SUBELEMENT T9 Antennas and feed lines [2 Exam Questions - 2 Groups] 1Antennas & Feedlines 2014

T9A – Antennas: vertical and horizontal polarization; concept of gain; common portable and mobile antennas; relationships between antenna length and frequency T9B – Feed lines: types of feed lines; attenuation vs. frequency; SWR concepts; matching; weather protection; choosing RF connectors and feed lines 2Antennas & Feedlines

Antenna Classifications Orientation – Horizontal – parallel to the Earth – Vertical – perpendicular to the Earth Directivity (Beam) – Yagi, Log Periodic, Quad, Dish Size – Wavelength – λ – ½ λ, ¼ λ, ⅝ λ, … 3Antennas & Feedlines

Horizontal Antennas Half Wavelength Dipole Antenna) 4Antennas & Feedlines Wavelength (meters) = F (MHz) ½λ Dipole length (inches) = Wavelength / 2 x 39 Half wavelength Meters to inches

½ λ Dipole Radiation 5Antennas & Feedlines Radiation pattern for a dipole placed ½ λ above ground looking down from above the antenna. Looks like a doughnut around the wire in 3D space. Pattern distorts to omnidirectional when placed low to the ground.

Vertical Antennas Quarter Wavelength Vertical 6Antennas & Feedlines Wavelength (meters) = F (MHz) ¼λ vertical length (inches) = Wavelength / 4 x 39 Quarter wavelength Meters to inches

Quarter Wave Vertical Radiation 7Antennas & Feedlines A side view of the radiation pattern of a 1/4 wave vertical. From above the pattern is round like a doughnut. A perfect ground would be the center of a metal car roof at VHF/UHF  Maximum Radiation Angle

Vertical Antenna 8Antennas & Feedlines Standard ¼ wave vertical has a feedpoint impedance of ~35 ohms Sloping ground radials downward raises feedpoint impedance

Beam Antennas Yagi Antenna 9Antennas & Feedlines Gain Boom Feedline Reflector Director Driven Element The reflector acts like a mirror The director acts like a lens

Yagi Radiation Pattern 10Antennas & Feedlines The yagi antenna focuses RF energy in one direction, giving the appearance of getting “free power.” This free power or Effective Radiated Power (ERP) can be expressed as antenna Gain in Decibels (dB) over a dipole (dBd) or isotropic resonator (dBi).

Yagi Radiation Pattern 11Antennas & Feedlines The yagi antenna focuses RF energy in one direction, giving the appearance of getting “free power.” This free power or Effective Radiated Power (ERP) can be expressed as antenna Gain in Decibels (dB) over a dipole (dBd) or isotropic resonator (dBi).

G9 - Antennas 12 Antennas & Feedlines Quad antenna

G9 - Antennas 13 Antennas & Feedlines Delta Loop

Antenna Traps Dipole, vertical and yagi antennas can contain tuned traps in their driven elements. The traps block (or trap) energy of a given frequency making a physically longer appear shorter electrically. 14Antennas & Feedlines In the dipole shown, any energy on the 15m band will stop at the 15m trap and the antenna will only appear to be the width of a 15m antenna. Similarly, 20m signals will stop at the 20m traps and only see the antenna between the traps. Only 40m signals will pass along the entire length.

Loaded Antennas “Rubber duck” antennas are loaded antennas where the antenna is wound into a coil to shorten it physically. This is not an efficient radiator and narrows the bandwidth but does allow portable operation. This is particularly important on the HF bands. 15Antennas & Feedlines The antennas on the left are called “screwdrivers” and use a motor and wiper inside the coil to adjust the amount of loading based on frequency. The center antenna has the whip attached with a “capacitance hat” to provide capacitance to counteract inductance in the load coil and improve performance.

