Presentation on theme: "Technician License Class"— Presentation transcript:
1 Technician License Class Propagation, Antennas andFeed Lines
2 Propagation Radio waves travel in straight lines. Except: Reflection. Bouncing off reflective surface.Refraction.Gradual bending while traveling through atmosphere.Diffraction.Bending around edge of solid object.
3 Propagation Radio waves travel in straight lines. Line-of-sight. Radio horizon.Distance at which radio signals are blocked by curvature of the earth.Slightly greater than optical horizon.Refraction increases radio horizon by about 15%.
5 Propagation Multi-path. Radio waves reflected off of many objects arrive at receive antenna at different times.Picket fencing.
6 Propagation Radio waves can pass through openings in solid objects. Longest dimension of opening at least 1/2λ.Because of shorter wavelength, UHF signals can pass through buildings better than VHF signals.
7 Propagation Tropospheric Ducting Radio waves can travel for long distances along boundaries of different temperature air layers.Propagation of 300 miles or more on VHF or UHF.
8 Change the batteries in your radio to a different type T3A01 -- What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted?Change the batteries in your radio to a different typeTurn on the CTCSS toneAsk the other operator to adjust his squelch controlTry moving a few feet or changing the direction of your antenna if possible, as reflections may be causing multi-path distortion
9 VHF signals lose power faster over distance T3A02 -- Why are UHF signals often more effective from inside buildings than VHF signals?VHF signals lose power faster over distanceThe shorter wavelength allows them to more easily penetrate the structure of buildingsThis is incorrect; VHF works better than UHF inside buildingsUHF antennas are more efficient than VHF antennas
10 Flip-flopping Picket fencing Frequency shifting Pulsing T3A06 -- What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?Flip-floppingPicket fencingFrequency shiftingPulsing
11 Frequency shift due to Faraday rotation T3A08 -- Which of the following is a likely cause of irregular fading of signals received by ionospheric reflection?Frequency shift due to Faraday rotationInterference from thunderstormsRandom combining of signals arriving via different pathsIntermodulation distortion
12 Knife-edge diffraction Faraday rotation Quantum tunneling T3C05 -- Which of the following effects might cause radio signals to be heard despite obstructions between the transmitting and receiving stations?Knife-edge diffractionFaraday rotationQuantum tunnelingDoppler shift
13 Tropospheric scatter D layer refraction F2 layer refraction T3C06 -- What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?Tropospheric scatterD layer refractionF2 layer refractionFaraday rotation
14 T3C08 -- What causes tropospheric ducting? Discharges of lightning during electrical stormsSunspots and solar flaresUpdrafts from hurricanes and tornadoesTemperature inversions in the atmosphere
15 T3C10 -- What is the radio horizon? The distance over which two stations can communicate by direct pathThe distance from the ground to a horizontally mounted antennaThe farthest point you can see when standing at the base of your antenna towerThe shortest distance between two points on the Earth's surface
16 Radio signals move somewhat faster than the speed of light T3C11 -- Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?Radio signals move somewhat faster than the speed of lightRadio waves are not blocked by dust particlesThe Earth seems less curved to radio waves than to lightRadio waves are blocked by dust particles
17 Propagation The Ionosphere. The upper layers of the atmosphere are ionized by UV radiation from the sun.30 to 260 miles above the surface.
18 Propagation The Ionosphere. The ionosphere is divided into layers or regions.Each layer has unique characteristics.
19 Propagation The Ionosphere. Some radio frequency ranges (HF & lower VHF frequencies) will be reflected off of the ionosphere & return to earth.Called “skip”.Distances well beyond the range of line-of-sight.Several hundred to several thousand miles.Maximum of about 2500 miles for a single hop.Can have multiple hops.
20 Propagation The Ionosphere. The higher the amount of ionization, the better radio waves are reflected off of the ionosphere.Amount of ionization varies with time of day.Sunrise to sunset higher ionization level.Amount of ionization varies with sunspot activity.More sunspots higher ionization level.Larger sunspots higher ionization level.Number & size of sunspots varies over an 11-year cycle.Currently in declining portion of Cycle 24.
22 Propagation The Ionosphere. Skip is not really reflection (bouncing) but rather refraction (bending).The shorter the wavelength (higher frequency), the less the signal is refracted (bent).At some frequency, the wave is no longer bent enough to return to earth.Critical frequency.Skip normally occurs in the F-layer (F1 & F2).Can occur in the E-layer.
