DX6ARC - Amateur Radio Club of Capiz

[Information] : Where a question shows [Information]. All the information given below that question is OK

Isotropic Radiator and Antenna Gain : [Information]
1. An isotropic antenna is an ideal antenna that radiates its power uniformly in all directions. There is no actual physical isotropic antenna. However, an isotropic antenna is often used as a reference antenna for the antenna gain. The antenna gain is often specified in dBi, or decibels over isotropic.....An isotropic antenna is a theoretical antenna that radiates equally in all directions - horizontally and vertically with the same intensity .... The concept of an isotropic antenna is often used as a reference antenna for the antenna gain.
2. Antenna gain (G) is the relative measure of an antenna's ability to direct or concentrate radio frequency (RF) energy in a specific direction or pattern......
3. dBd refers to the antenna gain with respect to a reference dipole antenna. A reference half wavedipole antenna is defined to have 2.15 dBi of gain.
4. dBi means decibels relative to isotropic radiator and is a measurement of the gain of an antenna in a particular direction relative to an isotropic radiator (equal radiation in every direction).
Effective Radiated Power (ERP or EIRP) [Information]
1. The difference between ERP and EIRP is that ERP compares the actual antenna to a half-wave dipole antenna, while EIRP compares it to a theoretical isotropic antenna.
2. ERP (Effective Radiated Power) is the total power radiated by an actual antenna relative to a half-wave dipole rather than a theoretical isotropic antenna.... A half-wave dipole has a power gain of 1.64 (2.15 dB) compared to an isotropic antenna.
3. EIRP (Effective Isotropic Radiated Power) is the total power radiated by a hypothetical isotropic antenna in a single direction. It gives the signal strength in the direction of the antenna's strongest beam.
4. The effective radiated power (ERP or EIRP) is the gain of an antenna (with respect to an isotropic radiator) multiplied by its input power........ERP = input power x antenna gain.......For example, a highly directional antenna with a gain of 7 has an input power of 1-kW. Its ERP is therefore 7 kW
Field Strength of radiated waves is expressed in
1. ohms per meter
2. amps per meter
3. volts per meter
4. waves per meter
Grounded antennas are known as ________
1. marconi antennas
2. yagi antennas
3. earth antennas
4. copper antennas
Half wave dipole is also known as a _____ antenna ?
1. bipole
2. copper
3. hertz
4. polar
Why are guy wires cut in different lengths?
1. to increase the transmitter output
2. to help secure the antenna mast
3. to increase the strength of the signal
4. to prevent re-radiation of signals
The angles created by comparing the half power points on the main radiation lobe to its maximum power points of an antenna is known as
1. beamwidth
2. bandwidth
3. wavewidth
4. dipole width
Antennas : Band Width : Front to Back ratio : Gain : Radiation : [Information]
1. Band Width :
  Q : What is the power measurement level of an antenna considered as half power points on the main radiation lobe.
  A : 3db
2. Front-to-back ratio : The ratio of power gain between the front and rear of a directional antenna. Ratio of signal strength transmitted in a forward direction to that transmitted in a backward direction.
3. Gain : The gain of an antenna (in any given direction) is defined as the ratio of the power gain in a given direction to the power gain of a reference antenna in the same direction. It is standard practice to use an isotropic radiator as the reference antenna in this definition
4. Radiation : or antenna pattern describes the relative strength of the radiated field in various directions from the antenna at a constant distance.
What is the term used when referring to the space orientation of the electromagnetic wave being radiated by a transmitting system?
1. magnetic radiation
2. electro radiation
3. polarization
4. space radiation
The ratio of the power radiated by the antenna to the square of the current at the feedpoint is______
1. resistance of the antenna
2. gain of the antenna
3. power of the antenna
4. wattage of the antenna
Waveguide equivalents of tuned transmission lines is_______
1. balanced reactors
2. tuned lines
3. twin feeder
4. frequency line
Log Periodic Antenna (LP) : [Information]
1. Is a multi-element, directional antenna designed to operate over a wide band of frequencies and has the ability to provide directivity and gain.
2. The most common form of log-periodic antenna is the log-periodic dipole array or LPDA, The LPDA consists of a number of half-wave dipole driven elements of gradually increasing length.
3. With a LP Antenna, the length and spacing of the elements increases logarithmically from one end of the boom to the other.
4. They are capable of operating over a frequency range of 2:1. They are mainly used at the high frequency (HF) band of the spectrum. They are also used at very high frequency (VHF) and ultra high frequency (UHF) bands as TV antennas.
A device used to connect antenna to the output tank of a transmitter in order to prevent the dc supply from reaching the antenna
1. switch
2. balun
3. transformer
4. an antenna coupler
Transmission lines normally used for frequencies above 186Hz
1. parallel wire line
2. wire line
3. twin feeder
4. open feeder
What is the wavelength if the frequency used is 300MHz?