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

T9A01 - What is a beam antenna? A. An antenna built from aluminum I-beams B. An omnidirectional antenna invented by Clarence Beam C. An antenna that concentrates signals in one direction D. An antenna that reverses the phase of received signals 17Antennas & Feedlines

T9A02 - Which of the following is true regarding vertical antennas? A. The magnetic field is perpendicular to the Earth B. The electric field is perpendicular to the Earth C. The phase is inverted D. The phase is reversed 18Antennas & Feedlines

T9A02 - Which of the following is true regarding vertical antennas? A. The magnetic field is perpendicular to the Earth B. The electric field is perpendicular to the Earth C. The phase is inverted D. The phase is reversed 19Antennas & Feedlines

T9A03 - Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface? A. A ground wave antenna B. A horizontally polarized antenna C. A rhombic antenna D. A vertically polarized antenna 20Antennas & Feedlines

T9A03 - Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface? A. A ground wave antenna B. A horizontally polarized antenna C. A rhombic antenna D. A vertically polarized antenna 21Antennas & Feedlines

T9A04 - What is a disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers? A. It does not transmit or receive as effectively as a full- sized antenna B. It transmits a circularly polarized signal C. If the rubber end cap is lost it will unravel very quickly D. All of these choices are correct 22Antennas & Feedlines

T9A04 - What is a disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers? A. It does not transmit or receive as effectively as a full-sized antenna B. It transmits a circularly polarized signal C. If the rubber end cap is lost it will unravel very quickly D. All of these choices are correct 23Antennas & Feedlines

T9A05 - How would you change a dipole antenna to make it resonant on a higher frequency? A. Lengthen it B. Insert coils in series with radiating wires C. Shorten it D. Add capacitive loading to the ends of the radiating wires 24Antennas & Feedlines

T9A05 - How would you change a dipole antenna to make it resonant on a higher frequency? A. Lengthen it B. Insert coils in series with radiating wires C. Shorten it D. Add capacitive loading to the ends of the radiating wires 25Antennas & Feedlines

T9A06 - What type of antennas are the quad, Yagi, and dish? A. Non-resonant antennas B. Loop antennas C. Directional antennas D. Isotropic antennas 26Antennas & Feedlines

T9A06 - What type of antennas are the quad, Yagi, and dish? A. Non-resonant antennas B. Loop antennas C. Directional antennas D. Isotropic antennas 27Antennas & Feedlines

T9A07 - What is a good reason not to use a “rubber duck” antenna inside your car? A. Signals can be significantly weaker than when it is outside of the vehicle B. It might cause your radio to overheat C. The SWR might decrease, decreasing the signal strength D. All of these choices are correct 28Antennas & Feedlines

T9A07 - What is a good reason not to use a “rubber duck” antenna inside your car? A. Signals can be significantly weaker than when it is outside of the vehicle B. It might cause your radio to overheat C. The SWR might decrease, decreasing the signal strength D. All of these choices are correct 29Antennas & Feedlines

T9A08 - What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? A. 112 B. 50 C. 19 D Antennas & Feedlines

Calculating Vertical Antenna Length 31 Radio Waves, Propagation and Antennas 2014 Precisely: F (MHz) = = Approximately : 146 MHz is the 2m band ¼ of 2m is 0.5m 1m is 39 inches, so 0.5m is 19.5 inches Note this is based on free space wavelength. A wave traveling through wire will be slower and have a shorter wavelength. A physical antenna will be smaller meter wavelength 2.05 meters / 4 x 39 inches = 20 inches

T9A08 - What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz? A. 112 B. 50 C. 19 D Antennas & Feedlines

T9A09 - What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna? A. 6 B. 50 C. 112 D Antennas & Feedlines

Calculating Dipole Antenna Length 34 Radio Waves, Propagation and Antennas 2014 Precisely: Approximately: 6m band ½ of 6 m is 3 m 1 meter is 39 inches, so 3 m is 117 inches Note this is based on free space wavelength. A wave traveling through wire will be slower and have a shorter wavelength. A physical antenna will be smaller F (MHz) = = 6 meter wavelength (6 meters / 2) x 39 inches = 117 inches

T9A09 - What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna? A. 6 B. 50 C. 112 D Antennas & Feedlines

Half Wavelength Dipole Antenna 36 Antennas & Feedlines

T9A10 - In which direction is the radiation strongest from a half-wave dipole antenna in free space? A. Equally in all directions B. Off the ends of the antenna C. Broadside to the antenna D. In the direction of the feed line 37Antennas & Feedlines

T9A10 - In which direction is the radiation strongest from a half-wave dipole antenna in free space? A. Equally in all directions B. Off the ends of the antenna C. Broadside to the antenna D. In the direction of the feed line 38Antennas & Feedlines

