Technician Licensing Class “T9”

1. Technician Licensing Class“T9” Our thanks to the Plano Amateur Radio Club, Plano, Texas

2. Amateur Radio Technician ClassElement 2 • ELEMENT 2 SUBELEMENTS • T1 - FCC Rules, station license responsibilities • T2 - Control operator duties • T3 - Operating practices • T4 - Radio and electronic fundamentals • T5 - Station setup and operation • T6 - Communications modes and methods • T7 - Special operations • T8 - Emergency and Public Service Communications • T9 - Radio waves, propagation, and antennas • T0 - Electrical and RF Safety

3. Radio waves, propagation, and antennas T9A • Antenna types – vertical, horizontal • A vertical antenna is an antenna that consists of a single element mounted perpendicular to the Earth's surface. • A horizontal antenna is a simple dipole mounted so the elements are parallel to the Earth's surface.

4. Radio waves, propagation, and antennas T9A • Concept of gain • The advantage of 5/8 wavelength over 1/4 wavelength vertical antennas is their radiation pattern concentrates energy at lower angles.

5. Radio waves, propagation, and antennas T9A • Concept of gain (cont) • A beam antenna is an antenna that concentrates signals in one direction. • The quad, Yagi, and dish are all types of directional or beam antennas.

7. Radio waves, propagation, and antennas T9A • Common portable and mobile antennas, losses with short antennas • A disadvantage of the "rubber duck" antenna supplied with most hand held radio transceivers is it does not transmit or receive as effectively as a full sized antenna. • A good reason not to use a "rubber duck" antenna inside your car is that signals can be 10 to 20 times weaker than when you are outside of the vehicle. • A magnet mount vertical antenna is one type of antenna that offers good efficiency when operating mobile and can be easily installed or removed.

8. Radio waves, propagation, and antennas T9A • Relationships between antenna length and frequency • The physical size of half-wave dipole antenna becomes shorter as the operating frequency increases. • The approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz is 19 inches. [Remember the relationship between wavelength and frequency.] • The approximate length, in inches, of a 6-meter half- wavelength wire dipole antenna is 112 inches. [Remember the relationship between wavelength and frequency.]

9. The ¼ & ½ Wave Vertical 234 f (MHz) Length of vertical in feet = Feed Point ¼ Wave 19” ½ Wave 112” Feed Point ¼ Wave Radials ½ Wave Radials

10. Radio waves, propagation, and antennas T9A • Dummy loads • The primary purpose of a dummy load is it does not radiate interfering signals when making tests. [Actually, it may radiate but the signal level radiated is usually well attenuated.]

11. Radio waves, propagation, and antennas T9B • Propagation • VHF/UHF signals not normally heard over long distances due to VHF and UHF signals usually not being reflected by the ionosphere. • When we hear a VHF signal from long distances a possible cause is sporadic E reflection from a layer in the ionosphere.

12. Ionospheric Layers

13. Critical Angle

14. Radio waves, propagation, and antennas T9B • Fading, Multipath distortion • Picket fencing is a term commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting. • If a station reports that your signals were strong just a moment ago, but now they are weak or distorted, try moving a few feet, random reflections may be causing multi-path distortion.

15. Radio waves, propagation, and antennas T9B • Fading, Multipath distortion (cont) • The most likely cause of sudden bursts of tones or fragments of different conversations that interfere with VHF or UHF signals is when strong signals are overloading the receiver and causing undesired signals to be heard. • Reflections • A way to reach a distant repeater if buildings or obstructions are blocking the direct line of sight path is to try using a directional antenna to find a path that reflects signals to the repeater.

16. Radio waves, propagation, and antennas T9B • Radio horizon, Terrain blocking • The radio horizon is the point where radio signals between two points are blocked by the curvature of the Earth. • VHF and UHF Radio signals usually travel about a third farther than the visual line of sight distance between 2 stations because the Earth seems less curved to radio waves than to light.

17. Radio horizon distance • The distance, D1 to the radio horizon for the transmitter is 1.415 times the square root of h1 (feet). • The theoretical maximum line-of-sight distance between two elevated points, presumably the transmitter (h1) and the receiver (h2), is the sum of the two distances to the radio horizon (D1 + D2).