1. 1m
2. 2 m
3. 3 m
4. 4 m
What is the speed of electromagnetic waves in free space (m/s = meters per second)
1. 1x10 raised to 8 m/s (100,000,000 m/s)
2. 4x10 raised to 8 m/s (400,000,000 m/s)
3. 2x10 raised to 8 m/s (200,000,000 m/s)
4. 3x10 raised to 8 m/s (300,000,000 m/s)
Gain of an antenna is a measurement of ratio of output power in an antenna in a certain direction compared to that of____
1. dipole antenna
2. vertical antenna
3. hybrid antenna
4. multi antenna
The unit of measurement of antenna field strength is
1. electromagnetic line of force
2. electromagnetic line of capacitance
3. electromagnetic line of inductance
4. electromagnetic line of current
Antennas which are grounded are know as _____
1. earth antennas
2. radial antennas
3. marconi antennas
4. dipole antennas
In order to effectively lengthen a Marconi type antenna top loading is
1. placing a inductance in series with the antenna
2. placing a capacitor in series with the antenna
3. lengthen the coaxial feeder.
4. add copper tube
What is coaxial cable ? [Information]
1. Coaxial cable is a type of cable that has an inner conductor surrounded by an insulating layer, surrounded by a conductive shielding. Many also have an insulating outer jacket
2. Coaxial cables are the most popular form of transmission line for getting our signals to and from our antennas.
3. Coaxial cable commonly used for Amateur Radio has an impedance of 50 ohms
Rhombic Antenna : [Information]
1. Also known as diamond antenna.....A horizontal antenna having four conductors forming a diamond or rhombus; usually fed at one apex (Impedance 600 Ω balanced) and terminated with a resistance or impedance at the opposite apex (the termination impedance is usually an 600 - 800 Ω ohm non inductive carbon resistor ).
2. The frequency range of operation of a Rhombic antenna is around 3MHz to 300MHz. This antenna works in HF and VHF ranges. The parameters (i.e., height above ground, leg length and angle between legs), govern the gain of the antenna for a specific frequency
3. The rhombic antenna is a highly directional array ideally-suited for medium to long haul circuits. Radiation angles vary with the design and ground coefficient
4. Having a 600 ohm balanced feeder, a balun can be used if connecting the feeder to a coaxial feeder....A Balun is a device used to connect a balanced line to an unbalanced line such as 50 ohm co- axial cable.
Rhombic Antenna : Advantages, Disadvantages and Applications : [Information]
1. Advantages : The following are the advantages of Rhombic antenna −
  Input impedance and radiation pattern are relatively constant :
  Multiple rhombic antennas can be connected :
  Simple and effective transmission :
2. Disadvantages : The following are the disadvantages of Rhombic antenna −
  Wastage of power in terminating resistor:
  Requirement of large space:
  Reduced transmission efficiency:
3. Applications : The following are the applications of Rhombic antenna −
  Used in HF communications:
  Used in Long distance sky wave propagations:
  Used in point-to-point communications:
What is parallel-conductor feed line?
1. two wires twisted around each other in a spiral
2. a center wire inside an insulating material which is covered by a metal sleeve or shield
3. a metal pipe which is as wide or slightly wider than a wavelength of the signal it carries
4. two wires side-by-side held apart by insulating rods
What is the unit of field intensity?
1. amp per meter (a/m)
2. ohm per meter (o/m)
3. volt per meter (v/m)
4. watt per meter (w/m)
The ratio of the voltage to the current along infinite line terminated in its own
1. characteristic impedance
2. resonant resistance
3. lower impedence
4. balanced resistance
Circuit or device that permits transmit and receive on one antenna ?
1. duplexer
2. resonant resistance
3. lower impedence
4. balanced resistance
A circuit device that permits two different transmitters to use one antenna
1. diplexer
2. duo switch
3. complexer
4. multi switch
On what tv channel does the 2nd harmonic of a 27MHz transmitter fall?
1. ch 1
2. ch 3
3. ch 4
4. ch 2
A plot of the relative strength or intensity of the antenna radiation as a function of the orientation in a given placed is called _______
1. electromagnetic pattern
2. dipole pattern
3. magnetic wave pattern
4. radiation pattern
The polarisation of an electromagnetic wave is defined by the direction of:
1. the propagation
2. the receiving antenna
3. the E field
4. the H field
The product of power fed to an antenna to its gain
1. power gain
2. output power
3. antenna power
4. signal gain
The ratio of current or voltage delivered to the antenna to the reflected back down the transmission line is known as____
1. power reflection
2. power factor
3. radiation resistance
4. reflection coefficient
What instrument is used to measure the received strength of a radio signal?
1. S Meter
2. A meter
3. Multi meter
4. Ohm meter
The unit used in indicating the difference between field strength of the fundamental radiation and the harmonic radiation
1. microvolts
2. A meter
3. Multi meter
4. Ohm meter
What is the effective radiated power of a transmitter fed with 1000W passing along a transmission line with a loss of 50W and an antenna gain of 3 ?
