Technician Licensing Class

1. Technician Licensing Class Antennas Page 151 to 157

2. Amateur Radio Technician ClassElement 2 Course Presentation ELEMENT 2 SUB-ELEMENTS (Groupings) About Ham Radio Call Signs Control Mind the Rules Tech Frequencies Your First Radio Going On The Air! Repeaters Emergency! Weak Signal Propagation 2

3. Amateur Radio Technician ClassElement 2 Course Presentation ELEMENT 2 SUB-ELEMENTS (Groupings) Talk to Outer Space! Your Computer Goes Ham Digital! Multi-Mode Radio Excitement Run Some Interference Protection Electrons – Go With the Flow! It’s the Law, per Mr. Ohm! Go Picture These! Antennas Feed Me with Some Good Coax! Safety First! 3

4. Antennas Main ideas • Horizontal or vertical • Antennas have ideal length based on the radio wavelength to be used. • Ideal length: “resonant” at half wavelength: 468 Half wavelength   feet f (in MHz) • Electric field is aligned with the antenna (horizontal or vertical). • Directional antennas: send/receive in one direction

5. Antennas: The Dipole 112 in. Size of every antenna is based on the frequency, or the wavelength, l. A “half-wave dipole” has length equal to ½ the wavelength. where f= freq in MHz Example: for f= 50 MHz (6 m band) Length = 468/50 = 9.36 ft, or 112" 468 Length = Half wavelength   feet f (in MHz)

6. Antennas: Vertical “Whips” Vertical whips are often attached to a magnet. So, they are often called “a “mag-mount.” Typically, they are ¼ wavelength. where f= freq in MHz Example: for f= 146 MHz Length = 234/146 = 1.6 ft, or 19.2” 234 Length = ¼ wavelength   feet f(in MHz) 19”

7. Antennas: “Beams” • Aligned antenna elements“beam” the radio signal in one main direction. • They also receive signals more effectively from that direction, and “reject” signals from the opposite direction. • They perform most efficiently near the design wavelength. • Different directional designs: Yagi, quad, dish. Antennas

8. Element 2 Technician Class Question Pool Antennas Valid July 1, 2010 Through June 30, 2014

9. T9A03 Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface? • A ground wave antenna • A horizontally polarized antenna • A rhombic antenna • A vertically polarized antenna

10. T9A10 In which direction is the radiation strongest from a half-wave dipole antenna in free space? • Equally in all directions • Off the ends of the antenna • Broadside to the antenna • In the direction of the feedline

11. T9A09 What is the approximate length, in inches, of a 6 meter ½-wavelength wire dipole antenna? • 6 • 50 • 112 • 236 112”

12. T9A05 How would you change a dipole antenna to make it resonant on a higher frequency? • Lengthen it • Insert coils in series with radiating wires • Shorten it • Add capacity hats to the ends of the radiating wires Higher frequencies are shorter Lowerfrequencies are longer

13. T9A02 Which of the following is true regarding vertical antennas? • The magnetic field is perpendicular to the Earth • The electric field is perpendicular to the Earth • The phase is inverted • The phase is reversed E 90º

14. T9A08 What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? • 112 • 50 • 19 • 12 19”

15. T9A06 What type of antennas are the quad, Yagi, and dish? • Non-resonant antennas • Loop antennas • Directional antennas • Isotropic antennas

16. T9A01 What is a beam antenna? • An antenna built from aluminum I-beams • An omnidirectional antenna invented by Clarence Beam • An antenna that concentrates signals in one direction • An antenna that reverses the phase of received signals

17. T8C01 Which of the following methods is used to locate sources of noise interference or jamming? • Echolocation • Doppler radar • Radio direction finding • Phase locking RDF

18. T8C02 Which of these items would be useful for a hidden transmitter hunt? • Calibrated SWR meter • A directional antenna • A calibrated noise bridge • All of these choices are correct

19. T3A05When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path? • Change from vertical to horizontal polarization • Try to find a path that reflects signals to the repeater • Try the long path • Increase the antenna SWR You can use a directional antenna to bounce your signal to reach a repeater blocked by a building.

20. T9A11 What is meant by the gain of an antenna? • The additional power that is added to the transmitter power • The additional power that is lost in the antenna when transmitting on a higher frequency • The increase in signal strength in a specified direction when compared to a reference antenna • The increase in impedance on receive or transmit compared to a reference antenna Remember 3db? 6db? That’s gain!

21. T3A03 What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands? • Right-hand circular • Left-hand circular • Horizontal • Vertical

22. T3A04 What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization? • The modulation sidebands might become inverted • Signals could be significantly weaker • Signals have an echo effect on voices • Nothing significant will happen