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Chapter 6
1 EMC defines the compatibility of electronic equipment to:
a. Static noise.
b.* Man made electromagnetic noise.
c. High supply voltages.
d. Battery operated equipment.
2 The one aim of EMC is to:
a.* Prevent pollution of the RF spectrum.
b. Encourage high power transmissions.
c. Discourage development of amateur radio.
d. Desensitize radio receivers.
3 Spurious oscillations caused by resonant of RF chokes can be
minimized by using:
a.* Low Q chokes.
b. Long power cables.
c. Non-inductive capacitors.
d. Non-resonant circuits.
4 unwanted signal is generated by a transmitter each time it is
keyed. It is removed by installing a small capacitor on the power
supply terminals. This unwanted signal is called:
a. Chirp.
b. Harmonic distortion.
c.* Spurious Oscillation.
d. Key clicks.
5 Self oscillations can occur when the output of an amplifier is
coupled to:
a. An antenna.
b. A dummy load.
c. A pi- filter network.
d.* The amplifier input.
6 An R.F. power amplifier is found to oscillate at its fundamental
frequency when the R.F. drive is removed. This effect is called:
a.* Self-oscillation.
b. Parasitic oscillation.
c. Harmonic oscillation.
d. Overload oscillation.
7 The cure for self oscillation in an audio amplifier is:
a. To increase voltage gain.
b. To filter the feedback signal.
c. To inductively couple the input stage.
d.* To introduce negative feedback.
8 The accuracy of the frequency of an amateur transmission can be
checked by using:
a. A sensitive dip-meter.
b.* Reference crystal marker oscillator.
c. An SWR meter.
d. An absorption wave meter.
9 An accurate crystal calibrator or a Frequency counter can be
used to determine the:
a. Deviation of a transmitter.
b. Exact output power of the carrier.
c.* Carrier frequency.
d. Sideband used on an SSB transceiver.
10 An inductively coupled absorption wave meter can commonly be
used to provide:
a.* Relative Field strength readings.
b. Standing wave ratios.
c. True power readings.
d. Accurate frequency readings.
11 Insufficient carrier suppression on an SSB Signal will cause:
a. distortion.
b. poor readability.
c. difficulty to set the receiver BFO.
d.* heterodynes on the audio frequencies.
12 An AM receiver tuned to the carrier frequency of an unmodulated
lower side band signal will hear:
a.* Nothing.
b. A distorted signal of 4KHz.
c. A clear tone.
d. A fully quiet carrier.
13 The carrier of an SSB signal is removed by a circuit known as:
a. A full wave rectifier.
b. A notch filter.
c.* A balanced modulator.
d. A discriminator.
14 To minimize mains hum on transmitted signals, all DC power
supplies should:
a. use a low DC voltage.
b. use a screened transformer.
c. be RF decoupled.
d.* use smoothing and regulator circuits.
15 The output of a full wave rectifier is connected to a series
regulator to:
a.* produce a constant output voltage.
b. reduce power dissipation.
c. filter out harmonics.
d. reduce the maximum current.
16 A 1000mfd capacitor across the DC output of a power supply:
a. Will increase any 100Hz ripple present.
b. Improve low frequency response.
c.* Remove AC rectified mains hum.
d. Decrease smoothed output voltage.
17 To minimize interference on adjacent channels, voice
frequencies should be kept below:
a. 500Hz.
b. 1KHz.
c.* 3Khz.
d. 5KHz.
18 So as not to cause unnecessary sideband splatter, the
percentage modulation of an AM signal must be kept below:
a. 25%
b. 50%
c. 75%
d.* 100%
19 What causes splatter?
a. Inadequate harmonic suppression in the final amplifier.
b.* Excessive bandwidth of a transmitter.
c. A poorly regulated transmitter power supply.
d. Insufficient drive to the final amplifier.
20 Intermodulation caused by a linear SSB amplifier is due to:
a.* Over driving the power level of the amplifier.
b. The operating frequency being to high.
c. Harmonic distortion.
d. Two modulating frequencies occurring at the same time.
21 Over-driving an SSB Linear amplifier can cause:
a. Improved communication.
b. A louder audio signal.
c. Lower power consumption.
d.* Distortion and splatter.
