How to Use These Supplements
These items are organized to match the Amateur Extra License Course chapter and lesson structure. Peruse them after completing each lesson to deepen your understanding. Open any chapter below to explore its resources.
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Before We Begin...
Introductory review & background resources
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Find an Exam Session Near You (ARRL)External
Enter your zip code to find a Volunteer Examiner exam session in your local area.
Mode CharacteristicsAudio
Audio lesson covering the characteristics of different transmission modes.
Loads of ModesArticle
Overview of transmission modes — AM, FM, SSB, CW, digital — relevant review before the Extra course.
SSB Bandwidth AdvantageVideo
Video explaining the bandwidth efficiency advantage of Single Sideband over AM.
Polarization EffectsVideo
Video demonstrating the effects of antenna polarization on signal quality.
Ham-Speak: Learning the LingoArticle
Common ham radio jargon, abbreviations, and Q-codes — useful review for the Extra course.
Conventional & Electronic Current (YouTube)Video
Conventional current flow vs. electron flow — foundational concept for circuit analysis.
AC vs DC (YouTube)Video
Alternating vs. direct current — behavior differences in circuits and power systems.
Time & Frequency Domain Signal ViewsArticle
How the same signal appears differently in the time domain and frequency domain — key for Extra-level signal analysis.
Time & Frequency Domain FFT AnalyzerApp
Explore and view signals in both time and frequency domain visualizations.
1
Operating Your Station
2 lessons — Common operating practices, amateur satellite operations
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1.1
Common Operating Practices
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Split-mode OperationsArticle
How and why to operate split — transmitting on one frequency while listening on another for DX pile-ups.
Simplex, Duplex, Offset, SplitArticle
Clarifying the differences between simplex, duplex, offset, and split operating modes.
The Difference with HFArticle
How HF operating differs from VHF/UHF — propagation, procedures, and etiquette on the HF bands.
Working DXArticle
Practical techniques for making DX contacts on HF — calling procedures and pile-up tactics.
Practical Signal ReportsArticle
How to give and receive meaningful RST signal reports on the HF bands.
Maidenhead Grid LocatorExternal
Interactive map tool for finding your Maidenhead grid square — used in VHF contests and satellite work.
ARRL Field DayArticle
What Field Day is all about — operating portable stations in the field and making the most of the annual event.
Why Radio Contest?Article
Why ham radio operators participate in contests and what makes contesting a rewarding part of the hobby.
Azimuthal Projection Map Creator (NS6T)External
Generate a custom azimuthal equidistant map centered on your location — shows beam headings to all parts of the world.
1.2
Amateur Satellite Operations
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Making Satellite ContactsArticle
How to make your first amateur satellite contact — equipment, tracking, Doppler correction, and operating tips.
Heavens-Above Satellite TrackingExternal
Real-time satellite pass predictions for your location — ISS, amateur satellites, and more.
AMSAT HomeExternal
The Radio Amateur Satellite Corporation — news, satellite status, and resources for amateur satellite operation.
AMSAT Transponder Satellite InfoExternal
Current linear transponder satellite frequency summaries — uplink and downlink frequencies for SSB/CW satellite work.
AMSAT Current Satellite StatusesExternal
Real-time operational status of AMSAT amateur satellites — check before planning a satellite QSO.
2
Rules & Regulations
3 lessons — Operational regs, station control, VE regulations
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2.1
Operational Regulations
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Allowable International ContactsArticle
Which countries permit third-party traffic and international contacts with US amateur stations.
RACES Regulations §97.407 (eCFR)External
Official FCC Part 97 RACES regulations — rules governing Radio Amateur Civil Emergency Service operations.
Prohibited Transmissions §97.113 (eCFR)External
FCC Part 97 prohibited transmissions — what amateur stations may not transmit under any circumstances.
Third-party Communications §97.115 (eCFR)External
FCC Part 97 rules governing third-party communications in the amateur service.
International Operations Info (ARRL)External
ARRL's guide to international reciprocal operating permits for US hams operating abroad.
IARP Info (ARRL)External
International Amateur Radio Permit — allows US hams to operate in participating IARP countries.
CEPT Info (ARRL)External
CEPT agreement — allows US General and Extra class hams to operate in European countries.
