By the end of this chapter, you will be able to: - confidently perform visual inspections to spot physical damage or deterioration in automation and radio frequency systems - choose the right types of tests based on the specific maintenance activities required - identify which system components need testing by understanding how the system functions - correctly test repaired or replaced components by following the manufacturer’s manuals - carry out a test run of the system to ensure it operates as intended - verify the system’s performance by comparing results to the original specifications - accurately record your test results according to standard operating procedures - ensure any modified systems are properly recertified and meet EMC requirements - safely dispose of waste materials in line with EHS regulations
Mastering these skills will help you maintain high-performing, safe, and compliant automation and radio frequency systems in the workplace.
Compiled by: Winnie Cherono
Radio frequency (RF) components are the parts that generate, carry, shape and receive signals at frequencies from about 3 kHz up to hundreds of gigahertz. In automation work they appear in wireless links between field sensors and controllers, telemetry units at remote pump stations, radio modems and remote-control receivers. At these frequencies a part no longer behaves as its symbol suggests: a short piece of wire acts as an inductor, the gap between two tracks acts as a capacitor, and a poor connector reflects power instead of passing it. Inspection and testing of RF components therefore uses methods and instruments that differ from low-frequency electronics.
Components are grouped as active or passive. Active components need a power supply to work and can add energy to a signal, so they amplify, generate or convert signals. Passive components need no supply to work: they store, dissipate, filter or transfer energy. The dc supply of most RF equipment comes from a regulated power supply fed from the 240 V single phase mains, or from a battery at a remote site.
The instruments below are used throughout this topic.
| Instrument | Specification | Use |
|---|---|---|
| Digital multimeter | Resistance, dc voltage and continuity ranges | Checks resistors, bias voltages, winding continuity and the centre conductor of a cable |
| Oscilloscope with 10:1 probe | Bandwidth at least five times the highest frequency to be viewed | Shows oscillator output, modulation envelope and waveform distortion |
| Spectrum analyser | Range covering the signal and its harmonics, 50 Ω input with attenuator | Shows carrier frequency, level in dBm, harmonics, spurious signals and noise floor |
| RF power meter with sensor | 50 Ω, range suited to the transmitter power | Measures forward output power; an attenuator protects the sensor at higher powers |
| SWR meter or vector network analyser | Frequency range of the antenna system | Measures VSWR and return loss of antennas and cables |
| Frequency counter | Time base more accurate than the tolerance being checked | Measures oscillator and crystal frequency |
| Signal generator | Calibrated RF level in dBm, with AM and FM | Supplies a known test signal to receivers and filters |
| Dummy load | 50 Ω, power rating above the transmitter output | Lets a transmitter run without radiating and without damage |
| LCR meter | Test frequency suited to the part | Measures inductance, capacitance, resistance and Q |
Safety comes before every test. Switch off and isolate the equipment from the 240 V single phase or 415 V three phase supply before opening it, and discharge any large capacitors, because a transmitter power stage can hold dangerous voltage after switch-off. Never touch a radiating antenna, never key a transmitter without a load or an antenna connected, and use a wrist strap on static-sensitive semiconductors. Transmitters may only operate on frequencies and at power levels licensed by the Communications Authority of Kenya, so test transmissions are made into a dummy load.
Active components amplify signals, generate oscillations, convert one frequency to another and switch signals. In automation, the same blocks appear in a telemetry link that sends a tank level from a remote borehole to a pump controller, in a wireless emergency-stop receiver on a conveyor, and in a radio-controlled gate or crane. Maintenance of these blocks follows two stages: a dead inspection with the power off, then live tests at the points where the manufacturer gives bias voltages, levels and frequencies.
A transmitter generates a carrier, impresses the information on it, amplifies the result to the required power and delivers it to the antenna. The usual chain is oscillator, modulator, driver amplifier, power amplifier, output filter and antenna connector. Each stage raises the signal level and must be checked against the manufacturer's specification.
