TECHNICAL NOTE / PROPAGATION
Sporadic-E
Sporadic-E can support very long 50 MHz contacts when ionized E-region patches form. Openings can shift rapidly in distance and bearing. Higher frequencies sometimes benefit under strong conditions, but success on 6 meters is not proof of a 2-meter opening.
Meteor scatter
Meteor trails can create brief, rapidly changing reflections, particularly useful around 50 and 144 MHz. Fast digital protocols such as MSK144 are designed for bursty conditions. A path may be workable by meteor scatter when normal tropospheric service is not.
Tropospheric enhancement
Temperature and humidity gradients influence refractivity. Stable inversions can favor unusually long VHF/UHF paths, but a local barometer reading cannot establish that a duct spans the full route.
EME / Moonbounce
Earth–Moon–Earth links face very large path loss and require careful accounting of antenna gain, receiver noise, pointing and lunar visibility. The apparent lunar disk is roughly half a degree across; broad antenna beamwidth does not eliminate large two-way path loss.
Modes and evidence
CW/SSB reports, FT8/Q65 decoding, beacons and validated on-air exchanges each add different evidence. Compare frequency, exact UTC time, polarization and geographic path before attributing a contact to a propagation mechanism.