1. 1000w
2. 2000w
3. 3000W
4. 4000w
What power is fed to an antenna if the surge impedance of the transmission line is 500 Ohms and the line current is 3 Amperes?
1. 4500 watts or 4.5KW
2. 4000 watts or 4KW
3. 3500 watts or 3.5KW
4. 3000 watts or 3.0KW
Antenna : Parasitic Elements : Reflector : Director plus Driven element (which is not a parasitic element) : [Information]
1. Parasitic Elements : An antenna element that receives and re-emits energy from the driven element, which has an effect on the performance of the antenna.......The elements, which are added do not possess an electrical connection between them to the driven element or the feed. They are positioned so that they lie in the induction field of the driven element. Hence, they are known as parasitic elements.
2. Reflector : If one of the parasitic element, which is 5% longer than driven element, is placed close to the driven element is longer, then it acts as a concave mirror, which reflects the energy in the direction of the radiation pattern rather than its own direction and hence is known as a reflector.
3. Director : A parasitic element, which is 5% shorter than the driven element, from which it receives energy, tends to increase radiation in its own direction and therefore, behaves like convergent convex lens. This element is called as a director. A number of directors are placed to increase the directivity.
4. Note : Driven element : The antennas radiate individually and while in array, the radiation of all the elements sum up to form the radiation beam. All the elements of the array need not be connected to the feed. The dipole that is connected to the feed is known as a driven element.
Characteristic of an antenna referring to its capability of beaming energy in a narrow range of directions
1. antenna gain
2. beam width
3. directivity
4. angle of electrical energy
What is the unit of magnetic field intensity?
1. mag per meter
2. ohms per meter
3. amps per meter
4. volts per meter
What is the parameter that compares the concentration of power in the given antenna to that of some reference antenna
1. gain of the antenna
2. antenna signal strength
3. decibels
4. magnetic flux
Radio Wave [Infomation]
1. A radio wave is an electromagnetic wave, consisting of electric (E) and magnetic (H) fields at right angles to each other, both at right angles to the direction of travel.The E-field determines polarisation and field strength (example is vertically polarised)
2. When the electric field line is parallel to the earths surface the polarization is said to be horizontal
3. When the electric field lines in a plane are perpendicular to the earths surface, the polarization is said to be vertical
4. What is the relation in degrees of the electric and magnetic fields in an electromagnetic wave? 90 degrees
What is the resistance of free space?
1. 189 Ohms
2. 240 Ohms
3. 278 Ohms
4. 377 Ohms
The gain in the direction of one of the major lobes of the radiation pattern is known as
1. minor gain
2. major gain
3. absolute gain
4. directive gain
Antenna loading coil : [Information]
1. The loading coil is an inductor placed in series with an antenna element in order to lower the antenna‘s resonant frequency and reduce the physical length of the antenna
2. Base loading:the loading coil is often placed at the base of the antenna, between it and the transmission line
3. Center loading: For better efficiency, the loading coil is sometimes inserted in the center of the antenna element itself
4. Top loading : A loading coil may be used, on its own or in conjunction with a capacity hat, to tune the antenna to resonance at a lower frequency.
Anternna: Vertical wave, Horizontal wave and Polarization [Information].
1. Polarization of an antenna is determined by: The orientation of the electric field relative to the Earth's surface
2. What does vertical wave polarization mean?
  The electric lines of force of a radio wave are perpendicular to the Earth's surface
3. What does horizontal wave polarization mean?
  The electric lines of force of a radio wave are parallel to the Earth's surface
To couple coaxial line to a parallel wire line it is best to use a ________
1. coated copper wire
2. swr meter
3. balun
4. frequency meter
How many directly driven elements does a Yagi have ?
1. two
2. one
3. four
4. three
In a receiver circuit, the circuit that intercepts radio signals from the atmosphere is the ________
1. antenna system
2. RF gain
3. antenna tuner
4. coaxial cable
The ratio of the power density radiated in a particular direction by the antenna to the power density that would be radiated by an isotropic antenna is known as ?
1. directive gain.
2. positive gain
3. maximum
4. reliable gain
One way of minimizing fading is _____
1. use a large antenna
2. use a directional antenna
3. use of diversity antenna
4. use a beam antenna
An antenna that uses the ground to complete its resonant circuit _________
1. marconi
2. vertical
3. dipole
4. end fed
For transmission line load matching over a range of frequencies it is best to use ______
1. wire feeder
2. double stub
3. co axial feeder
4. ribbon feeder
Zoning is used with a dielectric antenna in order to reduce the _________
1. brightness of lens
2. glare of the lens
3. dullness of the lens
4. bulk of the lens
A plot of the relative strength or intensity of the antenna radiation as a function of the orientation in a given plane is called ?
