Practical_Antenna_Handbook_0071639586

224 P a r t I I I : H i g h - F r e q u e n c y B u i l d i n g - B l o c k A n t e n n a s
Rope
/2
Rope
Insulator
Parallel
feeders
Tuner VSWR meter Coax to XMTR
Figure 8.4 End-fed Zepp antenna.
pattern between the end-fed Zepp and the center-fed dipole of Fig. 8.2. On 40 m, however,
the center-fed dipole still has a figure eight pattern similar to the one on 80, but
sporting about 2 dB more gain in the main lobe, which is slightly narrower as well. The
end-fed Zepp’s pattern, however, resembles a four-leaf clover (actually, two figure
eights at right angles to each other) with the pattern peaks at 45 degrees to the axis of
the wire. In fact, the end-fed Zepp’s 40-m pattern is remarkably similar to the center-fed
dipole’s 20-m pattern! If we were to continue to double the operating frequency a number
of times and compare patterns between
the two antennas, we would
51' 51'
observe that a given amount of main lobe
splitting occurs at a frequency for the center-fed
antenna that is twice as high as the
Zepp’s frequency.
Twin lead L
Z 0 (Feet)
300 29
450 34
L
50- coax
(any length)
G5RV Multiband Dipole
Figure 8.5 shows the basic dimensions of
the G5RV antenna, an antenna that has enjoyed
much popularity over the years. It
has been erected as a horizontal dipole, a
sloper, or an inverted-vee antenna. In its
standard configuration, each side of the
dipole is 51 ft long, and it is fed in the center
with a matching section of either 29 ft
Figure 8.5 G5RV antenna. (Courtesy of Hands-
On Electronics and Popular Electronics)