No F2 propagation on 6m? There is on 8m

Someone asked me "what difference does it make whether something is TEP or F-layer propagation?"

Many of us have been hoping that there might be F-2 propagation on 6m so that we could work some juicy DX. All I have seen so far this solar cycle is TEP. TEP is nice, with long paths, and even some from the northern hemisphere (see last posting). I have seen no F2 propagation on 50MHz yet, and anything I have seen is almost certainly TEP or related stuff.

I have seen contacts reported to the cluster claiming to be classic F-2 propagation, but on closer inspection these look like TEP or related methods. I am not the police force, nor a judge deciding which is which. I just try to decide so that I can make the most of the situation.

I have not seen classic F2 on 6m so I need to go down a band to illustrate what I mean. I have thought of showing a map of 10m but that is too crowded. So here is a screenshot of PSK Reporter on the "40MHz band".

40MHz signals shown on PSK Reporter 14 October 2023

You can see the TEP heading south from Europe to Africa. I recorded 15 different callsigns here that afternoon. We see that north-south type of propagation on 6m from time to time.

Then you can see the trans Atlantic paths heading West. I have not seen anything like that on 6m yet. There was a long, strong, F2 opening on 40MHz on 14 October between Canada and Europe.

So the difference is that TEP paths cross the equator around the equinox, or they are "F2 Single-Track" which from here heads towards the equator but does not cross it. On the other hand classic F2 is much more directly related to the sunspot cycle and you can sure it is that method if the path does not pass anywhere near the equator.

Now there may be classic F2 paths which cross the equator too and if we get widespread F2 openings I will be happy to see them. None here yet. TEP is very distinctive and although it is influenced by the solar cycle we have been seeing it around the equinox for years.

What difference does this make if something is one propagation mode rather than another? Well you could say no difference. Many amateurs just work what they hear. But for me who likes to seek out DX then I can hunt out TEP paths at certain times of the year more or less every year, whereas classic F2 is a solar maximum event on 50MHz. One clue is that if they come from totally different directions you can have a good idea which is which.

The map above seems to show that F2 paths have crossed the Atlantic at 40MHz. You have to be a bit careful with PSK Reporter or cluster paths because many are misreported. However in this case I am pretty confident that these reports are genuine.

It is easy to look at PSK Reporter or DX Maps and see long DX paths which may look like classic F2. Lately there have been many of these on 6m which are near and across the equator. The maps show the paths as great circle lines spreading far north and even north of Scotland. There is no point me hoping to get in on these openings. I reckon that these paths are TEP-related and do not come this far north at all. Nothing like that has come my way yet on 50MHz, and I am not expecting it from that type of propagation. From what I have seen, up here we have just had rare shots at TEP by Es linking.  

So there have now been signs that classic F2 has reached 40MHz. This has been widely reported. Will it reach 50MHz? I do not know. We shall see. Meanwhile, I am still looking for TEP.

I have to say that the evidence from 40MHz is very promising so I might get F2 to work on 50MHz very soon. Or maybe not.

Does it make any difference to know that what I am seeing at 6m is not classic F2? In my case, I think this knowledge helps me to point my antenna in the right direction at the right time. If you know what to expect you can be prepared. I am hoping for more TEP, and there is a chance some day for classic F2.

Some day. Maybe.

If I knew what was going to happen then 6m would be like 20m. I could not cope with that.

73 Jim

GM4FVM

Senegal on 6m. Not trans equatorial, but still TEP?

 I have been away again. This time to Poitiers in France

GM4FVM in the cafe in the Blossac gardens in Poitiers France (photo Mrs FVM).

This photo does look a bit like one earlier this year in Vught in the Netherlands, though with a different Belgian tipple. Anyway, no radio on this trip. I note that once again, on my second visit to Montparnasse station in Paris, I was stopped and asked for a ticket by an RATP official. I am not sure if it is because of the way I look. Maybe they had intelligence that I might be a ticket dodger. Still, I suppose two visits separated by 35 years is a small sample. I must watch out for this again, as the Metro journey from Gare du Nord to Montparnasse is never easy at the best of times.

What follows has been revised on 12 October 2023 to include updated diagrams. It has been developed into a fuller article and this should appear on this blog later.

Back in Scotland now, on 28 September I worked Elivra, 6W/IV3FSG, in Senegal on 6m.

50MHz contacts at GM4FVM on 28 September 2023

As usual, click the image to enlarge if necessary.

This contact reminds me of the one with TT8SN in Chad on 20 October 2022. This distances are similar - TT8SN is 5084km, while 6W/IV3FSG is 4766. Both are at the southern extreme on the Sahara desert. Both were happening at around the time of Trans Equatorial Propagation (TEP) further south into Africa. That posting can be found here.

At the time I pointed out that the propagation mode behind this contact to Chad was a mystery. Now after another one I feel a bit more certain as to how it happens.

In this recent case just before I worked 6W/IV3FSG I worked EA2AR and F5TMJ (LA3EQ had been worked 10 hours earlier). So there was Sporadic E towards the south of me. Later I heard V51WW in Namibia which was clearly TEP as he is on the other side of the Equator. I heard GM6NX working ZS6NK, so that is further evidence of crossing the Equator by TEP. Also, I could hear Spanish stations working V51JH and V51CO in Namibia. I was also hearing station in the same area when I worked TT8SN last year.

