Technician Technician License License Class Class Gordon West Gordon West Technician Class Manual Technician Class Manual Pages 132-141 Pages 132-141 Bandwidth & Interference Bandwidth & Interference Presented by Presented by Heart Of Texas Heart Of Texas Amateur Radio Club Amateur Radio Club (HOTARC) (HOTARC)
35
Embed
Technician License Class Gordon West Technician Class Manual Pages 132-141 Bandwidth & Interference Presented by Heart Of Texas Amateur Radio Club (HOTARC)
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Technician Technician License ClassLicense Class
Gordon West Gordon West Technician Class ManualTechnician Class ManualPages 132-141Pages 132-141
Bandwidth & Bandwidth & InterferenceInterference
Presented byPresented by
Heart Of Texas Heart Of Texas Amateur Radio ClubAmateur Radio Club
What are phone transmissions?What are phone transmissions?A.A. The use of telephones to set up an amateur The use of telephones to set up an amateur
radio contactradio contactB.B. A phone patch between amateur radio and A phone patch between amateur radio and
the telephone systemthe telephone system
C.C. Voice transmissions by radioVoice transmissions by radioD.D. Placing the telephone handset near a radio Placing the telephone handset near a radio
transceiver's microphone and speaker to transceiver's microphone and speaker to relay a telephone callrelay a telephone call
Which type of modulation is most commonly Which type of modulation is most commonly used for VHF and UHF voice repeaters?used for VHF and UHF voice repeaters?A.A. AMAMB.B. SSBSSBC.C. PSKPSK
D.D. FMFM
Think of the quiet quality of “FM broadcast radio.” Think of the quiet quality of “FM broadcast radio.” We mainly use SSB (narrower) on the HF bands, We mainly use SSB (narrower) on the HF bands, where the spectrum is so “precious.”where the spectrum is so “precious.”
What is the approximate bandwidth of a What is the approximate bandwidth of a frequency-modulated voice signal?frequency-modulated voice signal?A.A. Less than 500 HzLess than 500 HzB.B. About 150 kHzAbout 150 kHz
C.C. Between 5 and 15 kHzBetween 5 and 15 kHzD.D. More than 30 kHzMore than 30 kHz
Again, think of FM signals as over twice the Again, think of FM signals as over twice the width of SSB (which is 2-3 kHz).width of SSB (which is 2-3 kHz).
What is the normal bandwidth required for a What is the normal bandwidth required for a conventional conventional fast-scan TVfast-scan TV transmission using transmission using combined video and audio on the 70-centimeter combined video and audio on the 70-centimeter band? band?
A.A. More than 10 MHzMore than 10 MHz
B.B. About 6 MHzAbout 6 MHzC.C. About 3 MHzAbout 3 MHz
D.D. About 1 MHzAbout 1 MHz
Not just 6 kHz, butNot just 6 kHz, but 6000 kHz!!6000 kHz!!
What type of transmission is indicated by What type of transmission is indicated by the term the term NTSCNTSC? ? A.A. A Normal Transmission mode in Static CircuitA Normal Transmission mode in Static CircuitB.B. A special mode for earth satellite uplinkA special mode for earth satellite uplink
C.C. A standard A standard fast scanfast scan color color television signaltelevision signal
D.D. A frame compression scheme for TV signalA frame compression scheme for TV signal
Just remember that Just remember that NTSCNTSC is what we all grew up is what we all grew up watching! Today’s kids will only know digital TV!watching! Today’s kids will only know digital TV!
Which of the following is a form of Which of the following is a form of amplitude modulationamplitude modulation? ? A.A. Frequency modulationFrequency modulationB.B. Phase modulationPhase modulation
What is the primary advantage of single What is the primary advantage of single sideband over FM for voice transmissions? sideband over FM for voice transmissions?
A.A. SSB signals are easier to tune in SSB signals are easier to tune in than FM signalsthan FM signals
B.B. SSB signals are less likely to be bothered by SSB signals are less likely to be bothered by noise interference than FM signals.noise interference than FM signals.