22 Which of the following might be effective at reducing the risk
of parasitic oscillations in a low power VHF output stage?
a.* Ferrite beads on the emitter leads of the power device.
b. Ferrite beads on the microphone cable.
c. Ferrite beads in series with the microphone.
d. Ferrite beads on the loudspeaker leads.
23 Parasitic oscillations can cause interference, they are:
a. Of a very low frequency.
b. Always twice the operating frequency.
c.* High in frequency but not related to the operating frequency.
d. Always three times the operating frequency.
24 Any non-linear device will produce:
a.* Mixing products.
b. Amplification.
c. Filtering.
d. Key-clicks.
25 When a synthesized VFO oscillator is not locked to the
reference frequency, it will be:
a. Stable.
b. Equal to the reference frequency.
c.* Unstable.
d. Equal to the operating frequency.
26 A Domestic Receiver having an IF of 455kHz and receiving a
signal on 945kHz, experiences strong breakthrough from someone on
the 160m band. This could be caused by second channel interference
of:
a. 1,810 MHz.
b. 1,825 MHz.
c. 1,835 MHz.
d.* 1,855 MHz.
27 EMC defines the compatibility of electronic equipment to:
a. Static noise.
b.* Man made electromagnetic noise.
c. High supply voltages.
d. Battery operated equipment.
28 one aim of EMC is to
a.* Prevent pollution of the RF spectrum.
b. Encourage high power transmissions.
c. Discourage development of amateur radio.
d. Desensitize radio receivers.
29 A typical source of polluting electromagnetic interference is
caused by:
a. Electric musical instruments.
b. Video signals.
c. Audio signals.
d.* Arcing electrical switches.
30 A band pass filter :
a. Allows all frequencies to pass.
b. Attenuates all frequencies.
c.* Allows signals between two frequencies to pass.
d. increases bandwidth of a receiver.
31 A band stop filter :
a. Allows all frequencies to pass.
b. Attenuates all frequencies.
c. decreases bandwidth of a receiver.
d.* Attenuates signals between two frequencies.
32 A low pass filter is most likely to be found in :
a. A crystal oscillator.
b.* The output stage of an HF transmitter.
c. A TV antenna amplifier.
d. A mixer.
33 A Low pass filter:
a.* Attenuates all signals above a known cut-off frequency.
b. Introduces harmonics.
c. Removes RF signals from an input signal.
d. Requires the use of high gain amplifiers.
34 A high pass filter:
a. Introduces harmonics.
b. Removes RF signals from an input signal.
c. Requires the use of high gain amplifiers.
d.* Attenuates all signals below a known cutoff frequency.
35 The insertion loss of a filter in a feed line is lowest when:
a. The filter impedance is lower than the feed line.
b.* The impedances are matched.
c. The filter cutoff frequency is low.
d. The cutoff frequency is high.
36 What is a circuit called which passes electrical energy above a
certain frequency, but blocks electrical energy below that
frequency?
a. An input filter.
b. A low-pass filter.
c.* A high-pass filter.
d. A band-pass filter.
37 A ferrite bead around a piece of wire:
a. Decreases the wires impedance.
b. Protects the wire from damage.
c.* Blocks the flow of RF signals along the wire.
d. Improves power dissipation.
38 A braid breaking toroidial choke wound onto a coax feed line:
a.* Passes anti-phase currents.
b. Blocks anti-phase currents.
c. Passes in-phase common mode noise.
d. Acts as a balun.
39 An interfering signal picked up by a long feed line can be
attenuated by :
a. Raising the receiving antenna.
b. Replacing the feed line.
c. Correctly matching the feed line.
d.* Installing a toroidial choke.
40 n R.F. power amplifiers the DC wiring associated with the tank
circuit often pass through ferrite beads. The beads:
a.* Introduce local low pass filters in the wiring.
b. Cause high power losses at VHF.
c. Act as fine tuning controls for the tank circuit.
d. Increase the "Q" of the tank circuit.
41 To eliminate RF pickup on the outer screen of a coax cable:
a. Install a balun.
b. Remove the earth from the coax cable.
c.* Install a braid breaker.
d. Use lower loss coax cable.
