G5RV 40m Beam Antenna
Adding a 28 ft. piece of vertical wire to one end of a
102 ft. center-fed dipole turns it into a 40m beam with a very wide beamwidth.
From my QTH in Texas, I can cover virtually all of the USA.
The feedpoint impedance changes when the vertical wire is
added. To achieve a better match, W5DXP reduces the length of the
300 ohm matching section to 17 feet when configured as above. Also,
since the antenna is unbalanced by the single vertical wire, a good
choke is necessary at the twinlead/coax junction. As a bonus, 17 ft.
is also a good length for the matching section when the standard G5RV
is used on 30m.