G0ISW VHF DX Ultimate Resource Site

(V3.42) October 2024

DISTANCE <50-100km 100-400km 400-800km 800-2400km 2400-4800km 4800-7200km Over 7200km

Propagation type Line of Sight (LOS)
Tropo Scatter (TRS)

Tropo Ducting (TRD)
TRD + Sporadic-Es (TRDES)

Aurora (AU)

Auroral-E (AUE)

Sporadic-Es (ES) very rare at short 400-800km distance
(Not 144 MHz)
Sporadic-Es (ES)
x1 hop
Sporadic-Es (2xES)
x2 hops
Sporadic-Es (3xES)
x3 hops
(Seen at 90 MHz, but not 144MHz)
Sporadic-Es (4xES)
x4 hops
(Not 70/144MHz)

Meteor Scatter (MS) Trans Equatorial Propagation (TEP) TEP + Sporadic-Es (TEPES)

Aircraft Scatter (AS)
<------VHF UHF------>

F2 Layer reflection/refraction (F2)

PLEASE SEE COLOUR CODED NOTES BELOW FOR EACH TYPE OF PROPAGATION SHOWN ABOVE

Required conditions or assists with ID True Line of Sight is up to 50km, but can be extended by significant height ASL or by diffraction to maximum of 100km (LOS) Tropospheric Ducting requires stable High Air Pressure, as often seen associated with fog. Paths can be blocked by mountains. A Sea surface ducting path is required for the very longest rare distances (TRD) Distances of around 5000km on 144 MHz reported (TRDES)

Sporadic-E for the minimum 400km distance requires extremely high and rare MUF (ES)

50 MHz requires a MUF of 134 MHz

70 MHz requires a MUF of 188 MHz

90 MHz requires a MUF of 241 MHz

Shortest observed ES distances

50 MHz >401km

70 MHz >406km

90 MHz >603km

144 MHz >1481km

Sporadic-E extensively occurs from May to August on 50MHz, with a peak in June, with ES on 144MHz occurring less than 10% of that time. Band openings on 50 MHz can last for many hours, but the higher the VHF band the less time they last with some 144 MHz ES lasting as little as 5 minutes on occasion
Typically very high signal strengths on x1 hop distance. Shorter lived ES openings are sometimes possible at other times of year, especially during the major meteor showers or following intense solar flares
The angle of incidence is important too, it is thought that VHF radio signal angles of up to 28 degrees above the horizon will be reflected by ES, but any angle higher is likely to pass straight through the clouds.
For 50 MHz ES the minimum workable distance is in theory 400km as any shorter would be too high an angle of incidence with an elevation at 28 degrees plus.
Mostly observed during daylight hours with late morning and late afternoon peaks, usually reported as gone by local midnight, but can still be present later (ES)
x4 Sporadic-E hops are very rare as clouds all need to be in the ideal positions.
Usually requires a mostly daylight path with Europe to Japan seen several times on 50MHz
Seems to occur after intense solar flares generating widespread area of ES (4xES)

Daily, mostly short duration bursts of seconds or less, but can be a couple of minutes, especially seen during larger meteor showers (MS) Both stations need to be either side of the Magnetic Equator (TEP), but do not need to be equidistant. Most favourable time of year is near to Summer Equinox. Often misidentified as ES alone on DX cluster. Main distance component is TEP and both stations need to be on opposite sides of the Magnetic Equator (TEPES)

Daily, Tropo Scatter is very poor at 50 MHz, but good at 144 MHz, often associated with fading QSB (TRS)

Look for a Planetary Kp index of 5+. Beam between North to East. Raspy distorted tone & audio distortion due to Doppler shift, signals bounce back from the moving auroral curtain to other stations(AU)

Daily, around 4 minutes total QSO duration, VHF needs largest aircraft, UHF travels furthest distances (AS) Look for previous Planetary Kp index of 5+. Rare, short lasting <1 hour. Develops after Aurora propagation ends, signals don't display Doppler shift. Reflecting layer much higher than for ES, so longer signals more likely than for Aurora (AUE) F2 Favours Autumn to Spring months during the Solar Cycle Maximum, every 11 or 22 years (F2)
Most recently observed in 2024

VHF FT8 Transmission Periods
Northbound & Westbound	1st Period / Tx Even
Southbound & Eastbound	2nd Period / Tx Odd

Send a Formatted VHF DX Cluster spot



		Send formatted VHF DX Cluster spot
If you cannot see the full index shown on the left edge of your screen, please go to my main page at http://www.qsl.net/g0isw © Copyright G0ISW. Page last modified October 2024. All Rights Reserved.