2.2
Station Control & Restrictions
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Max Antenna Height at Airports (G1B01)Article
FCC height limits for amateur antenna structures and notification requirements for taller installations.
Station Control §97.109 (eCFR)External
FCC Part 97 station control rules — control operator requirements, remote control, and automatic control provisions.
2.3
Volunteer Examiner Regulations
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NCVEC OrganizationExternal
National Conference of Volunteer Examiner Coordinators — the organization that oversees amateur radio exam question pools.
ARRL VECExternal
ARRL Volunteer Examiner Coordinator — info on becoming a VE and finding ARRL exam sessions.
FCC List of VECsExternal
Official FCC list of all accredited Volunteer Examiner Coordinator organizations.
3
Propagation
2 lessons — HF propagation factors, VHF+ propagation
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3.1
HF Propagation Factors
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Chordal Hop PropagationArticle
How chordal hop propagation enables signals to travel very long distances with less loss than conventional multi-hop skip.
Sunspots & PropagationArticle
How solar activity and the sunspot cycle affect HF radio wave propagation through the ionosphere.
Variable Propagation ConditionsArticle
Why HF propagation varies dramatically throughout the day, season, and solar cycle.
D-layer AbsorptionArticle
How the ionospheric D-layer absorbs HF signals during daylight and why certain bands go quiet.
Skip FadeArticle
What causes skip zone fading and why distant stations can sometimes be stronger than nearby ones.
Spaceweather.comExternal
Daily solar weather — sunspot numbers, solar flux index, geomagnetic conditions, and propagation forecasts.
DX MapsExternal
Real-time map of ham radio contacts being made worldwide — see current propagation conditions visually.
Understanding Solar Indices (ARRL PDF)PDF
ARRL article explaining solar flux index, A-index, K-index, and how to interpret them for HF propagation prediction.
NOAA Space Weather ScalesExternal
NOAA's explanation of space weather scales — geomagnetic storm, solar radiation storm, and radio blackout categories.
3.2
VHF+ Propagation Factors
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Hepburn Tropo Ducting PredictionsExternal
William Hepburn's six-day forecast of tropospheric ducting conditions for VHF/UHF DX propagation worldwide.
Starting Guide to Meteor Scatter (ARRL PDF)PDF
ARRL QST article — getting started with meteor scatter communications on VHF bands.
MSK144: Getting on the air (K5ND)External
Learn the practical aspects of using MSK144 for meteor scatter.
Meteor Scatter OperationsExternal
Detailed overview of meteor scatter propagation — how it works, when to operate, and equipment requirements.
Meteor Scatter CW SoundVideo
Audio/video of actual meteor scatter CW signals — hear what meteor scatter sounds like.
4
Digital Modes
5 lessons — Encoding, FSK, packet, additional modes, ATV
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4.1
Digital Encoding Concepts
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Varicode (PSK31)Article
How PSK31's Varicode encoding achieves efficiency using variable-length character codes.
Baudot Code Table / DecoderExternal
Interactive Baudot code reference table and decoder — the 5-bit character set used in RTTY.
ASCII Code TableExternal
Complete ASCII character code table — the 7-bit character encoding used in most digital communications.
Gray CodeExternal
Gray code explained — the reflected binary code that minimizes bit transitions between consecutive values.
ARQ (Auto Repeat Query)Article
How ARQ error-correction systems automatically request retransmission of corrupted data packets.
4.2
Frequency Shift Keying Modes
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FT8 Starting Guide (YouTube)Video
Step-by-step guide to getting started with FT8 — software setup, operating procedures, and making contacts.
FT8 Operations Example (YouTube)Video
Demonstration of a complete FT8 QSO — calling, responding, and completing the contact exchange.
4.3
Digital Packet Modes
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APRS.fi Web Map InterfaceExternal
Real-time web map of APRS (Automatic Packet Reporting System) stations, weather stations, and objects worldwide.
PACTOR III Signal IdentificationExternal
Signal identification wiki entry for PACTOR III — audio samples and spectral characteristics of this HF digital mode.
PACTOR Description (ARRL)External
ARRL's overview of PACTOR — the high-performance HF packet protocol used for Winlink email and data transfers.
OFDM Detail (WiFi use)External
Orthogonal Frequency Division Multiplexing explained — the multi-carrier modulation technique used in WiFi and some ham digital modes.
