Persistent Signal Catalog · Class III
The Calder Ridge carrier
The Laboratories' longest-standing unresolved detection. A narrow-band signal near 18.6 kHz, recurring for more than fifty years, matching no known source.
The Laboratories' longest-standing unresolved detection. A narrow-band signal near 18.6 kHz, recurring for more than fifty years, matching no known source.
- Source
- FAL-PSC-1971-0447-PUB
- As of
- 2026-05-22
- Method
- Annual recurrence ledger; non-public station geometry removed.
Public packet
- frequency stability summary
- recurrence ledger by year
- instrument replacement cross-check
- known transmitter exclusion worksheet
Review controls
- Coordinate source
- Station-relative bearing retained in restricted record
- Uncertainty
- No public geolocation; record is held as a terrestrial station event
- Release state
- Public abstract with station geometry withheld
Processing notes
- narrow-band carrier extraction at 18.633 kHz
- receiver swap comparison across three hardware generations
- ephemeris and licensed transmitter rejection
- seasonal recurrence review using station downtime ledgers
Ordinary-source checks
- maintenance and station schedule review
- ordinary-source exclusion summary
- release review before public posting
Release limits
- no public claim is made about origin
- station-bearing material is not released
- automatic alerting is disabled until a current return clears manual review
Public release note
The public entry preserves recurrence behavior and frequency history. Exact receiver geometry, bearing logs, and maintenance crosswalks remain restricted.