Practical_Antenna_Handbook_0071639586

C h a p t e r 2 2 : R a d i o A s t r o n o m y A n t e n n a s 507
The feed system for stacked helixes is more complicated than for a single helix.
Figure 22.7A shows an end view of a set of four stacked helical antennas. Tapered lines
(TL) are used to carry signal from each element and the coaxial connector (B). In this
case, the coaxial connector is a feed-through barrel or back-to-back SO-239 device at the
center of the ground plane (B). A side view of the tapered line system is shown in Fig.
22.7B. The length of the tapered lines is 1.06l, while the center-to-center spacing between
the helical elements is 1.5l. The length of each side of the ground plane is 2.5l. In
the case of Fig. 22.7, the antenna is fed from the front of the ground plane.
A1
SA
B
SA
SCREEN
A2
B
SCREEN
A1
A3
TL
B
A2
TL
A4
Figure 22.7 Front view of quad helical antenna.
A