MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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Advanced 1
5.4.1 Advanced 1 (HF/VHF)
ADVANCED 1
mode measures impedance and SWR functions. There are six display functions available in this
mode:
- Magnitude and phase of load impedance (5.4.1.1)
- Series Equivalent impedance (5.4.1.2)
- Parallel Equivalent impedance (5.4.1.3)
- Return loss and Reflection coefficient (5.4.1.4)
- Resonance (5.4.1.5)
- Match efficiency (5.4.1.6)
5.4.1.1 Magnitude and Phase of Load Impedance
Magnitude and Phase of Impedance is the first mode in the advanced menu. The opening display first indicates:
and then flashes to:
In this mode, the MFJ-269 LCD displays frequency, impedance or Z magnitude (in ohms), and phase angle (
θ
)
of impedance. The meters indicate 50 ohm referenced SWR and load Impedance. The maximum impedance limit
is set at 1500 ohms, exceeding the limit results in an impedance display of (Z>1500).
Note:
Stray connector capacitance will be lower than 1500 ohms at frequencies higher than 30 MHz, and lower
as adapters and leads are added to the
ANTENNA
port. This small stray capacitance will not affect high
frequency measurements, and produces only minor errors in measurement of impedances under a few hundred
ohms at VHF.
Phase angle of impedance is another way of expressing R and X. Instead of providing R and X as separate
numerical quantities, a vector-type description of measured impedance is presented. Impedance (Z) is still
described as the length (magnitude) of a line representing the complex impedance. (This is the same Z as given in
other functions.) Besides Z, an angle between zero and 90 degrees is shown. This angle represents the phase
difference between current and voltage at the terminals of the analyzer.
When a reactance is present, voltage and current are no longer in phase (or exactly out-of-phase) and so the phase
angle increases from 0 degrees to a maximum angle of 90 degrees. The angle becomes 90 degrees when the load
is a pure reactance, and zero degrees when the load is a pure resistance.