Broadband-Hamnet MeshExternal
Amateur radio broadband mesh networking. Note: content is dated — see also AREDN for current development.
AREDN Mesh Network HomeExternal
Amateur Radio Emergency Data Network — current standard for amateur IP mesh networking for emergency communications.
4.4
Additional Digital Modes
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Digital Voice ModesArticle
Introduction to digital voice — D-STAR, DMR, Fusion/C4FM — how they work and how to get started.
PSK31 GuideExternal
Comprehensive guide to PSK31 operations — software, setup, frequencies, and making your first contact.
PSK31 Exchange (YouTube)Video
Video of a PSK31 QSO exchange — see the software waterfall display and contact format in action.
Learn CW Online (LCWO)External
Free online Morse code training using the Koch method — the most effective approach for learning CW.
I-Q ModulationArticle
Quadrature (I/Q) modulation explained — the technique enabling modern SDR and software-defined digital modes.
4.5
Amateur TV
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Amateur TV Handbook (ARRL PDF)PDF
ARRL Amateur Television Handbook — comprehensive guide to ATV operating, equipment, and technical standards.
ATV Info (RSGB)External
RSGB's Amateur Television resources — modes, frequencies, and getting started with ATV.
5
Electrical Circuit Principles
2 lessons — Complex impedance, resonant circuits & Q
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5.1
Complex Impedance
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Complex Impedance Part 1Article
Introduction to complex impedance — resistance, reactance, and phasor representation of AC circuits.
Capacitive ReactanceArticle
How capacitive reactance varies with frequency — Xc = 1/(2πfC) and its ham radio applications.
Calculating the Tangent (YouTube)Video
How to calculate the tangent of an angle — used in impedance phase angle calculations for Extra class topics.
Pythagorean Theorem (YouTube)Video
The Pythagorean theorem — used to calculate magnitude of complex impedance from resistance and reactance.
Calculating with Cosine (AC Power)Article
Using the cosine of phase angle in AC power calculations — real power, apparent power, and power factor.
Power Factor (YouTube)Video
Understanding power factor in AC circuits — real power, reactive power, and apparent power relationships.
5.2
Resonant Circuits and Q
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Resonance AnalogyArticle
Intuitive explanation of resonance in LC circuits — the foundation of tuned filters and antenna behavior.
Q: A Different ApproachArticle
How Q factor relates to circuit bandwidth — high Q means narrow bandwidth, low Q means broad bandwidth.
6
Hamtronics I: Components
5 lessons — Inductors, semiconductors, VHF+ packaging, photovoltaics, digital logic
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6.1
Inductors & Cores
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InductorsArticle
How inductors work, their role in RF circuits, and how inductance relates to coil construction and core material.
How Inductors Work I (YouTube)Video
How inductors store magnetic energy and oppose changes in current — Part 1 of a two-part explanation.
How Inductors Work II (YouTube)Video
Inductor behavior in AC circuits — reactance, impedance, and applications in RF filtering and tuning.
Transformer WindingsArticle
How transformer turns ratio determines voltage transformation — key for Extra-level power supply and impedance matching topics.
Transformer Winding DiametersArticle
How wire diameter in transformer windings affects current capacity and efficiency.
How Transformers Work (YouTube)Video
How transformers use electromagnetic induction to change AC voltage levels — core types and construction.
6.2
Semiconductor Components
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Capacitors Explained (YouTube)Video
How capacitors store and release electrical energy — construction, ratings, and use in RF circuits.
Transistors Explained (YouTube)Video
How transistors work as amplifiers and switches — BJT operation and applications in RF circuits.
Diodes Explained (YouTube)Video
How diodes work — PN junction, forward/reverse bias, rectification, and protection applications.
LEDs Explained (YouTube)Video
How light-emitting diodes work — electroluminescence, forward voltage, and applications in ham radio equipment.
Zener Diode Explained (YouTube)Video
How Zener diodes operate in reverse breakdown — voltage regulation and reference applications.
FET/JFET/MOSFET (YouTube)Video
Field-effect transistors — JFET and MOSFET operation, gate control, and use in RF amplifier circuits.
MOSFET (YouTube)Video
MOSFET operation in detail — enhancement and depletion modes, biasing, and power applications.
