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Quiz!!

Quiz!!. 75 W System. Z T. 50 W Line. Determine Z T for a matched load. Negligible Radiation. Half Wave Dipole. For l = l /2, Z T = 73 + 42.5 j W For l = 0.95 l /2, Z T ~ 72 W. Weaker Radiation. l. Strongest Radiation. Z T. Balanced Transmission Line. Gain ~ 1.64

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Quiz!!

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

  2. Negligible Radiation Half Wave Dipole For l = l/2, ZT = 73 + 42.5jW 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 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 X GD X X X X X X X X X X X 73 X b3dB X X

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