C.C. SSB signals use much less bandwidth SSB signals use much less bandwidth than FM signalsthan FM signals
D.D. SSB signals have no advantages at all in SSB signals have no advantages at all in comparison to other modes.comparison to other modes.
What effect might a break in a cable television What effect might a break in a cable television transmission line have on amateur communications? transmission line have on amateur communications? A.A. A break cannot affect amateur communicationsA break cannot affect amateur communicationsB.B. Harmonic radiation from the TV may cause the Harmonic radiation from the TV may cause the
amateur transmitter to transmit off-frequencyamateur transmitter to transmit off-frequency
C.C. TV TV interferenceinterference may result when the may result when the amateur station is transmitting, or amateur station is transmitting, or interference may occur to the amateur interference may occur to the amateur receiverreceiver
D.D. The broken cable may pick up very high voltages The broken cable may pick up very high voltages when the amateur station is transmittingwhen the amateur station is transmitting
Think of it as a “leak”—unwanted signals either leak out or leak in.
What is the proper course of action to take when a What is the proper course of action to take when a neighbor reports that your radio signals are interfering neighbor reports that your radio signals are interfering with something in his home? with something in his home? A.A. You are not required to do anythingYou are not required to do anythingB.B. Contact the FCC to see if other interference reports Contact the FCC to see if other interference reports
have been filedhave been filed
C.C. Check your stationCheck your station and make sure it meets and make sure it meets the standards of good amateur practicethe standards of good amateur practice
D.D. Change your antenna polarization from vertical to Change your antenna polarization from vertical to horizontalhorizontal
What should you do first if someone tells you that your What should you do first if someone tells you that your transmissions are interfering with their TV reception? transmissions are interfering with their TV reception?
A.A. Make sure that Make sure that your stationyour station is operating is operating properly and that it does not cause properly and that it does not cause interference to your own televisioninterference to your own television
B.B. Immediately turn off your transmitter and contact the Immediately turn off your transmitter and contact the nearest FCC office for assistancenearest FCC office for assistance
C.C. Tell them that your license gives you the right to trans-mit Tell them that your license gives you the right to trans-mit and nothing can be done to reduce the interferenceand nothing can be done to reduce the interference
D.D. Continue operating normally because your equipment Continue operating normally because your equipment cannot possibly cause any interferencecannot possibly cause any interference
T3 D02 T3 D02 (pg 137)(pg 137)Who is responsible for taking care of the interference if Who is responsible for taking care of the interference if signals from your transmitter are causing front end signals from your transmitter are causing front end overload in your neighbor's television receiver? overload in your neighbor's television receiver? A.A. You alone are responsible, since your transmitter is You alone are responsible, since your transmitter is
causing the problemcausing the problemB.B. Both you and the owner of the television receiver Both you and the owner of the television receiver
share the responsibilityshare the responsibilityC.C. The FCC must decide if you or the owner of the The FCC must decide if you or the owner of the
television receiver is responsibletelevision receiver is responsible
D.D. The owner of the television receiver is The owner of the television receiver is responsibleresponsible
Note Gordon’s comments on this question.Note Gordon’s comments on this question.
What should you do if a "Part 15" device in your neighbor’s What should you do if a "Part 15" device in your neighbor’s home is causing harmful interference to your amateur home is causing harmful interference to your amateur station? station?
A.A. Work with your neighborWork with your neighbor to identify the offending to identify the offending devicedevice
B.B. Politely inform your neighborPolitely inform your neighbor about the rules that about the rules that require him to stop using the device if it causes require him to stop using the device if it causes interferenceinterference
C.C. Check your stationCheck your station and make sure it meets the and make sure it meets the standards of good amateur practicestandards of good amateur practice
D.D. All of these answers are correctAll of these answers are correct
Repeaters use cavity notch filters that have very sharp skirts to keep the transmitter from interfering with the receiver, since they’re both active at the same time on very close frequencies.