1. energy pattern
2. radiation pattern
3. magnetic pattern
4. electro magnetic pattern
What is meant by antenna beamwidth ?
1. the amount of beamwidth occupied by the antenna
2. the height of the antenna
3. depends on the feeder used
4. the angle between the half power radiation points (-3 dB) points of the main lobe.
The antenna that exhibits vertical polarization is ______
1. vertical antenna
2. dipole antenna
3. end fed antenna
4. wire antenna
An antenna that is circularly polarized is the ______
1. spiral antenna
2. helical antenna
3. circular antenna
4. wire antenna
In an antenna array a parasitic element that is longer than the driven element is _______
1. base element
2. reflector
3. dipole element
4. director
Helical antennas are often used for satellite tracking at DHF because of _____
1. moon effect
2. discone shape
3. Faraday effect
4. small size
Yagi (Beam) Antenna [Information]
1. A Yagi (beam) antenna is a directional antenna consisting of a main driven element (typically a 1/2 wavelength dipole or folded dipole) and additional (parasitic) elements placed in front (director) and behind (refelector) of the main driven element to focus the energy for transmission in one direction, These parasitic elements increase the strength and narrow the antenna beam in the direction in front of the antenna. The more directors the Yagi has, the more forward antenna gain the antenna has. The practical gain of a Yagi is 6 to 20 dBi, depending on the number of elements.
2. Driven : The driven element of a Yagi is the feed point where the feed line is attached from the transmitter to the Yagi to perform the transfer of power from the transmitter to the antenna.
  A dipole driven element will be "resonant" when its electrical length is 1/2 of the wavelength of the frequency applied to its feed point.
3. Reflector : the Yagi antenna will generally only have one reflector, the reflector is around 5% longer than 1/2 wavelength and is behind the main driven element, i.e. the side away from the direction of maximum sensitivity...Typically a reflector will add around 4 or 5 dB of gain in the forward direction.
4. Director :The director(s) is the shortest of the parasitic elements and is placed in front of the main driven element.. The director(s) are resonant slightly higher in frequency than the driven element, and its length will be about 5% shorter.The director(s) length(s) can vary, depending upon the director spacing, the number of directors used in the antenna. Each director provides roughly 1 dB of gain.
On 7.045 mhz, the dimension of a half-wave dipole is_____
1. 22.53 feet
2. 33.75 feet
3. 66.63 feet
4. 132.5 feet
A radiator in an antenna array that is not directly connected to the output of the transmitter is_____
1. parasitic element
2. front element
3. rear element
4. ground element
What is the term used for an equivalent resistance which would dissipate the same amount of energy as that radiated from an antenna ?
1. electron resistance
2. antenna resistance
3. magnetic resistance
4. radiation resistance
The discone antenna is useful as a ________
1. HF receiving antenna
2. VHF receiving antenna
3. UHF receiving antenna
4. wire receiving antenna
On way of multibanding antennas is to install parallel tuned circuits, or traps. [Information]
1. For multiband operation traps are often used.Traps are tuned circuits that act somewhat like automatically switched inductors or capacitors, adding or subtracting from the length of the antenna according to the frequency of the signal.
2. A trap is a parallel Inductor/Capacitor combination, resonant on a particular frequency.
3. A trap is constructed from a capacitor and an inductor connected in parallel. It acts as an open switch on the frequency for which it is resonant. A trap is placed on each side of the dipole
4. The function of a trap is to automatically shorten an antenna for use on higher frequencies.
Parabolic Reflector - Dish - (Satellite) Antenna: [Information]
1. The parabolic reflector or dish antenna is the form of antenna which finds many uses in domestic satellite television reception, terrestrial microwave data links, general satellite communications and many more........
  Its size means that it is generally limited to use above 1GHz, although larger antennas may be used for frequencies down to about 100MHz.
2. A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish.
3. A dish antenna is usually operated with an unbalanced feed line. For satellite television reception, coaxial cable is used.
4. The most common feed types of parabolic antennas are : 1) Front feed(or Axial feed) : 2) Offset feed(or off-axis feed) : 3) Cassegrain design : 4) Gregorian design:
Mobile antennas: [Information]
1. For ¼-wavelength vertical antennas, a good ground plane is essential to good performance. Length in feet = 234 / f (MHz)..... 234 / 144 MHz = 1.62 feet
2. The antenna’s ground side (coaxial shield / mount connection) should be solidly electrically connected to the vehicle metal mass, such as the frame and body
3. Q: Why is a 5/8-wavelength vertical antenna better than a 1/4-wavelength vertical antenna for VHF or UHF mobile operations?..........A : 5/8-wavelength antenna has more gain and the angle of radiation is low
4. The 5/8-wavelength vertical antenna uses the standard formula : Feet = 585/f (MHz) or Meters = 178.308/f (MHz) ..... 585 / 144mhz = 4.06 feet
Trap Dipole: [Information]
1. This antenna uses tuned circuits (“traps”) to ‘disconnect’ the additional wire when used on the specified band this enables a single dipole to operate on multiple bands. The dipole length is determined by the lowest frequency band and the traps are used to electrically shorten the dipole for higher bands. Trap antennas can usually be designed to work well with two or three different HF bands, and designs combining fan and trap dipole features can provide more, with some trade-offs in efficiency and performance.
