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.
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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.
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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...
The FT8 signals sent and received by D4VHF according to the PSK Reporter website are shown at the end of this post.
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.
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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)
Txmtr Band Mode Distance Time (UTC)
SP5XMU 2m FT8 5609 km 15:47:00
SQ5AAG 2m FT8 5600 km 15:37:29
SP7NHS 2m FT8 5495 km 15:34:29
SP6VGJ 2m FT8 5328 km 15:47:00
OK1NI 2m FT8 5176 km 15:34:29
OK5TK 2m FT8 5130 km 15:38:59
OE3NFC 2m FT8 5101 km 16:11:29
DK1FG 2m FT8 4875 km 16:48:29
DJ8RZ 2m FT8 4829 km 15:45:30
DL2MS 2m FT8 4805 km 15:44:29
DK5YA 2m FT8 4777 km 16:00:59
DL5MFS 2m FT8 4772 km 15:41:00
DL1SBY 2m FT8 4772 km 15:41:29
DL6IAK 2m FT8 4672 km 13:21:26
DK5EW 2m FT8 4643 km 15:46:30
IK2DDR 2m FT8 4580 km 15:49:30
IK4ADE 2m FT8 4573 km 11:17:58
ON4KHG 2m FT8 4548 km 23:16:59
IK2LHP 2m FT8 4517 km 15:25:59
IK0ZYH 2m FT8 4513 km 11:57:26
IK2CHZ 2m FT8 4513 km 15:40:30
I2FAK 2m FT8 4462 km 15:39:30
F8DO 2m FT8 4260 km 13:18:58
G4RRA 2m FT8 4211 km 13:48:57
F6EAS 2m FT8 4166 km 14:12:28
F6IFX 2m FT8 4151 km 13:08:26
G3NJV 2m FT8 4090 km 13:54:27
G7RAU 2m FT8 4086 km 13:55:56
F6GLQ 2m FT8 4062 km 12:50:26
F1DUZ 2m FT8 4048 km 13:02:27
F6DBI 2m FT8 4020 km 12:59:56
F8DBF 2m FT8 3963 km 13:31:29
F6CIS 2m FT8 3850 km 12:43:26
Stations hearing D4VHF...(over 3400 kms)
Rcvr Band Mode Distance Time (UTC)
SP7NHS 2m FT8 5495 km 15:34:14
SP6RGB 2m FT8 5228 km 15:48:14
DJ8RZ 2m FT8 4829 km 15:43:12
DL5MFS 2m FT8 4772 km 15:44:46
DL1SBY 2m FT8 4772 km 15:42:12
DF2ZC 2m FT8 4726 km 12:40:14
DL5GAC 2m FT8 4665 km 15:47:45
DC2TH 2m FT8 4646 km 12:51:45
DK5EW 2m FT8 4643 km 15:47:45
HB9DBM 2m FT8 4535 km 15:32:44
IK2MKS 2m FT8 4528 km 15:42:15
HB9BIN 2m FT8 4525 km 15:23:11
G0SYP 2m FT8 4514 km 14:10:44
IK0ZYH 2m FT8 4513 km 11:51:11
F4TTR 2m FT8 4339 km 12:40:44
F0FYF 2m FT8 4329 km 15:42:14
GW7SMV 2m FT8 4317 km 13:43:44
GW4VXE 2m FT8 4280 km 18:52:12
GW1JFV 2m FT8 4264 km 18:53:41
EI8IQ 2m FT8 4256 km 18:59:15
G4RRA 2m FT8 4211 km 13:43:44
G8IXN 2m FT8 4110 km 14:05:14
G4LOH 2m FT8 4098 km 14:43:44
G3NJV 2m FT8 4090 km 14:15:45
G7RAU 2m FT8 4086 km 14:04:44
F6GLQ 2m FT8 4062 km 13:01:14
F1LFT 2m FT8 4061 km 13:03:14
F1DUZ 2m FT8 4048 km 12:48:14
F6DBI 2m FT8 4020 km 12:59:44
F6GNR 2m FT8 3997 km 08:31:41
F4IAA 2m FT8 3952 km 12:53:44
F6CIS 2m FT8 3850 km 12:53:44
EA2BHE 2m FT8 3598 km 12:40:44
EA2Z 2m FT8 3582 km 08:07:44
EA1IYG 2m FT8 3561 km 12:26:14
EA1BHB 2m FT8 3484 km 08:43:14
1) Just a note to say that there was a large M class flare on the sun on the 29th of May 2020. I don't know whether this had any impact on the extent or intensity of the Sporadic-E conditions but I include it here as a point of interest.