Published in What's New?

Ham Radio School Visualization Apps

A big part of the Ham Radio School method of helping students prepare for license exams with real comprehension of radio topics is visualization. Particularly when it comes to some of the more technical processes involved in radio science and engineering, we have found that student understanding of these topics extends directly from our extensive use of graphics, video, animations, and other tools that help them visualize these processes. As such, we provide ample visual models in our books, in our online course video lessons, and in our optional depth learning media at HamRadioSchool.com.

However, we recognize that while passive observation and consideration of these visual models can help instill solid comprehension, there are even more effective tools that blend visualization with student interaction. Web-hosted visualization apps that allow the student to experiment with the visualization model, changing input parameters and observing the results, is more engaging and more effective than passive observation for most learners.
With this philosophy in mind, we have recently developed several web-based visualization applications to allow students to experience learning interaction with some of the more challenging radio processes. These apps are generally geared towards the Technician License student, but more advanced students can also benefit from fiddling around a bit with them. We invite you to give them a try, and to provide us with feedback on them, if you like, in the spirit of continuing improvement.
 
Our visualization apps currently include the following:
  • AM Simulator - construct a baseband signal, watch it modulate an RF carrier.
  • FM Simulator - construct a baseband signa, watch it frequency modulate a carrier.
  • CW Simulator - enter text and see/hear it coded; adjust WPM speed & audio tone.
  • FSK Simulator - enter text and see/hear it coded as 2-, 4-, or 16-FSK signals.
  • QRM Simulator - see a spectrum scope and hear audio effects of inerfering SSB and CW signals; adjust signal positions and receive filter settings to hear results.
  • Fourier Transform Visualizer - construct complex waveforms by adding sine wave components and adjusting frequencies, amplitudes, and phases. View signals in the time domain and frequency domain to intutively understand Fourier Transforms.
  • Time & Frequency Domain FFT Analyzer - record your own audio and see its displayed in time and frequency domains; stock input signals available also.
  • Filter Simulator - record your own audio or use stock audio signals to explore various filter effects; see and hear high pass, low pass, band pass options.
  • SWR Wave Simulator - illustrates forward and reflected transmission line signals, the resultant standing waves, and computes SWR.
  • Ohm's Law Simulator - illustrates a simple DC circuit with lamp or LED and resistor; adjust supply voltage and resistance to see current effects and Ohm's Law calculations.
  • HF Dipole SWR Analyzer - Illustrates how a 20-meter band wire dipole modifications of length and loading impact the SWR curve of the antenna system; adjust antenna length and loading to see the SWR curve change in response.
  • Screwdriver Antenna SWR Analyzer - Illustrates the design options and tuning capabilities of a variable loaded vertical quarter-wave antenna across the HF bands from 80 to 10 meters; adjust loading coil size and position, antenna length, and capacitance hat features to observe SWR curve impacts.

Find all of our visualization apps here:  https://hamradioschool.com/vis-apps.html

We recommend a full-size monitor for the best experience with these apps. While they are mobile device responsive, the displays and controls fit much better for ease of interaction on the larger display real estate. 
 
AM Simulator: 

Provide input to the app by selecting and constructing a baseband modulating signal. Sum together modulating signal sine waveforms of different frequency and amplitude to see the resulting modulating signal and its impact on the modulated RF signal. Adjust the carrier frequency, the carrier amplitude, and the speed of the dynamic display, as desired. Alternatively, select the microphone option to input your own voice or sound and observe in real time the complexity of the signals. Freeze the displays for careful examination of the signals, or take a snapshot of the displays in .png format for downloading.

The AM Simulator lets you construct complex modulating signals from individual sine wave components and view the modulated carrier signal that results.
 

FM Simulator: 

Identical to the AM Simulator, but producing a visualization of a frequency-modulated RF carrier. Build a modulating signal with various sine wave inputs, or use your microphone for complex audio input. This simulator adds a slider control for FM deviation level, adjusting the relationship between baseband amplitude and RF carrier frequency deviation. The carrier deviations are somewhat exaggerated so that they are readily observed, as FM signal deviations are quite subtle. (A typical FM signal's 5 kHz deviation will result in wavelength variation of only about 0.14 millimeter.)

 
Like the AM Simulator, our FM Simulator allows the construction of complex baseband signals that are reflected in a simulation of the FM carrier deviations.
 
 
CW Simulator:
Enter a string of text, select a words-per-minute send speed, and view the carrier waveform on-off patterns or Morse Code along with a read out of the characters represented. Adjust the tone as desired that is produced with each dit and dah, all with perfect CW cadence between characters and words.
 
The CW Simulator lets you enter a text string and see and hear it accurately encoded as a CW signal.
 
 
Frequency Shift Keying (FSK) Digital Mode Simulator:  

Explore the fundamentals of digital modulation using FSK. Enter a text string to encode with 8-bit ASCII and select one of three FSK tone quantities: 2-FSK, 4-FSK, or 16-FSK. See and hear the message encoded using your selected FSK method, with each unique tone symbol color-coded for differentiation in the display as well as represented in a stairstep diagram. The commensurate binary digital values are also displayed under each color-coded wave segment, and each resultant text character is displayed with an underscore grouping the eight binary values that represent it. Zoom and display scroll controls are provided to enlarge the display when needed for careful examination of the results Easily compare symbol rates (baud) and data rates across the different FSK methods.

 
The FSK Digital Mode Simulator illustrates the basics of digital modulation with visuals and tones. Enter a text string to see and hear it encoded into ASCII binary code.
 
