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Technician Course, Module 2: The Wave
Covers NCVEC 2026-2030 Technician Pool, Subelement T3 (Radio Wave Propagation). Three questions on your exam come from this material.
Ray drives you up a fire road to a hilltop at sunset, parks, and clips a handheld to the dash. A repeater fifty miles away comes back to his call like it is across the street.
"Down in town, I cannot hit that machine at all," he says. "Same radio, same power. The only thing that changed is what is between me and it. Tonight you learn what a radio signal actually is, and why where matters as much as watts."
2.1What a Radio Wave Actually Is
Key up a transmitter and the antenna launches an electromagnetic wave: an electric field and a magnetic field, locked together at right angles to each other, traveling outward at the speed of light. In free space that is 300,000,000 meters per second. Every radio frequency travels at that same speed, from the longest longwave to the highest microwave. Nothing outruns anything.
Since the speed never changes, frequency and wavelength are locked together. Crank the frequency up and each cycle has less time to travel, so the wave gets shorter. Frequency up, wavelength down. Always.
The conversion is one piece of arithmetic you will use for the rest of your ham life:
Wavelength in meters = 300 divided by frequency in MHz
Try it. 146.52 MHz: 300 / 146.52 is right around 2. That is why we call it the 2-meter band. 52.525 MHz gives about 6 meters. 28.4 MHz gives about 10 meters. Hams name bands by their approximate wavelength in meters, and now you can decode every band name on the chart.
The spectrum also gets sliced into named ranges, and the exam wants three of them cold:
- HF (High Frequency): 3 to 30 MHz. The worldwide bands.
- VHF (Very High Frequency): 30 to 300 MHz. Home of 6 meters and 2 meters.
- UHF (Ultra High Frequency): 300 to 3000 MHz. Home of 70 centimeters.
Ray's memory trick: each range starts where the last one ended, and each is ten times wider than the one before. Learn the VHF boundaries (30 to 300 MHz) and the others fall into place on either side.
Knowledge Check 2.1
Tap an answer. In your own words first, then check yourself.
1. What is the velocity of a radio wave in free space?
2. What is the approximate wavelength of a 146 MHz signal?
3. Which frequency range is VHF?
T3B the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T3B01 What is the relationship between the electric and magnetic fields of an electromagnetic wave?
Answer They are at right angles
Tip In a radio wave the electric and magnetic fields sit at right angles to each other, 90 degrees apart.
T3B02 What property of a radio wave defines its polarization?
Answer The orientation of the electric field
Tip Polarization is set by which way the electric field points, so a vertical E field means a vertically polarized wave.
T3B03 What are the two components of a radio wave?
Answer Electric and magnetic fields
Tip A radio wave is just two fields traveling together, electric and magnetic.
T3B04 What is the velocity of a radio wave traveling through free space?
Answer Speed of light
Tip In free space a radio wave travels at the speed of light, the same as any electromagnetic wave.
T3B05 What is the relationship between wavelength and frequency?
Answer Wavelength gets shorter as frequency increases
Tip Wavelength and frequency are a seesaw, so as frequency goes up the wavelength gets shorter.
T3B06 What is the formula for converting frequency to approximate wavelength in meters?
Answer Wavelength in meters equals 300 divided by frequency in megahertz
Tip Wavelength in meters is 300 divided by the frequency in MHz, since 300 million m/s turns into a tidy 300 with MHz.
T3B07 In addition to frequency, which of the following is used to identify amateur radio bands?
Answer The approximate wavelength in meters
Tip We name bands by their rough wavelength in meters, so 146 MHz is the 2 meter band.
T3B08 What frequency range is referred to as VHF?
Answer 30 MHz to 300 MHz
Tip VHF is very high frequency, the 30 to 300 MHz stretch.
T3B09 What frequency range is referred to as UHF?
Answer 300 to 3000 MHz
Tip UHF is ultra high frequency, running from 300 to 3000 MHz, the decade just above VHF.
T3B10 What frequency range is referred to as HF?
