15,000km opening on 50 MHz between Australia & Europe - 4th June 2021

This will probably be my last post about the openings on 50 MHz between the north of Australia and Europe. Even though 15,000kms is a remarkable distance for 50 MHz near the bottom of the sunspot cycle and it may be a big deal for individual stations in Europe to work Australia, my interest is in the mode of propagation.

For the last few days, I've collected as much data as I could about these 6m Australia to Europe openings so that there is some sort of record online about them. Considering that they are now happening almost daily at present, I think the chances of them being solely due to multi-hop Spoardic-E is near zero. I don't believe it's possible to get 7-8 Sporadic-E hops at 50 MHz in the same direction day after day after day.

I'll keep a watch out for 50 MHz openings from Europe to the VK2/VK3 region which is the south-east of Australia as these are the exceptional openings at this stage.

Friday 4th June 2021: The map above shows the paths from VK4ABW in Darwin to Europe.

A list of the paths from European stations to Australia is shown below...

3000km Sporadic-E opening on 144 MHz from the Azores to Germany - 3rd June 2021

Thursday 3rd June 2021: There was a remarkable opening on the 3rd of June from the Azores in the North Atlantic to Europe with paths in excess of 3,000kms being recorded.

The FT8 map above from the PSK Reporter website for CU3EQ in the Azores with a cluster of reports out around the 3000km mark in Belgium, the Netherlands and Germany. A full list of stations is shown at the bottom of this post.

This is the map for CU3AA which has a similar pattern...

And this is the map for CU1AL...

For all three CU stations, paths in excess of 3000kms were open to Germany on 144 MHz.

Propagation Mode: As reported by stations on the DX Cluster, the primary propagation mode was Sporadic-E. However as the maximum range for one hop is in the region of 2300kms, something else had to make up the additional 700 or so kms.

There are two possibilities. 

One was Chordal Hop Sp-E with a bounce going from Sp-E to Sp-E cloud. This would however require two intense areas of Sporadic-E at just the right spot to support 144 MHz propagation.

The more likely scenario was that it was one Sporadic-E with a tropo extension. The weather charts show high pressure over the Azores...

The tropo forecast from the website of Pascal, F5LEN suggests that a few hundred kms of tropo around the Azores might be possible.

The Sporadic-E prediction map from Jim, G3YLA shows a kink in the Jet Stream to the south of Ireland which may have been a trigger mechanism for the Sporadic-E.

In his daily E's prediction on the PropQuest website, G3YLA wrote... "The sharp upper trough west of the UK is also a good source of atmospheric gravity waves (AGW) and the southerly jet stream from Portugal to Ireland could look good for paths to EA and CT with a possible extension by second hop to EA8/D4."

This region is shown in Purple above and is very close to where the 144 MHz Sporadic-E cloud was located.

Conclusion: It seems likely that the first few hundred kms were via tropo from the Azores and then coupled into a single Sporadic-E hop onwards to Europe.

Trans-Atlantic on 144 MHz??? The map below shows a 3000km circle centred on the Azores...

Considering there was a 3000km opening on 144 MHz between the Azores and Germany on the 3rd of June, sure a 3000km path on 144 MHz from the Azores to North America is possible?

Stations in St.John's, Newfoundland are close to the one hop Sporadic-E range. Stations in Nova Scotia would need a tropo extension.

If the North Atlantic is going to be bridged on 144 MHz then surely Canada to the Azores would be a first step in the process?

Reports from the PSK Reporter website...

15,000km opening on 50 MHz between the Canary Islands & Guam in the Pacific - 3rd June 2021

Thursday 3rd June 2021: Another day, another 15,000km opening on the 50 MHz band.... well almost. This time the longest opening seen on the PSK Reporter website was the 14,966km path between KG6DX on the island of Guam in the Pacific and EA8DBM on the island of Tenerife in the Canary Islands.

EA8/DF4UE on the neighbouring island of Lanzarote was just 150kms behind.

I checked the PSK Reporter site and there were paths open for both to multiple stations in Japan as well. IF the signals took the direct path then they crossed over the north of Russia.

16,000km+ opening on 50 MHz from Australia to the Canary Islands - 2nd June 2021

Wednesday 2nd June 2021: Another day and yet another opening on 50 MHz between Europe and Australia. 

