MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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The next display menu is:
This function will measure any type or impedance of line, including the length of Beverage or other antenna
antennas (if the termination is removed). Section 5.5.1.4 outlines the measurement procedures, or
HOW
to
measure something. Sections 5.5.1.1 through 5.5.1.3 describe a few things that can be measured.
5.5.1.1 DTF balanced lines
If a balanced line is used, operate the MFJ-269
only
from internal batteries. Keep the MFJ-269 a few feet away
from other conductors or earth, and do not attach any wires (other than the balanced line) to the analyzer. Use the
ANTENNA
connector’s shield for one lead and its center pin for the other. Two wire balanced lines
must
be
suspended in a reasonably straight line a few feet away from other objects by using good insulators. Avoid laying
the line against anything, including insulators, for any distance. Be sure to keep the line several conductor
spacings away from other conductors, even poor conductors like earth or concrete.
5.5,1.2 DTF Coaxial lines
Coaxial lines can lay in a pile or coil on anything, including a floor. Either battery or external power supplies can
be used to power the analyzer, and the MFJ-269 can be placed on or near large metallic objects with no ill
effects. Coaxial lines must connect normally, with the shield grounded to the outside of the connector.
5.5.1.3 DTF Antenna Length
Antenna length, such as the electrical length of longwires, dipoles, or Beverages, can be measured.
Measurements should ideally be made either through a good broadband matching transformer or by directly
connecting the antenna to the
ANTENNA
port of the analyzer.
To guarantee the most reliability and accuracy, it is a good idea to avoid appreciable lengths of feedline (more
than 1/32 wl) between the analyzer and the antenna. While measurements can be made with a transmission line
connected between the antenna and analyzer, false zero reactance crossings will be introduced from line
mismatch. Watching the SWR meter can help weed-out false reactance nulls when measuring antennas through a
transmission line.
To measure antenna length, treat the antenna like a transmission line and follow the procedure for measuring
distance to fault. With a dipole antenna, the result will be the length of one side of the antenna. With a longwire
or Beverage, it will be the entire antenna electrical length.
5.5.1.4 DTF measurement procedures
“Distance to Fault”
is the first measurement mode in the
“Advanced 2”
menu. This menu is reached by
pressing and holding the
MODE
and
GATE
buttons until
“Advanced 2”
appears on the display. It can also be
reached (and all other advanced modes) by stepping through
Advanced
modes by holding the
MODE
and
GATE
button until the display indicates
“Advanced 2”
(or other desired function).
CAUTION: THERE IS A ‘‘UHF’’ SWITCH LOCATED AT THE UPPER LEFT-HAND
SIDE OF THE ANALYZER. THIS SWITCH SHOULD BE PRESSED AND