VHF and UHF are usually described as line-of-sight. They are not, and the techniques below are where the most technically demanding operating in the hobby happens.
Meteor scatter
Millions of meteors enter the atmosphere daily, each leaving a briefly ionised trail that reflects VHF signals for a fraction of a second to a few seconds. Contacts of 500–1,300 miles on 6 m and 2 m are routine.
- Mode: MSK144 in WSJT-X, which packs an exchange into 72 ms bursts.
- When: early morning any day; far better during showers — Perseids in August, Geminids in
- Station: 100 W and a single yagi is enough on 6 m.
December, Quadrantids in January.
EME — moonbounce
Aim at the Moon, and roughly 2.5 seconds later your own signal comes back 250 dB weaker. It is the ultimate DX path: anyone who can see the Moon at the same time as you is workable.
- Mode: Q65 and JT65 make it achievable with a single yagi and 100–500 W on 2 m or 70 cm, which
- Watch for Doppler shift, spatial polarisation offset, and the extra path loss when the Moon is at
was impossible before weak-signal software.
apogee.
Tropospheric propagation
Temperature inversions — common over water, and after calm high-pressure evenings — form ducts that carry 2 m and 70 cm signals hundreds of miles. Check a tropo forecast map, then listen on the calling frequencies (144.200 and 432.100 MHz USB) rather than FM.
Sporadic E
Intense patches of ionisation in the E layer light up 6 m — the "magic band" — for minutes to hours, mostly in late spring and early summer, giving 500–1,400 mile openings and occasionally 2 m.
QRSS
Extremely slow Morse, with dot lengths of 3 to 120 seconds, decoded visually on a spectrogram rather than by ear. Milliwatt beacons on 30 m are received across oceans. It teaches more about signal-to-noise and bandwidth than any book.
What these have in common
Narrow bandwidth, patience, accurate time and frequency, and good antennas — see antenna theory and propagation.