42 A TV antenna coax feed line picks up an amateur transmission.
This can be resolved by trying to install:
a. A masthead amplifier to override the incoming interference.
b.* A braid breaker.
c. New TV coax cable.
d. Filters on the mains power plugs.
43 t is found that interfering signals are being induced on the
braid of an antenna down lead to a domestic FM radio by a 144 MHz
transmitter. One possible solution is:
a.* To fit a braid breaker filter on the antenna down lead
b. Remove the 144MHz transmitter earth lead.
c. To increase the 144MHz transmitter power.
d. To fit the 144MHz transmitter with a low pass filter.
44 The antenna of an amateur station must be located in a position
that :
a. Is easily accessible.
b. Is in line with other power lines.
c.* High field strengths will not be induced in domestic premises.
d. Is below all other structures.
45 The location of the feeder of an amateur antenna must be
a. Of a precise length.
b.* Kept away from other cable routes.
c. Not visible.
d. Kept close to other telephone cables.
46 The earthing of an amateur station is required to:
a. Give the mains a good earth.
b.* Minimize undesired RF voltages on the feeder and equipment.
c. To prevent mains earth leakage.
d. Enable the equipment to operate from batteries.
47 When operating a mobile HF set at home from a battery supply
using the base antenna, there is no breakthrough problem. When
using the same arrangement with an earthed battery charger also
connected, breakthrough also occurs on an electronic organ. The
possible cause is:
a. the production of harmonics at the transmitter.
b. very strong received signals.
c.* Poor RF earthing.
d. RF earthing is too good.
48 To minimize harmonic radiation most HF transmitters contain
a. A high pass filter.
b. A notch filter.
c.* A low pass filter.
d. Band pass filters.
49 The purpose of a low pass filter is to:
a. attenuate all frequencies apart from a specific one.
b. pass all frequencies apart from a specific one.
c.* pass all signals below a specified frequency but attenuate
frequencies above it.
d. attenuate all signals below a specified frequency but pass
frequencies above it.
50 The purpose of a high pass filter is to:
a. attenuate all frequencies apart from a specific one.
b. pass all frequencies apart from a specific one.
c. pass all signals below a specified frequency but attenuate
frequencies above it.
d.* attenuate all signals below a specified frequency but pass
frequencies above it.
51 The term "trap" when discussing filters describes a device
which:
a. increases signal output.
b. narrows the bandwidth of an antenna.
c.* acts as a notch filer.
d. acts as a dummy load.
52 The length of a co-axial trap used to filter out an interfering
signal is:
a.* a quarter wave length of the interfering signal.
b. a random length.
c. the wave length of the transmitter signal
d. 250mm.
53 A notch filter one quarter wavelength long used to filter out
an interfering signal on the VHF bands is called:
a.* a stub.
b. a balun.
c. a transformer.
d. an antenna tuning unit.
54 A minimum SWR reading on the feed line from a transmitter to an
antenna indicates:
a. No power is being radiated by the antenna.
b. The transmitter is switched off.
c.* The transmitter and antenna are optimally matched.
d. The antenna is not tuned to the desired frequency.
55 The ideal SWR to indicate a good match is:
a.* 1:1
b. 1:2
c. 1:0
d. 1:5
56 The SWR meter uses diodes to sample the standing waves on the
antenna feeder. This can introduce:
a. Distortion.
b.* Low level harmonics.
c. Filtering of noise.
d. Limiting of RF output.
57 What is standing wave ratio?
a. The ratio of forward and reflected inductances on a feed line.
b. The ratio of forward and reflected resistances on a feed line.
c. The ratio of forward and reflected impedances on a feed line.
d.* The ratio of forward and reflected currents on a feed line.
58 The SWR of an antenna is the measurement of forward power
compared to:
a. Impedance.
b.* Reflected Power.
c. Capacitance.
d. Inductance.
59 The device used to match a long wire antenna to the output of a
transmitter is called:
a. an SWR meter.
b. an amplifier.
c. an inverter.
d.* antenna tuning unit.
60 The term transmatch refers to a type of:
a.* Antenna tuning unit.
b. Transistor.
c. Antenna.
d. Transmitter.
