Mathematics
Not publishedof exam
ArithmeticFractions and percentagesSI prefixesFormula calculations
Technical Basics
Not publishedof exam
Circuit quantitiesPassive componentsAC theorySemiconductorsPower supplies
Transmitters and Receivers
Not publishedof exam
Transmitter stagesModulationReceiver stagesMixer productsAmplifier classes
Transmission Lines and Antennas
Not publishedof exam
Feedline lossesStanding wave ratioMatching unitsAntenna patternsEffective radiated power
Propagation
Not publishedof exam
WavelengthPolarisationIonospheric layersMUF and OWFFading
Interference and EMC
Not publishedof exam
Interference pathsReceiver overloadFiltersFerrite chokesStation layout
Safety
Not publishedof exam
Mains hazardsBattery hazardsAntenna erectionLightningRF exposure
Measurements
Not publishedof exam
Frequency checksRF powerSWR meterMultimeterCalibration limits
Quick Facts
- Paper
- Standard theory
- Format
- 50 multiple-choice questions
- Time
- 60 minutes
- Pass mark
- 70% · 35 correct
- Authority
- ACMA
- Delivery
- Accredited assessor
- Exam fee
- Free
- Formula sheet
- Provided
- Coverage
- Parts 3–8, 10–11
- Assumed knowledge
- Foundation syllabus
Formula Triangles
Cover the wanted quantity
E over I×RP over E×IThen rearrange
Formula Core
- Ohm voltage
- E=IR
- Ohm current
- I=E/R
- Ohm resistance
- R=E/I
- DC power
- P=EI
- Power via current
- P=I²R
- Power via voltage
- P=E²/R
- Period
- T=1/f seconds
- Frequency
- f=1/T hertz
- Wavelength
- λ(m)=300/f(MHz)
- Efficiency
- RF output/input × 100%
Reactance vs Impedance
Reactance
- Inductive or capacitive
- Frequency dependent
- Part of impedance
Impedance
- Total AC opposition
- Includes resistance
- Whole circuit quantity
Component effect versus total opposition
Component Combinations
- Series resistors
- Values add
- Parallel resistors
- Reciprocals add
- Series capacitors
- Reciprocals add
- Parallel capacitors
- Values add
- Series inductors
- Values add
- Parallel inductors
- Reciprocals add
- Capacitance
- Electric-field storage
- Inductance
- Magnetic-field storage
- Polarised capacitor
- Observe polarity
- Capacitor charge
- Can remain dangerous
Series vs Parallel Tuning
Series tuned
- Low resonant impedance
- Current becomes large
- XL equals XC
Parallel tuned
- High resonant impedance
- Supply current becomes small
- XL equals XC
Series low; parallel high
AC, Tuning, and Transformers
- RMS sine
- 0.707 × peak
- One cycle
- 360 degrees
- Reactance
- Component AC opposition
- Impedance
- Total AC opposition
- Resonance
- XL=XC
- Resonant impedance
- Purely resistive
- Q factor
- Lower losses mean higher Q
- Series tuning
- Low resonant impedance
- Parallel tuning
- High resonant impedance
- Transformer voltage
- Follows turns ratio
- Transformer current
- Inverse turns ratio
- Laminations
- Reduce eddy currents
Power and Semiconductors
- Half-wave rectifier
- One half-cycle
- Full-wave rectifier
- Both half-cycles
- Bridge rectifier
- Four-diode full-wave
- Smoothing
- Reduces ripple
- Diode PIV
- Must exceed reverse peak
- Forward voltage
- Diode conduction drop
- Zener diode
- Voltage regulation
- Varactor diode
- Voltage-variable capacitance
- NPN or PNP
- Common-emitter stage
- FET
- Common-source stage
- Transistor internals
- Not required
Sensitivity vs Selectivity
Sensitivity
- Weak-signal ability
- Signal strength limit
- Not adjacent rejection
Selectivity
- Separates nearby signals
- Filter bandwidth matters
- Not weak-signal ability
Hear weak versus reject nearby
Transmitter Chain
- Audio input
- Processes microphone signal
- Carrier oscillator
- Creates RF carrier
- VFO
- Tunes operating frequency
- Mixer
- Converts frequency
- Multiplier
- Raises carrier frequency
