Skewed path on the 24 MHz band between Europe and the Pacific - Nov 2023

I found this item in the most recent GB2RB news bulletin from the RSGB of interest... "Phil, GU0SUP reports working Jan, E51JAN on the North Cook Islands on 12m FT8 Fox and Hound mode at around 1630UTC. He said that, as it was almost dark, he didn't expect to hear anything, but had a good copy on him at 190 degrees, so gave him a call. He came straight back.

Phil said that this was a big surprise, and he is not sure how it worked. It was quite a skewed path, with pretty much no copy on the real headings, short or long path."

The map above roughly shows the various paths for this 24 MHz (12m) band contact. From GU0SUP's location on the island of Guernsey, the short path goes up over Greenland. The long path would go in the opposite direction (148 deg) and down over Africa.

The reported path of 190 degrees takes the signal down into the Atlantic region between South America and Africa.

Commentary... The QRZ page for GU0SUP says that he is using a TGM Communications MQ26 mini-beam which would have a very broad beamwidth. We can't know for certain if the actual path was 190 deg or not. 

All we can take from the report is that it wasn't short path or long path but was skewed in roughly a south-westerly direction.

The image above is one I made before for an opening on the 50 MHz band between Europe and the South Pacific with a skewed path. Post HERE

This most recent report for the 24 MHz may well be the same? Did the signals get trapped in the Trans-Equatorial Propagation (TEP) region and allow the skewed path westwards from Europe to the Pacific?

Skewed paths should be even more common and pronounced at a lower frequency like 24 MHz as compared to 50 MHz.

I suspect that the TEP region has a huge impact on signals that most of us don't appreciate. On the HF bands, so many people are using omni-directional antennas or beams with a very low beamwidth that skewed paths are not obvious unless they are at almost right angles to the short and long paths.

Food for thought... How many people on the HF bands are looking for DX-peditions or DX stations on the textbook short or long paths when they should be thinking outside the box and looking for skewed paths?

Skewed path opening on the 40 MHz band from New Zealand to England & Ireland - 13th March 2023

Monday 13th March 2023: Over the last few weeks, Paul G9PUV in the SE of England and Robbie, EI2IP in the SW of Ireland have been very active on the 40 MHz (8m) band. On the evening of the 13th of March, there was a remarkable opening when their FT8 signals were heard in New Zealand.

The map above shows the direct paths in Purple. The path from EI2IP goes over the Arctic to the west while the path from G9PUV goes east and over the far north of Russia, both highly unlikely paths at a frequency of 40 MHz.

The strange thing is that 40 MHz didn't seem to take the short path or the long path but a skewed path. A suggested path is shown above in Orange but in reality, we'll never know for sure the exact path.

Here are the reception reports from ZL1RS in New Zealand...

 Txmtr Band Mode Distance Time (UTC) SNR
WM2XEJ 8m FT8 13129 km 19:47:26 7
EI2IP 8m FT8 18096 km 19:35:14 -21
G9PUV 8m FT8 18206 km 18:54:14 -17

Note that ZL1RS was hearing the the experimental US station WM2XEJ as well at about the same time.

G9PUV: The map above shows the FT8 paths for Paul, G9PUV in the evening time. Note that there was a path also open to the Caribbean about 20 mins after the opening to New Zealand. 

These are the FT8 reports...

Txmtr Rcvr Band Mode Distance Time (UTC) SNR
G9PUV EA8/DF4UE 8m FT8 2730 km 19:18:00 -13
G9PUV EA1TX 8m FT8 1086 km 19:15:41 -15
G9PUV FG8OJ 8m FT8 6618 km 19:14:14 -11
G9PUV HC02 8m FT8 1657 km 19:14:14 -17
G9PUV HI0SDR/3 8m FT8 6983 km 19:14:00 -17
EA1TX G9PUV 8m FT8 1086 km 19:13:59 -14
G9PUV K6EU 8m FT8 8704 km 19:00:14 -21
G9PUV ZL1RS 8m FT8 18206 km 18:54:14 -17

G9PUV was using a log-periodic antenna at rooftop level and was beaming 195 degrees. The actual beam heading for New Zealand may have been some bit off this.

EI2IP: The map above shows the paths for EI2IP during the evening. Again, note that there was an opening to the Caribbean and the south-east of the USA.

