Technician · correct answers only, in question-pool order.
Receiver sensitivity describes how well a receiver can detect weak signals. Greater sensitivity means the receiver can recover usable information from a lower signal level.
A transceiver combines both transmitter and receiver functions in one unit, usually sharing controls and some circuitry.
A mixer combines two signals and produces new frequencies based on their sums and differences. Radios use mixers to translate signals from one frequency to another.
Selectivity is a receiver's ability to separate the desired signal from other signals on nearby frequencies.
An oscillator generates a repeating electrical signal at a defined frequency. Oscillators provide local signals for tuning, mixing, and modulation circuits.
A transverter shifts both transmitted and received RF between the transceiver's operating band and another amateur band.
PTT means Push-To-Talk. Grounding the PTT input commands the transceiver to leave receive mode and transmit.
Modulation places information such as speech onto an RF carrier by varying some characteristic of the carrier.
Some VHF power amplifiers need different internal bias or switching for linear SSB operation versus CW or FM. The mode switch configures the amplifier for the selected operating mode.
An RF power amplifier takes the transceiver's RF output and increases its power before the signal reaches the antenna system.
The Variable Frequency Oscillator supplies the tunable frequency reference that determines where the transceiver receives and transmits.
FM deviation increases with microphone audio level. Speaking farther from the microphone reduces the audio level and can reduce excessive deviation.
A strong nearby amateur signal can overload a broadcast receiver's front end if the receiver cannot reject signals outside its intended band.
Interference can result from direct overload by the desired transmitter frequency, from harmonics, or from other unwanted spurious emissions.
Many solid-state transmitters sense excessive reflected power caused by high SWR and automatically reduce output to protect their final amplifier devices.
If the amateur transmitter is operating properly but a nearby broadcast receiver is overloaded, filtering at that receiver's antenna input can reject the amateur signal before it reaches the receiver circuitry.
First verify that your own station is operating correctly and cleanly. If your transmissions do not interfere with your own receiver on the same channel, that helps separate transmitter problems from susceptibility in the neighbor's equipment.
A strong nearby FM broadcast signal can overload a 2-meter receiver. A band-reject filter attenuates the unwanted broadcast-band signal before it reaches the receiver.
Interference problems are best handled cooperatively: identify the offending device, verify that your station follows good amateur practice, and explain the interference rules politely.
Poorly installed cable-TV coax connectors can leak RF into the cable system. Checking and correcting the connectors is the first step before adding filters.
Distorted repeater audio can have several causes: slight transmitter mistuning, excessive microphone level, or a poor RF location that creates a weak or multipath signal.
RF can couple back into microphone wiring and re-enter the transmitter's audio stages. A clip-on ferrite choke adds impedance to that unwanted RF path and can stop the feedback.
A dummy load absorbs transmitter power without intentionally radiating it. That lets you test transmitters and amplifiers without putting a signal on the air.
An antenna analyzer measures impedance-related properties over frequency and is commonly used to find where an antenna is resonant.
A proper RF dummy load is approximately 50 ohms, non-inductive, and able to dissipate transmitter power as heat, usually with a heat sink.
An SWR of 1:1 means the feed line and load are perfectly matched, so there is no reflected power from an impedance mismatch.
High SWR can produce large reflected-power stresses at the transmitter output. Solid-state radios often reduce power automatically to protect their RF output transistors.
An SWR of 4:1 means the load is significantly mismatched to the transmission line. It is not a good impedance match.
Feed-line loss is real RF energy dissipated in the cable's resistance and dielectric losses. That lost energy ultimately becomes heat.
A directional wattmeter separates forward and reflected RF power. Those readings can be used to determine SWR.
Water changes the electrical properties of coaxial dielectric material and can corrode conductors. Moisture contamination is therefore a common cause of coax failure.
Sunlight can degrade an unprotected coax jacket. Once the jacket cracks, water can enter and damage the cable.
Foam dielectric contains more air than solid dielectric, reducing dielectric loss. That generally gives foam-dielectric coax lower attenuation per foot.
Electric potential difference is voltage, so the instrument used to measure it is a voltmeter.
Voltage is the difference in potential between two points. A voltmeter therefore connects across the component, in parallel.
To measure current, the meter must become part of the current path so the same current flows through the meter and the component.
Electric current is measured in amperes, and the instrument designed to measure current is an ammeter.
An ohmmeter contains its own small source. It applies a small current to the unknown resistance and uses the resulting voltage to determine resistance.
In resistance mode, a multimeter supplies its own test voltage. Applying external circuit voltage at the same time can damage the meter.
A basic multimeter commonly measures voltage and resistance, along with current on most models.
Acid-core solder contains corrosive flux intended for plumbing or metalwork. That residue can attack electronic conductors and components.
A cold solder joint forms when the solder or work was not heated properly. It often looks dull, rough, or lumpy instead of smooth and well flowed.
When an ohmmeter is connected across a large discharged capacitor, the meter initially supplies charging current. As the capacitor charges, current falls and the indicated resistance rises.
An ohmmeter supplies its own test current, so the circuit being measured must be unpowered to avoid bad readings or damage.