2. Sometimes the need to operate on two bands from a single antenna is required. One compromise antenna to use is a trapped dipole.
3. For multiband operation with a shortened radiator we can use the "trap dipole" or trap vertical.
4. The primary purpose of antenna traps is to permit multiband operation. Resonant LC circuits are used in parallel to isolate sections of the antenna effectively changing the antenna's "electrical length". This allows the antenna to be used for several bands rather than one static wavelength.
Velocity Factor (VF) : [Information]
1. Q : What is the velocity factor of a transmission line?
  A : The velocity factor is the term for the ratio of the actual speed at which a signal travels through a transmission line to the speed of light in a vacuum (free space).....The velocity factor of a radio wave in a vacuum is unity, or 100%
2. The dielectric materials used in the line determines the velocity factor of a transmission line....The velocity factor is based on the reciprocal of the square root of the dielectric constant of the material between the conductors so if it is mostly air it will approach 1.0.......Generally, the higher the velocity factor, the lower the loss through the cable.....
3. Co-Axial cables have velocity factors ranging from 0.65 to 0.85.....RG-8 coax has a 0.66 velocity factor which means the electromagnetic waves (signal) travel at 66% of the speed of light down the coax.....
4. 300 ohm (TV) twin lead velocity factor is around 0.82.......450 Ohm ladder line has a velocity factor between 0.9 and 0.95......Open-wire parallel transmission line (600 ohms) has a velocity factor around 0.98.
Folded Dipole: [Information]
1. The folded dipole antenna consists of a basic half-wavedipole, but with an added conductor connecting the two ends together, this makes a loop of wire to which feed is given at the center. As the ends appear to be folded back, the antenna is called a folded dipole antenna.
2. The folded dipole is well matched to 300 ohm balanced transmission lines, such as twin-feed ribbon cable
3. The folded dipole has a wider bandwidth than a single dipole
4. The folded dipole also exhibits a "balanced" feed characteristic whilst coaxial cable has an "unbalanced" characteristic....To match the 300 ohm impedance to 75/50 ohm coaxial feeder a 4 :1 balun can be used : Balun (balanced to unbalanced) is an electrical device that converts between a balanced signal and an unbalanced signal.
Half wave dipole: [Information]
1. The formula for calculating the approximate total top length of a half wave dipole...Half wave dipole total overall length in feet: 468 / frequency(MHz)...468/30 mhz = 15.6 ft (7 ft 8 in for one side)....For total top length in meters use 143/f(MHz)
2. The radiation pattern for a half wave dipole antenna shows that the direction of maximum radiation or sensitivity is at right angles to the axis of the RF antenna. The radiation falls to zero along the axis of the RF antenna
3. Radiation resistance of a half- wavelength dipole is 72 (73) ohms : A half wave dipole is often fed with a 50Ω feeder (co-axial).
4. The half wave dipole is a balanced antenna often fed with twin-lead feeder or open wire feeder.... A Balun is a device used to connect a balanced line to an unbalanced line such as 50 ohm co- axial cable.
The quarter wave vertical antenna can be used on all frequency bands including LF, MF, HF, VHF and beyond : [Information]
1. Quarter vertical approx height in feet.....234/frequency (MHz) ... 234/30 mhz = 7ft 8in
2. Has a omnidirectional radiation pattern (receiving or sending radio waves equally well in all directions)
3. The quarter wave vertical is an unblanced antenna and can be used with 50 ohm coaxial cable
4. The 1/4 vertical antenna is essentially 1/2 of a half wave dipole with the other “half” of the antenna a good grounding or counterpoise (raised above physical ground) system......The typical resonant feed point impedance of a 1/4 wavelength antenna is 30- 40 ohms.
What factors determine the characteristic impedance of a coaxial antenna feed line?
1. the diameter of the braid and the length of the line
2. the ratio of the diameter of the inner conductor to the diameter of the braid
Dipole matching: [Information]
1. if the minimum VSWR(Voltage Standing Wave Ratio) point occurs too low in frequency, the length of the antenna can be shortened...if the minimum VSWR occurs too high in frequency it means the antenna is too short and needs to be lengthened
2. The physical length of a half-wave dipole is slightly less than the theoretical length of half a wavelength dipole due to end effect. The speed of propagation in coaxial cable is slower than in air, so the wavelength in the cable is shorter.