Rcvr Band Mode Distance Time (UTC) SNR
FG8OJ 8m FT8 6092 km 19:52:44 -12
WW1L 8m FT8 4389 km 19:52:14 -2
K6EU 8m FT8 8152 km 19:52:12 -11
WM2XCC/JTDX 8m FT8 8244 km 19:49:58 -19
K1HTV-4 8m FT8 5390 km 19:40:45 -17
WM2XCC 8m FT8 8244 km 19:40:44 -20
PJ4MM 8m FT8 6895 km 19:39:11 -15
EA8/DF4UE 8m FT8 2676 km 19:37:00 -10
EA1TX 8m FT8 1223 km 19:36:11 -11
ZL1RS 8m FT8 18096 km 19:35:14 -21
HC02 8m FT8 1705 km 19:32:15 -11
N4WLO/3 8m FT8 6684 km 19:32:14 -17
HI0SDR/3 8m FT8 6405 km 19:32:00 -12
K5YT 8m FT8 6935 km 19:19:41 -24
HI0SDR 8m FT8 6461 km 19:06:30 -19
WM2XEJ 8m FT8 6135 km 19:06:14 -22
WP4G 8m FT8 6209 km 19:05:42 -17
N2OTO 8m FT8 6487 km 19:05:30 -8

EI2IP reports using a 4-element Yagi and was beaming at 200 degrees which is roughly pointing at South America.

WM2XEJ: It's interesting to look at the evening reports and paths for the US experimental station WM2XEJ in Georgia. You'll note that there was a path open both to ZL1RS at 19:47 UTC and to EI2IP at 19:35 UTC.

As you can see from the map above, it's not hard to imagine a situation where the path becomes skewed and then the EI to ZL path becomes possible. In that case, it's likely that the path was in the region of about 19,000kms.

Short Path or Long Path??? ...  Strictly speaking, it was probably a skewed short path for EI2IP and a skewed long path for G9PUV.  The more correct question is probably if the path was skewed or not? The more informative answer is that the path was skewed and learn from that.

Lessons: It's worth remembering that the TEP zone around the Geomagnetic Equator is likely to have a huge impact on any 40 MHz signals crossing it. I would take these points from this...

1) The date... We're in the middle of March and near the equinox.

2) The time... Roughly 18:45 to 20:00 UTC

3) Location... This applies to stations in the north of New Zealand and the NW of Europe.

4) Beam heading... Stations in New Zealand should beam at the Caribbean and stations in the UK and Ireland should beam at the South America or the Caribbean.

5) Skewed Paths.... Forget long path and short paths and direct lines on the map which can go all over the place when the other station is at the other side of the planet. 40 MHz signals are going to have a really tough time crossing over the north or south poles... look for skewed paths where the signal stays as close to the equator as possible.

6) 50 MHz... Any serious 50 MHz operators should be reading this and then trying to explore this path. If it can be done at 40 MHz then maybe 50 MHz is possible?

In conclusion: The Trans-Equatorial Propagation zone around the geomagnetic equator has a huge impact on low band VHF signals on the 40 MHz and 50 MHz bands. In the past, we only really had SSB and CW available in terms of popular modes. Now with so many stations on the one frequency using a weak signal mode like FT8, we can see signals that are buried in the noise. 

There are probably plenty of other skewed paths that are possible. The key is to get out of the fixed mindset of short path and long path and think about beaming at this TEP zone at an angle and see if a signal can propagate inside it or be bent by it.

It's likely the windows of opportunity will be short... the TEP zone ionization needs to be right and there may be sunrise or sunset peaks along the path.

It's likely that there are probably plenty more new skewed paths out there awaiting discovery.

Link... For more information on the 8m band, see my 40 MHz page.

Skewed path opening on the 50 MHz band between the S Pacific and Europe - 12th Mar 2023

12th March 2023: As we approach the equinox, there are a lot of TEP (Trans-Equatorial Propagation) openings between the south of Europe and South America on the 50 MHz band. As were near the peak of the solar cycle and with the solar flux up around the 150 mark, this is nothing special.

What is highly unusual however was the appearance in Europe of some stations in the South Pacific during the TEP opening!

E51WL is located on North Cook Island in the South Pacific and the 50 MHz paths are shown above. 

Things to note...

1) South America... There was an opening from E51WL to South America and was being reported by South American stations at around 23:00 UTC. At the same time, there was a TEP opening from South America to the south of Europe.

2) Direct SP... The map shows the paths on FT8 from E51WL to the south of Europe. The direct short paths travel far to the north.

3) Skewed Path... European stations were beaming towards South America when the path to E51WL was open. On KST Chat, SV1DH in Greece reports E51WL on a beam heading of 225 degrees, IW5DHN in the north of Italy reports 220 deg and IT9TYR in Sicily reports 240 deg. IW0FFK in Rome reports working E51WL at 235 deg but didn't have time to verify the beam heading.