QRM and Passband Simulator:
 
This app helps student envision a band's spectrum and interfering SSB or CW signals in the band. Realistic audio is produced simulating the effects of interference in these modes and the effects of adjusting high-cut and low-cut filters, changing receive filter bandwidth and limits. Controls allow the movement of two signals up and down the band to create various interference scenarios and to create a wide range of receive filter effects.
 
The QRM and Passband Tuning Simulator produces realistic audio effects as interfering signals are adjusted in band position and as filter bandwidth and position are changed.

Fourier Transform Visualizer:

This app lets you construct complex waveforms of any type from individual sine wave components. By adding sine components and manipulating the frequency, amplitude, and phase of each, any type of complex signal can be fabricated and displayed in the time domain view and the frequency domain view. Using the vector-summed output of linked circles, or epicycles, as analogs of sine components, an intuitive visual understanding of complex signal composition is gained. Presets provide standard square wave and sawtooth wave components, and an option to use fractional harmonic values illustrates how non-repeating, shifting signals result. Perfect for illustrating how Fourier Transforms provide an analysis of complex signal composition in the frequency domain, and an amazingly simple illustration of how any signal is a combination of various sinewave signals - a concept that is almost impossible to impart without a signal visualization tool.

 

Time and Frequency Domain FFT Analyzer:

Describing the time and frequency domains of signals is always a challenge for student. With this app you can record your own audio signal and see it represented in the time domain and the frequency domain. Zoom in and out on displays for detailed analysis. Playback the audio signal at reduced speed but without pitch / frequency shifts to examine the dynamics of the FFT analysis. Standard stock audio signals are also provided, such as square wave, sawtooth wave, sine wave, and sweeping sine wave signals.

The Time & Frequency Domain FFT Analyzer brings these two interconnected signal views to life for students.

Filter Simulator:

This app let's you see and hear the effects of various real-world filter types on audio. Like the Time and Frequency Domain FFT Analyzer, it depicts time and frequency domain views with filter effects depicted in the frequency domain view spectrum scope display. Select high-pass, low-pass, band-pass, band reject, or notch filter types and adjust bandwidth, sharpness, and center frequency. Record your own audio for examination with filtering or use stock options such as white noise. Playback audio at slow speed without pitch changes for careful dynamic analysis, and select from four different FFT window sample sizes. Student quickly obtain an intuitive comprehension of filter effects.

The Filter Simulator represents various filter effects visually and aurally. 
 
SWR and Wave Superposition Simulator:
 
Students often have a tough time visualizing the standing waves in a transmission line that are produced when an impedance mismatch exists at the antenna feed point. This app illustrates the voltage dynamics inside a transmission line, displaying a forward sine wave signal traveling right, a reflected sine wave signal traveling left, and the resultant sum of the two. The student can see the high voltage amplitude of the resulting standing waves and the low voltage amplitude of the standing waves. The ratio of these high and low voltages is computed and displayed as an SWR value. Watch the SWR increase and decrease as the reflected signal amplitude is adjusted. Use the slider controls to change the propagation speed, the amplitudes of forward and reflected signals, and the frequency of the wave. Independently display only the forward signal, only the reflected signal, or only the summed resultant, as desired.
 
Watch forward and reflected transmission line voltage waveforms be dynamically summed into resultant standing waves for SWR determination. Change the signal amplitudes and observe standing wave and SWR impacts.
 
 
Ohm's Law Simulator:
 
Students can see the changes is current flow and component illumination as adjustments are made to the supply voltage and the circuit resistance. A calculation of current is displayed with adjustments. Go too far and you'll toast the LED or lamp! Select various LED colors.
 
The Ohm's Lw Simulator provides an intuitive view of the relationship among voltage, current, and resistance.
 
HF Dipole Antenna SWR Analyzer
 
Students can adjust the length and loading of a 20-meter band dipole antenna and watch the SWR curve change in response. Trim the dipole shorter and see the SWR curve move higher in the spectrum, or lengthen it to move lower. Add inductive loading coils and watch the Q of the antenna narrow in response. Readouts provide detailed insights including antenna length, 2:1 SWR bandwidth and range, resonant frequency and lowest SWR, loading in microhenries, and estimated feedpoint impedance. The app provides an intuitive grasp of the relationships between the physical antenna parameters and the resulting SWR.
 
 
 
 
Screwdriver Antenna SWR Analyzer
 
For the advanced student, adjust the vertical antenna element length to observe SWR curve movement across the RF spectrum. The spectrum zooms and encompasses 80-meter band to 10-meter band (<3.0 MHz to >30 MHz). Simulating screwdriver antenna tuning capability, the student may adjust the number of loading coils applied in the antenna circuit by moving a simulated wiper across the coils, changing the inductive loading. The entire coil position may also be adjusted between the base to the middle position of the vertical antenna to reduce radiative resistance, resulting in observed SWR curve changes and feed point impedance changes. Optionally apply a capacitive hat to the antenna and adjust its size for enhanced loading, and even implement an antenna tuning network for tough scenarios. Band presets allow the automatic adjustment of all parameters for optimization in the selected band. When minimum SWR exceeds 2:1, optimization suggestions are provided by the app for the student. The simulation is based on a quarter-wave antenna with a perfect ground plane and uses the Wheeler coil inductance formula and a realistic radiative resistance model. Perfect for visually illustrating the various factors effecting loaded vertical antenna design and performance.
 
 
 
I hope you put our new visualization apps to good use for your own comprehension or for your instructional purposes. We will be using them for salient explanations in our online course video lessons beginning with the new 2026-2030 edition of the Technician License Course.

Enjoy fiddling with these apps, and if you have suggestions be sure to drop us a note with your ideas.

 
73,
Stu WØSTU

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