- Modulator
- Adds information
- Driver
- Feeds output stage
- Power amplifier
- Raises RF power
- Output filter
- Suppresses unwanted emissions
- ALC
- Limits transmitter drive
- Linear amplifier
- Preserves waveform
- Duty cycle
- Affects power rating
ALC vs AGC
ALC
- Transmitter control
- Limits amplifier drive
- Prevents excess output
AGC
- Receiver control
- Adjusts receiver gain
- Stabilises audio level
ALC transmits; AGC receives
Modulation and Data
- AM
- Carrier amplitude varies
- FM
- Carrier frequency varies
- SSB
- One sideband, carrier suppressed
- AM depth
- Modulation amount
- FM deviation
- Peak frequency shift
- Morse
- On-off carrier keying
- RTTY
- Frequency-shift keying
- PSK
- Carrier phase shifts
- Packet
- Data frames over radio
- Digital bandwidth
- Rises with data rate
Receiver Chain
- Sensitivity
- Weakest usable signal
- Selectivity
- Rejects nearby signals
- SNR
- Signal versus noise
- RF amplifier
- Boosts received RF
- Mixer and LO
- Create intermediate frequency
- IF amplifier
- Fixed-frequency gain and filtering
- Crystal filter
- Sharp IF selectivity
- Ceramic filter
- IF selectivity
- Demodulator
- Recovers information
- Audio amplifier
- Drives speaker
- AGC
- Stabilises received level
- RIT
- Offsets receive frequency
- Shared stages
- Oscillators and IF
ATU vs Balun
ATU
- Transforms impedance
- Tunes reactive load
- May sit transmitter-side
Balun
- Balanced-unbalanced interface
- Limits feedline radiation
- Useful with coaxial feed
Match impedance versus balance currents
Feedlines and Matching
- Velocity factor
- Always below one
- Line loss
- Rises with frequency
- VHF feedline
- Low loss matters
- Balanced antenna
- Use balun with coax
- Balun
- Limits feedline radiation
- Mismatch
- Creates reflected waves
- Standing waves
- Forward plus reflected
- SWR
- Mismatch indicator
- Acceptable SWR
- 1.5:1 or lower
- High SWR
- Raises feedline loss
- ATU
- Transforms impedance
- Shack ATU
- Line SWR remains
Antennas and ERP
- Antenna length
- Falls as frequency rises
- Dipole
- Half-wave, centre-fed
- Folded dipole
- Higher feedpoint impedance
- Ground plane
- Quarter-wave vertical
- Yagi
- Directional array
- End-fed wire
- Fed near one end
- Low radiation angle
- Favours long-distance paths
- Polarisation
- Set by electric field
- ERP
- Add gains; subtract losses
- Feedline exit
- Leave antenna at right angles
Layer Ladder
D absorbs; F goes far
D: daytime absorptionF2: longest single hopNight: F layers combine
MUF vs OWF
MUF
- Highest refracted frequency
- Path specific
- Upper usable boundary
OWF
- Preferred working frequency
- 15% below MUF
- Adds operating margin
Maximum limit versus working choice
Ionospheric Propagation
- Radio speed
- 300 million metres/second
- Electric field
- Perpendicular magnetic field
- Free space
- Straight-line spreading
- D layer
- Daytime low-frequency absorption
- E layer
- Ionospheric refraction
- Daytime F1/F2
- Separate upper layers
- Night F layer
- F1 and F2 combine
- F2 hop
- About 4000 km
- Multiple hops
- Worldwide paths
- Fading
- Received strength varies
- MUF
- Highest refracted frequency
- OWF
- 15% below MUF
- Seasonal change
- Alters useful bands
EMC First Aid
Power down, route right, filter entry
Minimum useful powerFeedline exits right-angleFilter entry path
Interference Triage
- Neighbour reports interference→Stay diplomatic(Gather symptoms)
- Every transmission triggers it→Check station first(Connections and earth)
- Only high power triggers it→Reduce RF power(Retest)
- Audio reproduces your voice→Add ferrite filtering(Audio-lead entry)
- Receiver front end overloads→Suitable RF filter(At victim input)
- Coax feeds balanced antenna→Install balun(Reduce common-mode current)
