MFJ-1775W Rotatable Mini-Dipole
Instruction Manual
10
6)
When all tuning is complete, install the plastic end caps on the outer ends of all spokes. Note that the
plastic end caps will lower the resonant frequency on all HF bands by 30-50 kHz. The plastic end
caps should fit snugly on the spokes. Should a cap fit too loosely, add a drop of glue to the spoke
end before sliding on the cap.
TYPICAL FINAL SPOKE LENGTHS FOR HF CW BAND OPERATION
•
60 Meters: 31-1/4” (full length) for two spokes on
one
loading coil only. 24-1/2” length for the
remaining six 40 meter spokes.
•
30 Meters: 12-1/4” length for all eight spokes.
•
17 meters: 12-1/4” length for all eight spokes.
•
12 meters: 10.5” length for all eight spokes.
GROUNDING CONSIDERATIONS
Although this antenna is designed to operate efficiently without the requirement of an earth ground, safety
grounding must still be provided to protect equipment, property and persons from the hazards of lighting
strikes and other weather related electrical discharges. In addition, the coaxial cable feeding the antenna
should have the shield grounded to eliminate the risk of any indoor equipment failure allowing hazardous
voltages that could create a shock hazard.
Adequate protection can be accomplished by grounding the shield of the coax to a good earth ground
where it enters the building, or directly burying the cable in the earth for several feet before it enters the
building. For maximum lightning protection, the coaxial cable should be totally disconnected from the
station during threatening weather conditions.
A less effective method of protecting station equipment is to install an in-line coaxial lightning arrestor
with a heavy duty ground wire to a suitable earth ground, or a safety switching system as part of the basic
ham station equipment.
