Misidentified Propagation mechanisms for Region 1 VHF DX records

I found the following Region 1 DX record distances for 50 MHz Sporadic-E contacts online today

Distance record on 50 MHz Propagation : ES

Band	Propagation	Call a	Loc	Call b	Loc	Mode	Date	Distance
50 MHz	ES	EI3KD	IO51VW	VK3ZL	QF22FE	FT8	2019-07-24	17370
50 MHz	ES	YO7VS	KN14VH	VK4KK	QG62MQ	CW	2000-01-25	15153
50 MHz	ES	9M6XRO	OJ85AW	CT3HF	IM12OP	CW	2011-07-01	13458
50 MHz	ES	IK0FTA	JN61GV	VK8AW	PH57KO	CW	2013-06-24	13261
50 MHz	ES	HA0DU	KN07TM	CE2/VE7SV	FF47FA	CW	2012-05-27	12858

They cannot be correct as Sporadic-E layers/clouds occur at a height of between 90-130km above the Earth's surface (average 110km) and with VHF being line of sight and the curvature of the Earth each hop maximum distance being around 2350 km, the same as for Meteor Scatter. 

Double hop Sporadic-E clouds are well documented and can extend the maximum distance to around 4700 km, rarer Triple hop to around 7000 km, but this all requires the maximum distances for each hop and the chances of three or more Sporadic-E clouds lining up perfectly get less and less plausible.

Whilst Sporadic-E occurs in the Northern Hemisphere between April to September, with a peak in June each year and a smaller event around December, it is extremely unlikely if not impossible that solely Sporadic-E can account for the 12000-17000 km distances shown in the table above.

In the last couple of years documented extreme long distance QSO's have taken place on 50 MHz between Australia and Europe, one well known example was the station of VK8AW who worked into Europe and the correct Propagation mechanism was identified as Trans Equatorial Propagation (TEP) from his station reaching approximately North Africa (equi distant) and then stations in Europe being reachable via Sporadic-E extending that distance so that two way QSO's could be made by those fortunate enough to be in the right Es hop distance.

If we look at the table above we can see the same station VK8AW working IK0FTA in June 2013 at a distance of 13261 km, this is again highly likely to be a TEP + Es combination given the distance and the time of year. It would require 5+ absolute maximum Es hops with clouds perfectly situated to allow that, simply not likely at all.

A significant part of the problem is that formatted DXcluster spots only have limited options of Propagation mode to be entered by the operator or observers, being either Es or TEP, but not both TEP+Es.

Let us look at the other entries

EI3KD to VK3ZL at 17370 km, would require 7+ perfect longest distance Es hops, so again cannot be correct. Interestingly VK3ZL is located in South Australia near Melbourne and looking at the globe it would mean TEP from him to around Israel together with double hop Northern hemisphere Sporadic-E to make the distance shown. Entirely possible in July.

YO7VS to VK4KK at 15153 km, would require 6+ perfect longest distance Es hops and it is in January so what Propagation mechanism could it have been, if not involving Es? Probably F2, the solar cycle peaked the following year when I heard VK via F2 on 50 MHz.

9M6XRO to CT3HF at 13458 km, would require 5+ perfect longest distance Es hops, again highly unlikely. 9M6XRO was located in Eastern Malaysia just to the North of the Equator, so presumably that would discount TEP also. CT3HF in on Madeira Island in the Atlantic West of Africa. 2011 was another solar cycle maximum year so probably F2 on 50 MHz.

Finally, HA0DU to CE2/VE7SV at 12858 km, would require 5+ perfect longest distance Es hops. Located near Santiago, Chile TEP would put the signal of CE2/VE7SV reaching NW Africa, within double hop Es distance from HA0DU. TEP +Es most probable in May.

My own best distance on 50 MHz was last week on 26th April 2023 working ZS6WN a distance of 9264 km, TEP + double hop Es.