3. the impedance of the dipole or beam changes as the antenna is raised or lowered to different heights above ground
4. The radio signal must be able to fit on the antenna as a standing wave. This condition of compatibility is called resonance. If a transmitter is to be able to "feed" energy into an antenna, the antenna must be resonant or it will not "take power" from the transmitter.
Wave Speed (c), Wavelength (λ) and Frequency (f) : [Information]
1. Wave speed is the distance a wave travels in a given amount of time, such as the number of meters it travels per second. Wave speed (and speed in general) can be represented by the equation: Speed = Distance / Time .......Wave speed is related to wavelength and frequency by the equation : Wave speed (c or v in m/s) = frequency (f in hz) x wavelength (λ in meters)..... c or v are sometimes used to denote wave speed.
  Radio waves travel at the speed of light 299,792,458 metres per second (m/s) : (300,000,000 meters per second).
2. Wavelength is the distance between corresponding points of adjacent waves.
  What is the wavelength of 144 MHz ?
  v (speed m/s) = f (frequency in Hz) x λ (wavelength in meters) therefore λ = v / f
  For 144 MHz, the wavelength 300,000,000 / 144,000,000 (Hz) = 2.08 meters
3. Frequency is the number of occurrences of a repeating event per unit of time.
  Frequency (Hz) = speed (m/s) / wavelength (Meters). What is the frequency of 40 meters? v = f x λ therefore f = v / λ = 300,000,000 / 40 = 7,500,000 Hz or 7,500,000 / 1,000,000 = 7.5 MHz
4. When using MHz and meters, a way to remember the relationship between speed, wavelength and frequency is to use 300 / meters = MHz
  Wavelength is 10 meters what is the frequency ? 300 / 10 meters = 30 MHz....Frequency is 30MHz what is the wavelength ? 300 / 30 MHz = 10 meters.
  Frequency 144 MHz = 300 / 144 = 2.08 meters : Meters 160 meters = 300 / 160 = 1.875 MHz
Antenna which is fed at a point of current is said to be:
1. voltage fed or low impedance fed
2. current fed or low impedance fed
3. capacitance fed
4. Resistance fed
An element in an antenna array that is directly connected to the output of the transmitter is known as _______
1. reflective element
2. driven element
3. parasitic element
4. directive element
The velocity factor of a transmission line depends on the _____
1. diameter of the wire used
2. the materials used
3. resistance of the feeder
4. dielectric constant of the material used
Cassegenian feed is used with a parabolic reflector to allow the_______
1. transfer of power from the transmitter to the antenna
2. a better match
3. feed to be place at a convenient point
4. less resistance
Top loading is sometimes used with an antenna in order to increase its _____
1. stability
2. signal
3. matching
4. effective height
The impedence measured at the input of a transmission line, when its length is infinite, is known as_______
1. resistive impedance
2. feeder impedance
3. characteristic impedance
4. line impedance
What device is used as an interface between the circuit and the outside electromagnetic field ?
1. speaker
2. antenna
3. telephone
4. headphones
Ground plane (Monopole) : Marconi : Vertical Antenna [Information]
1. Ground plane antenna is also known as a monopole antenna : A quarter-wave vertical dipole aerial in which the electrical image forming the other quarter-wave section is formed by reflection in a system of radially disposed metal rods or in a conductive sheet ... A quarter-wave monopole will have a radiation resistance of about 36.8 ohms if it is mounted above a good ground plane .... One feature of the ground-plane antenna is that it is omnidirectional.
2. Marconi antenna : If the antenna is connected to a good earth ground, it is called a Marconi antenna.
3. Vertical antennas are commonly installed at ground level, verticals can also be placed above the ground such as on the roof of a building in which case they would require counterpoises (radials). Such systems are sometimes described as "groundplanes"
4. If a ground plane cannot be made to earth, an artificial earth can be constructed of several quarter wave wires and be laid horizontally on the ground or buried in the earth.These horizontal wires at the base of the antenna are called radials.
The power density is immensely proportional to the square of the distance from the source. This is better known as the :
1. Murphy's Law
2. Radiation antenna Law
3. Inverse square Law
4. magnetic wave proportional Law
Which of the following is a common use of coaxial cable?
1. Carry RF signals between a radio and antenna
2. used for guying the antenna
3. Used instead of rope
4. To connect the transceiver to battery
What is used to effect good impedance match between the transmitter and the antenna?
1. coaxial cable
2. resistometer
3. antenna coupler
4. SWR meter
Approximately how long is the driven element of a Yagi antenna?
1. 1/4 wavelength
2. 1/3 wavelength
3. 1/2 wavelength
4. full wavelength
A device used to connect a balanced line to an unbalanced line ?
1. balun
2. balanced amplifier
3. balanced reactor
4. co-axial cable
Efficiency of an antenna : [Information]
1. The efficiency of an antenna is a ratio of the power delivered to the antenna relative to the power radiated from the antenna. A high efficiency antenna has most of the power present at the antenna's input radiated away. ... Being a ratio, antenna efficiency is a number between 0 and 1.