The inspection and test points are:
A safe functional test follows these steps:
Example: a telemetry transmitter is rated at 5 W. Converted to dBm, 5 W = 10 × log (5 000 mW) = 37.0 dBm. The power meter reads 3.2 W, which is 35.1 dBm. The ratio is 3.2 ÷ 5 = 0.64, a loss of 1.9 dB, so the technician checks the supply voltage, the power amplifier stage and the antenna match before the unit is returned to service. Detailed methods for power and frequency measurement are taught in Power output measurement and Frequency stability checks.
A receiver selects the wanted signal from the many that arrive at the antenna, amplifies it and recovers the information. Most receivers are superheterodyne: the signal passes through a low-noise RF amplifier, a mixer that converts it to a fixed intermediate frequency (IF), IF amplifiers and filters, a demodulator and an output stage. Two measures describe quality. Sensitivity is the weakest signal that still gives an acceptable output, and selectivity is the ability to reject signals on neighbouring channels.
Faults and checks:
Sensitivity is tested by connecting a signal generator through a 50 Ω cable to the antenna input and lowering the level until the output quality just meets the manufacturer's figure. Selectivity is tested by detuning the generator by one channel spacing and noting how much stronger the signal must be to give the same output.
Example: a receiver has a sensitivity of -110 dBm. In watts this is 10 raised to the power -14, or 0.01 pW. Across 50 Ω the voltage is V = √(P × R) = √(1 × 10⁻¹⁴ × 50) = 0.71 µV. The signal generator must be able to produce levels this small, which is why a calibrated attenuator is part of the test set.
An antenna converts the electrical signal from a transmission line into a radio wave, and a radio wave back into an electrical signal. Its length is tied to the wavelength. The wavelength in metres is λ = 300 ÷ f, with f in megahertz, and a half-wave dipole is cut to about 0.95 of half a wavelength because of end effects.
Common types:
Inspection covers the mounting and mast, the element lengths, the feed point, the connector and the cable run. Water in a connector, a corroded joint or a bent element changes the impedance and causes reflected power. The standing wave ratio (VSWR) is measured with an SWR meter or analyser: a low reading means the antenna accepts the power, a high reading means a mismatch or a fault.
Example: a technician cuts a half-wave dipole for 145 MHz. The wavelength is 300 ÷ 145 = 2.07 m, half of that is 1.03 m, and 0.95 of it gives 0.98 m overall. A directional power meter on the same link reads 50 W forward and 2 W reflected. The reflection coefficient is √(2 ÷ 50) = 0.2, so VSWR = (1 + 0.2) ÷ (1 - 0.2) = 1.5, the return loss is 20 × log (1 ÷ 0.2) = 14 dB, and 48 W reaches the antenna. Work at height is done with a harness and with the transmitter switched off.
A modulator places the information on a carrier by changing its amplitude, frequency or phase. A demodulator reverses the process at the receiver. Analogue systems use amplitude modulation (AM), frequency modulation (FM) and phase modulation, and data links use shift keying methods such as ASK, FSK and PSK, and combined methods such as QAM.
Typical demodulators are the diode envelope detector for AM, the discriminator or phase locked loop for FM, and the digital decoders in radio modems. Faults show as distortion, low recovered level, a hum or buzz on the output, or no recovered data. Checks use a known test signal at the input and an oscilloscope at the output.
Example: an AM carrier shows a largest envelope voltage of 8 V and a smallest of 2 V on the scope. The modulation depth is m = (8 - 2) ÷ (8 + 2) = 0.6, which is 60 percent. A depth above 100 percent distorts the signal and spreads energy onto adjacent channels.
Example: an FM transmitter is set to a deviation of 5 kHz with a 1 kHz test tone. The modulation index is 5 ÷ 1 = 5 and the occupied bandwidth by Carson's rule is 2 × (5 + 1) = 12 kHz. Calibration sets the deviation with a known tone and a deviation meter, so that the channel is not overfilled.