T9A11 - What is meant by the gain of an antenna? A. The additional power that is added to the transmitter power B. The additional power that is lost in the antenna when transmitting on a higher frequency C. The increase in signal strength in a specified direction when compared to a reference antenna D. The increase in impedance on receive or transmit compared to a reference antenna 39Antennas & Feedlines

T9A11 - What is meant by the gain of an antenna? A. The additional power that is added to the transmitter power B. The additional power that is lost in the antenna when transmitting on a higher frequency C. The increase in signal strength in a specified direction when compared to a reference antenna D. The increase in impedance on receive or transmit compared to a reference antenna 40Antennas & Feedlines

T9A12 - What is a reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service? A. It offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage B. It features a very high angle of radiation and is better for communicating via a repeater C. The 5/8 wavelength antenna completely eliminates distortion caused by reflected signals D. The 5/8 wavelength antenna offers a 10-times power gain over a 1/4 wavelength design 41Antennas & Feedlines

T9A12 - What is a reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service? A. It offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverage B. It features a very high angle of radiation and is better for communicating via a repeater C. The 5/8 wavelength antenna completely eliminates distortion caused by reflected signals D. The 5/8 wavelength antenna offers a 10-times power gain over a 1/4 wavelength design 42Antennas & Feedlines

T9A13 - Why are VHF or UHF mobile antennas often mounted in the center of the vehicle roof? A. Roof mounts have the lowest possible SWR of any mounting configuration B. Only roof mounting can guarantee a vertically polarized signal C. A roof mounted antenna normally provides the most uniform radiation pattern D. Roof mounted antennas are always the easiest to install 43Antennas & Feedlines

T9A13 - Why are VHF or UHF mobile antennas often mounted in the center of the vehicle roof? A. Roof mounts have the lowest possible SWR of any mounting configuration B. Only roof mounting can guarantee a vertically polarized signal C. A roof mounted antenna normally provides the most uniform radiation pattern D. Roof mounted antennas are always the easiest to install 44Antennas & Feedlines

T9A14 - Which of the following terms describes a type of loading when referring to an antenna? A. Inserting an inductor in the radiating portion of the antenna to make it electrically longer B. Inserting a resistor in the radiating portion of the antenna to make it resonant C. Installing a spring at the base of the antenna to absorb the effects of collisions with other objects D. Making the antenna heavier so it will resist wind effects when in motion 45Antennas & Feedlines

T9A14 - Which of the following terms describes a type of loading when referring to an antenna? A. Inserting an inductor in the radiating portion of the antenna to make it electrically longer B. Inserting a resistor in the radiating portion of the antenna to make it resonant C. Installing a spring at the base of the antenna to absorb the effects of collisions with other objects D. Making the antenna heavier so it will resist wind effects when in motion 46Antennas & Feedlines

G9C10 Which of the following is a Yagi antenna design variable that could be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth? A. The physical length of the boom B. The number of elements on the boom C. The spacing of each element along the boom D. All of these choices are correct 47

G9C10 Which of the following is a Yagi antenna design variable that could be adjusted to optimize forward gain, front-to-back ratio, or SWR bandwidth? A. The physical length of the boom B. The number of elements on the boom C. The spacing of each element along the boom D. All of these choices are correct 48

G9D01 What does the term "NVIS" mean as related to antennas? A. Nearly Vertical Inductance System B. Non-Visible Installation Specification C. Non-Varying Impedance Smoothing D. Near Vertical Incidence Sky wave 49

G9D01 What does the term "NVIS" mean as related to antennas? A. Nearly Vertical Inductance System B. Non-Visible Installation Specification C. Non-Varying Impedance Smoothing D. Near Vertical Incidence Sky wave 50

G9D04 What is the primary purpose of antenna traps? A. To permit multiband operation B. To notch spurious frequencies C. To provide balanced feed-point impedance D. To prevent out of band operation 51

G9D04 What is the primary purpose of antenna traps? A. To permit multiband operation B. To notch spurious frequencies C. To provide balanced feed-point impedance D. To prevent out of band operation 52

