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...

 Txmtr Rcvr Band Mode Distance Time (UTC) SNR
E51WL TR8CA 6m FT8 18331 km 22:53:59 -18
TR8CA E51WL 6m FT8 18331 km 22:23:12 -17
SV9CVY E51WL 6m FT8 17104 km 23:03:47 -22
E51WL SV9CVY 6m FT8 17104 km 22:22:59 -13
5B4ALJ E51WL 6m FT8 16948 km 22:56:41 0
E51WL 5B4ALJ 6m FT8 16948 km 22:53:59 -15
E51WL 5B4AIF 6m FT8 16935 km 22:59:29 -12
5B4AIF E51WL 6m FT8 16935 km 22:54:45 -7
9H1PA E51WL 6m FT8 16927 km 22:24:42 -12
OD5VB E51WL 6m FT8 16900 km 22:43:12 -3
OD5TX E51WL 6m FT8 16900 km 22:36:44 -8
IT9RZR E51WL 6m FT8 16834 km 22:28:42 -3
SV1RK E51WL 6m FT8 16800 km 22:45:12 2
SV1DH E51WL 6m FT8 16780 km 23:08:11 -12
IS0AWZ E51WL 6m FT8 16415 km 22:27:11 -2
IZ8CLM E51WL 6m FT8 16404 km 22:49:44 -16
IS0FWY E51WL 6m FT8 16402 km 22:27:46 -15
IK0VAQ E51WL 6m FT8 16297 km 22:53:12 -15
I0WTD E51WL 6m FT8 16244 km 22:49:42 -15
E51WL EA6SA 6m FT8 16122 km 23:03:28 -16
EA6SA E51WL 6m FT8 16122 km 22:55:26 -7
EA5IWZ E51WL 6m FT8 16064 km 22:54:12 -6
EA5GVH E51WL 6m FT8 16062 km 23:01:42 -16
EC5C E51WL 6m FT8 16056 km 22:31:15 -13
EA7L E51WL 6m FT8 16054 km 22:34:45 -11
EA5NW E51WL 6m FT8 16052 km 23:07:42 -12
EA5BY E51WL 6m FT8 16048 km 23:17:12 -15
E51WL EA5BY 6m FT8 16048 km 22:53:59 -18
E51WL IW5DHN 6m FT8 16035 km 22:35:29 -14
EA7KBX E51WL 6m FT8 16027 km 23:08:14 -12
EA5AJX E51WL 6m FT8 15975 km 22:55:29 -11
EA7BHO E51WL 6m FT8 15956 km 22:48:15 -15
EA3GCV E51WL 6m FT8 15916 km 22:45:12 -11
EA3CJ E51WL 6m FT8 15909 km 22:54:12 -12
EA3EDU E51WL 6m FT8 15902 km 22:58:42 -16
EA4BAS E51WL 6m FT8 15712 km 22:32:15 -15
CT1IUA E51WL 6m FT8 15683 km 22:17:31 -17
CT1EHX E51WL 6m FT8 15682 km 22:43:12 -12
EA1AF E51WL 6m FT8 15530 km 22:28:44 -8
CT1DIZ E51WL 6m FT8 15487 km 22:52:12 -7
F4BKV E51WL 6m FT8 15398 km 22:28:45 -14
CT1JOP E51WL 6m FT8 15373 km 22:50:14 -17
CT3KN E51WL 6m FT8 15225 km 22:25:46 -18

FT8 reports for 3D2AG (over 16,000kms)...

Txmtr Rcvr Band Mode Distance Time (UTC) SNR
TZ1CE 3D2AG 6m FT8 19090 km 23:20:28 -15
3D2AG EA8/DF4UE 6m FT8 18300 km 01:28:26 -8
3D2AG EA8AXT 6m FT8 18220 km 23:21:29 -4
TT8SN 3D2AG 6m FT8 18111 km 22:45:43 -1
3D2AG TT8SN 6m FT8 18111 km 22:43:26 12
EA8RH 3D2AG 6m FT8 18101 km 01:02:43 -12
3D2AG EA8RH 6m FT8 18101 km 00:38:29 -4
3D2AG EA8DBM 6m FT8 18094 km 01:57:14 -16
EA8DBM 3D2AG 6m FT8 18094 km 23:44:13 4
3D2AG EA8TL 6m FT8 18092 km 00:56:56 -13
EA8TL 3D2AG 6m FT8 18092 km 23:24:43 0
3D2AG EA8XNX 6m FT8 18091 km 23:25:58 -9
3D2AG EA8RCP 6m FT8 17991 km 22:43:29 -14
3D2AG EA8DO 6m FT8 17984 km 23:21:27 16
EA8DO 3D2AG 6m FT8 17984 km 22:50:13 -6
EA5NW 3D2AG 6m FT8 17786 km 23:42:13 -16
3D2AG D44EO 6m FT8 17533 km 00:58:57 -16
CT1EEB 3D2AG 6m FT8 17410 km 23:35:44 -20
ZD7MY 3D2AG 6m FT8 16201 km 22:50:43 -18