MFJ-269C Instruction Manual LF/HF/VHF/UHF SWR Analyzer
25
15.814 MHz 1st
DTF Xs= 51
Note that
1st
is flashing on and off. This display is prompting you to use
Tune
to
find the frequency
where the Impedance Meter shows the lowest reading for Xs
(as close to Xs=0 as possible). When you
find that frequency, press and hold
Gate
until the flashing
1st
on the display stops flashing. Then release
Gate
quickly.
The display now indicates the first frequency data point and the blinking
1st
will change to a blinking
2nd
:
21.324 MHz 2nd
DTF Xs= 0
3.
Now, switch the
Frequency
selector to the
next lower band
and look again for the closest value to
Xs
=0. Slowly adjust
Tune
higher or lower in frequency until the
Impedance Meter
indicates the
next
low
Impedance Meter
reading and reactance
Xs=
0 (or as low as possible).
68.511 MHz 2nd
DTF Xs=1
4.
Press the
“GATE”
button again to lock in the second frequency, and the display will change to
indicate distance in feet:
The
Dist. to Fault
reading is the
Physical Distance in Feet
to a transmission line fault or mis-termination.
To obtain the true physical distance, the analyzer multiplies
Electrical Distance
by the feedline
Vf
entered
in step 1. This reading will only be as accurate as the velocity factor you entered. To find the
Electrical
Length in Feet
, you must program the velocity factor as
Vf=1.00
in step 1.
5.
After determining the
DTF
, press
Mode
to view the
Distance to Fault in feet
plus the
Electrical
Length in Degrees
at the current frequency setting.
68.511 Mhz
o
As you
Tune
the analyzer frequency, the electrical length of the line will be re-calculated. Note that
Electrical Length
repeats at 360 degrees and returns to zero. As a result, it isn't possible to obtain a
reading greater than 359 degrees. This feature is intended to help you trim long lines to desired multiples
of 1/4 or 1/2 wavelength.
6.
Pressing
Mode
once more prompts
the analyzer to calculate the physical length for
one wavelength of
line
(
1
λ
)
using the entered
Vf
at the frequency shown on the display (remember, this is the length using
the Vf set in step 1). If you select a Vp of .5, the result will be the physical length of a half wavelength in
free space.