6 Meter Kit adds 6 meter coverage to the HF6V.
The vertical wire from clamp (A) together with the adjacent section of the
antenna form a short-circuited quarter-wave transmission line which cancels
current flow. At the lower (open) end of this quarter-wave section a very high
impedance is created that effectively divorces the upper part of the antenna on
six meters, leaving only the lower section to radiate as a 3/4 wave monopole.
Why 3/4 wave rather than 1/4 wave? Because the vertical plane pattern of the
former breaks into two lobes, one at zero degrees and the other at 40 degrees,
thus affording both low-angle and skywave propagation. Further, the radiation
resistance of a 3/4 wave radiator is almost twice that of a 1/4 wave radiator, so
for a given earth loss resistance the taller antenna should be more efficient,
particularly when operated at ground level.
Adjustment for resonance or lowest SWR at a particular frequency may be
made by adjusting the length of the wire or in the placement of the upper clamp
along the antenna. In general, the wire may be lengthened to lower resonance
or shortened a slight amount to raise it. Alternatively, the upper clamp (and the
entire 6 meter assembly) may be placed higher on the antenna to lower
resonance or slightly lower to raise resonance.
If the antenna is to be mounted more than a foot or so above the earth, several
resonant radials may be required for low SWR operation on 6 meters.