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MFJ-259B/MFJ-269 Distance to Fault Procedure

Solution
Before to try to clearify your doubs about the MFJ-259B Distance to Fault
methodology I should apologize for the 5.5, Distance to Fault mode "To
measure fault distance" confusing text. I think that you are correct about
the graphic position and test "unmatched" position.

About the two step 2 displays: The first one at 21.324 MHz with the 2nd
blinking indication, shows the zero ohm reactance read at that frequency.
The second display would be just a general reading obtained while tuning
the analyzer tracking for the another consecutive zero ohm frequency spot.
That display should be set over a correctly written step 3.

With respect the step 3, I sincerely believe that we should forget about
it. A more general increase or decrease frequency term should have been
used. On the other hand step 3 and 4 should be sharing the same spot.

Your interpretation about the "higher or lower in frequency" meaning is
exactly right. 

Let try to explain it in a different way, using some of the actual manual
paragraphs .

1.) Select a frequency where the Impedance meter is at the lowest
deflection possible and where minimum reactance  displayed on the MFJ-259B
LCD, or where the reactance crosses zero.  The reactance zero-crossing
frequency is the frequency where reactance rises when the MFJ-259B is
adjusted either higher or lower in frequency.

[That would be the display indicated over the step 1]

2.) Press the “GATE” button at that reactance zero-crossing frequency.  The
blinking  “1st”  will change to a blinking “2nd”.

[That would be over one of the displays shown over the step 2]

3.) Tune the analyzer higher or lower in frequency until the Impedance
meter reads the very next lowest impedance point on the meter, and 
reactance displayed on the LCD crosses zero or is at the lowest possible
again.  A non-zero minimum of a few ohms is acceptable. Be very careful to
avoid any tuning frequency gap if switching an antenna analyzer band was
required.

[On this case a frequency tune up procedure was followed in order to get
the 68.511 MHz zero-crossing frequency. The 39.756 MHz display could be
introduced here as a general one.]

4.) Press the “GATE” button again at the new zero-crossing frequency, and
the display will indicate distance in feet.

Multiply the distance in feet by the velocity factor of the cable.  The
result is the physical distance in feet.

Example: The MFJ-259B indicates 13 feet, and the cable is a standard foam
cable with a velocity factor of 0.80.  13 multiplied by .80 is 10.4 feet. 
The fault is about 10.4 feet away. 
Article details
Article ID: 70
Company: MFJ
Date added: 2017-01-12 14:31:23
Views: 131

 
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