Monthly SDR Challenge: Improve an ADS-B Baseline

[Pavel]

Short answer: The challenge is to measure a seven-day ADS-B baseline, change one station variable, measure a second seven-day period and publish a privacy-safe comparison. The submission window is the calendar month in which the thread is posted; results can be added until 23:59 UTC on the month's final day.

Before you start​

• Define the project's purpose and one measurable success criterion before listing hardware.
• Document the complete RF and data path, including antenna, feedline, filters, gain, SDR, sample rate, software and processing output.

Step-by-step method​

1. Step 1: Baseline days 1–7: keep antenna, location, coax, filter and gain unchanged. Export daily unique aircraft, total messages, median messages per second, 90th-percentile range and a redacted polar plot.
2. Step 2: Choose exactly one change: antenna height or orientation, feedline, 1090 MHz filter, LNA position or manual gain. Record the hypothesis before installing it.
3. Step 3: Test days 8–14 under the same decoder version and daily observation hours. Note outages and exclude them transparently rather than filling missing time with zero.
4. Step 4: Submit title, country or broad region, SDR, antenna, software/version, baseline table, changed variable, second table, percentage differences, two redacted plots and a short conclusion.

Concrete example​

Example submission: RTL-SDR V4, readsb, rooftop quarter-wave, gain 32.8 dB; then only add a 1090 MHz filter. Baseline 90th-percentile range 212 km and 4.8 million messages versus 226 km and 5.4 million, with 2 hours of outage disclosed.

How to judge the result​

A valid entry has at least seven complete days before and after, one changed variable, the required five metrics and no exact home coordinates or feeder credentials. The goal is a documented result, including no improvement.

What to record​

• Use equal observation windows and unchanged receiver settings for before-and-after comparisons.
• Include raw counts, signal-to-noise ratio or error rate alongside screenshots so the improvement is measurable.
• Record failed approaches and constraints; they often make a build log more useful than a polished final photograph.

Common mistakes​

• Changing several parts between baseline and result, then crediting one component without evidence.
• Publishing a polished result without the versions, settings, failures and measurement needed to reproduce it.
• Changing antenna, adding an LNA and retuning gain together disqualifies causal comparison because no single change can be credited.

Final check​

Repeat the baseline or rebuild from the written log. Publish the result only when another member can follow the RF chain, settings and measurement without relying on private files or unstated changes.