This is the third such opening this year on 144 MHz where there has been a maritime tropo duct from Cape Verde Islands up to the south-west coast of the Iberian peninsula and then a Sporadic-E opening from that region.
The first such mixed propagation mode was back on the 9th of June 2019 to Italy, Slovenia and Austria. The second was on the 3rd of July 2019 when three stations in Germany heard D41CV.
What was significant for the third opening however was that there was a successful FT8 contact made with DK5AI in Germany, an amazing distance of 4966 kms.
The map above shows the stations that were heard by or had heard D41CV on FT8 on 144 MHz.
While the tropo duct off the coast of Africa was probably stable, the Sporadic-E opening up into Europe seems to have come in two distinct phases.
The four German stations were around 15:08 to 15:40 UTC. The other signals were around 16:34 to 17:40 UTC.
Update : This is the log of FT8 contacts made by D41CV on the 23rd of July. Red contacts are Sp-E + tropo. Black is tropo only...
This is a screen shot of the FT8 contact between D41CV and DK5AI...
This is the tropo prediction map from F5LEN showing the maritime tropo duct up along the west coast of Africa.
Considering this is the third such opening this ear, it might be easy to take it for granted but we shouldn't. A distance of 4,966 kms on 144 MHz is really incredible.
Just for fun, lets suppose that DK5AI was able to work that distance across the Atlantic. This is how far his signal would reach...
The future...5000+ kms??... It's very likely that we haven't seen the maximum distance yet for this mixed propagation path. The marine duct off the west coast of Africa seems to exist for long periods of time so that is a significant factor. The big variable is of course the requirement for a Sporadic-E opening on 144 MHz to complete the path.
Stations in the north of Germany near Hamburg or in Denmark may well be within one Sp-E hop of the coast of Portugal. If this coincided with a marine duct to Cape Verde, contacts in the region of 5,200 kms may be possible.
Links...
1) D4C contest team on Twitter
2) F5LEN Tropo prediction for D4
7 comments:
Great Post John, nice pictures and description!
73 Wolf Dk5AI
Another outstanding report, as usual...
I suppose the info provided in a timely manner pushed you forward...
Many thanks John.
73, Andrea HB9DUR
This is the kind of stuff that excites me about propagation on VHF and up.
Great report !
73 de Jan, OZ9QV
Thanks Wolf, Andrea & Jan
I just know that in six months time, it will be very difficult to look back and find out what happened. That's why I think it's important to put as much information as possible now about the openings up on the site so at least there is a record of it.
73's de John, EI7GL
I think that the coupling point from the E-S to the tropo duct will be around 100Km to the West of Portugal in the Atlantic Ocean. Just at the tip of the North Westerly 'finger' in the F5LEN plot. During this event I was hearing EA8DBM for over 1 hour by the same mechanism but my coupling point into the duct was wrong for a path to D4.
The work done by G4LOH on 144MHz mixed mode coupling gives a good view on how the mechanism works but prediction is something else! Earlier on the 23rd I had failed to make a tropo + MS contact with EA8TX. My suspicion is that the duct was too far South for the shorter (than e-s) MS reflections to couple.
The path that interests me the most is EA1 to VO1 or even VE1, by dual mode, which I think, although longer, has a much greater chance that EI or G to VO1.
73
John G4SWX
Not to forget that our Cape Verde-based station is equipped free of charge by an AIS receiver to monitor VHF propagation. By monitoring the number of ships detected and the direction, we have always been able to find the right direction of the opening and the potential distance.
D4C has been using this service for several years yet.
The equipment provider is the company Vesseltracker and here one can apply for the free of charge hardware https://www.vesseltracker.com/en/static/antenna-partner.html and enjoy several benefit as antenna partner.
Let's develop VHF further!
73 de Andrea HB9DUR
Nice event again, good job!
73 Thierry F4BDG JN18
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