G9D05 What is the advantage of vertical stacking of horizontally polarized Yagi antennas? A. Allows quick selection of vertical or horizontal polarization B. Allows simultaneous vertical and horizontal polarization C. Narrows the main lobe in azimuth D. Narrows the main lobe in elevation 53

G9D05 What is the advantage of vertical stacking of horizontally polarized Yagi antennas? A. Allows quick selection of vertical or horizontal polarization B. Allows simultaneous vertical and horizontal polarization C. Narrows the main lobe in azimuth D. Narrows the main lobe in elevation 54

G9D06 Which of the following is an advantage of a log periodic antenna? A. Wide bandwidth B. Higher gain per element than a Yagi antenna C. Harmonic suppression D. Polarization diversity 55

G9D06 Which of the following is an advantage of a log periodic antenna? A. Wide bandwidth B. Higher gain per element than a Yagi antenna C. Harmonic suppression D. Polarization diversity 56

G9D10 Which of the following describes a Beverage antenna? A. A vertical antenna constructed from beverage cans B. A broad-band mobile antenna C. A helical antenna for space reception D. A very long and low directional receiving antenna 57

G9D10 Which of the following describes a Beverage antenna? A. A vertical antenna constructed from beverage cans B. A broad-band mobile antenna C. A helical antenna for space reception D. A very long and low directional receiving antenna 58

T9B – Feed lines types of feed lines; attenuation vs. frequency; SWR concepts; matching; weather protection; choosing RF connectors and feed lines 59Antennas & Feedlines

Load Matching Amateur transceivers have a 50 ohm output impedance Coax and antennas should be as close to 50 ohms as possible to insure maximum power transfer Any mismatch creates “standing waves” that can be measured with an SWR or directional watt meter An SWR of 1:1 indicates perfect power transfer As SWR increases above 2:1, modern transmitters will automatically reduce output to protect from damage All feed lines have “loss” that increases with frequency and length caused by resistance in the line Standing waves will eventually be either radiated or lost as heat in the feed line 60

61 Hardline, Heliex, and Coax Hard line Coax Air Core Hard line

Standing Waves 62

T9B01 - Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line? A. To reduce television interference B. To allow the efficient transfer of power and reduce losses C. To prolong antenna life D. All of these choices are correct 63Antennas & Feedlines

T9B01 - Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line? A. To reduce television interference B. To allow the efficient transfer of power and reduce losses C. To prolong antenna life D. All of these choices are correct 64Antennas & Feedlines

T9B02 - What is the impedance of the most commonly used coaxial cable in typical amateur radio installations? A. 8 ohms B. 50 ohms C. 600 ohms D. 12 ohms 65Antennas & Feedlines

T9B02 - What is the impedance of the most commonly used coaxial cable in typical amateur radio installations? A. 8 ohms B. 50 ohms C. 600 ohms D. 12 ohms 66Antennas & Feedlines

T9B03 - Why is coaxial cable used more often than any other feed line for amateur radio antenna systems? A. It is easy to use and requires few special installation considerations B. It has less loss than any other type of feed line C. It can handle more power than any other type of feed line D. It is less expensive than any other types of feed line 67Antennas & Feedlines

T9B03 - Why is coaxial cable used more often than any other feed line for amateur radio antenna systems? A. It is easy to use and requires few special installation considerations B. It has less loss than any other type of feed line C. It can handle more power than any other type of feed line D. It is less expensive than any other types of feed line 68Antennas & Feedlines

T9B04 - What does an antenna tuner do? A. It matches the antenna system impedance to the transceiver's output impedance B. It helps a receiver automatically tune in weak stations C. It allows an antenna to be used on both transmit and receive D. It automatically selects the proper antenna for the frequency band being used 69Antennas & Feedlines

T9B04 - What does an antenna tuner do? A. It matches the antenna system impedance to the transceiver's output impedance B. It helps a receiver automatically tune in weak stations C. It allows an antenna to be used on both transmit and receive D. It automatically selects the proper antenna for the frequency band being used 70Antennas & Feedlines

T9B05 - What generally happens as the frequency of a signal passing through coaxial cable is increased? A. The apparent SWR increases B. The reflected power increases C. The characteristic impedance increases D. The loss increases 71Antennas & Feedlines