6.3
VHF+ Component Packaging
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Surface Mount Technology (YouTube)Video
Introduction to SMT components and PCB assembly — the standard in modern ham radio equipment.
Surface Mount Facility (YouTube)Video
Tour of a PCB surface mount assembly facility — how modern electronic equipment is manufactured.
IC Packaging Types (YouTube)Video
Overview of IC package types — DIP, SOIC, QFP, BGA — and their VHF+ performance characteristics.
6.4
Photovoltaics & Optoelectronics
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How LCDs WorkArticle
How liquid crystal display technology works — used in transceiver displays and other ham radio equipment.
Simple Solar Power SystemArticle
Building a small solar power system for portable and emergency ham radio operations.
Basic Solar Power System (YouTube)Video
Setting up a basic solar power system — panels, charge controllers, batteries, and inverters.
6.5
Digital Logic Devices
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Logic Gates (YouTube)Video
AND, OR, NOT, NAND, NOR, XOR logic gates — truth tables and how they build digital circuits.
Combining Logic Gates (YouTube)Video
How to combine basic logic gates to build more complex digital functions and circuits.
7
Hamtronics II: Analog Circuits
4 lessons — Amplifiers, filters, power supplies, oscillators
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7.1
Amplifiers
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Operational AmplifiersArticle
Op amp fundamentals — inverting, non-inverting, and comparator configurations in ham radio circuits.
Vacuum TubesArticle
How vacuum tubes work and why they remain in use for high-power ham radio amplifiers today.
Op Amp AnalysesArticle
Analysis of op amp circuit configurations — gain formulas, virtual ground, and feedback network calculations.
7.2
Filters & Matching Networks
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Filter SimulatorApp
Explore various filter shapes and bandwidths applied to stock and custom-recorded audio signals.
Low Pass Filters 1 (YouTube)Video
RC and LC low pass filter design — cutoff frequency, rolloff characteristics, and applications.
Low Pass Filters 2 (YouTube)Video
Advanced low pass filter concepts — Butterworth, Chebyshev, and Bessel filter characteristics.
High Pass Filters (YouTube)Video
High pass filter design — cutoff frequency calculation and applications in ham radio signal processing.
Tuning a Duplexer Filter (YouTube)Video
How to tune a cavity duplexer filter for repeater use — practical procedure for minimizing insertion loss.
Repeater Duplexer Repair (YouTube)Video
Practical duplexer repair and tuning — diagnosing and fixing duplexer problems in a repeater installation.
7.3
Power Regulators & Supplies
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Bleeder Resistors in SuppliesArticle
Why power supplies use bleeder resistors — safety discharge of filter capacitors and voltage regulation.
Linear Supply Function (YouTube)Video
How a linear regulated power supply works — transformer, rectifier, filter, and regulator stages.
Linear Supply vs. SMPS (YouTube)Video
Comparing linear and switch-mode power supplies — efficiency, noise, size, and use cases.
Linear/SMPS Performance (YouTube)Video
Performance comparison of linear vs. switch-mode power supplies — ripple, regulation, and transient response.
7.4
Oscillators & Signal Generators
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Oscillator Basics (YouTube)Video
How oscillator circuits generate stable RF frequencies — LC, crystal, and VCO types explained.
Colpitts Oscillator (YouTube)Video
The Colpitts oscillator circuit — how capacitive voltage divider feedback produces stable oscillation.
Hartley Oscillator (YouTube)Video
The Hartley oscillator circuit — inductive voltage divider feedback and frequency determination.
Direct Digital Synthesis 1 (Analog Devices)External
Analog Devices technical article on DDS — architecture, phase accumulator, and DAC operation in detail.
Direct Digital Synthesis 2 (DigiKey)External
DigiKey's practical guide to DDS — how it generates precise frequencies and its advantages over analog VCOs.
Direct Digital Synthesis 3 (YouTube)Video
Video explanation of DDS frequency synthesis — how the phase accumulator and lookup table generate sine waves.
8
Processing Signals
3 lessons — Modulation/demodulation, FM processing, DSP
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8.1
Modulation & Demodulation
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AM SimulatorApp
Simulates amplitude modulation of an RF carrier by a baseband signal such as audio — see AM modulation in action.
Understanding SSBArticle
Clear conceptual explanation of SSB — how it suppresses the carrier and one sideband to concentrate power.