The longest path on the day however seems to have been between VK4ABW in Darwin on the north coast of Australia and EA8DBM on the island of Tenerife in the Canaries. The 50 MHz path which was on the FT8 mode works out to be around 16,220kms.

Just to put that in perspective, that's the same distance from Darwin to the Great Lakes in North America.

As the map shows above, the 50 MHz was also open to Europe and it managed to open up to G7RAU in the far south-west of England as well.

Txmtr Rcvr Band Mode Distance Time (UTC)
VK4ABW EA8DBM 6m FT8 16221 km 08:04:59
VK4ABW G7RAU 6m FT8 14234 km 07:09:27
VK4ABW OG2A 6m FT8 12147 km 07:56:45
VK4ABW LY2BAW 6m FT8 12144 km 08:47:42
VK4ABW LY2IJ 6m FT8 12094 km 07:32:29
VK4ABW YL2CP 6m FT8 12090 km 07:03:29
VK4ABW ES6RQ 6m FT8 12047 km 07:02:59
YL2GD VK4ABW 6m FT8 11984 km 06:59:44
UR5LAK VK4ABW 6m FT8 11332 km 08:59:44
VK4ABW UR0MC 6m FT8 11224 km 08:13:59
UT4MF VK4ABW 6m FT8 11166 km 08:38:14

* * * 

VK8MS in Darwin also heard EA8DBM but nothing from Europe.

Txmtr Band Mode Distance Time (UTC)
EA8DBM 6m FT8 16234 km 08:03:44

* * *

VK6KXW on the west coast of Australia managed to hear three stations in Europe.

Txmtr Rcvr Band Mode Distance Time (UTC)
IK0AGU VK6KXW 6m FT8 13357 km 05:26:29
YL2GD VK6KXW 6m FT8 12968 km 07:29:14
UT8IO VK6KXW 6m FT8 11840 km 05:57:44

* * *

There was also a path from VK4WTN on the east coast of Australia to two stations in eastern Europe.

Txmtr Rcvr Band Mode Distance Time (UTC)
VK4WTN UA4CC 6m FT8 13307 km 05:09:59

UR5LAK VK4WTN 6m FT8 13967 km 05:37:44

* * *

Mode of Propagation: The 50 MHz band has been open between Europe and Australia for four of the last fives days. Whatever the mode of propagation is, the simple 'it must be multi-hop Sporadic-E' is probably not the full explanation. 

It would be interesting to know if European stations working Japan, China and Australia are experiencing any skewed paths or is everything on the correct beam heading?

50 MHz opening between Guam and Europe - 1st June 2021

Tuesday 1st June 2021: Over the last week or more, there have been openings from Europe to Japan on 50 MHz with distances in the region of 9,000kms. There was an interesting opening on the 1st of June however from Europe to the island of Guam in the Pacific.

The map above from the PSK Reporter website shows the paths that were open for KG6DX on Guam with maximum distances in the region of 12,000kms.

From a European perspective, a contact with a station out in the Pacific would be considered really good for say down on the HF bands but it's pretty amazing for 50 MHz, a VHF band.

When I checked the PSK Reporter website, I had a quick look at the last FT8 signal reports for the stations in Europe and they were generally down in the -10 to -20dB region. It looks as if maybe one or two might have possibly made a very weak CW contact while SSB would have been impossible. 

That assumption is based on the available data which is limited but it does suggest that the opening was marginal.

The opening to Europe seems to have been from roughly 05:40 to 07:00 UTC.

Propagation Mode: The interesting thing about this 12,000km opening is that because everything is north of the equator, we can rule out TEP (Trans-Equatorial Propagation). If it was multi-hop Sporadic-E then it may have been 6 hops or so. 

For something so 'sporadic', these multi-hop openings seem to be happening a lot.

The paths from stations in Europe to Guam are shown below...

50 MHz opening from Australia to Europe - 1st June 2021

 

Tuesday 1st June 2021: Yet another opening on 50 MHz from Australia to Europe but this one was perhaps not as good as previous days.

Update: Roger, VK3FZ reports that he made a successful contact with OZ3K in Denmark.
VK3FZ to OZ3K on 50.315283 in FT8 at 2021-06-01 05:42:00Z (OZ: Denmark)
Sent -21, Received -15
Antenna: 6-element LFA Yagi

A list of paths to Europe is shown below...

