VHF Propagation Identification(V3.50) June 2026
DISTANCE	<50-100km	100-400km	400-800km	800-2400km	2400-4800km			4800-7200km	7200-9600km	9600-14000km
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  (50-90 MHz not 144 MHz)	Sporadic-Es (ES) x1 hop (50 to 144 MHz*)	Sporadic-Es (2xES)  x2 hops (50 to 144 MHz)			Sporadic-Es (3xES)  x3 hops (50-90 MHz, not 144MHz)	Sporadic-Es (4xES)  x4 hops (50 MHz not 70 to 144MHz)
			Meteor Scatter (MS)					TEP + Sporadic-Es (TEPES)
		Aircraft Scatter (AS) <------VHF     UHF------>						Trans Equatorial Propagation (TEP)
								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 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 VHF ES distances by band  50 MHz >400km 70 MHz >400km 90 MHz >600km 144 MHz >1400km	Sporadic-E extensively occurs from May to August (Northern Hemisphere) on 50MHz, with a peak in June, with ES on 144MHz occurring less than 10% of that time. It is inherently unstable and temporary. Typically very high signal strengths on x1 hop distance even with low power levels. The angle of incidence is important too, it is thought that VHF radio signal angles of up to 30 degrees above the horizon will be reflected by ES, but any angle higher is likely to pass straight through the ES clouds.  For 50 MHz ES with a MUF of 55 MHz the minimum workable distance is in theory around 1500km, the higher the MUF gets the shorter the distances become to an absolute minimum of 400km at a MUF of 134 MHz or higher 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) M or X class solar flares and especially CME can trigger ES outside of normal Summer season whilst shorter lived ES openings are sometimes possible at other times of year, especially during the major meteor showers					4xES hops very rare as clouds all need to be in ideal positions.   Europe to Japan seen a few times on 50MHz, not TEP Requires intense solar flares/CME for widespread Multi Continental ES (4xES)
			Short duration bursts of seconds or less, but can be a couple of minutes, especially during meteor showers (MS)				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)
		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(AU)				Stations need to be either side of the Magnetic Equator. Most favourable time of year is near to Summer Equinox (TEP)
		Daily, around 4 minutes total QSO duration, VHF needs largest aircraft, UHF travels furthest distances (AS)		Look for Planetary Kp index of 5+. Rare, short lasting <1 hour. Develops after Aurora propagation ends, no Doppler shift. Reflecting layer higher than ES, 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

 

 

 

 

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