Answer 3 to 30 MHz
Tip HF is high frequency, 3 to 30 MHz, the classic shortwave skip range.
T3B11 What is the approximate velocity of a radio wave in free space?
Answer 300,000,000 meters per second
Tip A radio wave in free space moves at about 300,000,000 meters per second, the speed of light.
T3B12 Which of these frequencies travels at the highest velocity in free space?
Answer All radio frequencies travel at the same velocity
Tip Frequency does not change the speed, so in free space all radio waves travel at the same velocity.
2.2The Wave Meets the Real World
Back in the truck, Ray rolls slowly down the hill while you hold a conversation on the repeater. Your signal starts to flutter, chopping in and out in rapid little slices.
"Hear that? Picket fencing." The signal is arriving at the repeater by more than one path at once, bouncing off hills and buildings, and the copies alternately reinforce and cancel each other as you move. That is multipath, and it explains one of the strangest things a new ham discovers: moving an antenna just a few feet can change a VHF signal from unreadable to full quieting, because you moved out of a cancellation spot. On data transmissions, multipath shows up as increased error rates.
Then there is polarization: the orientation of a wave's electric field, which follows the orientation of the antenna that launched it. A vertical antenna makes a vertically polarized wave. Two rules of thumb come from this:
- FM repeater and mobile work uses vertical polarization, because whips on cars and handhelds are vertical.
- Long-distance CW and SSB weak-signal work on VHF and UHF uses horizontal polarization by convention.
Mismatch them across a line-of-sight path (you vertical, the other station horizontal) and the received signal strength drops dramatically. On HF you get a pass: signals refracted by the ionosphere come back elliptically polarized, so either vertical or horizontal antennas work for ionospheric paths.
The environment takes its cut too. Vegetation absorbs UHF and microwave signals, which is why the forest can eat your 70-centimeter signal. Precipitation reduces range at microwave frequencies. And down on 10 and 6 meters, fog and rain have little effect at all. The lower the frequency, the less the weather cares.
When the path is blocked, all is not lost. Signals can bend over a sharp obstacle like a ridge line, an effect called knife-edge diffraction, and a directional antenna can sometimes find a reflected path to a repeater by aiming at a building or hillside instead of at the repeater itself.
Knowledge Check 2.2
Tap an answer. In your own words first, then check yourself.
1. Your mobile 2-meter signal flutters rapidly as you drive. What is this called, and what causes it?
2. What describes the polarization of a radio wave?
3. Buildings block your direct path to a distant repeater and you have a beam antenna. What is worth trying?
T3A the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T3A01 Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?
Answer Multipath propagation cancels or reinforces signals
Tip At VHF, signals arrive by several paths and add or subtract, so moving a few feet can swap a dead spot for a strong one.
T3A02 How does vegetation affect UHF and microwave signals?
Answer Absorbs signals, leading to poor reception of weak signals
Tip Trees and leaves soak up UHF and microwave energy, so weak signals fade out when the path runs through heavy vegetation.
T3A03 What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?
Answer Horizontal
Tip Weak-signal CW and SSB operators on VHF and UHF point their beams horizontal, so match them and keep your antenna horizontal too.
T3A04 What is the effect of antenna cross-polarization over a line-of-sight VHF or UHF path?
Answer Received signal strength is reduced
Tip If your antenna and the other station are polarized at 90 degrees, most of the signal is lost and the received strength drops.
T3A05 When using a directional antenna, how might your station be able to communicate with a distant repeater if buildings or obstructions are blocking the direct line of sight path?
Answer Try to find a path that reflects signals to the repeater
Tip When a building blocks the direct path, aim the beam at a wall or hill and let the reflection carry you into the repeater.
T3A06 What is the meaning of the term “picket fencing”?
Answer Rapid flutter on mobile signals due to multipath propagation
Tip Picket fencing is that rapid flutter on a moving signal, caused by multipath as the car changes position moment to moment.
T3A07 What weather condition might decrease range at microwave frequencies?
Answer Precipitation
Tip Rain and snow scatter and absorb microwaves, so precipitation cuts your range up where the wavelengths are tiny.