An RF amplifier raises the power or voltage of a radio signal without changing its frequency. A low-noise amplifier (LNA) sits at the receiver input and adds as little noise as possible. A driver amplifier raises the level to feed the next stage, and a power amplifier at the transmitter output supplies the final power to the antenna. Gain, bandwidth, linearity, efficiency and input and output match are the main parameters.
Amplifier classes trade linearity against efficiency. Class A is linear but wastes much of its supply as heat, so it suits low-level stages. Class C is efficient but distorts the amplitude, so it suits constant-amplitude signals such as FM. Classes AB and B sit between these two and are used where a modulated signal must be amplified faithfully.
Typical faults and checks:
Example: an input of 20 mW (13 dBm) gives an output of 2 W (33 dBm). The gain is 10 × log (2 ÷ 0.02) = 20 dB. If this power stage runs at an efficiency of 50 percent, it takes 4 W from the supply and turns 2 W into heat, which the heat sink must remove.
An oscillator produces a steady alternating signal from a dc supply. It is an amplifier with positive feedback arranged so that the signal returning to the input is in step with the signal already there and is just large enough to sustain itself. The frequency is set by a tuned circuit, a crystal or a delay element.
Types in common use are LC oscillators (Hartley and Colpitts), crystal oscillators, voltage-controlled oscillators (VCO) whose frequency follows a control voltage, and RC oscillators for low frequencies. For an LC circuit the frequency is f = 1 ÷ (2π√(LC)).
Example: L = 1 µH and C = 100 pF give f = 1 ÷ (2π × √(1 × 10⁻⁶ × 100 × 10⁻¹²)) = 1 ÷ (2π × 10⁻⁸) = 15.9 MHz.
Frequency stability matters because a receiver or transmitter must stay on its channel. Temperature changes, supply voltage changes and the load all pull an oscillator off frequency. A crystal gives far better stability than an LC circuit, a regulated supply removes the voltage effect, and a buffer stage after the oscillator isolates it from the load. Drift is expressed in parts per million (ppm). Example: an LC oscillator nominally at 15.92 MHz drifts by 4.8 kHz as it warms up, which is 4 800 ÷ 15 920 000 × 10⁶ = about 300 ppm, far outside what a crystal oscillator would show.
Faults and tests:
A mixer combines two signals in a non-linear device so that the output contains the sum and the difference of their frequencies. In a receiver the mixer combines the incoming signal with the local oscillator to give the fixed intermediate frequency, fIF = |fLO - fRF|. In a transmitter it moves a lower frequency up to the carrier. Mixer types are the single diode mixer, the double-balanced diode ring and the active mixer built with transistors.
A mixer also responds to an unwanted image frequency, which lies on the other side of the local oscillator at the same distance as the wanted signal. Filtering ahead of the mixer reduces it.
Example: a receiver is tuned to 98.0 MHz and uses an intermediate frequency of 10.7 MHz with the local oscillator above the signal. The local oscillator runs at 98.0 + 10.7 = 108.7 MHz. The image frequency is 108.7 + 10.7 = 119.4 MHz, and the sum product of 98.0 + 108.7 = 206.7 MHz is removed by the IF filter.
Faults and checks:
Data converters connect the analogue world to digital circuits. An analogue-to-digital converter (ADC) turns a voltage into a binary number and a digital-to-analogue converter (DAC) does the reverse. In automation they sit on analogue input and output cards for 4 to 20 mA loops and 0 to 10 V signals, and in radio equipment they digitise an intermediate frequency for processing in software.
The main parameters are:
The size of one step is the least significant bit, LSB = Vref ÷ (2 to the power N). Example: a 12-bit converter with a 3.3 V reference has 4 096 codes and an LSB of 3.3 ÷ 4 096 = 0.806 mV. A signal limited to 200 kHz needs a sampling rate above 400 kS/s, and a practical design samples faster and places an anti-aliasing filter before the converter.
