1. Quiz!!
75 W System
50 W Line ZT
Determine ZT for a matched load.

2. Half Wave Dipole l ZT Negligible Radiation
For l = l/2, ZT = j W
For l = 0.95l/2, ZT ~ 72 W
Weaker Radiation l
Strongest Radiation ZT
Balanced Transmission Line
Gain ~ 1.64
~ 2.15 dBi
Weaker Radiation
Radiation Pattern exhibits line (cylindrical) symmetry with respect to Dipole Axis.
Negligible Radiation

3. Quarter Wave Dipole (Vertical Marconi)
For l = 0.95l/4, ZT ~ 37 W
Radiation pattern is identical to half wave dipole above ground plane, zero radiation below ground plane.
Unbalanced Transmission Line
(Co-ax) l ZT
Perfectly Conducting Planar Reflector
(Ground Plane)
Balanced Transmission Line
Reflected image of driven element.

4. Practical Quarter Wave Whip
Weaker Radiation
Strongest Radiation
Unbalanced Transmission Line
(Co-ax)
Weaker Radiation
Imperfectly Conducting Ground Plane
Ground Plane Systems:
Large Metal Sheet
Highly conductive terrain
Radial conductors buried in earth
Radial Conductors emanating from antenna mast (Counterpoise)

5. Folded Half Wave Dipole
l ~ l/2 ZT
Balanced Transmission Line
ZT ~ 288 W
Provides consistent gain over broader bandwidth.
Pattern same as half wave dipole

6. Yagi-Uda Antenna
The Yagi-Uda antenna is constructed with one driven element and several parasitic elements.
Driven element
Directors
Directors
Gain 3
9 dBi 6
11.5 dBi 11
13 dBi
Reflector
Strongest Radiation

7. Log Periodic Antenna
Log Periodic Antenna produces less gain than Yagi-Uda, but has broader bandwidth.

8. Loop Antennas Direction of Propagation – Magnetic Field lines shown
Yields maximum response when magnetic field lines are perpendicular to plane of loop – yields sharp null when magnetic field lines are parallel to plane of loop. Used for direction finding.

9. Dish Antennas D

10. Problems in Text GD X X X X X X X X X X X X 73 X
b3dB X X