MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
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The Dist. to Fault reading shows the physical distance in feet to a transmission line fault or mistermination. To
obtain the true physical distance, the analyzer multiplies electrical distance by feedline velocity factor entered in
step 1. This reading will be only as accurate as the velocity factor you enter allows. To find the electrical length
in feet, you must program the velocity factor as
“Vf=1.00”
in step 1.
6.)
Pressing the MODE button once (after finding a valid DTF) displays the distance to fault in feet and the
electrical length of the line (in degrees) at the frequency the analyzer is set on:
6 8 .5 1 1 M h z
o
As the displayed frequency is changed, the electrical length of the line is re-calculated. Note that
electrical
length repeats at 360 degrees
, and returns to zero. Because of this, it is impossible to obtain a reading larger
than 359 degrees. This feature helps you trim long lines to desired multiples of 1/4 or 1/2 wavelength.
7.)
Pressing the
MODE
button again causes the analyzer to calculate the length of one wavelength of line for the
velocity factor and at the frequency of the display. Remember, this is the length of a full wavelength (360
degrees) at the frequency selected and with Vp selected in step 1. If you select a Vp of .5, the result will be the
physical length of a half wavelength in freespace.
To confirm reliability, make two or more groups of measurements on different starting frequencies at least one
octave apart. If measured distances agree, the distances measured are confirmed.
If a different wavelength is required
see .
As with other modes, pressing the
MODE
button steps back to the beginning.
5.5.2 Calculator Functions (direct access)
The MFJ-269 performs calculator functions. These functions can also be accessed from Distance to Fault modes.
This functions:
1.) Calculates length in feet of a transmission line or conductor for the number of electrical degrees (up to 359
degrees) of a transmission line or conductor for the velocity factor and length entered and the frequency selected
(see
5.5.2.1
).
2.) Calculates electrical degrees (up to 359 degrees, at which point it repeats again at zero) for the velocity factor
entered, the electrical length programmed, and the frequency selected (see
5.5.2.2
).
5.5.2.1 Line Length in Degrees