Receivers, transmitters, transceivers, and transverters
In the early days of radio, radio amateurs used separate receivers and transmitter units. Nowadays, however, most use radios that combine function both as the transmitter and receiver. These unit are called transceivers.
T7A02
What is a transceiver?
A. A device that combines a receiver and transmitter
B. A device for matching feed line impedance to 50 ohms
C. A device for automatically sending and decoding Morse code
D. A device for converting receiver and transmitter frequencies to another band
Often, HF transceivers are used with devices called transverters that convert the signals from their HF transceiver to the VHF, UHF, and even microwave bands. Transverters take the output of an HF transceiver, normally set to the 10 m (28 MHz) band and output a VHF, UHF, or microwave signal. Conversely, they receive a VHF, UHF, or microwave signal and output a signal in the 10 m band that is demodulated by the HF transceiver.
T7A06
What device converts the RF input and output of a transceiver to another band?
A. High pass filter
B. Low-pass filter
C. Transverter
D. Phase converter
Many, if not most, new amateurs buy a handheld transceiver, called an “HT,” as their first transceiver. One disadvantage of using a handheld transceiver is that the maximum output power is generally only 5 W, and because of this, they have limited range. To get around this limitation, you can use an RF amplifier to boost the power.
T7A10
What device increases the transmitted output power from a transceiver?
A. A voltage divider
B. An RF power amplifier
C. An impedance network
D. All these choices are correct
T7A09
What is the function of the SSB/CW-FM switch on a VHF power amplifier?
A. Change the mode of the transmitted signal
B. Set the amplifier for proper operation in the selected mode
C. Change the frequency range of the amplifier to operate in the proper segment of the band
D. Reduce the received signal noise
When talking about a transceiver’s specifications, we still refer to its receiver and transmitter. The two most important receiver specifications are sensitivity and selectivity.
T7A01
Which term describes the ability of a receiver to detect the presence of a signal?
A. Linearity
B. Sensitivity
C. Selectivity
D. Total Harmonic Distortion
T7A04
Which term describes the ability of a receiver to discriminate between multiple signals?
A. Discrimination ratio
B. Sensitivity
C. Selectivity
D. Harmonic distortion
To improve the sensitivity of a receiver, you can use an RF preamplifier. An RF preamplifier amplifies signals that you want to receive.
T7A11
Where is an RF preamplifier installed?
A. Between the antenna and receiver
B. At the output of the transmitter power amplifier
C. Between the transmitter and the antenna tuner
D. At the output of the receiver audio amplifier
Many HF transceivers have some version of a superheterodyne receiver. A superheterodyne receiver converts an incoming radio signal to an intermediate frequency, or IF. The circuit that does this is the mixer.
T7A03
Which of the following is used to convert a signal from one frequency to another?
A. Phase splitter
B. Mixer
C. Inverter
D. Amplifier
When transmitting or receiving, we want to generate an RF signal with a specific frequency. To do that, we use an oscillator.
T7A05
What is the name of a circuit that generates a signal at a specific frequency?
A. Reactance modulator
B. Phase modulator
C. Low-pass filter
D. Oscillator
To transmit a voice or data signal, we have to combine an audio frequency signal from the microphone with the RF carrier signal generated by the transmitter. This is done with a circuit called a modulator, and the process of combinging speech with an RF carrier signal is called modulation.
T7A08
Which of the following describes combining speech with an RF carrier signal?
A. Impedance matching
B. Oscillation
C. Modulation
D. Low-pass filtering
Symptoms, causes, and cures of common transmitter and receiver problems
Since Murphy’s Law—the law that states if anything can go wrong, it will—applies to amateur radio as much as it does to any other pursuit, at some point you will have to deal with problems. These may include overload, distortion, feedback, and radio frequency interference, or RFI.
Let’s first consider radio frequency interference.
T7B03
Which of the following can cause radio frequency interference?
A. Fundamental overload
B. Harmonics
C. Spurious emissions
D. All these choices are correct
Any of these could cause interference to a TV set or radio or even computer speakers, and you will want to take steps to find and eliminate that interference. The first thing that you should do if your neighbor complains about interference is to make sure that your station is functioning properly by making sure that your transmissions do not cause interference to your radios or televisions.
T7B06
Which of the following actions should you take if a neighbor tells you that your station’s transmissions are interfering with their radio or TV reception?
A. Make sure that your station is functioning properly and that it does not cause interference to your own radio or television when it is tuned to the same channel
B. Immediately turn off your transmitter and contact the nearest FCC office for assistance
C. Install a harmonic doubler on the output of your transmitter and tune it until the interference is eliminated
D. All these choices are correct
While it’s not very likely that your amateur radio station will interfere with a neighbor’s cable TV service, it can sometimes occur. If you are interfering with a neighbor’s cable TV service, first check the coax connectors.
T7B09
What should be the first step to resolve non-fiber optic cable TV interference caused by your amateur radio transmission?
A. Add a low-pass filter to the TV antenna input
B. Add a high-pass filter to the TV antenna input
C. Add a preamplifier to the TV antenna input
D. Be sure all TV feed line coaxial connectors are installed properly
Your amateur radio station may interfere with a nearby radio receiver if your signal is so strong that the receiver cannot reject the signal even though your signal is not on the frequency to which the receiver is tuned. This is called fundamental overload.
T7B02
What would cause a broadcast AM or FM radio to receive an amateur radio transmission unintentionally?
A. The receiver is unable to reject strong signals outside the AM or FM band
B. The microphone gain of the transmitter is turned up too high
C. The audio amplifier of the transmitter is overloaded
D. The deviation of an FM transmitter is set too low
To reduce or eliminate fundamental overload, you can install a filter at the radio or TV input to block the interfering signal.
