Notes for class 17 Jan 2026

• 17 January 2026
• community,
• class,
• Omaha

Class can be fun

1. ARRL Slides
2. NoteBook LM (Google will want you to sign in )
3. Cute Radio Wave Simulation
4. Free, as in beer, book on Technician exam by KB6NU

Matt N3PAY's bits

1. Section 4.4 Practical Antenna Systems (slides 77-119)
2. Section 5.4 Power Supplies and Batteries (slides 91-104)
3. Section 6.4 Nets (slides 53-78)

Section 4.4 Practical Antenna Systems (slides 77-119)

Terms

Core Formula: Wavelength is proportional to frequency

Question: "What is the formula that converts frequency to wavelength? How does this relate to things like the 2 meter band, 70 centimeter band, 20 meter band, etc."

The formula for converting frequency to wavelength is based on the speed of radio waves, which travel at the speed of light (approximately 300,000,000 meters per second),. To simplify the math for radio work, you can divide the speed of light by the frequency.

For practical calculations using Megahertz (MHz), the formula is:

$$ \text{Wavelength (in meters)} = \frac{300}{\text{Frequency (in MHz)}} $$

Conversely, if you know the wavelength, you can determine the frequency using:

$$ \text{Frequency (in MHz)} = \frac{300}{\text{Wavelength (in meters)}} $$

Relationship to Amateur Bands Amateur radio bands are often identified by their approximate wavelength rather than their specific frequency range. The formula demonstrates the inverse relationship between the two: as the frequency gets higher, the wavelength gets shorter.

• 2 Meter Band: This band spans 144 MHz to 148 MHz. If you calculate the wavelength for 148 MHz ($300 / 148$), the result is approximately 2.03 meters, which is why it is referred to as the 2-meter band.
• 6 Meter Band: This band begins at 50 MHz. Using the formula ($300 / 50$), the result is exactly 6 meters.
• 70 Centimeter Band: This band is in the UHF range (around 440 MHz). Calculating $300 / 440$ yields approximately 0.68 meters, or 68 centimeters (commonly referred to as the 70 cm band).

This conversion is essential for building antennas, as antenna lengths are physical fractions of these wavelengths (such as a 1/2 wave dipole or 1/4 wave vertical),.

Visualize relationship

Question: "Is there an webpage that allows me to visualize the relationship between wavelength and frequency? Perhaps something where I can change the frequency and the wave is represented on screen with the wavelength marked."

TL;DR https://phet.colorado.edu/sims/cheerpj/radio-waves/latest/radio-waves.html?simulation=radio-waves

NoteBookLM's answer

Based on the provided study materials, the texts explain the mathematical relationship between frequency and wavelength—specifically that they are inversely related and calculated using the speed of light ($300,000,000$ meters per second). They also describe the physical structure of the wave, noting that electric and magnetic fields travel at right angles to one another.

However, the provided source documents do not contain a link to an interactive webpage or software tool that visualizes this relationship dynamically.

Outside Information: Recommended Visualization Tool To achieve the specific visual aid you described for your class, I recommend the PhET Interactive Simulations project provided by the University of Colorado Boulder.

• Tool Name: PhET "Radio Waves & Electromagnetic Fields"
• Why it fits your query: It allows you to manually oscillate a transmitter (changing the frequency) and visually see the waves radiating outward. You can demonstrate that moving the transmitter slowly (low frequency) creates large gaps between wave peaks (long wavelength), while moving it quickly (high frequency) creates peaks that are close together (short wavelength).

Teaching Application using your Sources You can use such a visualization to reinforce the specific examples found in your "Practical Antenna Systems" section notes:

1. The Inverse Relationship: As you increase the frequency in the simulation, students will see the wavelength shrink. This visually proves the text's rule: "the lower the frequency, the longer the wavelength, and vice versa".
2. Band Identification: You can relate the visual to the text's example that the 6-meter band (50 MHz) has a long wave, whereas the 2-meter band (144 MHz) has a much shorter wave.
3. Antenna Size: This visualizes why a 1/2 wave dipole for 40 meters (7 MHz) is physically much larger (approx. 66 feet) than a 1/2 wave dipole for 2 meters (approx. 19 inches).

Section 5.4 Power Supplies and Batteries (slides 91-104)

Question: "Generate a table of all the terms used in Tech Module 5 section 4 (that's slides 91 through 104) of the Tech Module 5 PDF file."

Here is the table of terms used in Section 5.4: Power Supplies and Batteries (slides 91 through 104) of the Tech Module 5 PDF.

Section 6.4 Nets (slides 53-78)

Quetion: Generate a table of all the terms used in Tech Module 6 section 4 (that's slides 53 through 78) of the Tech Module 6 PDF file.

Here is the table of terms found in Section 6.4: Nets and Section 6.5: Communications for Public Service (covering slides 53 through 78) of the Tech Module 6 PDF.

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