23 Propagation The Ionosphere. The highest frequency that can be used to communicate between 2 points is called the Maximum Useable Frequency (MUF).The lowest frequency that can be used to communicate between 2 points is called the Lowest Useable Frequency (LUF).MUF & LUF vary depending on amount of ionization of the ionosphere.
25 Propagation The Ionosphere. E-Layer Propagation. Sporadic-E. Aurora. Any time during solar cycle.Early summer & mid-winter10m, 6m, & 2m.Aurora.Rapid signal strength changes.Sounds fluttery or distorted.Primarily 6m.Meteor scatter.
26 Propagation The Ionosphere. The lowers regions of the ionosphere absorb radio waves.Primarily D-layer.Some absorption in E-layer.The longer the wavelength (lower frequency), the more absorption.
27 The stratosphere The troposphere The ionosphere The magnetosphere T3A11 -- Which part of the atmosphere enables the propagation of radio signals around the world?The stratosphereThe troposphereThe ionosphereThe magnetosphere
28 They are too weak to go very far T3C01 -- Why are direct (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?They are too weak to go very farFCC regulations prohibit them from going more than 50 milesUHF signals are usually not reflected by the ionosphereThey collide with trees and shrubbery and fade out
29 Signals are being reflected from outer space T3C02 -- Which of the following might be happening when VHF signals are being received from long distances?Signals are being reflected from outer spaceSignals are arriving by sub-surface ductingSignals are being reflected by lightning storms in your areaSignals are being refracted from a sporadic E layer
30 Signals from distances of 10,000 or more miles are common T3C03 (B)-- What is a characteristic of VHF signals received via auroral reflection?Signals from distances of 10,000 or more miles are commonThe signals exhibit rapid fluctuations of strength and often sound distortedThese types of signals occur only during winter nighttime hoursThese types of signals are generally strongest when your antenna is aimed west
31 Gray-line propagation T3C04 -- Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands?BackscatterSporadic ED layer absorptionGray-line propagation
32 10 meters 6 meters 2 meters 70 cm T3C07 -- What band is best suited for communicating via meteor scatter?10 meters6 meters2 meters70 cm
33 T3C09 -- What is generally the best time for long-distance 10 meter band propagation via the F layer?From dawn to shortly after sunset during periods of high sunspot activityFrom shortly after sunset to dawn during periods of high sunspot activityFrom dawn to shortly after sunset during periods of low sunspot activityFrom shortly after sunset to dawn during periods of low sunspot activity
34 All of these choices are correct T3C12 -- Which of the following bands may provide long distance communications during the peak of the sunspot cycle?Six or ten meters23 centimeters70 centimeters or 1.25 metersAll of these choices are correct
35 Antenna Fundamentals Definitions: Antenna: Converts an RF electrical signal into an electromagnetic wave (radio wave) or vice versa.Any electrical conductor can act as an antenna.Some sizes & configurations work better than others.Feed-line: Conducts the RF electrical signal to/from the antenna.a.k.a. – Transmission Line.
36 Antenna Fundamentals Definitions: Feed Point: Place where the feed-line is connected to antenna.Feed Point Impedance: Ratio of RF voltage to RF current at the feed point.If impedance is pure resistance (no reactance) then antenna is said to be “resonant”
37 Antenna Fundamentals Definitions: Antenna Elements: Conductive parts of an antenna.Driven Element: Element that feed-line is connected to.Driven Array: More than one driven element.Parasitic Element(s): Element(s) not directly connected to feed-line.
38 Antenna Fundamentals Polarization. An electromagnetic wave consists of an electric wave & a magnetic wave at right angles to each other.Polarization is the orientation of the electric wave with respect to the earth.
39 Antenna Fundamentals Polarization. If electric wave is horizontal (parallel to the ground), then wave is said to be horizontally polarized.If electric wave is vertical (perpendicular to the ground), then wave is said to be vertically polarized.
41 Antenna Fundamentals Polarization. The direction of the electric field is the same as the direction of the antenna element.Loop antennas & circular polarization are exceptions.If polarizations are not matched, reduced signal strength results.Polarization of sky wave signals (skip) is random & continuously changing.Elliptically polarized.Any polarization antenna may be used.