Want to “stop” (be deaf to) nearby transmitter on this
What type of filter should be connected to a TV What type of filter should be connected to a TV receiver as the first step in trying to prevent RF receiver as the first step in trying to prevent RF overload from a nearby 2-meter transmitter? overload from a nearby 2-meter transmitter? A.A. Low-pass filterLow-pass filterB.B. High-pass filterHigh-pass filterC.C. Band pass filterBand pass filter
D.D. Notch filterNotch filterJust like those notch filters used for repeaters, this sends the unwanted frequencies to ground.Note Gordon’s caution on pg 138.
What is the major cause of telephone interference? What is the major cause of telephone interference?
A.A. The telephone wiring is inadequateThe telephone wiring is inadequate
B.B. Tropospheric ducting at UHF frequenciesTropospheric ducting at UHF frequencies
C.C. The telephone was not equipped with The telephone was not equipped with adequate adequate interferenceinterference protection when protection when manufactured.manufactured.
D.D. Improper location of the telephone in the homeImproper location of the telephone in the home
What is the most likely cause of telephone What is the most likely cause of telephone interference from a nearby transmitter? interference from a nearby transmitter?
A.A. Harmonics from the transmitterHarmonics from the transmitter
B.B. The transmitter's signals are causing The transmitter's signals are causing the telephone to act like a radio the telephone to act like a radio receiverreceiver
What is a logical first step when attempting to What is a logical first step when attempting to cure a radio frequency interference problem in a cure a radio frequency interference problem in a nearby telephone?nearby telephone?
A.A. Install a low-pass filter at the transmitterInstall a low-pass filter at the transmitter
B.B. Install a high-pass filter at the transmitterInstall a high-pass filter at the transmitter
C.C. Install an RF filter at the telephoneInstall an RF filter at the telephoneD.D. Improve station groundingImprove station grounding
These filters are only effective if the signal is coming through the phone line. If it is being picked up by the telephone’s circuitry directly, there is no filter that can remove it.
Which of the following may be useful in Which of the following may be useful in correcting a radio frequency interference correcting a radio frequency interference problem? problem?
A.A. Snap-on ferrite chokesSnap-on ferrite chokes
B.B. Low-pass and high-pass filtersLow-pass and high-pass filters
C.C. Notch and band-pass filtersNotch and band-pass filters
D.D. All of these answers are correctAll of these answers are correct
What could be happening if another operator tells you What could be happening if another operator tells you he is hearing a variable high-pitched whine on the he is hearing a variable high-pitched whine on the signals from your signals from your mobilemobile transmitter? transmitter? A.A. Your microphone is picking up noise from an open Your microphone is picking up noise from an open
windowwindowB.B. You have the volume on your receiver set too highYou have the volume on your receiver set too highC.C. You need to adjust your squelch controlYou need to adjust your squelch control
D.D. The power wiring for your radio is picking The power wiring for your radio is picking up noise from the up noise from the vehicle'svehicle's electrical electrical systemsystem
What is the most likely cause of sudden bursts of What is the most likely cause of sudden bursts of tones or fragments of different conversations that tones or fragments of different conversations that interfere with VHF or UHF signals? interfere with VHF or UHF signals?
A.A. The batteries in your transceiver are failingThe batteries in your transceiver are failing
B.B. Strong signalsStrong signals are overloading the are overloading the receiver and causing undesired signals receiver and causing undesired signals to be heardto be heard
C.C. The receiver is picking up low orbit satellitesThe receiver is picking up low orbit satellites
D.D. A nearby broadcast station is having transmitter A nearby broadcast station is having transmitter problemsproblems
What should you do if you receive a report that What should you do if you receive a report that your transmissions are causing splatter or your transmissions are causing splatter or interference on interference on nearby frequenciesnearby frequencies? ?
A.A. Increase transmit powerIncrease transmit power
B.B. Change mode of transmissionChange mode of transmission
C.C. Report the interference to the equipment Report the interference to the equipment manufacturermanufacturer
D.D. Check transmitter for Check transmitter for off frequencyoff frequency operation or spurious emissionsoperation or spurious emissions