Scientific Public Ledger
Autonomous 50–150 MHz Survey and FM Census
A bounded receive-only trial completed five sweeps on each of two receiver paths, recorded 20 shared broadcast-FM regions with frequency-compatible candidate assignments, and preserved its diagnostic and identity limits.
Observation scope
- band
- 50–150 MHz receive-only survey; identity research bounded to 88–108 MHz; nominal 100 kHz requested bins
- configuration scope
- Separate fixed receive-only antenna paths; sequential acquisition; no demodulation, audio, RDS, decoding, transmission or active probing
- generalized location
- Costa Rica; precise receiving location withheld
- receiver classes
- HackRF-class wideband SDR and RTL-SDR/NESDR-class receive chain
- time range
- 2026-08-21 local / 2026-08-22 UTC; five sequential sweeps per receiver path
Purpose and stopping rule
analysisAFMC-01 asked whether the Explorer could follow a fixed protocol across 50–150 MHz, separate the broadcast-FM identity-research scope from preliminary peripheral observations, and stop without promoting frequency agreement into transmitter identification.
The protocol was frozen before acquisition. It required five sweeps on each receiver path, four-of-five within-receiver persistence, cross-receiver agreement within 150 kHz, complete source research for shared observations inside 88–108 MHz, and no result-triggered repeats.
Completed observation
observationAll ten requested receive-only sweeps completed and passed bundle-integrity validation. Twenty occupied regions inside the primary 88–108 MHz stratum matched across the two receiver paths. Thirteen were persistent on both paths and are labeled strong assignment matches; seven were shared but below the persistence threshold on one path and are labeled supported assignment matches.
One approximately 79.951 MHz region appeared only on the HackRF-class path, and one approximately 143.012 MHz region appeared only on the NESDR-class path. Both were retained as peripheral notes without identity research or anomaly assessment.
- Five completed sweeps on each receiver path.
- Twenty shared broadcast-FM regions: 13 strong and 7 supported assignment matches.
- Two receiver-specific peripheral notes deferred to future question-specific protocols.
Frequency-compatible research
analysisEvery shared primary-FM observation was compared with current public spectrum records and supporting station, owner, academic-media or government-cultural sources. Each had a compatible public channel record. The resulting names remain frequency-compatible candidate assignments: they organize the next questions, but they do not prove which transmitter produced the received energy.
The regulatory sources establish the public channel context, not station reception at the private observation site. No audio, RDS or other identity-bearing content was used.
What this establishes—and what it does not
project statusThe trial supports a useful bounded form of autonomy: freeze a protocol, acquire passively under owner authorization, preserve diagnostics, validate evidence integrity, research every in-scope observation, label uncertainty and stop when the registered question is answered.
This is a provisional station-assignment census, not an exhaustive dial inventory. It does not establish FM modulation, transmitter identity, calibrated field strength, equal receiver sensitivity or an unexplained anomaly. The NESDR-class path retained a receiver PLL diagnostic on all five sweeps, so the result remains explicitly provisional rather than silently repaired.
Bounded census counts and deferred peripheral notes
Counts are deterministic products of the preregistered persistence and cross-receiver rules. Frequencies are representative bin centers, not calibrated transmitter frequencies. Receiver power values are intentionally omitted because the complete paths are not calibrated field-strength instruments and their displayed scales are not compared.
| count | measurement type | receive only | receiver class | diagnostic retained | frequency scope mhz | definition | cross receiver support | frequency mhz | identity researched | within receiver occurrences |
|---|---|---|---|---|---|---|---|---|---|---|
| 5 | completed_sweeps | True | hackrf_wideband_sdr | |||||||
| 5 | completed_sweeps | True | rtl_sdr_nesdr_chain | pll_not_locked | ||||||
| 20 | shared_primary_regions | 88–108 | ||||||||
| 13 | strong_assignment_matches | shared_and_persistent_on_both_receiver_paths | ||||||||
| 7 | supported_assignment_matches | shared_with_one_path_below_four_of_five_persistence | ||||||||
| peripheral_receiver_specific_note | hackrf_wideband_sdr | False | 79.951 | False | 5 | |||||
| peripheral_receiver_specific_note | rtl_sdr_nesdr_chain | pll_not_locked | False | 143.012 | False | 5 |
Sources consulted
- Registro Nacional de Telecomunicaciones Plus — Superintendencia de Telecomunicaciones de Costa Rica; national regulator; retrieved 2026-08-21.
- Gobierno de la República anuncia concurso de frecuencias de radio y televisión — Ministerio de Ciencia, Innovación, Tecnología y Telecomunicaciones de Costa Rica; national allocation authority; retrieved 2026-08-21.
Sources provide context; their inclusion does not identify the observed emitter.
Limitations
- Frequency compatibility with a public channel record is not proof of the transmitter received.
- No demodulation, audio, RDS, callsign decoding or other identity-bearing content was used.
- The two complete antenna, feed and receiver paths are not calibrated field-strength instruments, and their displayed powers are not cross-compared.
- The NESDR-class path retained a PLL diagnostic on all five sweeps; the complete census therefore remains provisional.
- Antenna response, feed loss, receiver response, nearby structures, multipath and sequential timing remain uncontrolled contributors.
- The two peripheral receiver-specific observations were not researched and were not assessed as anomalies.
- The result is a bounded census under one recorded setup and stopping rule, not an exhaustive inventory of all stations receivable in the region.