61 An antenna tuning unit "ATU" can often produce:
a.* Additional filtering to harmonic radiation.
b. Severe harmonic distortion.
c. Increased bandwidth.
d. Spurious oscillations.
62 The main reason for providing substantial mains earthing points
on radio frequency electronic equipment is:
a.* To provide a path for RF to be bypassed to earth.
b. To provide a path for fault currents to be passed to earth.
c. To bypass all spurious signals to earth.
d. To increase earth resistance.
63 Earthing the screen on a coaxial feed line will:
a.* Reduce pickup of an RF transmitted signal by the feed line.
b. Decrease earth resistance.
c. Increase earth resistance.
d. Eliminate noise.
64 The leads used to connect RF equipment to earth should be:
a. Connected to the nearest mains plug earth terminal.
b.* As short as possible.
c. Bare copper wire.
d. Connected via a suitable resistor.
65 In order to prevent the feeder to an antenna from radiating it
should be:
a. As long as possible.
b. Cut to an exact length.
c.* Screened and earthed.
d. Run close to the antenna.
66 One of the following is not a balanced antenna:
a. An inverted "V".
b.* A Vertical Quarter wave antenna.
c. A Dipole.
d. A Quad.
67 The open wire unscreened balanced feeder has normally:
a.* Neither wire earthed.
b. Both wires earthed.
c. One wire earthed.
d. An open circuit at the one end.
68 How does the amount of attenuation of a 2 meter radio frequency
signal passing through a coaxial cable differ from that of 160
meters?
a.* The attenuation is greater at 2 meters.
b. The attenuation is less at 2 meters.
c. The attenuation is the same at both frequencies.
d. The difference in attenuation depends on the emission type
being used.
69 As operating frequency decreases, what happens to conductor
loss in a feed line?
a.* It decreases.
b. It increases.
c. It remains the same.
d. It increases to infinity.
70 As operating frequency increases, what happens to dielectric
loss in a feed line?
a. It decreases.
b. It reduces to zero.elektromagnetiese
c. It remains the same.
d.* It increases.
71 The balun is used with antennas to:
a. Increase the power output of an antenna.
b.* Match a balanced antenna to an unbalanced feeder.
c. Reduce the antenna impedance.
d. Reduce the length of the antenna.
72 The device required to connect a co-axial cable to a dipole is:
a. A masthead amplifier.
b. An open wire feed line.
c.* A balun.
d. A resistor.
73 The ideal position for a balun is:
a. Close to the transmitter.
b. Halfway between the transmitter and the antenna.
c. In a screened box next to the SWR meter.
d.* At the connections of the antenna.
74 In considering the equipment and power levels in a densely
populated neighborhood, it might be advisable to:
a. Keep the antenna as low as possible.
b.* Locate the antenna as remotely as possible from the neighbors.
c. Use maximum output power.
d. Always use long feed lines.
75 The best place for an HF beam to minimize interference for an
amateur living in a semi detached house is:
a. On the joint chimney stack in the centre of the roof.
b. Overhanging the next door’s roof space.
c.* As high and far away as possible.
d. As low and far away as possible.
76 An antenna runs close and parallel to an overhead power line,
there may be the possibility of:
a. Harmonic generation.
b. 50 Hz modulation on all signals.
c.* Producing mains borne interference.
d. Cheap power.
77 A battery operated tape player picks up and reproduces an
amateur transmission. This is most like due to:
a.* High field strength of the transmission picked up by the
electronic circuits in the tape recorder.
b. An unlicensed operator.
c. Harmonics in the output signal.
d. The amateur transmission being off frequency.
78 A portable TV receiver only picks up interference from an
amateur station when running off a mains power supply cord. This
is possibly due to:
a.* Pickup of the signal in the connecting lead.
b. Low supply voltage.
c. An unearthed connector.
d. Poor signal reception.
79 The burglar alarm infra red sensors and automatic light switch
of the neighbors’ house are activated by the keying of an amateur
transmitter. The best remedy would be to:
a.* Screen the movement sensors from RF fields.
b. Replace the alarm.
c. Improve alarm sensitivity.
d. Change output transmitter frequency.
