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Advanced trial exam
What is the current flowing through a 24 ohm resistor connected across 240 volts?
24,000 amperes
0.1 amperes
10 amperes
216 amperes
The ends of a half-wave dipole the
voltage and current are both high
voltage is high and current is low
voltage and current are both low
voltage low and current is high
The velocity factor of a coaxial cable with solid polythene dielectric is about
0.66
0.1
0.8
1.0
To convert nanofarads to picofarads requires
multiplication by 1,000
division by 1,000
multiplication by 10,000
division by 10,000
A variation in received signal strength caused by slowly changing differences in path lengths is called
absorption
fading
fluctuation
path loss
Two 20 uH inductances are connected in series. The total inductance is
10 uH
20 uH
40 uH
80 uH
A transistor with 5v across it and 10mA of flowing through it will be dissipating
50mW
50W
5W
5mW
The level of ionisation in the upper atmosphere relies on the
mixing effect of hot and cold air
earth's magnetic field
solar radiation
all of the aboven
The practical efficiency of a Class 'A' amplifier is approximately
20-40%
80-95%
50-70%
90-100%
Two FM signals transmit on the same frequency but only one is heard due to the
capture effect
modulation index
de-emphasis
pre-emphasis
For a circuit to oscillate it requires
appropriate CTCSS encoding
positive feedback
negative feedback
suppression of filtering
The main purpose of an automatic level control (ALC) circuit in an SSB transmitter is to
compress peaks of audio input
prevent the power amplifier being driven into non-linearity
measure the transmitter's output voltage
give a meter indication of speech input level
For a given frequency, the physical length of half-wave dipole antenna
needs to becomes longer as the frequency increases
has no relation to the frequency
needs to be shortened as the frequency increase
should be shortened as the frequency decreases
A requirement of using low-level AM modulation of a transmitter is
modulator to be biased in Class C
to modulate the final (PA) stage
all stages to be Class C amplifiers
all stages after modulation are linear
The signal from a frequency modulated transmitter has
an amplitude which varies with the modulating waveform
a frequency which varies with the modulating waveform
a single sideband
no sidebands
The correct colour coding for the neutral wire in a flexible mains lead is
brown
blue
yellow and green
white
In the circuit diagram shown the PIV across each diode is
7.07 volts
28.28 volts
40 volts
40.48 volts
The impedance at the feed point of a folded dipole antenna is approximately
300 ohm
150 ohm
75 ohm
100 ohm
In a bipolar transistor the base-emitter junction must be
reverse biased
forward biased
unbiased
alternating forward and reverse
In a transformer carrying an AC current the field of the energised winding generates a signal in another winding of the device by means of
eddy currents
mutual induction
polling magnetism
hysteresis
The function of a buffer amplifier is to
increase the power level significantly
reduce loading effects on the previous stage
store energy until required
provide power supply regulation
This filter circuit is that of a
high pass filter
band pass filter
notch filter
low pass filter
The bandwidth of a typical SSB transmission on the HF amateur bands is
1.2 KHz
3.0 KHz
5.5 KHz
9.0 KHz
A varactor diode acts like a variable
resistance
voltage regulator
inductance
capacitance
In frequency modulation the term modulation index refers to the
amount of frequency shift each side of the unmodulated carrier frequency
ratio of the frequency deviation to the frequency of the modulating wave
level of effective radiated power
ratio of the highest frequency to the frequency of deviation
In this audio amplifier C3 acts as a
low-pass filter element
coupling capacitor
bypass capacitor
high-pass filter element
A sine-wave alternating current of 10 ampere peak has an RMS value of
5 amperes
7.07 amperes
14.14 amperes
20 amperes
The receiver stage most likely to have selective filters is
RF amplifier
IF amplifier
AF amplifier
Buffer amplifier
A superhet receiver for SSB reception has an insertion oscillator to
replace the suppressed carrier for detection
phase out the unwanted sideband signal
reduce the passband of the IF stages
beat with the received carrier to produce the other sideband
A band-stop filter will
pass frequencies each side of a band
stop frequencies each side of a band
stop frequencies above a certain value
stop frequencies below a certain value
A suitable meter used to measure antenna impedance is
reflectometer
wave meter
noise bridge
deviation meter
Image interference in a superhet receiver results from an unwanted signal on
twice the frequency to which the receiver is tuned
twice the intermediate frequency away from the desired signal
the same frequency as the local oscillator
half the frequency to which the receiver is tuned
The most likely cause of parasitic oscillations in a transmitter is
rectification in a modulator
carrier oscillator variations
stray circuit inductance and capacitance
negative feedback
In this block diagram of a phase locked loop the voltage controlled oscillator is stage number
1
2
3
4
The ratio of inductive reactance to the effective resistance of a coil is called
self-inductance
mutual inductance
coefficient of coupling
Q
A gain in power of 30 dB is the same as a power ratio of
10
100
1,000
10,000
Capacitive top loading or a 'capacity hat' on a vertical antenna will
decrease the electrical length
dramatically increase its bandwidth
improve its RF power rating
increase the electrical length
The distance from the far end of the ground wave to the nearest point where the sky wave returns to the earth is called the
skip distance
radiation distance
skip angle
skip zone
Transmitter power amplifiers can generate parasitic oscillations on
the transmitter's output frequency
harmonics of the transmitter's output frequency
frequencies unrelated to the transmitter's output frequency
VHF frequencies only
A correct detector for FM signals is a
product detector
discriminator
balanced modulator
filtered loop detector
Tropospheric ducting long distance propagation normally occurs
below 3MHz
above 30MHz
below 30Mhz
on all amateur bands
A transformer with 100 turns on the primary winding and 10 turns on the secondary winding is connected to 230 volt AC mains. The voltage across the secondary is
10 volts
23 volt
110 volts
2300 volts
Radio wave polarisation is defined by the orientation of the radiated
magnetic field
electric field
inductive field
capacitive field
When distortion occurs in a non-linear device driven by a signal comprising more than one frequency this is called
phase distortion
harmonic distortion
intermodulation distortion
linearity resultant distortion
Small ferrite beads are sometimes threaded over the input leads of transistors in RF amplifiers in order to
reduce the noise level
tune the amplifier
neutralise the amplifier
suppress parasitic oscillation
The dynamic range of a receiver is the
ability to produce high fidelity audio through its speaker
level at which powerful signals begin to have distortion
difference between the minimum discernible signal and the maximum signal without overload
selectivity of a wanted signal without adjacent channel interference
The sensitivity of a multi-meter is expressed in terms o
decibels per scale
ohms per volt
full scale deflection
display or needle movement damping factor
The duty cycle of an amateur RTTY transmission is
50%
10
1
100
The purpose of a balun in a transmitting antenna system is to
protect the antenna system from lightning strikes
balance harmonic radiation
reduce unbalanced standing waves
match unbalanced and balanced transmission lines
The hfe or beta of a transistor is its
breakdown voltage
current gain
switching rate
maximum operating temperature
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