SSB Bandwidth AdvantageVideo
Video explaining the advantages of SSB over AM for HF voice communication.
SSB Audio RequiredArticle
Why an SSB transmitter produces no RF output without audio input — understanding PEP and average power.
Heterodyne Receiver FunctionArticle
How the superhet receiver uses frequency mixing and IF stages to achieve selectivity and sensitivity.
Receiver Signal DiscriminationArticle
How receiver selectivity and dynamic range determine a radio's ability to reject unwanted signals.
SSB Receive FiltersArticle
How receiver IF bandwidth filters affect SSB signal quality and selectivity.
QRM and Receive Filtering SimulatorApp
Interactively explore realistic SSB and CW receive filter effects with interfering signals in the band.
8.2
FM Signal Processing
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FM SimulatorApp
Simulates frequency modulation of an RF carrier — watch how audio input causes the carrier frequency to deviate.
FM BandwidthArticle
Why FM signals occupy more bandwidth than AM or SSB — the trade-off between bandwidth and audio quality.
Carson's Rule on FM BandwidthArticle
Carson's Rule for estimating FM signal bandwidth — a key formula for occupied spectrum calculations.
8.3
Digital Signal Processing
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Digital Signal ProcessingArticle
How DSP improves modern ham radio receivers — filtering, noise reduction, and demodulation in software.
Direct Digital ConversionArticle
How direct-conversion SDR receivers digitize the RF signal — ADC/DAC in the signal path.
I-Q ModulationArticle
Quadrature (I/Q) signal processing — the technique enabling software-defined radio demodulation.
Fourier Analysis — Square Wave (YouTube)Video
Fourier analysis of a square wave — decomposing it into its harmonic components using the Fourier series.
Fourier Analysis — Sawtooth (YouTube)Video
Fourier analysis of a sawtooth wave — the basis for understanding digital signal spectrum and DSP filtering.
9
Station Performance & Measurement
2 lessons — Noise & spurious emissions, measuring performance
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9.1
Noise & Spurious Emissions
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Intermodulation Products (YouTube)Video
How intermodulation distortion generates spurious signals — IMD products and their effect on receiver performance.
3rd Order Intercept (YouTube)Video
Third-order intercept point (IP3) — the key figure of merit for receiver and amplifier linearity performance.
Types of RF InterferenceArticle
Categories of RFI — conducted, radiated, intermodulation, and harmonic interference.
Ignition Interference (Mobile)Article
Vehicle ignition noise in mobile installations and practical suppression techniques.
Mobile RFI ProblemsArticle
Part 2 of the mobile installation series — diagnosing and solving RFI problems in vehicle installations.
Part 15 DevicesArticle
FCC Part 15 unlicensed devices and how they can cause interference to amateur radio stations.
9.2
Measuring Performance
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10 Uses for a MultimeterArticle
Practical applications of a DMM in the ham shack — voltage, current, resistance, continuity, and more.
Oscilloscope Basics (YouTube)Video
Getting started with an oscilloscope — controls, probes, triggering, and reading waveforms.
Spectrum AnalyzerArticle
How a spectrum analyzer displays signal energy vs. frequency — essential for evaluating transmitter performance.
Using a Spectrum Analyzer (YouTube)Video
Practical spectrum analyzer operation — setting span, resolution bandwidth, and interpreting displays.
Spectrum Analyzer Operations (YouTube)Video
Advanced spectrum analyzer measurements — marker functions, peak detection, and spurious signal identification.
VNA Antenna Measurement (YouTube)Video
Using a Vector Network Analyzer to measure antenna impedance, SWR, and return loss.
10
Antennas
6 lessons — Types, performance, impedance matching, transmission lines, Smith Chart, special antennas
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10.1
Types of Antennas
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dBi vs. dBdArticle
Antenna gain reference units — converting between dBi and dBd and understanding what each means.
Trimming a Dipole WireArticle
How to adjust dipole antenna length for resonance and minimum SWR on your target frequency.
Yagi Driven ElementArticle
The role of the driven element in a Yagi and how parasitic directors and reflectors shape the pattern.
Yagi Basics (YouTube)Video
Yagi antenna fundamentals — elements, spacing, and how gain and directivity are achieved.
Near Vertical Incidence Antenna (NVIS)Article
NVIS antenna design and operating techniques for regional HF communications within 300 miles.