A test applies a known voltage from a calibrated source and reads the code. Example: 1.650 V should read 1.650 ÷ 3.3 × 4 096 = code 2 048. A code that stays fixed, bits that are always set, or a reading that jumps points to a damaged converter, a noisy reference or a missing anti-aliasing filter.
A phase locked loop (PLL) forces a voltage-controlled oscillator to follow a reference frequency exactly. It has four blocks: a phase detector that compares the reference with the oscillator output, a low-pass loop filter that smooths the result into a control voltage, the voltage-controlled oscillator, and often a divider by N in the feedback path. When the loop is locked the divided output frequency equals the reference, so the output is fout = N × fref.
Uses include frequency synthesisers that select radio channels, FM demodulators and clock recovery circuits.
Example: a synthesiser with a 25 kHz reference and N = 4 000 gives 25 kHz × 4 000 = 100.000 MHz. Changing N to 4 001 moves the output to 100.025 MHz, one channel step up.
Checks and faults:
An RF transistor amplifier is a single amplifying stage built round a transistor chosen for the operating frequency. Bipolar transistors (BJT) and field effect transistors (FET) are both widely used. Power MOSFETs are used in higher-power stages, and gallium arsenide FETs for low-noise work at microwave frequencies. The transition frequency of the transistor must be well above the operating frequency or the gain collapses.
Design and maintenance care centres on five points:
At RF every lead is part of the circuit, so replacement parts are fitted with leads as short as the original and in the same position. MOSFET and gallium arsenide devices are damaged by static, so a wrist strap and an earthed bench mat are used.
Example: a stage runs from 12 V with a 220 Ω collector resistor and the collector current is designed to be 20 mA. The voltage across the resistor is 0.020 × 220 = 4.4 V, so the collector should read 12 - 4.4 = 7.6 V. A reading near 12 V means the transistor is not conducting, and a reading near 0.2 V means it is saturated or shorted. A diode test on the base-emitter junction should show about 0.6 V in the forward direction.
Noise is unwanted random energy that adds to the signal and limits the weakest signal a receiver can use. Thermal noise arises from the random motion of charge in any conductor and has the power N = k × T × B, where k = 1.38 × 10⁻²³ J/K, T is the temperature in kelvin and B is the bandwidth in hertz. At 290 K this equals -174 dBm in each hertz of bandwidth. Other sources are shot noise in semiconductors, flicker noise at low frequencies, and external noise from variable-speed drives, welding equipment and switching power supplies.
The noise figure NF tells how much a stage worsens the signal-to-noise ratio: NF = 10 × log (SNR in ÷ SNR out), in dB. When stages are cascaded, the first stage matters most. Friis' formula gives F = F1 + (F2 - 1) ÷ G1, with F and G as ratios rather than decibels.
Example: an LNA with a noise figure of 1.5 dB (F = 1.413) and a gain of 20 dB (G = 100) feeds a mixer with a noise figure of 8 dB (F = 6.31). The combined noise factor is 1.413 + (6.31 - 1) ÷ 100 = 1.466, or about 1.47, which is 1.66 dB. Without the LNA the receiver would have a noise figure of 8 dB. For a 15 kHz channel the thermal noise is -174 + 10 × log (15 000) = -132.2 dBm. With the 1.66 dB noise figure and a required signal-to-noise ratio of 12 dB, the weakest usable signal is -132.2 + 1.66 + 12 = about -118.6 dBm.
Testing and reducing noise:
Passive components need no supply to operate. They store energy in electric or magnetic fields, dissipate it as heat, or transfer it between circuits, and they determine the impedance, frequency response and power distribution of RF circuits. At high frequency each part also has unwanted properties: a resistor has some inductance, a capacitor has lead inductance and an inductor has stray capacitance, so every part has a self-resonant frequency above which it no longer behaves as intended. Passive parts fail by drifting in value, opening, shorting or being damaged by heat, so a good inspection looks at colour changes, cracks and tracks, and the measurements are made with the part out of circuit or with one lead lifted.