(V3.42) October 2024
DISTANCE	<50-100km	100-400km	400-800km	800-2400km	2400-4800km	4800-7200km	Over 7200km
Propagation type	Line of Sight (LOS)	Tropo Scatter (TRS)
		Tropo Ducting (TRD)				TRD + Sporadic-Es (TRDES)
		Aurora (AU)
				Auroral-E (AUE)
			Sporadic-Es (ES) very rare at short 400-800km distance (Not 144 MHz)	Sporadic-Es (ES) x1 hop	Sporadic-Es (2xES) x2 hops	Sporadic-Es (3xES) x3 hops (Seen at 90 MHz, but not 144MHz)	Sporadic-Es (4xES) x4 hops (Not 70/144MHz)
			Meteor Scatter (MS)		Trans Equatorial Propagation (TEP)		TEP + Sporadic-Es (TEPES)
		Aircraft Scatter (AS) <------VHF UHF------>				F2 Layer reflection/refraction (F2)
PLEASE SEE COLOUR CODED NOTES BELOW FOR EACH TYPE OF PROPAGATION SHOWN ABOVE
Required conditions or assists with ID	True Line of Sight is up to 50km, but can be extended by significant height ASL or by diffraction to maximum of 100km (LOS)	Tropospheric Ducting requires stable High Air Pressure, as often seen associated with fog. Paths can be blocked by mountains. A Sea surface ducting path is required for the very longest rare distances (TRD)				Distances of around 5000km on 144 MHz reported (TRDES)
			Sporadic-E for the minimum 400km distance requires extremely high and rare MUF (ES) 50 MHz requires a MUF of 134 MHz 70 MHz requires a MUF of 188 MHz 90 MHz requires a MUF of 241 MHz Shortest observed ES distances 50 MHz >401km 70 MHz >406km 90 MHz >603km 144 MHz >1481km	Sporadic-E extensively occurs from May to August on 50MHz, with a peak in June, with ES on 144MHz occurring less than 10% of that time. Band openings on 50 MHz can last for many hours, but the higher the VHF band the less time they last with some 144 MHz ES lasting as little as 5 minutes on occasion Typically very high signal strengths on x1 hop distance. Shorter lived ES openings are sometimes possible at other times of year, especially during the major meteor showers or following intense solar flares The angle of incidence is important too, it is thought that VHF radio signal angles of up to 28 degrees above the horizon will be reflected by ES, but any angle higher is likely to pass straight through the clouds. For 50 MHz ES the minimum workable distance is in theory 400km as any shorter would be too high an angle of incidence with an elevation at 28 degrees plus. Mostly observed during daylight hours with late morning and late afternoon peaks, usually reported as gone by local midnight, but can still be present later (ES)			x4 Sporadic-E hops are very rare as clouds all need to be in the ideal positions. Usually requires a mostly daylight path with Europe to Japan seen several times on 50MHz Seems to occur after intense solar flares generating widespread area of ES (4xES)
			Daily, mostly short duration bursts of seconds or less, but can be a couple of minutes, especially seen during larger meteor showers (MS)		Both stations need to be either side of the Magnetic Equator (TEP), but do not need to be equidistant. Most favourable time of year is near to Summer Equinox.		Often misidentified as ES alone on DX cluster. Main distance component is TEP and both stations need to be on opposite sides of the Magnetic Equator (TEPES)
		Daily, Tropo Scatter is very poor at 50 MHz, but good at 144 MHz, often associated with fading QSB (TRS)
		Look for a Planetary Kp index of 5+. Beam between North to East. Raspy distorted tone & audio distortion due to Doppler shift, signals bounce back from the moving auroral curtain to other stations(AU)
		Daily, around 4 minutes total QSO duration, VHF needs largest aircraft, UHF travels furthest distances (AS)		Look for previous Planetary Kp index of 5+. Rare, short lasting <1 hour. Develops after Aurora propagation ends, signals don't display Doppler shift. Reflecting layer much higher than for ES, so longer signals more likely than for Aurora (AUE)		F2 Favours Autumn to Spring months during the Solar Cycle Maximum, every 11 or 22 years (F2) Most recently observed in 2024