B-006
Subelement B-006
Section B-006-005
Section B-006-005
What does an SWR reading of 1:1 mean?
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Correct AnswerThe best impedance match has been attained
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An impedance transformer is needed at the antenna feed point
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An antenna tuner is needed at the transmitter
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Reflected power equals forward power
SWR is a measure of the impedance match in the antenna system. A Standing Wave Ratio (SWR) of '1 to 1' is an ideal condition indicating no reflected energy. The impedance of the load at the end of the transmission line matches the Characteristic Impedance of the line. Impedance Match has been achieved. A Standing Wave Ratio (SWR) of '1.5 to 1' would indicate a fairly good match, while a very high SWR would indicate a short-circuit or an open circuit somewhere along the transmission line.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What does an SWR reading of less than 1.5:1 mean?
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Correct AnswerA fairly good impedance match
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A serious impedance mismatch, something may be wrong with the antenna system
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An antenna gain of 1.5
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An impedance match that is too low
SWR is a measure of the impedance match in the antenna system. A Standing Wave Ratio (SWR) of '1.5 to 1' is a totally acceptable condition indicating little reflected energy. A '1 to 1' ratio would indicate a perfect match, while a very high SWR would indicate a short-circuit or an open circuit somewhere along the transmission line.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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What is the most likely cause of erratic readings on an SWR meter?
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Interference from electrical power lines
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Lack of a balun at the antenna feed point
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Transmitting into the wrong antenna
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Correct AnswerIntermittent connection in the antenna system
SWR is a measure of the impedance match in the antenna system. A 'jumpy' (erratic) reading resulting from the sometimes on, sometimes off electrical contact, would indicate a loose connection in the antenna system.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
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Which of the following can cause a high SWR reading?
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Replacing RG-213 coaxial cable with RG-58
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Grounding the shield of the coaxial cable at the building entrance
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Using a very long transmission line
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Correct AnswerAn open or short circuit in the antenna system
SWR is a measure of the impedance match in the antenna system. A very high SWR, indicating that most if not all energy sent up the line is reflected back, could indicate that a short-circuit or open circuit exists somewhere along the line. Alternatively, it might simply mean that the antenna is cut for a totally different frequency.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What is the main adverse effect due to operating with high SWR?
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Increased receive noise level
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Increased transmission line radiation
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Correct AnswerIncreased transmission line loss
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Increased common-mode current
'Standing Waves' result from the interaction of the forward power sent from the transmitter towards the antenna and the reverse power reflected back by an improper impedance match. The interaction produces a repeating pattern of voltage (and current) peaks and troughs along the line. Peaks in voltage and current result in additional losses. SWR is also known as 'Voltage Standing Wave Ratio (VSWR)': it is a measure of the peak voltage to the minimum voltage on the standing wave.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What instrument is useful in adjusting the physical length of an antenna?
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Capacitance meter
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Multimeter
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Correct AnswerAntenna analyzer
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Frequency meter
An "antenna analyzer" measures the impedance and the standing wave ratio of an antenna system. All such instruments can do so at a specific frequency, many can present graphical data over a range of frequencies.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
If the characteristic impedance of the transmission line does not match the antenna input impedance then:
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the antenna will not radiate any signal
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the SWR reading falls to 1:1
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Correct Answerstanding waves are produced in the transmission line
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heat is produced at the junction
'Standing Waves' result from the interaction of the forward power sent from the transmitter towards the antenna and the reverse power reflected back by an improper impedance match. The interaction produces a repeating pattern of voltage peaks and troughs along the line. SWR is also known as 'Voltage Standing Wave Ratio (VSWR)': it is a measure of the peak voltage to the minimum voltage on the standing wave.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
The result of the presence of standing waves on a transmission line is:
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perfect impedance match between transmitter and transmission line
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Correct Answerreduced transfer of RF energy to the antenna
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maximum transfer of energy to the antenna from the transmitter
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lack of radiation from the transmission line
What does an SWR meter measure to determine the SWR?
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Correct AnswerForward and reflected voltage
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Common-mode current
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Conductor temperature
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Radiated RF energy
'Standing Waves' result from the interaction of the forward power sent from the transmitter towards the antenna and the reverse power reflected back by an improper impedance match. The standing wave ratio can be determined from measurements of the forward and reflected voltages. If the reflected energy suffered a significant loss along the line, an SWR reading taken at the station will appear lower.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What information can be obtained with an antenna analyzer?
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Correct AnswerSWR of the antenna system over a range of frequencies
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Front-to-back ratio of the antenna
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Radiation pattern of the antenna
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Gain of the antenna
An "antenna analyzer" measures the impedance and the standing wave ratio of an antenna system. All such instruments can do so at a specific frequency, many can present graphical data over a range of frequencies.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
What is the effect of line loss on the SWR reading at the station?
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It has no effect, because forward and reflected power are both affected
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It decreases the SWR, because less power reaches the antenna
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Correct AnswerIt decreases the SWR, because reflected energy is attenuated
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It has no effect, because SWR compares voltages
'Standing Waves' result from the interaction of the forward power sent from the transmitter towards the antenna and the reverse power reflected back by an improper impedance match. The standing wave ratio can be determined from measurements of the forward and reflected voltages. If the reflected energy suffered a significant loss along the line, an SWR reading taken at the station will appear lower.
Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.
Tags: none
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