So that seems to sew it all up. There was Es from here to Spain, there was TEP from Spain across the equator to Africa, and presumably Es linking to TEP from Scotland to Africa. Es linking to TEP. Problem solved. That must be how I worked Senegal.

Erm... there is a flaw in this logic. Senegal is not across the Equator from Scotland. It is 14 degrees north of the Equator. Ah but, you say, that is the Geographic Equator. For this purpose we have to consider the Geomagnetic Equator, which is diverted north across Africa. True, but the diversion is not enough to put the Geomag Equator north of Senegal. From what I can see it passes just south of Senegal.

One of the many representations of the Geomag Equator on the internet

None of these images on the internet are too clear. But I conclude that the Geomag Equator passes just south of Senegal, maybe about 12 degrees north of the Geographic Equator.

So if the signal from 6W/IV3FSG was an example of  TEP propagation, it did not cross either of the Equators. There seems to be something in the expression "Trans Equatorial" which suggests to me a crossing of the Equator.

OK, having read various articles, especially those written by James Kennedy K6MIO/KH6, I think I have now got some sort of a grasp of this. Based on his ideas I have created a diagram showing the process.

Generalised representation of classic TEP (after K6MIO/KH6)

This shows the "classic" impression of TEP. Ionisation well up along the Geomag Equator and rises up into the F-layer, forming two "anomalies" or "electron pools" as K6MIO/KH6 describes them. The signal path rises from one side of the Equator, gets deflected twice at the anomalies, and reaches the receiving station on the other side of the Equator (and then presumably extending by Es to reach me). Great for V51WW in Namibia, but not so good at explaining hearing 6W/IV3FSG from Senegal.

However, K6MIO/KH6 does have an explanation of observed propagation effects which does explain both stations being on the same side of the Equator. In this case, I reckon "Trans Equatorial" refers to the effect in the ionosphere as shown by VK4YEH. This type of TEP is decidedly one sided.

K6MIO/KH6 describes the one sided effect as "Single-Lane F2" propagation. In his articles he shows diagrams of many TEP paths which are entirely in the north "Lane" reaching only north of the Geomag Equator. The paths he shows are mostly across the Pacific and several run generally south east to north west, but he also shows one running north east to south west . However, in the text he suggests that they can run north-south. The path to Senegal from me runs north east to south west at azimuth of 201 degrees.

James also says that the two stations must be within about 2000km of the same ionisation peak and if north-south they must be on opposite sides of the lane. Now I have done a little back of the envelope investigation of these figures in relation to my QSO. If indeed Senegal is close to the Geomag Equator (which the internet maps suggests it is) then it is far on the opposite side of the lane from Europe. James' article suggests that the skip points will be between 10 and 20 degrees from the Geomag Equator.

OK, assuming that TEP got the signal to Spain and Es carried it the rest of the way, my calculations suggest that the Senegal-Spain section would be about 3000km and the Spain-Scotland section would be about 1700km. These are both well within the potential of the two propagation modes. All the other conditions in the K6MIO/KH6 paper seems to be met. This looks like "Single-Lane F2" as described in the TEP articles.

K6MIO/KH6 has done proper scientific research and analysis, I have just read his articles. I am no earth scientist. I have used his ideas as the basis for a diagram which I think represents the situation on 28 September when I worked Elvira in Senegal.

50MHz situation on 28 September 2023

I come to the conclusion that Single-Lane F2 is the method of propagation behind both of these contacts - partly by being convinced by K6MIO/KH6's scientific rigour - and partly by ruling out the alternative explanations.

Multi-hop Es looks very unlikely. I hate to write "never", but I cannot think of me ever seeing multi-hop Es at this time of year. Sure, there is Es all year, but outside the peak season (in my experience) it is single hop only. It would need to be three hops for this contact, two would not be enough. Add to that the time which was 19:30 local, and then multi-hop Es at this time of year seems extremely explanation. In July, maybe, but not in late September. Unless of course there is new type of multi-hop Es ....

Ordinary F-layer? I am pretty sure that the southern African stations were TEP and not F-layer propagation. There are  a few signs of what might have been classic F-layer propagation but not enough to convince me that it has happened yet. Of course, TEP is F-layer propagation, but a very different type.

No, given that there was classic TEP and single-hop Es at the same time as this QSO this definitely looks like Es linking to "non-Trans-Equatorial-TEP" or to give it a better name "Single-Lane F2 associated with TEP".

I could say a lot more about Es linking and the distances involved in single-lane TEP, but I will not do it here. Let me just leave this as an idea. The idea is that when there is classic TEP around linking me in Scotland with the far south of Africa, there also seems to be [something] linking me with much further north in Africa. These shorter paths do not cross the equators. I believe that the [something] is single-lane TEP. In believing this I have thought about classic F-layer and multi-hop sporadic E propagation and rejected both as likely candidates.

OK, maybe [something] is another entirely new propagation method which just happens to occur when I hear other TEP. I doubt it.

Just because the path of a contact does not cross the equator does not mean we can rule out that it is caused by a trans-equatorial effect, such as TEP. 

I see this type of propagation posted as TEP. The correct name in the articles is "Single-Lane F2" but as it is associated with TEP I doubt if anybody is going to change their idea of what to call it. So I will continue to post it as TEP for now as it is not classic F2 propagation either. Put another way, I do not believe that these contacts would have happened but for the TEP event which was noted at the same time. 

Bit of a description dilemma there for now.

73 Jim

GM4FVM