Build a wireless link budget

Print every path-loss, receive-power, margin and Fresnel calculation before making a bounded radio-placement decision.

Radio Rosa: I want you to inspect every gain and loss before trusting the final margin., your practice guide

Radio Rosa: I want you to inspect every gain and loss before trusting the final margin.
Predict the reading, then compare it with the measurement.

Python 3 in your browser (JupyterLite)

Python · no install

Tier 2 · Web · paste-in setup · No account

Version tested: Python 3.12.7 / Pyodide 0.27.6 in JupyterLite 0.6.4; Chromium 148.0.7778.96; captureSource playwright:jupyterlite. Date: 2026-09-10.

Open the notebook in your browser and run each Python cell; no install or account is needed.

Three ways to run: use JupyterLite here with no install; run main.py locally from the downloadable lab folder; or open the same notebook in Google Colab.

Open in your browser (new tab)

Steps

Screens captured against Python 3 in your browser (JupyterLite) Python 3.12.7 / Pyodide 0.27.6 in JupyterLite 0.6.4; Chromium 148.0.7778.96; captureSource playwright:jupyterlite on 2026-09-10; the tool may have moved on — the text steps are the contract.

  1. Step 1

    Do
    In the JupyterLite notebook, run the Step 1 cell to freeze the fictional 868 MHz radio assumptions.
    You will see
    Input: execute notebook step 1 with its stated deterministic fixture. Observed: fictional point-to-point outdoor link Observed: frequency=868 MHz; tx=14 dBm; antenna gains=2+2 dBi Observed: Required design reserve=10 dB; no measured site data is implied.
    Why it matters
    Expected: the model begins with explicit 868 MHz radio and link assumptions. The run uses 14 dBm transmit power, 2+2 dBi gains, and 2 dB cable loss. Stating sensitivity and reserve makes the later margin calculation auditable. Limit: no site measurement is implied.

  2. Step 2

    Do
    In the JupyterLite notebook, run the Step 2 cell to calculate free-space loss at four distances.
    You will see
    Input: execute notebook step 2 with its stated deterministic fixture. Observed: 10 51.21 Observed: 100 71.21 Observed: 1000 91.21
    Why it matters
    Expected: free-space path loss increases with distance at the fixed 868 MHz frequency. The run gives 51.21 dB at 10 m, 71.21 dB at 100 m, and 91.21 dB at 1 km. These are formula outputs using distance in km and frequency in MHz. Limit: free-space loss omits the local environment.

  3. Step 3

    Do
    In the JupyterLite notebook, run the Step 3 cell to compare free-space and log-distance models.
    You will see
    Input: execute notebook step 3 with its stated deterministic fixture. Observed: 10 51.21 67.00 15.79 Observed: 100 71.21 94.00 22.79 Observed: 500 85.19 112.87 27.68
    Why it matters
    Expected: the log-distance model produces greater loss than FSPL at these distances. At 500 m the run reports 112.87 dB modeled loss versus 85.19 dB FSPL. The difference is the modelled extra loss under n=2.7 and PL(1 m)=40 dB. Limit: both models use assumptions rather than site data.

  4. Step 4

    Do
    In the JupyterLite notebook, run the Step 4 cell to build the receive-power and margin ledger.
    You will see
    Input: execute notebook step 4 with its stated deterministic fixture. Observed: 10 67.00 -51.00 69.00 Observed: 500 112.87 -96.87 23.13 Observed: 1000 121.00 -105.00 15.00
    Why it matters
    Expected: received power and margin fall as the modeled path grows. At 1 km the run gives -105.00 dBm and 15.00 dB margin. Margin is calculated against the stated -120 dBm receiver sensitivity. Limit: fading, interference, and implementation losses remain outside this ledger.

  5. Step 5

    Do
    In the JupyterLite notebook, run the Step 5 cell to calculate midpoint Fresnel clearance.
    You will see
    Input: execute notebook step 5 with its stated deterministic fixture. Observed: 100 1.47 0.88 Observed: 500 3.29 1.97 Observed: 1000 4.65 2.79
    Why it matters
    Expected: the 60% first-zone clearance requirement grows with path length. At 1 km the calculated midpoint radius is 4.65 m and 60% clearance is 2.79 m. This flags a terrain and antenna-height check for a real path. Limit: the model assumes an equal two-leg midpoint path.

  6. Step 6

    Do
    In the JupyterLite notebook, run the Step 6 cell to compare three sensitivity and data-rate modes.
    You will see
    Input: execute notebook step 6 with its stated deterministic fixture. Observed: LoRa 0.3kbps -137 32.00 Observed: LoRa 5.5kbps -120 15.00 Observed: FSK 50kbps -105 0.00
    Why it matters
    Expected: the three assumed sensitivities produce different 1 km margins. The local run reports 32, 15, and 0 dB for the listed radio modes. The table exposes a sensitivity-versus-data-rate planning trade-off. Limit: airtime cost and actual radio performance are not modeled.

  7. Step 7

    Do
    In the JupyterLite notebook, run the Step 7 cell to make a bounded placement decision.
    You will see
    Input: execute notebook step 7 with its stated deterministic fixture. Observed: 1 km log-distance margin is below the 10 dB design reserve. Observed: Action: shorten the path or improve placement, then run a measured site survey. Observed: The table is a planning hypothesis, not proof of packet delivery.
    Why it matters
    Expected: the result compares the modeled 1 km margin with the stated 10 dB reserve. Observed: step 4 reports 15.00 dB at 1 km, but this step says that margin is below 10 dB. Interpretation: those local outputs conflict; do not rely on the REVISE message until the decision logic is reconciled. Limit: the planning calculation still needs a measured site survey.

Chapter checks

These questions refer to the chapter’s examples. Use the return links to review their answers.

  1. A node has good average signal strength but intermittent packet loss. What should the learner consider?

    Return to the chapter’s knowledge check

  2. A sensor reports strong RSSI, but packet retries increase whenever nearby equipment is active. What should you review first?

    Return to the chapter’s knowledge check

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