MFJ MFJ-269, Instruction Manual, Page: 12 / 40

MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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4.2 HF/VHF Main modes
4.2.1 Antenna system SWR
Note: 50 ohms is the default SWR impedance. This unit can be set to impedances other than 50 ohms
in the Advanced 3 menu.
To measure SWR of an antenna or an antenna tuner input:
a.) If the antenna does not use a dc grounded element and feed system, momentarily short the antenna lead from
shield to center. This prevents static charges from damaging the MFJ-269’s zero bias detector diodes.
b.) Immediately connect (in the case of a non-dc grounded feed system) the antenna lead to the MFJ-269
“ANTENNA” connector.
c.) Set the
“FREQUENCY” knob to the proper frequency range.
d.) Turn the MFJ-269
“POWER” switch on, while watching the display. Battery voltage should be “OK”, and
indicate more than 11 volts and less than 16 volts.
e.) The main or opening mode opening menu displays frequency, SWR, resistance, and reactance on the LCD,
and SWR and impedance on the analog meters. In this mode, the resistance (real part) and reactance (imaginary
part) of the system impedance is displayed in ohms.
f.) Adjust the “TUNE” knob until the counter displays the desired frequency, or until you find the lowest SWR.
Advanced antenna measurement modes are available and described in section 5.0. Many advanced descriptions
are just different ways of displaying the same basic information given in the
MAIN (or normal opening) mode
menu. Unless you fully understand the meaning of terms used in advanced mode measurements, we suggest you
avoid them.
Antenna hints:
Display readings are always the SWR, impedance and resonant frequency of the
antenna system ONLY at the point in the system the MFJ-269 is connected. The
impedance and resonant frequency (frequency where reactance crosses zero) at the
point where this unit is connected might not be the resonant frequency of the antenna
itself. This happens because a transmission line can add reactance or cancel reactance,
and change the impedance and resonant frequency of the antenna system.
This unit displays the antenna’s complex impedance, 50 ohm SWR (unless another
impedance is selected and measured in Advanced mode 3), and resonant frequency as
modified by transmission line “effects” of the feedline and other components between