42 The modulation sidebands might become inverted 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 invertedSignals could be significantly weakerSignals have an echo effect on voicesNothing significant will happen
43 Electromagnetic Electrostatic Surface acoustic Magnetostrictive T3A07 -- What type of wave carries radio signals between transmitting and receiving stations?ElectromagneticElectrostaticSurface acousticMagnetostrictive
44 Digital modes are unusable T3A09 -- Which of the following results from the fact that skip signals refracted from the ionosphere are elliptically polarized?Digital modes are unusableEither vertically or horizontally polarized antennas may be used for transmission or receptionFM voice is unusableBoth the transmitting and receiving antennas must be of the same polarization
45 The orientation of the electric field T3B02 -- What property of a radio wave is used to describe its polarization?The orientation of the electric fieldThe orientation of the magnetic fieldThe ratio of the energy in the magnetic field to the energy in the electric fieldThe ratio of the velocity to the wavelength
46 T3B03 -- What are the two components of a radio wave? AC and DCVoltage and currentElectric and magnetic fieldsIonizing and non-ionizing radiation
47 Gravity waves Sound waves Radio waves Pressure waves T5C07 -- What is a usual name for electromagnetic waves that travel through space?Gravity wavesSound wavesRadio wavesPressure waves
48 T9A02 -- Which of the following is true regarding vertical antennas? The magnetic field is perpendicular to the EarthThe electric field is perpendicular to the EarthThe phase is invertedThe phase is reversed
49 Antenna Fundamentals Decibels. The difference in strength between 2 signals is often expressed in decibels (dB).Ratio between 2 valuesLogarithmic scale.
50 Antenna Fundamentals Decibels. Commonly used to: Specify gain of an amplifier.Specify gain of an antenna.Specify loss in a feed line.
51 Antenna Fundamentals Decibels. dB = 10 log10(P1/P2) Ratio between 2 valuesOne value is often a standard reference value.Logarithmic scale.Power ratio:dB = 10 log10(P1/P2)
52 Antenna Fundamentals dB Ratio 1.000 -1 0.794 -2 0.631 -3 0.501 -4 1.000-10.794-20.631-30.501-40.398-50.316-60.250-70.200-80.159-90.126-100.100dBRatio1.00011.25921.58531.99542.51253.16264.00075.01286.31097.9431010.00
53 T5B09 -- What is the approximate amount of change, measured in decibels (dB), of a power increase from 5 watts to 10 watts?2 dB3 dB5 dB10 dB
54 T5B10 -- What is the approximate amount of change, measured in decibels (dB), of a power decrease from 12 watts to 3 watts?-1 dB-3 dB-6 dB-9 dB
55 T5B11 -- What is the approximate amount of change, measured in decibels (dB), of a power increase from 20 watts to 200 watts?10 dB12 dB18 dB28 dB
56 Antenna Fundamentals Antenna Gain. Omni-directional antennas radiate equally in all directions.Directional antennas focus radiation in one or more specific directions.a.k.a. – Beam antennas.Gain is the apparent increase in power in a particular direction because energy is focused in that direction.Measured in decibels (dB)
57 Antenna Fundamentals Radiation Patterns. A way of visualizing antenna performance.The further the line is away from the center of the graph, the stronger the signal in that direction.
59 T9A11 -- What is meant by the gain of an antenna? The additional power that is added to the transmitter powerThe additional power that is lost in the antenna when transmitting on a higher frequencyThe increase in signal strength in a specified direction when compared to a reference antennaThe increase in impedance on receive or transmit compared to a reference antenna
60 Feed Lines and SWR Feed Lines. Feed lines are used for: Connecting RF signals between radio and antenna.Connecting RF signals between pieces of equipment.Feed lines are constructed using special materials and configurations.Maintain constant impedance.Minimize losses.
61 Feed Lines and SWR Feed Lines. Coaxial cable. Usually shortened to “coax”.Most popular type.Easy to work with.Low characteristic impedance.Typically 50Ω or 75Ω.Moderate to high loss.Loss varies with frequency.Higher frequency higher loss.
62 Feed Lines and SWR Feed Lines. Coaxial cable. Energy lost in feed line is converted to heat.Loss is primarily determined by size of cable & by insulating material.Larger diameter Lower loss.Air is lowest loss insulator.Foam dielectric coax has lower loss than solid dielectric coax because it has more air.Air-insulated hard line.
63 Feed Lines and SWR Feed Lines. Parallel-wire transmission line. Open-wire line, window line, twin lead.More difficult to work with.High characteristic impedance.Typically 300Ω to 600Ω.Very low loss.