T3A08 What is a likely cause of irregular fading of signals propagated by the ionosphere?
Answer Random combining of signals arriving via different paths
Tip Ionospheric signals split and recombine over different path lengths, and that random mixing shows up as irregular fading.
T3A09 Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?
Answer Either vertically or horizontally polarized antennas may be used for transmission or reception
Tip The ionosphere twists polarization into an ellipse, so either a vertical or a horizontal antenna will work for the contact.
T3A10 What effect does multi-path propagation have on data transmissions?
Answer Error rates are likely to increase
Tip Multipath smears the timing of a data signal, so bits get garbled and the error rate climbs.
T3A11 Which region of the atmosphere can reflect HF radio waves?
Answer The ionosphere
Tip Only the ionosphere bends HF waves back to Earth, which is how HF makes those long skip contacts.
T3A12 What effect does fog or rain have on 10-meter and 6-meter band signals?
Answer Little effect
Tip At 10 and 6 meters the wavelengths are long compared to raindrops, so fog or rain has little effect.
2.3Beyond the Horizon
"Now the fun part," Ray says. "Everything past where you can see."
Start with the baseline: VHF and UHF are mostly line-of-sight. But the radio horizon is farther away than the visual horizon, because the atmosphere refracts radio waves slightly, bending them a little past the curve of the Earth. That is the normal daily reach of your 2-meter signal, and it is why height beats power every time. Simplex UHF signals are rarely heard beyond that radio horizon because UHF signals are usually not propagated by the ionosphere.
HF plays a different game entirely. High above the ground, solar radiation ionizes a region of the atmosphere called the ionosphere, and the ionosphere can bend HF signals back down to Earth hundreds or thousands of miles away. This is why long-distance ionospheric propagation is far more common on HF than on VHF: it is the defining difference between the two worlds. The F region does the heavy lifting, and it runs on sunlight. The best long-distance 10-meter F-region propagation happens from dawn to shortly after sunset during periods of high sunspot activity. At the peak of the sunspot cycle, the F region gets energetic enough to carry 10 meters and even 6 meters around the planet.
Then come the special events, the propagation modes that make VHF operators drop what they are doing:
- Sporadic E. Patches of intense ionization form unpredictably in the E region and suddenly there are strong signals from beyond the horizon on 10, 6, and even 2 meters. It is the most common source of surprise long-distance openings on those bands.
- Tropospheric ducting. A temperature inversion in the atmosphere forms a duct that guides VHF and UHF signals about 300 miles on a regular basis. Coastal and summer weather patterns are famous for it.
- Meteor scatter. Meteors burn up and leave brief ionized trails that reflect signals. The band best suited for it is 6 meters.
- Auroral propagation. Signals bounce off the aurora, and they come back distorted with a characteristic raspy sound. CW survives the trip better than voice.
"Six meters gets called the Magic Band," Ray says, "because on any given afternoon it can be dead quiet or wide open to another continent, and you find out by listening."
Knowledge Check 2.3
Tap an answer. In your own words first, then check yourself.
1. Why can your 2-meter signal reach slightly past the visible horizon?
2. Occasional strong out-of-nowhere signals on 10, 6, and 2 meters usually indicate which propagation mode?
3. What causes tropospheric ducting?
T3C the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T3C01 Why are simplex UHF signals rarely heard beyond their radio horizon?
Answer UHF signals are usually not propagated by the ionosphere
Tip UHF normally punches straight through the ionosphere instead of bouncing, so simplex signals quit at the radio horizon.
T3C02 What is a characteristic of HF communication compared with communications on VHF and higher frequencies?
Answer Long-distance ionospheric propagation is far more common on HF
Tip HF bounces off the ionosphere far more readily than VHF, so long-distance skip is a routine HF trait.
T3C03 What is one characteristic of VHF signals received via auroral backscatter?
Answer They are distorted, with a characteristic raspy sound
Tip Auroral backscatter reflects VHF off the shimmering aurora, adding a rough, raspy distortion to the signal.
