Special Propagation — Sporadic E, Grey Line, and Beyond - Propagation

Special Propagation — Sporadic E, Grey Line, and Beyond

Sporadic E (Es) — The Magic of 6 Metres

Every amateur's favourite surprise: random patches of intense ionisation in the E layer that can reflect signals well into the VHF range — especially on 6 metres (50 MHz), and sometimes even 2 metres!

Most common in Australian summer (November–February)
Single-hop distances: 500–2300 km
Unpredictable — can last minutes or hours
When it opens on 6m, get on air fast! It won't last forever.

Operator tip: Monitor 50.110 MHz (the 6m calling frequency) and propagation beacons. When sporadic E opens, you'll suddenly hear stations that are normally well beyond your range. Multi-hop Es can occasionally reach across the Pacific.

Grey-Line Propagation

The grey line is the sunset/sunrise boundary on Earth. Along this line, something special happens:

The D layer has just disappeared (sunset side) or not yet formed (sunrise side)
But the F layer still has enough ionisation to reflect signals
This creates a low-absorption "duct" for signals on the low bands

The opening is brief — typically 10–30 minutes around sunrise and sunset. Both stations need to be near the grey line. This is prime time for 160m and 80m DX.

Tropospheric Ducting

Not all propagation involves the ionosphere! Temperature inversions in the lower atmosphere (troposphere, 0–12 km) can create "ducts" that trap VHF/UHF signals:

Most common over water or flat terrain
Can extend VHF/UHF range to 1000+ km
Important for 2m and 70cm DX
Often accompanied by fog or haze conditions

Earth-Moon-Earth (EME / Moonbounce)

The ultimate DX: bounce your signal off the Moon! The Moon is ~384,000 km away, so the round trip is ~768,000 km. This requires:

High-gain antennas (large Yagi arrays or dishes)
High power (400W — the legal limit is helpful here!)
Very sensitive receivers
Path loss is approximately 250+ dB — enormous!
Common on 144 MHz, 432 MHz, and 1296 MHz

Satellite Communication

Amateur radio satellites (OSCAR series and others) provide relay capability. Key considerations:

Doppler shift: LEO satellites move fast — the frequency shifts as the satellite approaches (+) and recedes (−)
You need to track the satellite and continuously adjust frequency
Common uplink/downlink: 145/435 MHz, 435/145 MHz