18. Radio waves, propagation, and antennas T9B • Wavelength vs. penetration • UHF signals often work better inside of buildings than VHF signals since the shorter wavelength of UHF signals allows them to more easily penetrate urban areas and buildings. • [This means 440 mHz (70 centimeters) signals, being UHF have a better chance of penetration inside buildings than 144 mHz ( 2-meters) signals do.]

19. Radio waves, propagation, and antennas T9B • Antenna orientation • If the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization signals could be as much as 100 times weaker. • A good thing to remember when using your hand-held VHF or UHF radio to reach a distant repeater is to keep the antenna as close to vertical as you can.

20. Radio waves, propagation, and antennas T9C • Feedline types, Losses vs. frequency, matching and power transfer • Coaxial cable is used more often than any other feed line for amateur radio antenna systems because it is easy to use and requires few special installation considerations. • The characteristic impedance of the most commonly used coaxial cable in typical amateur radio installations is 50 Ohms.

22. Radio waves, propagation, and antennas T9C • SWR concepts • In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmitter. • It is important to have a low SWR in an antenna system that uses coaxial cable feedline to allow the efficient transfer of power and reduce losses. • A reading on a SWR meter of 1 to 1 (1:1) indicates a perfect impedance match between the antenna and the feed line.

23. Radio waves, propagation, and antennas T9C • Measuring SWR • A Directional wattmeter could be used to determine if your feedline and antenna are properly matched.

24. Radio waves, propagation, and antennas T9C • SWR concepts (cont) • A loose connection in your antenna or feedline might be indicated by erratic changes in SWR readings. • The SWR value, 2 to 1 (2:1) is where the protection circuits in most solid-state transmitters begin to reduce transmitter power. • The power lost in a feed line is converted into heat by losses in the line.

25. The Antenna Tuner “Antenna Tuners” do not really tune antennas. They provide an impedance match between the transmitter and antenna system.

26. Radio waves, propagation, and antennas T9C • Weather protection • Losses can increase dramatically in older coaxial cables that are exposed to weather and sunlight for several years. • The outer sheath of most coaxial cables is black in color because black provides protection against ultraviolet damage. • Feedline failure modes • Moisture contamination is the most common reason for failure of coaxial cables.

27. Take Aways • Vertical antenna perpendicular to earth • Horizontal antenna parallel to earth • Beams concentrate signals in one direction • Quad, Yagi, and Dish are directional antennas • Rubber duck antenna not as effective as full sized • 10-20 times reduction in signal strength inside car with rubber duck versus outside antenna

28. Take Aways (cont) • Mag mount antenna good efficiency in mobile • Lower angle of radiation … 5/8 has more gain than 1/4 wavelength • Half-wave dipole shorter when frequency increases • 146 mHz quarter-wave … 19 inches • Half-wave 6-meter dipole 112 inches • Dummy load … no interferring radiation when testing

29. Take Aways (cont) • VHF/UHF signals not reflected by ionsphere … not good for long distances • Hear VHF long distance … sporadic E reflection in ionsphere • Rapid fluttering from mobiles stations … picket fencing is term • You were strong, now weak … move a few feet • Strong overloading receiver … sudden bursts of tones or fragments of conversations • Directional antenna to reach distant repeater if buildings or obstructions block direct LOS

30. Take Aways (cont) • Coax cable most used feed line due to ease of use and few special installation considerations • Coax is commonly 50 ohms • SWR … load matching to a transmitter • For efficient transfer of power and reduction of loss, low SWR important • One to one … 1:1 … perfect match • Directional wattmeter used for feedline and antenna matching

31. Take Aways (cont) • Loose connections can cause erratic SWR readings • SWR of 2:1 where some protection circuits reduce power • Power lost in feed line converts to heat by losses in the line • Losses increase with older coax exposed to weather • Black cover offers protection against untraviolet damage • Moisture is most common cause of failure for coax