T9B05 - What generally happens as the frequency of a signal passing through coaxial cable is increased? A. The apparent SWR increases B. The reflected power increases C. The characteristic impedance increases D. The loss increases 72Antennas & Feedlines

Connector Types 73Antennas & Feedlines

T9B06 - Which of the following connectors is most suitable for frequencies above 400 MHz? A. A UHF (PL-259/SO-239) connector B. A Type N connector C. An RS-213 connector D. A DB-25 connector 74Antennas & Feedlines

T9B06 - Which of the following connectors is most suitable for frequencies above 400 MHz? A. A UHF (PL-259/SO-239) connector B. A Type N connector C. An RS-213 connector D. A DB-25 connector 75Antennas & Feedlines

T9B07 - Which of the following is true of PL-259 type coax connectors? A. They are preferred for microwave operation B. They are water tight C. They are commonly used at HF frequencies D. They are a bayonet type connector 76Antennas & Feedlines

T9B07 - Which of the following is true of PL-259 type coax connectors? A. They are preferred for microwave operation B. They are water tight C. They are commonly used at HF frequencies D. They are a bayonet type connector 77Antennas & Feedlines

T9B08 - Why should coax connectors exposed to the weather be sealed against water intrusion? A. To prevent an increase in feed line loss B. To prevent interference to telephones C. To keep the jacket from becoming loose D. All of these choices are correct 78Antennas & Feedlines

T9B08 - Why should coax connectors exposed to the weather be sealed against water intrusion? A. To prevent an increase in feed line loss B. To prevent interference to telephones C. To keep the jacket from becoming loose D. All of these choices are correct 79Antennas & Feedlines

T9B09 - What might cause erratic changes in SWR readings? A. The transmitter is being modulated B. A loose connection in an antenna or a feed line C. The transmitter is being over-modulated D. Interference from other stations is distorting your signal 80Antennas & Feedlines

T9B09 - What might cause erratic changes in SWR readings? A. The transmitter is being modulated B. A loose connection in an antenna or a feed line C. The transmitter is being over-modulated D. Interference from other stations is distorting your signal 81Antennas & Feedlines

82 Coax Cable Signal Loss (Attenuation) in dB per 100ft LossRG-174RG-58RG-8XRG-213RG-69913LMR-400 O.D.0.100in0.195in0.242in0.405in0.270in0.405in 1MHz1.9dB0.4dB0.5dB0.2dB 0.3dB 10MHz3.3dB1.4dB1.0dB0.6dB 0.4dB0.5dB 50MHz6.6dB3.3dB2.5dB1.6dB1.4dB0.9dB 100MHz8.9dB4.9dB3.6dB2.2dB2.0dB1.4dB 200MHz11.9dB7.3dB5.4dB3.3dB2.8dB1.8dB 400MHz17.3dB11.2dB7.9dB4.8dB4.3dB2.6dB 700MHz26.0dB16.9dB11.0dB6.6dB5.6dB3.6dB3.5dB 900MHz27.9dB20.1dB12.6dB7.7dB6.0dB4.2dB3.9dB 1GHz32.0dB21.5dB13.5dB8.3dB6.1dB4.5dB4.1dB Imped50ohm 75ohm50ohm

T9B10 - What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables? A. There is no significant difference between the two types B. RG-58 cable has less loss at a given frequency C. RG-8 cable has less loss at a given frequency D. RG-58 cable can handle higher power levels 83Antennas & Feedlines

T9B10 - What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables? A. There is no significant difference between the two types B. RG-58 cable has less loss at a given frequency C. RG-8 cable has less loss at a given frequency D. RG-58 cable can handle higher power levels 84Antennas & Feedlines

T9B11 - Which of the following types of feed line has the lowest loss at VHF and UHF? A. 50-ohm flexible coax B. Multi-conductor unbalanced cable C. Air-insulated hard line D. 75-ohm flexible coax 85Antennas & Feedlines

T9B11 - Which of the following types of feed line has the lowest loss at VHF and UHF? A. 50-ohm flexible coax B. Multi-conductor unbalanced cable C. Air-insulated hard line D. 75-ohm flexible coax 86Antennas & Feedlines

End of SUBELEMENT T9 Antennas and feed lines 87Antennas & Feedlines 2014