T3C04 Which of the following types of propagation is most commonly associated with occasional strong signals on the 10-, 6-, and 2-meter bands from beyond the radio horizon?
Answer Sporadic E
Tip Sporadic E is the usual reason 10, 6, and 2 meters suddenly open with strong signals from past the horizon.
T3C05 Which of the following effects may allow radio signals to travel beyond obstructions between the transmitting and receiving stations?
Answer Knife-edge diffraction
Tip A sharp ridge or rooftop can bend signals over the top by knife-edge diffraction, reaching stations behind the block.
T3C06 What type of propagation is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis?
Answer Tropospheric ducting
Tip Tropospheric ducting bends VHF and UHF along the lower atmosphere, giving steady contacts out to about 300 miles.
T3C07 What band is best suited for communicating via meteor scatter?
Answer 6 meters
Tip Meteor scatter works best on 6 meters, bouncing short bursts off the ionized trails of meteors.
T3C08 What causes tropospheric ducting?
Answer Temperature inversions in the atmosphere
Tip Ducting forms when a warm layer sits over cooler air, a temperature inversion that traps and guides the signal.
T3C09 What is generally the best time for long-distance 10-meter band propagation via the F region?
Answer From dawn to shortly after sunset during periods of high sunspot activity
Tip For 10 meter F region skip, work it from dawn to just after sunset when sunspot numbers are high.
T3C10 Which of the following bands may provide long-distance communications via the ionosphere’s F region during the peak of the sunspot cycle?
Answer 6 and 10 meters
Tip At a sunspot peak the F region gets charged enough to carry even 6 and 10 meters over long distances.
T3C11 Why is the radio horizon for VHF and UHF signals more distant than the visual horizon?
Answer The atmosphere refracts radio waves slightly
Tip The atmosphere refracts radio waves just a bit, so they curve past the visual horizon and the radio horizon reaches farther.
Review: every Exam Anchor from this module
T3B A radio wave is electric and magnetic fields at right angles, traveling at the speed of light (300,000,000 meters per second), the same velocity for all frequencies. Wavelength in meters = 300 / frequency in MHz. Wavelength gets shorter as frequency increases. Bands are identified by approximate wavelength in meters. HF is 3 to 30 MHz, VHF is 30 to 300 MHz, UHF is 300 to 3000 MHz.
T3A Multipath: signals arriving via multiple paths cancel or reinforce, causing VHF strength changes over a few feet, rapid mobile flutter called picket fencing, irregular ionospheric fading, and higher data error rates. Polarization is the orientation of the electric field. Horizontal for VHF/UHF CW and SSB weak-signal work, and cross-polarization reduces received strength. Ionospheric signals are elliptically polarized, so either antenna orientation works. Vegetation absorbs UHF and microwaves, precipitation cuts microwave range, fog and rain barely touch 10 and 6 meters. Knife-edge diffraction bends signals over obstructions, and reflections can carry a signal around a blocked path. The ionosphere is the region that can reflect HF radio waves.
T3C The radio horizon is farther than the visual horizon because the atmosphere slightly refracts radio waves. UHF is rarely heard beyond it because UHF is not usually propagated by the ionosphere. Long-distance ionospheric propagation is far more common on HF. Best 10-meter F-region DX: dawn to shortly after sunset, high sunspot activity. At the sunspot cycle peak, 6 and 10 meters can go worldwide via the F region. Sporadic E brings occasional strong beyond-the-horizon signals on 10, 6, and 2 meters. Tropospheric ducting, caused by temperature inversions, regularly carries VHF/UHF about 300 miles. Meteor scatter works best on 6 meters. Auroral signals sound raspy and distorted. Knife-edge diffraction gets signals past obstructions.
Before you move on
You now know what a wave is, how to convert frequency to wavelength, why bands have names in meters, what multipath and polarization do to real signals, and every propagation mode the exam asks about. More importantly, you know why the hilltop beat the valley.
Module 3 goes inside the wire: voltage, current, Ohm's Law, and the power math you will use every time you connect a radio to a battery.
© 2026 Anthony Pelfanio, K4DIA. All rights reserved.