Electrical and Physical length of a half wave dipole : [Information]
1. A half-wave dipole has an electrical length of λ / 2 (wavelength divided by 2) .....Such a dipole has a feedpoint impedance consisting of 73Ω resistance and + 43Ω reactance.
Phased Vertical Antennas : [Information]
1. Two or more identical vertical antennas can be installed as a phased array. When excited by RF energy, gain is achieved by control of the directional pattern. ... Most effective spacing for a bi-directional array is 1/2 wave length....The number of antenna elements in the phased array antenna is determined by the directivity specification.
2. When two verticals are excited in phase the radiation is broadside to the plane of the verticals, offering substantial gain and bi-directional characteristics. Side nulls offer excellent signal cancellation to the undesired direction.
The equivalent of transmission line in higher or microwave frequencies:
1. ribbon cables
2. open wire feeder
3. tuned feeder
4. coaxial cables
Matching antennas to feed line....Delta : Gamma and Stub : [Information]
1. Delta : The delta matching system matches a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places spaced a fraction of a wavelength each side of element center.
2. Gamma : Is the name of an antenna matching system that matches an unbalanced feed line to an antenna by feeding the driven element both at the center of the element and at a fraction of a wavelength to one side of center.
3. Stub : Is the name of the matching system that uses a section of transmission line connected in parallel with the feed line at the feed point.
Voltage and Current Nodes : [Information]
1. On an antenna, the points of minimum current and minimum voltage are known as current and voltage nodes.
2. The presence of reflected power, along with the forward power, sets up a pattern of voltage maxima (loops) and minima (nodes) on the transmission line.
3. Half wave dipole has maximum current and minimum voltage at the center with minimum current and maximum voltage at the ends.
Antenna : [Information]
1. An antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. ... These time-varying fields radiate energy away from the antenna into space as a moving transverse electromagnetic field wave, a radio wave.
2. The radio signal must be able to fit on the antenna as a standing wave. This condition of compatibility is called resonance. If a transmitter is to be able to "feed" energy into an antenna, the antenna must be resonant or it will not "take power" from the transmitter.
3. Impedance : Maximum energy transfer of rf at the design frequency occurs when the impedance of the feed point is equal to the impedance of the feedline.
Feedline : In a radio antenna, the feed line (feedline), or feeder, is the cable or other transmission line that connects the antenna with the radio transmitter or receiver. In a transmitting antenna, it feeds the radio frequency (RF) current from the transmitter to the antenna, where it is radiated as radio waves [Information]
1. Open Wire (Parallel Transmission Line) : is two independant wires separated by insulated spacers
2. Twin-lead cable : is a two-conductor flat cable used as a balanced transmission line to carry radio frequency (RF) signals. It is constructed of two stranded copper or copper-clad steel wires, held a precise distance apart by a plastic (usually polyethylene) ribbon.
3. Coaxial cable : consists of a wire center conductor and a braided or solid metallic "shield" conductor, usually copper or aluminum surrounding it. The center conductor is separated from the outer shield by a dielectric, usually plastic foam, to keep the separation between the two conductors precisely constant
4. Waveguide : is used at microwave (SHF) frequencies, at which other types of feedline have excessive power losses. A waveguide is a hollow metallic conductor or pipe. It can have a circular or square cross-section.
Radiation resistance: [Information]
1. Radiation resistance is that part of an antenna's feedpoint resistance that is caused by the radiation of electromagnetic waves from the antenna, as opposed to loss resistance (also called Ohmic resistance) which generally causes the antenna and its surroundings to heat up.
2. The total of radiation resistance and loss resistance is the electrical feed point resistance of the antenna. For a half wave dipole antenna the radiation resistance will vary between approximately 60 and 90Ω for all practical heights on the HF bands.
Balanced and Unbalanced Feeder [Information]
1. Balanced feeder is a form of antenna feeder that can be used for feeding balanced antennas (i.e. antennas that do not have one connection taken to ground)...A dipole/doublet/folded dipole are a form of balanced antennas.
2. A balanced or twin feeder consists of two parallel conductors The currents flowing in both wires run in opposite directions but are equal in magnitude. As a result the fields from them cancel out and no power is radiated or picked up.
3. An unbalanced line is a transmission line, often coaxial cable, whose conductors have unequal impedances with respect to ground; as opposed to a balanced line....Examples of unbalanced antennas are Marconi / Ground Plane / Vertical when one side is connected to the vertical, the other is ‘earthed’, i.e. connected to the ground.
4. Coaxial feeder is an unbalanced feeder.... It is a type of unbalanced line, the shield conductor is usually connected to electrical ground. Coaxial cable's advantage is that the enclosing shield conductor isolates the cable from external electromagnetic fields, so it is very immune to interference.