64 Feed Lines and SWR Characteristic Impedance. Every transmission line has a characteristic impedance.Measure of how RF energy flows down the line.NOT the same as the ohmic resistance of the conductors that make up the line.
65 Feed Lines and SWR Characteristic Impedance. Coaxial cable. Characteristic impedance primarily determined by ratio of diameter of shield to diameter of center conductor.Larger ratio higher impedance.50Ω = RG-8, RG-8X, RG-58, RG-174.75Ω = RG-6, RG-11, RG-59.
66 Feed Lines and SWR Characteristic Impedance. Parallel-wire transmission line.Characteristic impedance determined by ratio of diameter of conductors to distance between them.Larger distance higher impedance.Smaller diameter higher impedance.
67 T7C07 -- What happens to power lost in a feed line? It increases the SWRIt comes back into your transmitter and could cause damageIt is converted into heatIt can cause distortion of your signal
68 T7C12 -- Which of the following is a common use of coaxial cable? Carrying dc power from a vehicle battery to a mobile radioCarrying RF signals between a radio and antennaSecuring masts, tubing, and other cylindrical objects on towersConnecting data signals from a TNC to a computer
69 T9B02 -- What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?8 ohms50 ohms600 ohms12 ohms
70 It is easy to use and requires few special installation considerations T9B03 -- Why is coaxial cable used more often than any other feed line for amateur radio antenna systems?It is easy to use and requires few special installation considerationsIt has less loss than any other type of feed lineIt can handle more power than any other type of feed lineIt is less expensive than any other types of feed line
71 The apparent SWR increases The reflected power increases T9B05 -- What generally happens as the frequency of a signal passing through coaxial cable is increased?The apparent SWR increasesThe reflected power increasesThe characteristic impedance increasesThe loss increases
72 Multi-conductor unbalanced cable Air-insulated hard line T9B11 -- Which of the following types of feed line has the lowest loss at VHF and UHF?50-ohm flexible coaxMulti-conductor unbalanced cableAir-insulated hard line75-ohm flexible coax
74 Feed Lines and SWR Standing Wave Ratio (SWR). If feed line impedance = antenna impedance:All energy is delivered to the antenna.Prefect match.SWR = 1:1.If feed line impedance ≠ antenna impedance:Some energy reflected back towards the source.Reflected energy often lost as heat.SWR = ZLine / ZAnt or SWR = ZAnt / ZLine
75 Feed Lines and SWR Standing Wave Ratio (SWR). Rule-of-thumb guidelines:1:1 = Perfect.2:1 = Acceptable.Most modern transmitters will automatically reduce transmitter output power when SWR is above 2:1.2:1 to 3:1= Useable (with tuner).Many transceivers have an internal antenna tuner which will match SWR’s up to 3:1.3:1 or more = Really bad.
76 T7C03 -- What, in general terms, is standing wave ratio (SWR)? A measure of how well a load is matched to a transmission lineThe ratio of high to low impedance in a feed lineThe transmitter efficiency ratioAn indication of the quality of your station’s ground connection
77 T7C04 -- What reading on an SWR meter indicates a perfect impedance match between the antenna and the feed line?2 to 11 to 31 to 110 to 1
78 T7C05 -- What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?2 to 11 to 26 to 110 to 1
79 T7C06 -- What does an SWR reading of 4:1 indicate? Loss of -4dBGood impedance matchGain of +4dBImpedance mismatch
80 To reduce television interference T9B01 -- Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line?To reduce television interferenceTo allow the efficient transfer of power and reduce lossesTo prolong antenna lifeAll of these choices are correct
81 T9B09 -- What might cause erratic changes in SWR readings? The transmitter is being modulatedA loose connection in an antenna or a feed lineThe transmitter is being over-modulatedInterference from other stations is distorting your signal
82 Practical Antenna Systems Dipoles and Ground Planes.Dipole.Most basic antenna.Two conductors, equal length.Feed line connected in the middle.Total length is 1/2 wavelength (1/2 λ).Length (feet) = 468 / Frequency (MHz).
83 Practical Antenna Systems Dipoles and Ground Planes.Dipole.
84 Practical Antenna Systems Dipoles and Ground Planes.Dipole.
85 Practical Antenna Systems Dipoles and Ground Planes.Dipole.
86 Practical Antenna Systems Dipoles and Ground Planes.Ground Plane.One half of a dipole that is oriented perpendicular to the Earth’s surface.Other half of the dipole is replaced by a ground-plane.EarthCar roof, trunk lid, or other metal surface.Radial wires.Length (feet) = 234 / Frequency (MHz).Omni-directional.