80 A 432 MHz causes breakthrough to a nearby TV receiver. Which of
the following filters could be fitted in the TV down lead in order
to minimize the breakthrough problem?
a.* Faraday filter.
b. Audio filter.
c. Low Pass filter.
d. Band Pass filter.
81 A neighbor's TV is suffering from breakthrough when you
transmit on the 144MHz band. The TV uses a “bunny ear” antenna.
There is no problem with your TV which receives the same station
but using a 10 element beam above the roof. A possible cure is:
a.* An external antenna for your neighbors TV.
b. A “bunny ear” antenna for your TV.
c. A pre-amplifier between the neighbors “bunny ear” antenna and
their TV.
d. Use of twin feeder for the neighbors “bunny ear” TV antenna.
82 Pick-up in the IF stage of a TV receiver usually results in:
a.* Problems with the picture.
b. Poor power supply regulation.
c. Random channel changing.
d. No audio output.
83 A neighbor complains about breakthrough to their TV receiver
but says it goes away when they disconnect the antenna. This also
co-insides with your transmissions. As a first step:
a. Try a mains filter.
b. Suggest they use a “Bunny ear” antenna.
c.* Try a filter in the TV down lead.
d. Renew the antenna cable.
84 A corroded connector on a neighbor's TV receiving antenna may
cause:
a.* Unwanted mixing products due to it exhibiting diode
properties.
b. Mains rectification.
c. Enhanced signal reception due to its filtering properties.
d. Increased amplification.
85 I.F. break through in a television receiver is characterized by
interference:
a. On a single channel.
b. On the low frequency channels.
c. On the high frequency channels.
d.* On all channels.
86 Fundamental overload of a domestic television receiver can
occur when:
a. Harmonics of a transmitted signal fall within the receiver pass
band.
b. An amateur transmitter operates on the TV. receiving frequency.
c. Interference is restricted to a single channel.
d.* The unwanted signal exceeds the dynamic range of the TV
receiver RF Amplifier.
87 mage or second channel interference is caused by an unwanted
signal on a frequency depending upon the receiver IF frequency.
Which formula correctly defines the difference between the wanted
and the interfering frequencies?
a. F (image) = 2 x Local Oscillator frequency.
b. F (image) = IF frequency + Local Oscillator frequency.
c. F (Image) = 2 x (IF Frequency) + Local Oscillator frequency.
d.* F (Image) = 2 x (IF Frequency) + Wanted frequency.
88 A neighbor's Hi-fi system is suffering from RF breakthrough.
One possible cure would be:
a. Ferrite beads on the transmitter lead.
b. A capacitor across the transmitter lead.
c.* Screened wire for the speaker leads.
d. An open wire feeder for the transmitter.
89 What is an effective way to reduce or eliminate radio frequency
interference to high fidelity systems?
a. Install bypass inductors.
b.* Install bypass capacitors.
c. Install metal oxide varistors.
d. Install bypass resistors.
90 What should you do if your properly-operating amateur radio
equipment is the source of interference on a neighbor's telephone
equipment?
a. Make internal adjustments to the neighbor's telephone
equipment.
b.* Assist the neighbor in contacting a phone service
representative about installing RFI filters.
c. Tell the neighbor that it's not your fault, and there is
nothing you can do.
d. Ground and shield the local telephone distribution.
91 Radio interference to high fidelity and other audio amplifier
equipment:
a.* Can be cured by fitting filters to the audio equipment.
b. Is caused mainly by harmonic radiation.
c. Is caused by fundamental overload.
d. Can be cured by eliminating parasitic oscillations within the
audio equipment.
92 Masthead TV reception amplifiers are usually sensitive to
overloading. The reason being:
a. They are mounted high up on antenna masts.
b. They are powered via the coax feed line cable.
c.* They are wide band and receive many signals simultaneously.
d. They are not adequately earthed.
93 When setting up a station for the first time in a new area, the
amateur operator should:
a. Use maximum power to evaluate interference objections.
b.* Evaluate possible interference to his own domestic equipment.
c. Only use indoor antennas.
d. Only operate from battery power.
94 When testing a radio transmitter under repair it should be:
a.* Connected to a dummy load.
b. Powered from the mains.
c. Battery operated.
d. Be carried out by a licensed amateur only. |
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