10.2
Performance Factors
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Understanding SWR (YouTube)Video
What SWR means, how it's measured, and how impedance mismatch creates standing waves on a transmission line.
Using an SWR Meter (YouTube)Video
Practical SWR meter operation — calibration, forward/reflected power reading, and interpreting results.
Reflection Coefficient (Wikipedia)External
The reflection coefficient Γ — the ratio of reflected to incident wave amplitude, related to SWR and return loss.
EIRP and Gain (YouTube)Video
A thorough explanation of EIRP and gain using simple mathematical descriptions.
10.3
Impedance Matching & Phasing
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SWR Wave SimulatorApp
Visualize the voltage traveling waves in a transmission line and how they interact to determine SWR.
Dipole ImpedanceArticle
Why a center-fed half-wave dipole has approximately 72 ohms impedance and how height above ground affects this.
SWR Perfect MatchArticle
What a 1:1 SWR reading means and why a perfect impedance match maximizes power transfer.
Good SWR & ResonanceArticle
The relationship between antenna resonance and SWR — when low SWR indicates a well-matched system.
Phased Antennas 1 (YouTube)Video
Introduction to phased antenna arrays — how phasing two elements changes the radiation pattern and gain.
Phased Antennas 2 (YouTube)Video
Phased array design for directional gain — spacing, phasing networks, and practical implementations.
Phased Antennas 3 (YouTube)Video
Advanced phased array concepts — endfire vs. broadside arrays and steering the pattern direction.
10.4
Transmission Lines
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Characteristic Impedance (AD5GG)External
Clear explanation of characteristic impedance — what it is, what determines it, and why it matters in RF systems.
Standing Waves AnimationExternal
Interactive animation of standing wave formation on transmission lines — visualize incident, reflected, and standing waves.
SWR Illustration (Penn State)External
Penn State physics demonstration of SWR on transmission lines — interactive visualization of standing wave patterns.
Coaxial Cable Signal LossArticle
How coaxial cable loss varies with frequency and length — selecting the right cable for your installation.
What Coaxial Cable to Use?Article
Practical guide to selecting coaxial cable — RG-8, RG-213, LMR-400, and when to use each type.
10.5
Smith Chart
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Smith Chart Basics (YouTube)Video
Introduction to the Smith Chart — what it represents and how to read impedance values from it.
Understanding Smith Chart (YouTube)Video
Deeper understanding of the Smith Chart — using it for impedance matching and transmission line analysis.
10.6
Special Antennas
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Log Periodic AntennaArticle
How log periodic antennas provide broadband directional gain — useful for covering multiple HF bands.
Beverage Antenna Setup (YouTube)Video
Setting up a Beverage antenna — the long-wire receiving antenna prized for its directional low-noise characteristics on LF/HF.
Rhombic Angle Effects Model (YouTube)Video
Computer model showing how the leg angle of a rhombic antenna affects its radiation pattern and gain.
Rhombic Height Effects Model (YouTube)Video
Computer model showing how rhombic antenna height above ground affects the elevation angle of maximum radiation.
Dish Transmit & Receive Wavefronts Model (YouTube)Video
Animation of parabolic dish antenna wavefronts — how a dish focuses transmitted and received signals at microwave frequencies.
11
Safety
RF exposure, electrical safety, tower grounding
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RF Exposure & MitigationArticle
The factors determining RF exposure levels — power, frequency, duty cycle, distance, and antenna gain.
RF Exposure Calculator (Hintlink/VP9KF)External
Online calculator for RF power density and MPE compliance evaluation for amateur radio stations.
RF BurnsArticle
How RF energy causes burns — safe practices when working around transmitting antennas.
Electric Shock ProtectionArticle
How electrical shock occurs and the protective measures required in amateur radio installations.
Tower GroundingArticle
Proper tower and antenna grounding to protect your station from lightning and static discharge.
RF Safety (ARRL)External
ARRL's comprehensive safety resource — RF exposure, electrical safety, tower safety, and emergency procedures.
Grounding & Bonding Book (ARRL)External
ARRL's comprehensive reference on station grounding and bonding for RF performance and lightning protection.
Ward Silver Grounding Video (YouTube)Video
Ward Silver N0AX's detailed presentation on ham radio station grounding and bonding practices.