- Feedline parallels antenna→Reroute at right angles(Reduce coupling)
- Problem persists→Seek technical advice(ACMA may assist)
EMC Control
- RF-stage entry
- Antenna-path interference
- IF-stage entry
- Receiver conversion path
- Audio entry
- Long leads conduct RF
- Wideband amplifiers
- Strong-signal overload
- Audio nonlinearity
- Demodulates RF
- Low-pass filter
- Passes lower frequencies
- High-pass filter
- Passes higher frequencies
- Band-pass filter
- Passes selected band
- Notch filter
- Rejects selected band
- Ferrite beads
- Suppress common-mode RF
- Balanced antenna
- Usually fewer EMC issues
- Minimum power
- Reduces field strength
- Feedline routing
- Right angle from antenna
- Vehicle EMC
- Protect electronic controls
- Neighbour complaint
- Use diplomacy
Shock Response
Switch off before touching
Isolate power firstCall emergency servicesCPR may follow
Station Safety
- High voltage/current
- Both are dangerous
- Approval label
- Required mains equipment
- Safety earth
- Provides fault path
- Active-lead fuse
- Limits excess current
- Fuse replacement
- Use specified rating
- Damaged lead
- Authorised repair only
- Emergency switch
- Clearly marked OFF
- Electrical accident
- First isolate power
- Shock casualty
- Never touch while powered
- Emergency response
- Call help; consider CPR
- Batteries
- Fumes, chemicals, explosion
- Antenna exclusion
- Protect people and animals
- RF danger
- Frequency, power, proximity
- Safe distance
- Depends on ERP and antenna
- Antenna erection
- Use qualified persons
- Mains lines
- Keep antennas well clear
- Thunderstorm
- Disconnect; never operate
- Headphones
- Avoid excessive volume
- Station security
- Block unauthorised access
Measurement Picker
- Check transmitter frequency→Frequency counter(Mind calibration)
- Need external reference→Standard transmission(Availability varies)
- Check dial calibration→Crystal calibrator(Spot frequencies)
- Measure RF output→Calibrated power device
- Check antenna match→SWR meter
- Measure potential difference→Voltmeter mode(Across circuit)
- Measure circuit current→Ammeter mode(Through circuit)
- Measure resistance→Ohmmeter mode(Power off first)
Test Instruments
- Crystal calibrator
- Frequency reference
- Frequency counter
- Direct frequency reading
- Standard transmission
- External frequency reference
- RF power
- Use calibrated device
- SWR meter
- Checks matching
- Multimeter voltage
- Connect across circuit
- Multimeter current
- Connect through circuit
- Multimeter resistance
- Power circuit off
Common Traps
Theory is not certification
Theory is one component ≠ Regulations and practical remain
Shack ATU limits
Transforms presented impedance ≠ Antenna-side line SWR remains
SWR meaning
SWR indicates mismatch ≠ Feedline loss also matters
Gain-control mix-up
ALC controls transmission ≠ AGC controls reception
OWF direction
OWF sits below MUF ≠ Subtract fifteen percent
Electrical casualty
Isolate power first ≠ Never touch while energised
Amplifier power rating
Duty cycle changes loading ≠ Mode choice affects heating
Filter direction
Low-pass keeps lower frequencies ≠ High-pass keeps higher frequencies
Last Minute
- 1.Memorise every supplied formula
- 2.Practise same-value component networks
- 3.Trace transmitter blocks in order
- 4.Trace superhet receiver blocks
- 5.Match filters to entry paths
- 6.Know SWR and ATU limits
- 7.Recall five named antennas
- 8.Sketch ionospheric layers
- 9.Separate MUF from OWF
- 10.Choose each measuring instrument
- 11.Rehearse electrical accident response
- 12.Check formula-sheet units
- 13.Target at least 35 correct
- 14.Answer all 50 questions
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