A resistor limits current, sets bias levels and divides voltage. At RF the construction matters. Carbon film and metal film resistors suit most circuits, chip resistors suit surface-mount boards because their leads are almost absent, and wire-wound resistors are avoided because the winding is an inductor. As a rough guide, each millimetre of lead adds about 1 nH, which is significant at high frequency. A 50 Ω termination resistor or dummy load must have a power rating well above the power it absorbs.
Resistors are read from the colour code. Example: yellow, violet, red, gold is 4, 7 and a multiplier of 100, so 4.7 kΩ with a tolerance of ±5 percent. The acceptable range is 4 700 × 0.95 = 4 465 Ω to 4 700 × 1.05 = 4 935 Ω. A reading outside this range means the resistor has drifted, usually upward, after overheating.
Inspection and test:
Example: a 50 Ω dummy load that absorbs a 10 W transmitter carries V = √(10 × 50) = 22.4 V and I = √(10 ÷ 50) = 0.45 A, so a 25 W rating gives a safe margin.
A capacitor stores energy in an electric field. In RF circuits capacitors tune resonant circuits, couple signals while blocking dc, decouple supply lines and form filters. Ceramic capacitors of the C0G (NP0) type are stable and are used in tuned circuits. Silver mica and film types suit precision work. Trimmer capacitors give adjustable tuning. Electrolytic capacitors are used for power supply smoothing but not for RF coupling, because their inductance and loss are high at radio frequencies.
Reactance falls as frequency rises: Xc = 1 ÷ (2π × f × C). Example: a 100 pF capacitor has Xc = 159 Ω at 10 MHz and 15.9 Ω at 100 MHz, so it passes RF easily while blocking dc.
The difference from a resistor is that a capacitor stores energy and returns it to the circuit, while a resistor turns it into heat. The reactance of a capacitor changes with frequency, while the resistance of an ideal resistor does not. A capacitor shifts the current ahead of the voltage by 90 degrees, while a resistor keeps them in step.
Inspection and test:
An inductor stores energy in a magnetic field. Air-core coils have low loss and suit high frequencies. Coils wound on ferrite or iron powder cores give more inductance in less space. RF chokes pass dc and block RF. The reactance is XL = 2π × f × L, and the quality factor Q = XL ÷ R shows how little energy the coil wastes.
Example: a 1 µH coil at 10 MHz has XL = 2π × 10 × 10⁶ × 1 × 10⁻⁶ = 62.8 Ω. If the coil resistance is 0.5 Ω, then Q = 62.8 ÷ 0.5 = 126.
Inspection and test:
A quartz crystal is a thin slice of quartz that vibrates mechanically at a very precise frequency when an electric field is applied across it. The behaviour is equivalent to a series resonant circuit with a parallel capacitance, so a crystal has a series and a parallel resonant frequency. Crystals set the frequency of oscillators and also form narrow filters.
The frequency tolerance is stated in ppm and the crystal is specified with a load capacitance. Example: a 10 MHz crystal with a tolerance of ±20 ppm may run anywhere between 10 MHz - 200 Hz and 10 MHz + 200 Hz, since 10 × 10⁶ × 20 × 10⁻⁶ = 200 Hz, which is 9.9998 MHz to 10.0002 MHz.
Inspection and test:
An RF transformer transfers a signal between circuits through magnetic coupling and can change voltage, current and impedance at the same time. It is built on a ferrite toroid or a coil former. Uses are impedance matching between stages, the balun that joins a balanced antenna to an unbalanced cable, coupling between tuned stages in IF amplifiers, and electrical isolation. The impedance ratio equals the square of the turns ratio: Zp ÷ Zs = (Np ÷ Ns)².
