This post is now in two parts.
The original post is shown in
Part 1 below.
The updated information with the log from D4VHF is shown in
Part 2 further down the post.
* * * * *
Part 1...
On
Friday the 29th of May 2020, there was an extensive Sporadic-E opening across Europe which reached as high as
144 MHz allowing stations across the continent to make many fine contacts.
The most extraordinary contacts however was probably the opening from the Cape Verde Islands off the coast of Africa to Poland on 144 MHz. The longest path recorded seems to have been when the FT8 signals from
D4VHF were heard by
SP5XMU in Warsaw, a distance of just over
5,600kms.
The map above shows the stations on FT8 that reported hearing or were heard by
D4VHF. The most intensive part of the Sporadic-E seems to have been along a narrow corridor stretching from Lyon in France to Warsaw in Poland.
Mode of Propagation... It seems very likely that there were two propagation modes at work for this extraordinary path from the Cape Verde Islands to Central Europe.
As shown by the tropo prediction map above courtesy of F5LEN, there is a reasonably stable maritime tropo duct from the Cape Verde Islands to south coast of Portugal, a distance of about 2,800kms.
The path from Poland to the south-west of the Iberian Peninsula was spanned by a Sporadic-E opening which was in progress across Europe at the time.
As with openings of this nature, there is always the possibility of double hop Sporadic-E which can't be discounted for a good part of the path. However, this tropo duct off the north-west coast of Africa is a remarkably steady feature and it seems to be there for a large part of the year. It's hard to imagine that it didn't play a major part in the opening.
 |
| FT8 screenshot from D4VHF |
In 2019, there were other similar mixed Sporadic-E & tropo duct openings from Cape Verde to Italy and Germany. The distances involved with this opening to Poland though are exceptional.
* * * * *
PART 2...
Update. Now that the dust has settled, we can look at the log of D4VHF and who they worked...
While many stations heard D4VHF on FT8, a much smaller number managed to make a contact.
Here is the log...
2020-05-29,10:05:15, CT1END,IM58,144.175900,FT8,-07,-04,,,
2020-05-29,11:10:00, IK4ADE,JN54,144.175900,FT8,-07,-09,,,
2020-05-29,11:57:15, IK0ZYH,JN62,144.175900,FT8,-15,-17,,,
2020-05-29,12:15:45, EA8AJC,IL18,144.175900,FT8,+28,+17,,,
2020-05-29,12:36:00, F6EAS,,144.175900,FT8,+04,+02,,,
2020-05-29,12:43:30, EC1KV,,144.175900,FT8,-15,-15,,,
2020-05-29,12:49:15, F1DUZ,IN97,144.175900,FT8,-18,-19,,,
2020-05-29,12:52:00, F6CIS,,144.175900,FT8,-15,-19,,,
2020-05-29,12:59:45, F6DBI,IN88,144.175900,FT8,-03,-07,,,
2020-05-29,13:22:30, F8DBF,IN78,144.175900,FT8,-06,-08,,,
2020-05-29,13:47:00, G4RRA,,144.175900,FT8,-15,-16,,,
2020-05-29,13:49:00, G8BCG,,144.175900,FT8,+00,-16,,,
2020-05-29,13:52:00, GW7SMV,,144.175900,FT8,-05,-16,,,
2020-05-29,13:54:30, G3NJV,IO70,144.175900,FT8,-15,-01,,,
2020-05-29,13:55:30, G7RAU,IN79,144.175900,FT8,-13,-13,,,
2020-05-29,14:19:15, CT1IUA,IM67,144.175900,FT8,-16,-12,,,
2020-05-29,15:27:00, DJ8RZ,JN58,144.175900,FT8,-08,-10,,,
2020-05-29,15:30:45, DL5MCG,,144.175900,FT8,-09,-19,,,
2020-05-29,15:34:45, I2FAK,JN45,144.175900,FT8,+10,-11,,,
2020-05-29,18:41:15, CT1ANO,IN51,144.175900,FT8,-18,-19,,,
2020-05-29,18:55:15, CU2GI,HM77,144.175900,FT8,-19,-18,,,
2020-05-30,08:39:45, EA8AIN,IL18,144.175900,FT8,-09,+08,,,
2020-05-30,16:21:30, EA7FDW,IM76,144.175900,FT8,-11,-12,,,
2020-05-30,16:44:45, EA7E,IM66,144.175900,FT8,-18,-20,,,
2020-05-30,16:49:45, CT1EYQ,IM58,144.175900,FT8,-18,-17,,,
2020-05-30,17:16:45, EC2AGL,IN91,144.175900,FT8,-06,-16,,,
2020-05-30,17:22:45, CT1ADT,IM57,144.175900,FT8,-13,-07,,,
The FT8 signals sent and received by D4VHF according to the PSK Reporter website are shown at the end of this post.