T7B05
How can fundamental overload of a non-amateur radio or TV receiver by an amateur signal be reduced or eliminated?
A. Block the amateur signal with a filter at the antenna input of the affected receiver
B. Block the interfering signal with a filter on the amateur transmitter
C. Switch the transmitter from FM to SSB
D. Switch the transmitter to a narrow-band mode
The process can work the other way, too. When driving by the antenna of a high-power broadcast station you may notice that your VHF transceiver is picking up the broadcast station signal. This is often the result of overload.
T7B07
Which of the following can reduce overload of a VHF transceiver by a nearby commercial FM station?
A. Installing an RF preamplifier
B. Using double-shielded coaxial cable
C. Installing bypass capacitors on the microphone cable
D. Installing a band-reject filter
The band of frequencies that you want to reject is the band that includes the broadcast station frequency.
Interference works both ways. Your neighbors may have wireless devices that can interfere with your station. While they are responsible for eliminating the interference, chances are they don’t have the expertise necessary to find and eliminate the interference, so your best option is to try and work with them.
T7B08
What should you do if something in a neighbor’s home is causing harmful interference to your amateur station?
A. Work with your neighbor to identify the offending device
B. Politely inform your neighbor that FCC rules prohibit the use of devices that cause interference
C. Make sure your station meets the standards of good amateur practice
D. All these choices are correct
Perhaps the most common problem that amateur radio operators have is distorted or noisy audio when transmitting. There are many reasons for poor audio.
T7B10
What might be a problem if you receive a report that your audio signal through an FM repeater is distorted or unintelligible?
A. Your transmitter is slightly off frequency
B. Your batteries are running low
C. You are in a bad location
D. All these choices are correct
T7B11
What is a symptom of RF feedback in a transmitter or transceiver?
A. Excessive SWR at the antenna connection
B. The transmitter will not stay on the desired frequency
C. Reports of garbled, distorted, or unintelligible voice transmissions
D. Frequent blowing of power supply fuses
Sometimes, garbled or distorted audio when operating FM is the result of over-deviation.
T7B01
What can you do if you are told your FM handheld or mobile transceiver is over-deviating?
A. Talk louder into the microphone
B. Let the transceiver cool off
C. Change to a higher power level
D. Talk farther away from the microphone
Using basic test instruments and soldering
The most common test instrument in an amateur radio shack is the multimeter. Multimeters are called that because they combine the functions of a voltmeter, ohmmeter, and ammeter into a single instrument.
T7D07
Which of the following measurements are made using a multimeter?
A. Signal strength and noise
B. Impedance and reactance
C. Voltage and resistance
D. All these choices are correct
The voltmeter function of the multimeter is used to measure electromotive force, more commonly known as voltage. You measure the voltage across a component or circuit by connecting the leads in parallel with the component.
T7D01
Which instrument would you use to measure electric potential?
A. An ammeter
B. A voltmeter
C. A wavemeter
D. An ohmmeter
T7D02
How is a voltmeter connected to a component to measure applied voltage?
A. In series
B. In parallel
C. In quadrature
D. In phase
In order to avoid damaging the multimeter, make sure that it’s set to the voltage setting, not the resistance setting when you want to measure voltage.
T7D06
Which of the following can damage a multimeter?
A. Attempting to measure resistance using the voltage setting
B. Failing to connect one of the probes to ground
C. Attempting to measure voltage when using the resistance setting
D. Not allowing it to warm up properly
The ohmmeter function of a multimeter is used to measure resistance. The way an ohmmeter measures the resistance of a circuit is by supplying a known current to the circuit, measuring the voltage across the circuit, and then calculating the resistance using Ohm’s Law, R = V/I. Because we’re actually measuring voltage, we connect an ohmmeter in parallel with a component to measure its resistance.
T7D05
How is an ohmmeter connected to a component to measure its resistance?
A. In parallel
B. In series
C. In cascade
D. All these choices are correct
T7D11
Which of the following precautions should be taken when measuring in-circuit resistance with an ohmmeter?
A. Ensure that the applied voltages are correct
B. Ensure that the circuit is not powered
C. Ensure that the circuit is grounded
D. Ensure that the circuit is operating at the correct frequency
T7D10
What reading indicates that an ohmmeter is connected across a large, discharged capacitor?
A. Increasing resistance with time
B. Decreasing resistance with time
C. Steady full-scale reading
D. Alternating between open and short circuit
The ammeter function of a multimeter is used to measure current. You connect an ammeter in series with a circuit so that the current flowing through the circuit also flows through the ammeter.
T7D04
Which instrument is used to measure electric current?
A. An ohmmeter
B. An electrometer
C. A voltmeter
D. An ammeter
T7D03
When configured to measure current, how is a multimeter connected to a component?
A. In series
B. In parallel
C. In quadrature
D. In phase
In addition to knowing how to make electrical measurements, knowing how to solder is an essential skill for amateur radio operators.
T7D08
Which of the following types of solder should not be used for radio and electronic applications?
A. Acid-core solder
B. Lead-tin solder
C. Rosin-core solder
D. Tin-copper solder
T7D09
What is the characteristic appearance of a cold tin-lead solder joint?
A. Dark black spots
B. A bright or shiny surface
C. A rough or lumpy surface
D. Excessive solder
We call a poor solder joint a “cold” solder joint because it’s usually the result of not applying enough heat to the joint. When you don’t apply enough heat to a solder joint, the solder does not flow smoothly between the metal surfaces to be joined and often does not make a good connection.
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