32. Take Aways (cont) • Two points blocked by curvature of earth is radio horizon • VHF/UHF signals travel about a third farther than visual LOS … earth less curved to radio waves than light • UHF signals penetrate urban areas/building … shorter wavelength • Cross polarization weakens signals about 100 times • Keep HT VHF/UHF antenna vertical

33. Element 2 Technician Class Question PoolT9 Valid July 1, 2006 Through June 30, 2010

34. T9A01 What is a beam antenna? • An antenna built from metal I-beams • An antenna that transmits and receives equally well in all directions • An antenna that concentrates signals in one direction • An antenna that reverses the phase of received signals

35. T9A02 What is an antenna that consists of a single element mounted perpendicular to the Earth's surface? • A conical monopole • A horizontal antenna • A vertical antenna • A traveling wave antenna

36. T9A03 What type of antenna is a simple dipole mounted so the elements are parallel to the Earth's surface? • A ground wave antenna • A horizontal antenna • A rhombic antenna • A vertical antenna

37. T9A04 What is a disadvantage of the "rubber duck" antenna supplied with most hand held radio transceivers? • It does not transmit or receive as effectively as a full sized antenna • It is much more expensive than a standard antenna • If the rubber end cap is lost it will unravel very quickly • It transmits a circular polarized signal

38. T9A05 How does the physical size of half- wave dipole antenna change with operating frequency? • It becomes longer as the frequency increases • It must be made larger because it has to handle more power • It becomes shorter as the frequency increases • It becomes shorter as the frequency deceases

39. T9A06 What is the advantage of 5/8 wavelength over 1/4 wavelength vertical antennas? • They are easier to match to the feed line than other types • Their radiation pattern concentrates energy at lower angles • They pick up less noise • Their radiation pattern concentrates energy at higher angles

40. T9A07 What is the primary purpose of a dummy load? • It does not radiate interfering signals when making tests • It will prevent over-modulation of your transmitter • It keeps you from making mistakes while on the air • It is used for close in work to prevent overloads

41. T9A08 What type of antennas are the quad, Yagi, and dish? • Antennas invented after 1985 • Loop antennas • Directional or beam antennas • Antennas that are not permitted for amateur radio stations

42. T9A09 What is one type of antenna that offers good efficiency when operating mobile and can be easily installed or removed? • A microwave antenna • A quad antenna • A traveling wave antenna • A magnet mount vertical antenna

43. T9A10 What is a good reason not to use a "rubber duck" antenna inside your car? • Signals can be 10 to 20 times weaker than when you are outside of the vehicle • RF energy trapped inside the vehicle can distort your signal • You might cause a fire in the vehicle upholstery • The SWR might increase

44. T9A11 What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? • 112 inches • 50 inches • 19 inches • 12 inches

45. T9A12 What is the approximate length, in inches, of a 6-meter 1/2 wavelength wire dipole antenna? • 6 inches • 50 inches • 112 inches • 236 inches

46. T9B01 Why are VHF/UHF signals not normally heard over long distances? • They are too weak to go very far • FCC regulations prohibit them from going more than 50 miles • VHF and UHF signals are usually not reflected by the ionosphere • They collide with trees and shrubbery and fade out

47. T9B02 What might be happening when we hear a VHF signal from long distances? • Signals are being reflected from outer space • Someone is playing a recording to us • Signals are being reflected by lightning storms in our area • A possible cause is sporadic E reflection from a layer in the ionosphere

48. T9B03 What is the most likely cause of sudden bursts of tones or fragments of different conversations that interfere with VHF or UHF signals? • The batteries in your transceiver are failing • Strong signals are overloading the receiver and causing undesired signals to be heard • The receiver is picking up low orbit satellites • A nearby broadcast station is having transmitter problems

49. T9B04 What is the radio horizon? • The point where radio signals between two points are blocked by the curvature of the Earth • The distance from the ground to a horizontally mounted antenna • The farthest point you can see when standing at the base of your antenna tower • The shortest distance between two points on the Earth's surface

50. T9B05 What should you do if a station reports that your signals were strong just a moment ago, but now they are weak or distorted? • Change the batteries in your radio to a different type • Speak more slowly so he can understand your better • Ask the other operator to adjust his squelch control • Try moving a few feet, random reflections may be causing multi-path distortion.