Some points...
1) SSB V FT8... For a Sporadic-E opening on 144 MHz, a mode like SSB would be much better in terms of speed. However, look at the signal strengths in the log. Most are in the minus dB range so a SSB QSO would probably have
not been possible.
As for what would be a better mode is up for debate. Marginal contacts via CW? Faster digital modes like FT4? No matter what mode was used, there would have always been incomplete contacts and a limit to how many would get in the log.
2) Mode of Propagation... From what we know, there seems to be two components.
First, there is a marine duct off the west coast of Morocco which allows VHF signals to propagate from Cape Verde Islands up to the Canary Islands (1500kms), Portugal & Spain (3000kms) and the UK (4000kms).
According to one of the operators of D4VHF...Mark EA8FF, there was no tropo between D4 and EA8 or EA7 at the time. And yet, this marine duct over the sea was probably present for a good part of the path. I don't think we can discount it and yet, there must surely be Sporadic-E openings on 144 MHz in that part of the world as well? We can't always assume it's a marine duct.
While we can debate the paths from D4 to the coasts of Portugal or the south of Spain, those signals from further north were almost certainly via Sporadic-E.
The question is was it tropo & Sp-E, multi-hop Sp-E at 144 MHz?? Just in terms of probability, I personally don't believe in triple hop Sporadic-E at 144 MHz. Double maybe, triple?!?!
3) Sporadic-E to the UK... The problem with just a list of stations is that there are like data points for a graph, they don't make much sense until you draw the graph. In the same vein, when you generate a map and see the location of the stations, you can see patterns.
Again, see the map above. Note how the UK stations are strung out in a nice narrow line. This is a classic Sporadic-E footprint. The furthest station was GW7SMV at just over 4300kms.
4) Poland... The other unusual dimension to this opening was the unusual opening at the same time from Portugal to Poland. See the QSO map below from Tom,
SP5MXU...
As you can see, SP5XMU was able to work stations in Portugal at a distance of almost 2800kms. What is unusual about this is that the usual maximum distance for one-hop Sporadic-E is about 2300kms. Where did the extra 500kms come from?
This is usually explained by say a tropo extension at one or both ends. Another is the possibility of chordal hop as suggested by SO3Z in the comments. In that scenario, the signal is going between two Sporadic-E clouds before returning to the ground again.
The chordal hop theory may help explain how the 144 MHz signals covered at least part of the 5600km distance from Cape Verde Islands to Poland.
Part 2 Conclusion... In the past with traditional modes like SSB and CW, we could be reasonably sure about the mode of propagation on VHF bands like 2 metres. Now with digital modes like FT8 we are seeing signals buried in the noise which makes it harder to be certain about how the signal was propagated.
I know FT8 isn't popular with everyone but the new digital modes are allowing radio amateurs to discover paths on VHF that we never knew existed.
* * * * *
Equivalent Distances... As always, it's interesting to look at some maps to put these remarkable distances in perspective.
The 5600 km distance from the Cape Verde Islands to Warsaw would reach as far north as Oslo, the capital of Norway.
It's hard to believe but the whole island of Iceland is actually closer!
From a western perspective, the equivalent distance reaches as far as Washington DC in the USA.
Remember, there are no satellites or moonbounce involved here. This is a 144 MHz signal being propagated by Sporadic-E and tropo.
What if...??? The map of the USA above suggests maybe one potential extraordinary path. From time to time, there seems to be a tropo duct across the Atlantic from Care Verde to the the Caribbean. Could this be extended even further to the west by a Sporadic-E opening at the same time???
FT8 signals heard by D4VHF...(over 3400kms)