87 Practical Antenna Systems Dipoles and Ground Planes.Ground Plane.
88 Practical Antenna Systems Dipoles and Ground Planes.Ground Plane.
89 Practical Antenna Systems Dipoles and Ground Planes.Mobile antennas.Most mobile antennas are a variation of the ground plane.If antenna cannot be a full 1/4λ long, an inductor (coil) is added to make antenna electrically longer.Mounting antenna in center of roof gives most uniform radiation pattern.
90 Practical Antenna Systems Dipoles and Ground Planes.Mobile antennas.A popular mobile antenna for VHF & UHF is the 5/8λ vertical.Lower angle of radiation.Provides a gain of 1.5 dB over a 1/4λ vertical.
91 Practical Antenna Systems Dipoles and Ground Planes.“Rubber Duck” Antennas.Variation of the ground-plane.Commonly used on hand-held transceivers.Coil of wire enclosed in rubber (plastic) covering.Shorter than normal ground-plane.Much less efficient than full-sized ground-plane.Side note: Using a rubber duck antenna inside your vehicle is not a good idea because….Signals are weaker due to shielding by car body.
92 Practical Antenna Systems Loop Antennas.Loop of wire.Circumference is one wavelength (1λ) long.Circular, triangular (delta), or square (quad).Mounted vertically or horizontally.If mounted vertically, can be either vertically or horizontally polarized.
93 A horizontally polarized antenna A rhombic antenna T9A03 -- Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?A ground wave antennaA horizontally polarized antennaA rhombic antennaA vertically polarized antenna
94 It does not transmit or receive as effectively as a full-sized antenna T9A04 -- What is a disadvantage of the “rubber duck” antenna supplied with most handheld radio transceivers?It does not transmit or receive as effectively as a full-sized antennaIt transmits a circularly polarized signalIf the rubber end cap is lost it will unravel very quicklyAll of these choices are correct
95 Insert coils in series with radiating wires Shorten it T9A05 -- How would you change a dipole antenna to make it resonant on a higher frequency?Lengthen itInsert coils in series with radiating wiresShorten itAdd capacitive loading to the ends of the radiating wires
96 It might cause your radio to overheat T9A07 -- What is a good reason not to use a “rubber duck” antenna inside your car?Signals can be significantly weaker than when it is outside of the vehicleIt might cause your radio to overheatThe SWR might decrease, decreasing the signal strengthAll of these choices are correct
97 T9A08 -- What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?112501912
98 T9A09 -- What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna? 50112236
99 Equally in all directions Off the ends of the antenna T9A10 -- In which direction is the radiation strongest from a half-wave dipole antenna in free space?Equally in all directionsOff the ends of the antennaBroadside to the antennaIn the direction of the feed line
100 T9A12 -- What is a reason to use a properly mounted 5/8 wavelength antenna for VHF or UHF mobile service?It offers a lower angle of radiation and more gain than a 1/4 wavelength antenna and usually provides improved coverageIt features a very high angle of radiation and is better for communicating via a repeaterThe 5/8 wavelength antenna completely eliminates distortion caused by reflected signalsThe 5/8 wavelength antenna offers a 10-times power gain over a 1/4 wavelength design
101 Roof mounts have the lowest possible SWR of any mounting configuration T9A13 -- Why are VHF or UHF mobile antennas often mounted in the center of the vehicle roof?Roof mounts have the lowest possible SWR of any mounting configurationOnly roof mounting can guarantee a vertically polarized signalA roof mounted antenna normally provides the most uniform radiation patternRoof mounted antennas are always the easiest to install
102 T9A14 -- Which of the following terms describes a type of loading when referring to an antenna? Inserting an inductor in the radiating portion of the antenna to make it electrically longerInserting a resistor in the radiating portion of the antenna to make it resonantInstalling a spring at the base of the antenna to absorb the effects of collisions with other objectsMaking the antenna heavier so it will resist wind effects when in motion
103 Practical Antenna Systems Directional Antennas.Directional antennas focus or direct RF energy in a desired direction.Gain.Apparent increase in power in the desired direction (both transmit and receive).
