MFJ-269C Instruction Manual LF/HF/VHF/UHF SWR Analyzer
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5.5.1.2 DTF Coaxial lines
Coaxial line placement is not critical -- you may lay in a pile or coil it on the floor. Use internal batteries
or external power to run the analyzer, and place it on any convenient surface (conductive or not). Connect
coaxial lines normally, with the shield grounded to the outside of the connector.
5.5.1.3 DTF Antenna Length
To measure the electrical length of wire antennas (longwires, dipoles, Beverages), connect through a good
broadband matching transformer -- or by connecting directly to the analyzer's Antenna port.
To ensure accuracy, avoid using any 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 will help you weed-out false reactance nulls when measuring antennas through a
transmission line.
To determine antenna length, treat the antenna like a transmission line, following the procedure for
measuring Distance To Fault. For a dipole, your result will be the electrical length of one leg. For a
longwire or Beverage, it will be electrical length for the entire antenna.
5.5.1.4 DTF Measurement Procedures
Distance to Fault is the first measurement mode in Advanced-2. To enter the mode, press and hold the
Mode and Gate buttons until Advanced-2 appears on the screen. From other Modes, step through the
menu holding the Mode and Gate button.
The first menu that appears is:
The Gate button increases Vf, Mode decreases it.
1. Set the Vf to the factory specified velocity factor of the transmission line. This data is required to for
Physical Length calculations that will be displayed later. For Electrical Length in Feet, set Vf to unity
(1.00).
Note: An Incorrect Vf setting will not cause an errors in electrical measurements such as Length in
Degree. However it will cause an error in physical length calculations, such as Dist. to Fault .
2. After setting the Vf, press Gate and Mode simultaneously to lock-in the value. The display indicates:
and after a few seconds changes to (sample screen):
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