Gains and Losses [Information]
1. Gains and Losses are expressed in dB's ..... 3dB x 2 times or a half : 6 dB x 4 times or a quarter.....9dB x 8 times or an eighth ..... 10dB x 10 times or a tenth etc...
2. Every 1dB of gain raises the output power 20%, where 3dB doubles the output power.......Every 1dB of loss in the system represent a 20% loss of power........Just as in gain, 3dB of loss represents a loss of 50% of power.
3. If a feeder has a 3dB loss at 14MHz and is fed with 200 watts only half (100 watts) will be radiated by the antenna....A 6dB feeder loss at 14MHz will result in only a quarter (50 watts) of the power being radiated from the antenna.
4. If an antenna has a gain of +3 dB and the feeder a -3 dB loss through the coax, the +3 dB gain of the antenna and the - 3dB of the coax (feeder) cancel each other out meaning a 100 watt station has an effective radiated power (ERP) of 100 watts.
SWR (Standing Wave Ratio) and VSWR (Voltage Standing Wave Ratio) [Information]
1. SWR is about impedance match, telling us how well the antenna or antenna system is matched to the transmitter......VSWR is the ratio of the highest voltage anywhere along the transmission line to the lowest.Amateur radio transceivers are designed to work with an impedance of 50 ohms (load), if we use 50 ohm coax cable to feed the transceiver power (signal) to a antenna which has 50 ohm impedance then all the power will be radiated by the antenna.......Since the voltage doesn't vary in an ideal system, its VSWR would be 1.0 (or, as commonly expressed, 1:1)
2. Any antenna impedance change will cause a mismatched of impedances which results in some of the power to be reflected back toward the source leading to peaks and valleys in the voltage at various times and distances along the feeder.....VSWR measures these voltage variances.........VSWR is measured as a ratio, i.e. 1:1 for no reflected power, 2:1, 3:1 and so forth. An open or a short circuit will be ∞:1.....The higher is the value of VSWR, the higher is the mismatch.....A low SWR means that the antenna is transmitting a satisfactory amount of RF (radio frequency) power instead of sending it back into the transmitter
3. If a feeder has a 3dB loss at 14MHz and is fed with 200 watts only half (100 watts) will be radiated by the antenna....A 6dB feeder loss at 14MHz will result in only a quarter (50 watts) of the power being radiated from the antenna.
4. If an antenna has a gain of +3 dB and the feeder a -3 dB loss through the coax, the +3 dB gain of the antenna and the - 3dB of the coax (feeder) cancel each other out meaning a 100 watt station has an effective radiated power (ERP) of 100 watts.
Transceiver (transmitter) output [Information]
1. On many modern transceivers, one side of the transmitter output is at the chassis-ground potential. This is said to make the output "unbalanced."
2. If we are feeding a balanced antenna such as a half-wave dipole with a coax cable, we could use a "balun" to transition between the "balanced" antenna and the "unbalanced" coaxial line ….. Lots of amateurs use coax with dipoles without using a balun.
A half wave dipole with a overall top length of 22ft and 2 inches (6.77 metres) would be suitable for use on the ____ meter band.
1. 10
2. 15
3. 20
4. 40
Properties of 1/8, 1/4 and 1/2 wavelength sections of feeders: Shorted and Open [Information]
1. Q: What impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end?
  A: An inductive reactance.
  
  Q: What impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end?
  A: A capacitive reactance.
2. Q: What impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?
  A: Very low impedance
  
  Q: What impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?
  A: Very high impedance
3. Q:What impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?
  A: Very high impedance
  
  Q: What impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?
  A: Very low impedance
Horn Antenna [Information]
1. Horn antenna: They are widely used at UHF and microwave frequencies, above 300 MHz to 40 GHz. The input impedance is slowly varying over this wide frequency range, allowing low voltage standing wave ratio (VSWR) over the wide bandwidth.
2. The horn antenna is used for the transmission and reception of microwave signals and has a gain between 10 - 25 dBi.
Helical Antenna [Information]
1. Helical (Helix) antenna, the conducting wire is wound in helical shape and connected to the ground plate with a feeder line…The frequency range of operation of helical antenna is around 30MHz to 3GHz.
2. This antenna can be used to include...transmission/reception of the Hf, VHF and up to microwave signals through the ionosphere, radiometry or satellite applications.
3. The benefits of the helical antenna is it has a wide bandwidth, is easily constructed, has a real input impedance, and can produce circularly polarized fields, that is the polarization of the helical antenna is circular (vertical or horizontal in equal parts).
Radio wave polarisation is defined by the orientation of the radiated:
1. magnetic field
2. electrical field
3. inductive field
4. capacitance field
73 de 4F3EW - 7 November 2021

DU6MOT • Aklan, Philippines

NTC Class A Element 9 (IX)