Example: matching 50 Ω to 200 Ω needs an impedance ratio of 4, so the turns ratio is √4 = 2 to 1. A mains transformer in the equipment power supply works on the voltage ratio instead: a transformer from 240 V to 12 V has a turns ratio of 240 ÷ 12 = 20 to 1.
Inspection and test:
A transmission line carries RF power from the transmitter to the antenna and signals between units with little loss. Coaxial cable is the usual choice, with a characteristic impedance of 50 Ω for most radio and test equipment. Microstrip lines on circuit boards do the same job inside equipment. Loss increases with frequency and cable length, and the velocity of the wave in the cable is slower than in air. For solid polyethylene cable the velocity factor is about 0.66. Example: a quarter-wave section for 145 MHz is 2.07 ÷ 4 × 0.66 = 0.34 m long.
Poor line design or poor maintenance causes serious faults. A mismatch reflects power back to the source and raises the VSWR, power is lost as heat in the cable, and the power amplifier overheats. Water in a connector, a sharp bend, a crushed cable or the wrong connector type all change the impedance. Inspection covers the connectors, the weather sealing, the cable route and the sheath, and a cable test measures continuity of the centre conductor and the screen and the VSWR of the cable with its load.
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Create a free accountThis chapter provided a comprehensive overview of the key components used in radio frequency and automation systems, beginning with active RF components such as transmitters, receivers, antennas, modulators, amplifiers, oscillators, mixers, data converters, phase locked loops, transistor amplifiers, and the concept of noise and noise figures. It further examined passive components including resistors, capacitors, inductors, crystals, and transformers, highlighting their roles within RF circuits. The discussion then shifted to automation components, covering sensors, transducers, actuators, attenuators, operational amplifiers, controllers, programmable logic controllers, and industrial computers, emphasizing their functions in control systems. Important automation system isolation points were identified, such as circuit breakers, fuses, and isolators, which are critical for system safety and maintenance. The chapter addressed fault analysis techniques by describing the characteristics of short circuits, methods to identify open circuits, and common symptoms of grounding faults. It outlined testing procedures focusing on continuity testing, verifying signal integrity, and inspecting isolation points to ensure proper system operation. Finally, the chapter emphasized the importance of accurately recording test findings as part of effective system maintenance and troubleshooting.
Which of the following is an active RF component?
a) Resistor
b) Capacitor
c) Oscillator
d) Transformer
(2 marks)
Describe the primary function of a phase locked loop (PLL) circuit in radio frequency systems. (3 marks)
Type: Individual
| Tools & Equipment | Materials |
|---|---|
| Multimeter | Solder wire |
| Oscilloscope | Insulation tape |
| Signal generator | Equipment labels |
| Soldering iron | Safety dustcoat/overall |
| Desoldering pump | |
| Tweezers | |
| Cleaning brush |
| S/N | Item | Quantity |
|---|---|---|
| 1 | RF transistor amplifier module | 1 Pc per Candidate |
| 2 | RF amplifier board | 1 Pc per Candidate |
| 3 | Multimeter | 1 Pc per Candidate |
| 4 | Oscilloscope | 1 Pc per 2 Candidates |
| 5 | Signal generator (100 MHz to 1 GHz) | 1 Pc per 2 Candidates |
| 6 | Soldering iron | 1 Pc per Candidate |
| 7 | Solder wire 20 cm | 20 cm per Candidate |
| 8 | Desoldering pump | 1 Pc per Candidate |
| 9 | Insulation tape | 1 roll per 5 Candidates |
