MFJ-993 IntelliTuner Automatic Antenna Tuner
Instruction Manual
©
2003-2004 MFJ Enterprises, Inc.
20
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Never try to load a G5RV or center fed dipole on a band below the half-wave design frequency. If
you want to operate an 80-meter antenna on 160 meters, feed either or both conductors as a longwire
against the station ground.
To avoid problems matching or feeding any dipole antenna with high impedance open wire lines, keep the
lines around these lengths. [The
worst possible
line lengths are shown in brackets]:
160 meters dipole:
35-60, 170-195 or 210-235 feet
[Avoid 130, 260 ft]
80 meters dipole:
34-40, 90-102 or 160-172 feet
[Avoid 66, 135, 190 ft]
40 meters dipole:
42-52, 73-83, 112-123 or 145-155 feet
[Avoid 32, 64, 96, 128 ft]
Some slight trimming or adding of feedline may be necessary to accommodate the higher bands.
WARNING
To avoid problems, a dipole antenna should be a full half-wave on the lowest band. On 160
meters, an 80 or 40 meters antenna fed the normal way will be extremely reactive, with only a
few ohms of feedpoint resistance. Trying to load an 80 meters half-wave dipole (or shorter)
antenna on 160 meters can be a disaster for both your signal and the tuner. The best way to
operate 160 meters with an 80 or 40 meters antenna is to load either or both feedline wires (in
parallel) as a longwire. The antenna will act like a “T” antenna worked against station ground.
Summary of Contents for MFJ-993
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