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MFJ-1796W
The following tips will help you obtain an even better SWR on 5.3 MHz than the tuning method
used on other bands. On 60 meters the lowest SWR is usually not obtained with the top and
bottom loading spokes adjusted to the same frequency.
60 Meters: If you desire operation below 6 MHz the lowest SWR will be obtained by adding
two extra long spokes to the bottom 60 meter loading coil assembly. It is best to add the spokes
on opposite sides of the coils, closest to the horizontal as possible (perpendicular to the vertical
element.) Short 60 meter spokes from both coils can then be trimmed equal amounts to resonate
the antenna. This will leave the bottom loading assembly with two spokes that are longer than
the top.
Begin tuning by trimming one 40 meter spoke from each end of the antenna by cutting off
small, equal sections from the inside end of the spoke until the antenna resonates approximately
15 KHz below the desired operating frequency. Use the chart below to approximate the amount
of spoke to be trimmed. Trimming only one spoke from the top or bottom results in half the
frequency change.
60 M: 1" trimmed off a pair of spokes equals approximately 20 KHz
30 M: 1" trimmed off a pair of spokes equals approximately 100 KHz
17 M: 1" trimmed off a pair of spokes equals approximately 175 KHz
12 M: 1" trimmed off a pair of spokes equals approximately 250 KHz
2. If the SWR is acceptable at the desired operating frequency the adjustment for that band may be
skipped.
3. Now tune progressively higher frequency bands by trimming pairs of spokes(one top one
bottom). Keep each pair of capacitance spokes equal in size. 30 meters must be the second HF
band adjusted, 17 the third and 12 meters last. After adjusting 12 meters go back and check the
other bands. Tighten all spoke screws.
4. Final frequency adjustments can be made by trimming spokes on the bottom hat only when the
antenna is permanently mounted.
symmetrical trimming of the top spokes is perfectly acceptable so long as the frequency is
changed less than 30 KHz on 60 meters and 60 KHz on the higher bands with the final
adjustment. The result of attempting to move the resonant frequency too far with only the
bottom spokes will be an increase in the SWR of the antenna at the resonant frequency.
NOTE: The spokes can also be bent toward another spoke in the same mounting ring to raise
the frequency slightly without cutting.
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 from allowing hazardous voltages from appearing indoors
and creating a shock hazard.
The minor adjustment of bottom spokes without the
WARC Band Vertical Antenna
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