Think of a plus sign: +. That's what an electromagnetic wave looks like when you look down the length of it. One component (the electric field) oscillates up and down while the other component (the magnetic field) oscillates left and right. The two fields are perpendicular to each other and both are perpendicular to the direction the wave travels, so they meet at right angles.

Memory aids:

• Visualize a plus sign: the two arms are at right angles
• "All right angles" — both field components and the direction of travel are mutually perpendicular

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An electromagnetic radio wave has both an electric field and a magnetic field, and those two fields are at right angles to each other. Polarization is defined by the orientation of the electric field vector as the wave propagates. Although the magnetic field is perpendicular to the electric field, conventions use the electric-field direction to describe polarization. Polarization is not related to the wave velocity or any energy ratio between the fields.

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Radio waves are electromagnetic waves because they consist of oscillating electric and magnetic fields that travel through space. The electric and magnetic fields are oriented at right angles to each other and to the direction the wave is moving.

Because radio waves are made of electric and magnetic fields, components that store energy in those fields—capacitors (electric field) and inductors (magnetic field)—are useful in antenna tuning. Antenna tuners commonly use variable capacitors and inductors for that reason.

Other terms in related areas of electronics are not the two components of a radio wave: voltage and current are electrical quantities used to feed or measure signals, impedance and reactance describe how circuits interact with signals, and ionizing vs non‑ionizing radiation describes biological effects, not the fields that make up the wave.

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Radio waves are electromagnetic waves, the same type of wave as visible light, infrared, ultraviolet, X-rays, and gamma rays. All electromagnetic waves travel at the same speed in free space — the speed of light (denoted c), about 3.00 × 10^8 meters per second. Sound waves are mechanical waves that require a medium (air, water, solid) and travel much more slowly, so they do not share this speed.

Memory aids:

• Radio waves = light (same family: electromagnetic waves)
• Speed of light c ≈ 3.00 × 10^8 m/s (about 186,000 miles/second)
• Sound needs a medium; light/radio do not

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Frequency and wavelength are inversely proportional: as frequency increases, wavelength decreases. Wavelength is the distance between successive peaks of a wave; frequency is the number of those peaks (cycles) that pass a point each second. If there are more cycles in the same amount of time (higher frequency), each cycle must take up less distance, so the distance between peaks (wavelength) is shorter.

Memory aids:

• Visualize a sine wave: the horizontal distance between peaks is the wavelength; more peaks in the same horizontal span means shorter distance between peaks (higher frequency).
• Remember the phrase: "More cycles, less distance" to recall that higher frequency means shorter wavelength.

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Wavelength in meters equals 300 divided by frequency in megahertz.

\begin{align} \lambda _\text{ (meters)} = \frac{300}{f_\text{ (MHz)}} \end{align}

Knowing this will help you with quite a few of the problems in the Technician class question pool!

For example, if you see the frequency \(150\text{ MHz}\) and need to know what band it is in, divide the speed of light by the frequency. MHz cancels out, which leaves you with \(\frac{300}{150\text{ MHz}} = 2\text{ meters}\)!

The \(150\text{ MHz}\) frequency is exactly in the middle of the 2-meter band. If your number is not quite on (e.g. \(\frac{300}{144\text{ MHz}} = 2.08\text{ meters}\)) that's okay, because the bands have a little play both above and below the "wavelength" number.

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Ever wonder where the value \(300\) comes from?

Here's the general form of the equation above:

\[\lambda \times f = c\]

The units are all basic SI units (International System of Units or Metric System) -- let's add them for clarity:

\[\lambda_\text{ (meters)} \times f_\text{ (Hz)} = c_\text{ (meters per second)}\]

The speed of light \(c\) is a constant, so we can plug that value in: \begin{align} \lambda_\text{ (meters)} \times f_\text{ (Hz)} &= 3.00 \times 10^8\text{ m/s} \end{align}

There are \(10^6\text{ Hz}\) in each \(\text{MHz}\), so let's divide both sides by \(10^6\) and simplify: \begin{align} \frac{\lambda_\text{ (meters)} \times f_\text{ (Hz)}}{10^6} &= \frac{3.00 \times 10^8\text{ m/s}}{10^6}\\ \lambda_\text{ (meters)} \times \frac{f_\text{ (Hz)}}{10^6} &= 3.00 \times 10^2\text{ m/s}\\ \lambda_\text{ (meters)} \times f_\text{ (MHz)} &= 300 \text{ (units combined)}\\ \lambda_\text{ (meters)} &= \frac{ 300 }{ f_\text{ (MHz)}}\\ \end{align}

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Amateurs commonly identify bands by their approximate wavelength in meters as well as by frequency. For example, saying “the 2‑meter band” refers to the amateur allocation around 144–148 MHz (which has a wavelength of about 2 meters). Similarly, terms like “70 centimeter band” or “33 centimeter band” are used to refer to their respective frequency ranges. The wavelength designation is simply another convenient way hams refer to a frequency range.