| 10 | Tweezers | 1 Pc per Candidate |
| 11 | Safety dustcoat/overall | 1 Pc per Candidate |
| 12 | Cleaning brush (soft bristle) | 1 Pc per Candidate |
| 13 | Equipment labels | 5 Pcs per Candidate |
| Items to be Evaluated | Marks Available | Marks Obtained | Comments |
|---|---|---|---|
| TASK 1: Preparation and Safety | |||
| Wore Personal Protective Equipment including dustcoat/overall (Award 1 mark if worn correctly, otherwise 0) | 1 | ||
| Ensured clean and organized working area before starting (Award 1 mark if area is clean and tools arranged, otherwise 0) | 1 | ||
| Sub-Total | 2 | ||
| TASK 2: Visual Inspection | |||
| Checked RF transistor amplifier and RF amplifier board for physical damage, corrosion, or loose connections (Award up to 3 marks for thorough visual inspection and identifying issues) | 3 | ||
| Sub-Total | 3 | ||
| TASK 3: Testing and Fault Diagnosis | |||
| Used multimeter to test continuity and resistance of amplifier components and connections (Award 3 marks if continuity tests are correctly performed and recorded) | 3 | ||
| Applied signal generator input to RF transistor amplifier and observed output on oscilloscope (Award 4 marks if input and output signals are correctly measured and interpreted) | 4 | ||
| Measured amplifier gain and verified it matches expected values (Award 4 marks if gain measurement is accurate and correctly recorded) | 4 | ||
| Identified any faulty components requiring repair or replacement (Award 3 marks if faults are correctly identified and documented) | 3 | ||
| Sub-Total | 14 | ||
| TASK 4: Repair and Maintenance | |||
| Performed soldering to replace or reattach faulty components on amplifier boards (Award 4 marks for neat, secure solder joints without cold soldering) | 4 | ||
| Cleaned RF active components and circuit boards using cleaning brush (Award 2 marks if components are cleaned thoroughly without damage) | 2 | ||
| Applied insulation tape where necessary to ensure safety and prevent shorts (Award 1 mark if insulation is applied properly) | 1 | ||
| Sub-Total | 7 | ||
| TASK 5: Final Testing and Reporting | |||
| Performed final continuity and functionality tests on repaired components (Award 3 marks if tests confirm full functionality) | 3 | ||
| Prepared a maintenance report including equipment identification, date/time, tasks performed, tools/materials used, observations and findings, and signed the report (Award up to 5 marks for complete and accurate maintenance report) | 5 | ||
| Sub-Total | 8 | ||
| PRODUCT CHECKLIST | |||
| RF transistor amplifier and RF amplifier board are fully functional with correct gain and signal output (Award 10 marks if amplifier gain and output meet specifications without distortion) | 10 | ||
| Sub-Total | 10 | ||
| GRAND TOTAL | 44 | ||
Type: Individual
| Tools & Equipment | Materials |
|---|---|
| Multimeter | Dry Cell Batteries 1.5V |
| Soldering Iron | Solder Wire |
| Set of Screwdrivers | Insulated Connecting Wires |
| Side Cutter | Equipment Labels |
| Combinational Pliers |
| S/N | Item | Quantity |
|---|---|---|
| 1 | 5W RF Transmitter and Receiver Unit (150mm x 100mm x 50mm) | 1 Pc per Candidate |
| 2 | Dry Cell Batteries 1.5V | 2 Pcs per Candidate |
| 3 | Multimeter | 1 Pc per Candidate |
| 4 | Soldering Iron | 1 Pc per Candidate |
| 5 | Solder Wire 20 cm | 20 cm per Candidate |
| 6 | Insulated Connecting Wires (Red and Black) 1 mm2 | 1 meter per Candidate |
| 7 | Set of Screwdrivers | 1 Set per Candidate |
| 8 | Side Cutter | 1 Pc per Candidate |
| 9 | Combinational Pliers | 1 Pc per Candidate |
| 10 | Equipment Labels | 5 Pcs per Candidate |
| 11 | Personal Protective Equipment (Dustcoat/Overall) | 1 Set per Candidate |
| Items to be Evaluated | Marks Available | Marks Obtained | Comments |
