MFJ-269C Instruction Manual LF/HF/VHF/UHF SWR Analyzer
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term is unfamiliar to you, it's probably wiser to avoid using it to influence your decision-making until you
understand its full technical meaning.
Information Sources: A basic understanding of transmission line and antenna behavior and terminology
is very important in understanding Advanced Mode information provided by the MFJ-269C. Many
explanations are available in the ARRL Handbooks, and they probably suffice for most amateur
applications. Avoid unedited or self-edited amateur handbooks or articles, or at least confirm their
accuracy by checking the information against reliable professional sources. For complex questions or
critical information, we recommend using textbooks written, reviewed, and edited by professional
engineers.
Accuracy Notes: The MFJ-269C contains a 50-ohm bridge, with voltage detectors across each bridge leg.
A twelve-bit microcontroller processes these voltages and, by applying the proper formulas, displays
useful information. The basic calculations are resistance, reactance, SWR, and complex impedance. In
some modes, the system cross checks itself and displays a weighted average of the most accurate
measurement methods, or searches for certain impedance conditions. System resolution is limited mostly
by diode linearity, calibration stability, and external noise or signals.
While we have attempted to make this unit as accurate as possible, most formulas contain squares and
other complex functions. A certain amount of error is unavoidable, especially at high or low impedance
values and especially at higher VHF or UHF frequencies.
5.2 Accessing Advanced Modes
The advanced mode is reached by pressing and holding the Gate and Mode buttons at the same time for
several seconds. After a delay of a few seconds, a series of Advanced messages numbered 1 through 3
appear. When you see the mode you want, quickly release the buttons. If you hold the buttons long
enough, the display will eventually loop back through the MAIN menu and repeat the cycle.
*LF/ HF/VHF operation: The following modes are available from each of these Advanced menus:
Advanced-1 Magnitude and phase of load impedance
(Section 5.4.1) Series and Parallel Equivalent Impedances
Return Loss and Reflection coefficient
Resonance
Match Efficiency
Advanced-2 Velocity Factor setup
(Section 5.5) Distance to Fault measurement
Line length in degrees calculation
Advanced-3 Characteristic Impedance setup
(Section 5.6) Normalized SWR impedance (display only)
Coax loss
* UHF operation: The following modes are available from each of these Advanced menus:
Advanced-1 Return Loss and Reflection coefficient
(Section 5.4.2) Match Efficiency
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