MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
25
5.5 Advanced 2
CAUTION: THERE IS A ‘‘UHF’’ SWITCH LOCATED AT THE UPPER LEFT-HAND
SIDE OF THE ANALYZER. THIS SWITCH SHOULD BE PRESSED AND
LOCKED FOR UHF OPERATION ONLY WHEN UHF OPERATION IS DESIRED
AND ONLY AFTER THE UNIT IS POWERED UP. FOR INFORMATION ON
UHF OPERATION, SEE SECTION 3.4
This mode measures physical or electrical distance to a fault (a short or open or large impedance bump),
electrical length in degrees, and also calculates the length of a wavelength.
This mode 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).
Advanced 2
The opening display of
Advanced 2
is:
This display prompts the operator to set the correct feedline velocity factor. Velocity factor is increased by
pressing the
GATE
button, and decreased by pressing the
MODE
button. When the correct Vf is reached, press
both buttons at the same time to lock the value in. Set the Vf to the known Vf of the transmission line. This
setting will affect the
physical length
of the line displayed later. If you want to know the
electrical length
in feet,
set Vf for to unity (1.00).
NOTE: Incorrect Vf settings do not cause errors in electrical measurements, such as
“Length in
Degrees”
. Incorrect Vf settings will cause an error in physical length calculations, such as
“Dist. to Fault”
displayed in feet.
At UHF, internal capacitance of the diodes and lead lengths through the connector and connections create errors
in other measurements, so only SWR and SWR related functions are displayed. Unfortunately there is now way
to cure these problems without causing the MFJ-269 to become unreliable at HF, and any cures would require a
calibration fixture to be used at UHF every time a series of measurements are made.
5.5.1 Distance to fault (DTF) (for HF/VHF only)