|---|---|---|---|
| TASK 1: Preparation and Safety | |||
| Wore Personal Protective Equipment (Dustcoat/Overall) (Award 1 mark if worn correctly, otherwise 0) | 1 | ||
| Ensured clean and safe working area before starting (Award 1 mark if area is clean and free from hazards, otherwise 0) | 1 | ||
| Sub-Total | 2 | ||
| TASK 2: Inspection and Maintenance Checklist Preparation | |||
| Prepared maintenance checklist including equipment identification (name and model) (Award 1 mark if checklist contains correct identification, otherwise 0) | 1 | ||
| Listed inspection tasks to be performed (Award 1 mark if tasks are clearly listed, otherwise 0) | 1 | ||
| Listed maintenance tasks to be performed (Award 1 mark if maintenance tasks are listed, otherwise 0) | 1 | ||
| Listed required tools and materials (Award 1 mark if tools and materials are listed, otherwise 0) | 1 | ||
| Sub-Total | 4 | ||
| TASK 3: Visual Inspection and Cleaning | |||
| Performed visual inspection of transmitter and receiver components (Award up to 3 marks for thorough inspection noting damage, corrosion, loose connections) | 3 | ||
| Cleaned radio frequency components and circuit board (Award 2 marks if cleaning is thorough and no damage caused, otherwise 0) | 2 | ||
| Sub-Total | 5 | ||
| TASK 4: Fault Identification and Repair | |||
| Tested continuity at multiple test points using multimeter (Award 5 marks if continuity tests are correctly performed and interpreted, otherwise 0) | 5 | ||
| Tested power input to transmitter and receiver (Award 3 marks if power input test is correctly done and results recorded, otherwise 0) | 3 | ||
| Tested speaker output and audio quality (Award 3 marks if speaker output test is correctly done and documented, otherwise 0) | 3 | ||
| Identified and repaired faults such as broken cables or solder joints (Award 5 marks if faults are accurately identified and repaired effectively, otherwise 0) | 5 | ||
| Sub-Total | 16 | ||
| TASK 5: Final Testing and Verification | |||
| Verified transmitter output power meets 5 watts specification (Award 3 marks if verified correctly using appropriate method, otherwise 0) | 3 | ||
| Confirmed receiver sensitivity and clarity (Award 3 marks if receiver performance is tested and confirmed, otherwise 0) | 3 | ||
| Sub-Total | 6 | ||
| TASK 6: Maintenance Report Compilation | |||
| Documented equipment identification (name and model) (Award 2 marks if correctly documented, otherwise 0) | 2 | ||
| Recorded date and time of maintenance (Award 2 marks if recorded correctly, otherwise 0) | 2 | ||
| Listed maintenance tasks performed (Award 3 marks if listed comprehensively, otherwise 0) | 3 | ||
| Identified maintenance personnel (Award 2 marks if personnel identified, otherwise 0) | 2 | ||
| Listed tools and materials used (Award 2 marks if listed correctly, otherwise 0) | 2 | ||
| Recorded observations and findings (Award 3 marks if observations are clear and complete, otherwise 0) | 3 | ||
| Included signature of maintenance personnel (Award 1 mark if signature present, otherwise 0) | 1 | ||
| Sub-Total | 15 | ||
| PRODUCT CHECKLIST | |||
| Transmitter and receiver unit tested and verified to operate at 5W output with clear audio and stable signal (Award 10 marks if all tests pass and unit is fully operational, otherwise 0) | 10 | ||
| All repaired joints are neat, soldered properly without cold joints (Award 5 marks if soldering quality is professional and reliable, otherwise 0) | 5 | ||
| Maintenance checklist and report are complete, accurate, and legible (Award 5 marks if documentation is complete and clearly presented, otherwise 0) | 5 | ||
| Sub-Total | 20 | ||
| GRAND TOTAL | 68 | ||
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