104 Practical Antenna Systems Directional Antennas.The most common type of directional antenna is the beam.All beam antennas have parts called elements.Metal rods.Loops of wire.
105 Practical Antenna Systems Directional Antennas.Elements.Driven element.Connected to the radio by the feed line.Reflector element.Behind the driven element.Director element(s).In front of the driven element.Can have more then one director.
106 Practical Antenna Systems Directional Antennas.The most common type of beam antenna is the Yagi-Uda array.Normally just called a “Yagi”.Invented in 1926 by Dr. Shintaro Uda in collaboration with Dr. Hidetsugu Yagi.Rod-like elements.Similar to TV antennas.
107 Practical Antenna Systems Directional Antennas.Yagi antennas.Horizontally-polarized Yagi antennas are commonly used for long distance, weak signal CW & SSB communications on VHF & UHF.
108 Practical Antenna Systems Directional Antennas.Quad Antennas.Square wire loop elements.
109 Practical Antenna Systems Directional Antennas.Parabolic Dish.Large, round, curved reflector.Very high gain.
110 Right-hand circular Left-hand circular Horizontal Vertical T3A03 -- What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands?Right-hand circularLeft-hand circularHorizontalVertical
111 Change from vertical to horizontal polarization T3A05 -- When 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 polarizationTry to find a path that reflects signals to the repeaterTry the long pathIncrease the antenna SWR
112 T9A01 -- What is a beam antenna? An antenna built from aluminum I-beamsAn omnidirectional antenna invented by Clarence BeamAn antenna that concentrates signals in one directionAn antenna that reverses the phase of received signals
113 T9A06 -- What type of antennas are the quad, Yagi, and dish? Non-resonant antennasLoop antennasDirectional antennasIsotropic antennas
114 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Feed line selection and maintenance.Coax vs. Open Wire.Coax easier to use.VHF & UHF installations almost always use coaxial cable.Open wire has lower loss.Normally used only with HF wire antennas.
115 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Feed line selection and maintenance.Need to consider:Frequency.Length of cable.Power level.Budget.Loss.Larger cable generally has lower loss.Foam dielectric has lower loss.
117 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Feed line selection and maintenance.Coaxial cable must be protected.Worst enemy is moisture getting into the cable.Moisture increases loss in cable.Avoid nicks or cuts in outer jacket.Prolonged exposure to sunlight can result in tiny cracks in outer jacket which can admit moisture.Seal outside connections against moisture.Avoid sharp bends or turns.
118 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Coaxial Feed Line Connections.4 main types commonly used in amateur radio.UHF.Type “N”.BNC.SMA.
119 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Coaxial Feed Line Connections.UHF Connectors.Most common type.Up to 150 MHz.High power (>1.5 kW).Not constant impedance.Not weather resistant.Inexpensive.Plug = PL-259.Socket = SO-239.
120 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Coaxial Feed Line Connections.Type “N” Connectors.Up to 10 GHz.High power (>1.5 kW).Constant impedance.Both 50Ω and 75Ω versions.Weather resistant.Relatively expensive.Relatively difficult to install.
121 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Coaxial Feed Line Connections.BNC Connectors.Up to 4 GHz.Low power.Constant impedance.Both 50Ω and 75Ω versions.Commonly used on:Older hand held radios.Test equipment.
122 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Coaxial Feed Line Connections.SMA Connectors.Up to 18 GHz.Low power.Constant impedance.Only 50Ω available.Used on most new hand held radios.
123 Moisture contamination Gamma rays The velocity factor exceeds 1.0 T7C09 -- Which of the following is the most common cause for failure of coaxial cables?Moisture contaminationGamma raysThe velocity factor exceeds 1.0Overloading
124 Ultraviolet resistant jackets prevent harmonic radiation T7C10 -- Why should the outer jacket of coaxial cable be resistant to ultraviolet light?Ultraviolet resistant jackets prevent harmonic radiationUltraviolet light can increase losses in the cable’s jacketUltraviolet and RF signals can mix together, causing interferenceUltraviolet light can damage the jacket and allow water to enter the cable
125 It has more loss per foot It cannot be used for VHF or UHF antennas T7C11 -- What is a disadvantage of air core coaxial cable when compared to foam or solid dielectric types?It has more loss per footIt cannot be used for VHF or UHF antennasIt requires special techniques to prevent water absorptionIt cannot be used at below freezing temperatures
126 Practical Antenna Systems Soldering.A process in which two or more metal items are joined together by melting and flowing a filler metal into the joint.The filler metal is called solder.Flux is a material used to prevent the formation of oxides during the soldering process.
