches the opening
“MAIN”
measurement functions, press the
MODE
switch once.
Note: You can step through other menus and back to this mode by repeatedly pressing the mode
button.
c.) The display should momentarily flash
“Coax Loss”.
d.) Read the loss in dB at any frequency this unit covers.
4.2.3 Capacitance
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