¶ AM/FM Modulation — Education Toolkit (Grade 8)
Observe amplitude modulation (AM) and frequency modulation (FM) wave signals in the time and frequency domain using the COSMOS Education Toolkit web interface running on two SDR nodes.
¶ Overview
This tutorial is part of the COSMOS Education Toolkit and targets a Grade 8 science lesson. Students observe how a carrier wave is modified by an information signal under two modulation schemes — AM (amplitude modulation) and FM (frequency modulation) — and compare the results in time and frequency domain plots delivered through a browser-based interface.
The experiment runs on two preconfigured SDR nodes (sdr2-s1-lg1 as node #1 and sdr2-md1 as node #2). Students interact entirely through the toolkit web interface; no command-line access is required during the lesson itself. Setup (loading the toolkit software) is handled by the testbed operator before the class session begins.
The educational standard addressed is MS-PS4-1: develop a model and use mathematical representations to describe waves including frequency, wavelength, and the relationship between amplitude and energy.
¶ Learning outcomes
After completing this tutorial you will be able to:
- Distinguish between AM and FM modulation by examining time-domain and frequency-domain waveform plots.
- Explain how changing the information signal type (square vs. sine) and carrier frequency affects the modulated waveform.
- Record and compare observations across modulation schemes and articulate interpretations in a scientific discussion.
¶ At a glance
| Difficulty | Beginner |
| Estimated time | TODO: verify |
| Domain / sandbox | TODO: verify — source references sdr2-s1-lg1 and sdr2-md1; likely the BED or a NYC testbed domain |
| Topic group | Education Toolkit |
| Last verified | Not re-tested (migrated 2026-06-20) |
¶ Prerequisites
Background knowledge
- Basic wave concepts: frequency, wavelength, amplitude.
- Familiarity with time-domain and frequency-domain representations of signals.
- Completion of the COSMOS Education Toolkit setup tutorial — this tutorial assumes the toolkit is already installed and running on the nodes.
Account & access
- A COSMOS account — register here.
- An approved reservation on the domain above — see Make a reservation.
- SSH access to the domain console (for operator setup) — see SSH access.
¶ Resources required
Devices / nodes
| Resource | Role | Qty | Notes |
|---|---|---|---|
sdr2-s1-lg1 |
Node #1 (transmitter/receiver) | 1 | SDR node; identified in source as node #1 |
sdr2-md1 |
Node #2 (transmitter/receiver) | 1 | SDR node; identified in source as node #2 |
Disk images
| Image | Load onto | Provides |
|---|---|---|
| TODO: verify | sdr2-s1-lg1, sdr2-md1 |
COSMOS Education Toolkit web application + SDR software |
Software components
| Component | Version | Source |
|---|---|---|
| COSMOS Education Toolkit | TODO: verify | Preinstalled in the toolkit disk image; see toolkit setup tutorial |
| Toolkit web interface | TODO: verify | Served on port 8081 on each node |
Spectrum / RF / special
The experiment generates modulated RF signals between the two SDR nodes. Frequency and power parameters are controlled through the toolkit web interface. No manual RF configuration is required by students.
¶ Topology
Two SDR nodes (sdr2-s1-lg1 = node #1, sdr2-md1 = node #2) run the COSMOS Education Toolkit. Each node exposes a web interface on port 8081 reachable from the student's browser through the COSMOS portal or a forwarded port. Students select which node starts the AM or FM experiment via the web UI.
¶ Setup
These steps are performed by the testbed operator (instructor/TA) before the class session. Students do not need console access.
-
Complete all steps in the COSMOS Education Toolkit setup tutorial to install and start the toolkit on both nodes.
-
Reserve the resources and log into the console:
ssh <username>@console.<sandbox>.cosmos-lab.org -
Make sure the nodes are off before imaging:
omf tell -a offh -t system:topo:allres -
Load the toolkit image onto both nodes:
omf load -i <toolkit-image>.ndz -t <node1>,<node2> -
Turn the nodes on and confirm they are up:
omf tell -a on -t <node1>,<node2> omf stat -t <node1>,<node2> -
Verify the toolkit web interface is reachable on port 8081 on each node:
http://localhost:8081
¶ Instructions
¶ Step 1 — Open the toolkit web interface
Open the web interface of either node #1 (sdr2-s1-lg1) or node #2 (sdr2-md1) at:
http://localhost:8081
If all steps in the toolkit setup were completed correctly, you should see the toolkit home page.
¶ Step 2 — Navigate to the Grade 8 science lesson
-
Press the Science radio button to open the science lesson plan webpage.
-
Select Grade 8.
-
Select AM/FM Modulation.
The new page shows a detailed description of the experiment, the educational standards addressed (MS-PS4-1), and the experiment execution instructions. Expand the Remote Experiment section on that page.
Note: The COSMOS Education Toolkit contains 100+ lesson plans and labs. Only a subset currently support remote experimentation on COSMOS. The website is updated over time as more experiments become available for remote execution.
¶ Step 3 — Observe the AM signal
-
Press
STARTon either node #1 (sdr2-s1-lg1) or node #2 (sdr2-md1) to begin the AM experiment. -
Try different information wave signals (square and sine) and different carrier frequencies. Observe the effect of these two parameters on both the original information signal and the AM signal in the time domain and frequency domain plots.
-
Take notes on your observations.
-
When done, press the appropriate
STOPbutton to complete the AM experiment.
|
|
|---|---|
| (a) Amplitude modulation of a signal | (b) Frequency modulation of a signal |
¶ Step 4 — Observe the FM signal
-
Press
STARTon either node #1 or node #2 to begin the FM experiment. -
Repeat the process from Step 3: vary the information wave type (square and sine) and the carrier frequency. Observe the time-domain and frequency-domain plots.
-
Take notes on your observations.
-
Press the appropriate
STOPbutton when done.
¶ Step 5 — Compare and discuss
Compare the AM and FM observations:
- How does the signal look different in the time domain for AM vs. FM?
- How does the signal look different in the frequency domain for AM vs. FM?
- How does the information wave type (square vs. sine) affect the modulated signal in each scheme?
After all students complete their handouts, share out observations and interpretations with the class.
¶ Verification
- The toolkit web interface loads on port 8081 for both nodes.
- Selecting Grade 8 → AM/FM Modulation shows the experiment page with a Remote Experiment section.
- Pressing
STARTproduces live time-domain and frequency-domain waveform plots. - Switching between square and sine information signals produces visibly different waveforms.
- Pressing
STOPhalts the experiment cleanly.
¶ Cleanup
omf tell -a offh -t system:topo:allres
No omf save needed unless the toolkit image was modified.
¶ Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Web interface not reachable on port 8081 | Toolkit not started / nodes not fully booted | Confirm nodes are ACTIVE via omf stat; SSH into the node and verify the toolkit process is running |
| Waveform plots do not appear after pressing START | SDR not responding or toolkit misconfigured | Verify the toolkit setup steps were completed; restart the toolkit service on the node |
| No Remote Experiment section visible | Toolkit version does not support this lesson remotely | Confirm the correct toolkit disk image is loaded; consult the toolkit setup tutorial |
¶ References
- COSMOS Education Toolkit setup tutorial
- Make a reservation
- SSH access
- NGSS standard MS-PS4-1 — wave properties and mathematical representations
Author(s): COSMOS team (original: Panagiotis Skrimponis, NYU; Nikos Makris, NYU) · Last verified: Not re-tested (migrated 2026-06-20) · Tested image/release: TODO: verify · Tags: education, modulation, am, fm, sdr, education-toolkit, grade-8