127 Practical Antenna Systems Soldering.Types of solder.Standard solder.Mixture of tin & lead.Ratio of tin to lead is adjusted for lowest melting temperature.63/37 or 60/40.Melting point is about 183°C (361°F).Lead-free solder.Mixture of tin & silver.Mixture of tin, silver, & copper.Melting point is about 40°C (72°F) hotter than standard solder.
128 Practical Antenna Systems Soldering.Types of flux.Resin.Used for electrical/electronic connections.Acid.Used for plumbing.NEVER use acid–core solder or acid flux to solder electronic connections!
129 Practical Antenna Systems Soldering.It takes a little bit of skill to make a good solder joint.Good solder joint is bright & shiny.If joint is not heated enough or if it is moved before it cools, it can result in a “cold solder joint”.Cold solder joint is dull & grainy-looking.
130 Acid-core solder Silver solder Rosin-core solder Aluminum solder T7D08 -- Which of the following types of solder is best for radio and electronic use?Acid-core solderSilver solderRosin-core solderAluminum solder
131 T7D09 -- What is the characteristic appearance of a cold solder joint? Dark black spotsA bright or shiny surfaceA grainy or dull surfaceA greenish tint
132 Practical Antenna Systems Practical Feed Lines and Associated Equipment.SWR Meters and Wattmeters.SWR Meter.a.k.a. – SWR bridge.Connects between transmitter & feed line.Displays amount of mismatch (SWR) between transmitter & antenna system.Antenna system = antenna + feed line.Make adjustments to antenna system to minimize mismatch.
133 Practical Antenna Systems Practical Feed Lines and Associated Equipment.SWR Meters and Wattmeters.SWR Meter.
134 Practical Antenna Systems Simple SWR Meter.Set to “FWD”.Adjust “CAL” for full scale reading (SET).Set to “REF” & read SWR.Practical Feed Lines and Associated Equipment.SWR Meters and Wattmeters.
135 Practical Antenna Systems Practical Feed Lines and Associated Equipment.SWR Meters and Wattmeters.Cross-needle SWR meter.No adjustments necessary.
136 Practical Antenna Systems Directional Wattmeter.Measures both forward power (PF) & reflected power (PR).SWR can then be calculated from PF & PR.Practical Feed Lines and Associated Equipment.SWR Meters and Wattmeters.
137 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Antenna Tuner.One way to make antenna matching adjustments is to use an antenna tuner.Antenna tuners are impedance transformers.When used appropriately they are effective.When used inappropriately all they do is make a bad antenna look good to the transmitter…the antenna is still bad.
138 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Antenna Tuner.a.k.a. -- Transmatch.Does NOT “tune” the antenna.Makes transmitter think all impedances are matched.
139 Practical Antenna Systems Measures antenna impedance (Z).Resistance (R).Reactance (X).Several other useful functions.Practical Feed Lines and Associated Equipment.Antenna analyzer.
140 Practical Antenna Systems Practical Feed Lines and Associated Equipment.Dummy Load.A non-radiating load used for testing.Non-inductive resistor & heatsink.Typically 50Ω.
141 In series with the feed line, between the transmitter and antenna T4A05 -- Where should an in-line SWR meter be connected to monitor the standing wave ratio of the station antenna system?In series with the feed line, between the transmitter and antennaIn series with the station's groundIn parallel with the push-to-talk line and the antennaIn series with the power supply cable, as close as possible to the radio
142 T7C01 -- What is the primary purpose of a dummy load? To prevent the radiation of signals when making testsTo prevent over-modulation of your transmitterTo improve the radiation from your antennaTo improve the signal to noise ratio of your receiver
143 A VTVM An antenna analyzer A Q meter A frequency counter T7C02 -- Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?A VTVMAn antenna analyzerA Q meterA frequency counter
144 Directional wattmeter T7C08 -- What instrument other than an SWR meter could you use to determine if a feed line and antenna are properly matched?VoltmeterOhmmeterIambic pentameterDirectional wattmeter
145 T7C13 -- What does a dummy load consist of? A high-gain amplifier and a TR switchA non-inductive resistor and a heat sinkA low voltage power supply and a DC relayA 50 ohm reactance used to terminate a transmission line