While it's difficult to know the exact beam heading with a modest antenna at a frequency of 50 MHz, it still shows that the signal was coming from the direction of South America on a beam heading of about 240 degrees, not on the direct short path heading to the north-west. i.e. the path was skewed.

For the stations in the eastern half of the Mediterranean, the short path actually goes to the east while the long path would go down over Africa and cross the Antarctica to reach the Cook Islands. Regardless of long path or short path, the signal was at roughly 240 degrees and skewed.

Fiji to Europe... 3D2AG on the island of Fiji was also reported in the Iberian Peninsula and the Canary Islands.

Note the direct short paths from CT1BOH in Portugal and EA5NW in Spain go over the Arctic. In reality, it was a skewed path to the south-west.

On the map above, there are several paths to EA8... the Canary Islands. I suspect that these may have been skewed to the south as well.

As for the how???.... There is a theory that the signal can get propagated westwards between the north and south boundaries of the TEP zone. Eventually the signal escapes further west where the direct path via F2 layer propagation is more favourable.

I put together a simple diagram above which shows this concept.

In Conclusion... Skewed paths like this have been reported in the past but now with so many stations using a weak signal mode like FT8 on one frequency, these skewed paths should become a lot more obvious.

The key take away point is that for very distant paths, don't always assume a signal is on the direct short path.

It would be interesting to see more stations in the Pacific exploring these skewed paths to Europe. Obviously doing it near the equinox is important as well as the time of day... around 22:00-23:00 UTC.

It might be an idea to also try a quieter frequency than 50.313 MHz and use the appropriate time slot for transmitting.

Questions, questions, questions... I wonder if there is an equivalent but longer skewed path from Europe to the South Pacific to the east rather than the west? 

Maybe 8-9pm local time for each station in the Pacific? 

A skewed long path rather than a skewed short path? 

Is it too early in the morning for 50 MHz signals in Europe?

Does it happen on the higher HF bands all the time but nobody notices or knows any better?

***

Signal reports for E51WL and 3D2AG are shown below.

FT8 reports (15,000kms +) for E51WL...

Skewed propagation path on 28 MHz between Australia & South America - Dec 2021

Recently, Scott VK4CZ reported a skewed path on 28 MHz between Australia and South America.

The image above shows what happened. The direct and shortest path from VK4CZ to CE2SV is 11,800kms and is shown in Green. The beam heading from eastern Australia is 142 degrees.

VK4CZ however found that the FT8 signals from CE2SV peaked at about 70 degrees, a skewed path that was about 70 degrees off the direct path.

Scott mentions that the skewed path opening was from 21:00 - 22:00 UTC and I believe at that time period, the sun was directly over the centre of the Pacific.

VK4CZ was using an ICOM IC-7600 with a 5-element monoband Yagi for 28 MHz at 20 metres above ground level.

Scott, VK4CZ writes... "It's been amazing to see the scatter path to South America out of the North Pacific available again on 10m yesterday and again this morning. This path was a consistent feature through the peak of last cycle, and with digital modes it's becoming available now!

Worked/seen this morning were HK (Columbia), LU (Argentina) and CE (Chile) all peaking at a QTF of 70. Direct QTF for CE 145... so well off a direct path.

It's an interesting propagation mode that I regularly observe across the Pacific. As I understand, it's trans-equatorial scatter.

The same path should be available to Africa in the afternoon/evenings from here.

The likelihood of it also being available at 50MHz is high.... we'll just need the cycle to progress towards the peak to be sure.

A couple of cycles back, I heard Peter PY5CC in Brazil on 6m CW using the same path (albeit late afternoon when TEP peaked to KH6 / Hawaii)."

Analysis... This is my understanding of what happened and I'm open to correction. Directly under the sun near the equator, the solar radiation is at it's highest and the F layer of the ionosphere is highly ionized with a high maximum usable frequency (MUF).

This is usually split into two zones of high electron density either side of the geomagnetic equator but in December, the southern one is much larger.

This can be thought to be like a tube like structure that is stretched out east-west.

The above graphic is a bit rough but you can get the general idea of the signal hitting the F layer from the side.

Skewed paths are a fascinating subject and are allow serious DXers and contesters to exploit paths when the direct path isn't possible. This is especially true on the higher HF bands like 28 MHz where the shortest east-west paths are often closed.

I suspect these skewed paths happen a lot more often than we realise especially now that so many people are using weak signal modes like FT8.