Memory aids:

• “2‑meter band” ≈ 144–148 MHz
• “70 cm” refers to the 440 MHz region
• “33 cm” refers to the ~902 MHz region
• Wavelength (meters) ≈ 300 ÷ frequency (MHz) — useful for quick conversions

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One thing that often confuses new hams is that the terms "HF", "VHF", and "UHF" refer to different parts of the radio spectrum, and "High Frequency" (HF) is actually lower in frequency than "Very High Frequency" (VHF).

The ranges are thus:

• HF (High Frequency) is from 3 MHz to 30 MHz
• VHF (Very High Frequency) is from 30 MHz to 300 MHz (and includes the popular 2‑meter band at 144–148 MHz)
• UHF (Ultra High Frequency) is from 300 MHz to 3000 MHz

A helpful way to think about the boundaries is in terms of wavelength: 30 MHz corresponds to about a 10‑meter wavelength, and 300 MHz corresponds to about a 1‑meter wavelength, so VHF covers roughly 10 meters down to 1 meter.

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UHF stands for Ultra High Frequency and refers to frequencies from 300 MHz up to 3000 MHz (3 GHz). The HF, VHF, and UHF bands are contiguous ranges of the radio spectrum and are commonly defined as:

• HF (High Frequency): 3 MHz to 30 MHz
• VHF (Very High Frequency): 30 MHz to 300 MHz (includes the popular 2‑meter amateur band at 144–148 MHz)
• UHF (Ultra High Frequency): 300 MHz to 3000 MHz

Because the units change (kHz vs MHz), it’s easy to be misled by answer choices that use kHz; UHF is specified in MHz, not kHz.

Memory aids / mnemonics:

• Think of the prefixes: H (High) = lower frequency range than V (Very High) and U (Ultra High) = highest of the three.
• Remember the powers of ten: HF 3–30 MHz, VHF 30–300 MHz, UHF 300–3000 MHz.
• Don’t confuse kHz with MHz — UHF is in the MHz/GHz range, not kHz.

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One thing that often confuses new hams is that the terms "HF," "VHF," and "UHF" actually refer to different parts of the radio spectrum, with "HF" or "High Frequency" referring to frequencies that are lower than VHF and UHF but are the highest of the lower bands commonly used by amateur radio operators. In other words, HF frequencies may be called "high frequency," but they are lower in frequency than "very high frequency" and "ultra high frequency".

HF is the band used for long-distance (often global) HF contacts because signals in this range can be reflected by the ionosphere. That defining range is 3 MHz to 30 MHz, which is why this range is referred to as HF.

Although frequencies from 300 kHz to 3000 kHz exist, they are in the Medium Frequency (MF) range and are very rarely used by hams.

Memory aids / quick reference:

• LF (Low Frequency): 30 kHz to 300 kHz
• MF (Medium Frequency): 300 kHz to 3000 kHz
• HF (High Frequency): 3 MHz to 30 MHz
• VHF (Very High Frequency): 30 MHz to 300 MHz (includes the popular 2 meter band at 144–148 MHz)
• UHF (Ultra High Frequency): 300 MHz to 3000 MHz

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Radio waves are electromagnetic waves, so in free space they travel at the speed of light, about 3 × 10^8 meters per second (300,000,000 m/s). This is the standard approximate value used for calculating relationships between frequency and wavelength.

Memory aids / quick tricks:

• Use 300 (million) divided by frequency in MHz to get wavelength in meters: wavelength (m) ≈ 300 / frequency (MHz).
• Example: 150 MHz → 300 / 150 = 2 meters (the 2-meter band).
• Think “300 million m/s” or “3 × 10^8 m/s” as the speed of light in vacuum.

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Radio frequencies are literally the same type of wave as light; just like all light travels at the same speed in a vacuum, so too radio frequencies travel at the same speed in free space.

The “in free space” part is important, since waves at different frequencies may be affected differently when traveling through materials such as water or glass. In a vacuum, however, all electromagnetic waves—radio or light—travel at the same speed.

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