INDEPENDENT AMATEUR RADIO STATION—:—:— UTC

UN7GUN / REFERENCE

Propagation

Band conditions by time, season, SFI and K index.

02

Band propagation

A practical orientation table, not a prediction. Actual openings depend on solar and geomagnetic activity, season, path and local noise.

Band	Night	Morning	Day	Evening	Best season	Typical path	Notes
160 m	excellent	weak	—	good	winter	day ~50 km; night up to 3,000 km and DX	sunrise/sunset windows; summer storm noise
80 m	excellent	weak	weak	excellent	winter	day 300–500 km; night 500–3,000 km	strong summer QRN
40 m	excellent	good	good	excellent	all year	day 300–1,500 km; DX at night	regional by day, worldwide at night
30 m	good	good	good	excellent	all year	1,000–5,000 km; evening DX	CW and digital only; bridge between 40 and 20 m
20 m	weak	excellent	excellent	excellent	all year; best spring/autumn	DX 2,000–15,000 km	main DX band; may close soon after winter sunset
17 m	—	good	excellent	good	spring, autumn	DX	quieter than 20 m; needs moderate solar activity
15 m	—	weak	excellent	weak	spring, autumn, winter	daytime DX	solar-dependent; often closed near solar minimum
12 m	—	weak	good	weak	spring, autumn	daytime DX	usually needs high solar activity
10 m	—	weak	good	weak	spring, autumn; summer Es	worldwide near cycle peak; Es 500–2,000 km	long paths with low power when open
6 m	—	weak	good	weak	May–August (Es)	Es 1,000–2,200 km; farther by double hop	F2 near solar peak; sudden openings
2 m	local	local	local	local	autumn tropo	line of sight 30–100 km; farther via repeaters	inversion tropo can reach hundreds of km
70 cm	local	local	local	local	autumn tropo	20–60 km; repeaters	bends around obstacles less than 2 m

Solar flux (SFI)

Below 70: upper HF bands are often difficult.
70–100: moderate conditions.
100–150: good prospects on 20–15 m.
Above 150: 12 and 10 m may open widely.

K index

K 0–1: quiet geomagnetic conditions.
K 2–3: normal to unsettled.
K 4: disturbed; polar paths may degrade.
K 5+: geomagnetic storm conditions.