Another 50 MHz opening between Australia & Europe - Mon 31st May 2021

Following on from the weak opening on the 29th of May, there was another 50 MHz opening between Europe and Australia on Monday the 31st of May 2021.

The above map from the PSK Reporter website shows the almost 15,000km path that was open for VK4MA on the east coast of Australia.

SP4K 6m FT8 14993 km 07:43:30
LY2BAW 6m FT8 14683 km 07:46:59

***

There was a much bigger opening from VK4ABW on the north coast but he is also quite a bit closer with distances just over 12,000kms.

VK4ABW SM7CAD 6m FT8 12650 km 09:11:56
VK4ABW YL2CZ 6m FT8 12300 km 09:11:59
VK4ABW OG3G 6m FT8 12228 km 08:43:59
VK4ABW OH1MN 6m FT8 12199 km 08:44:29
VK4ABW OG2A 6m FT8 12147 km 08:43:59
VK4ABW LY2BAW 6m FT8 12144 km 08:46:57
VK4ABW OH7KM 6m FT8 12113 km 08:22:30
VK4ABW YL2II 6m FT8 12104 km 09:12:59
VK4ABW OH3SR 6m FT8 12091 km 08:22:26
VK4ABW YL2CP 6m FT8 12090 km 09:11:59
OH3JR VK4ABW 6m FT8 12081 km 08:36:44
VK4ABW ES5PC 6m FT8 11999 km 08:44:59

***

The longest paths came from the south-east of Australia. VK3OT was hearing the Ukraine.

UR5LAK VK3OT 6m FT8 14102 km 05:57:11
UR0MC VK3OT 6m FT8 13989 km 06:02:11

***

The longest path seems to have been between VK3ZL and SP4K in Poland at 15,459kms

SP4K VK3ZL 6m FT8 15459 km 05:20:44
UR0MC VK3ZL 6m FT8 14163 km 06:41:44

***

Propagation Mode: We're back to the same question again... How do 50 MHz signals from Europe reach Australia near the bottom of the sunspot cycle?

The easy 'go to' answer was that it was multi-hop Sporadic-E, case closed. 

The problem I'm starting to have with this is down to probabilities. 

Take SP4K in Poland. What are the chances of one hop Sp-E in the direction of Australia capable of supporting a 50 MHz signal? It's late May, it's the Summer Sp-E season so it's pretty high. 

Two hops?... What is the probability of getting two Sp-E regions spaced at just the right distance to allow a double hop at 50MHz? The probability is obviously lower.

Follow that same logic and apply it to 3 hops, 4 hops and so on. By the time we get to 15,459kms, we're probably looking at 8 hops. 

What is the probability of getting eight Sporadic-E clouds capable of supporting 50 MHz spaced at just the right distance from each other... all the way from Europe to Australia?

And if that probability wasn't low enough, what then is the probability of 8 hop Sp-E on 50 MHz from Europe to Australia on two out of three days?

I think the probability is now so low that there must be some other answer. Perhaps TEP (Trans-Equatorial Propagation) from Australia to China accounts for a large part of it? Some other propagation mode?

I'm not sure the simple 'It must be multi-hop Sporadic-E' adds up anymore.

Weak opening from Europe to Australia on 50 MHz - 29th May 2021

Sat 29th May 2021: It looks as if there was a weak opening from Europe to Australia on the 50 MHz with a few weak FT8 signals making it through.

Txmtr Rcvr Band Mode Distance Time (UTC)

DF5VAE VK4HJ 6m FT8 15477 km 06:05:29

UT7UV VK4HJ 6m FT8 14545 km 04:18:44

SP3MM VK4CZ 6m FT8 15564 km 07:10:14
VK4CZ UT2XQ 6m FT8 14683 km 06:59:59

SP4K VK3OER 6m FT8 15383 km 05:17:41

It looks as if there was a successful FT8 contact between VK4CZ in Australia and SP3MM in Poland, a distance of about 15564kms. The signals seem to have been quiet weak and were in the range of -16dB to -20dB which is below what is audible to the human ear i.e. a cw contact would not have been possible.

As for the propagation mode, it seems likely it was multi-hop Sporadic-E with possibly eight hops required. I say 'likely' as I sometimes wonder what are the chances of getting eight Sp-E hops in a row at 50 MHz.

We still have all of June to go yet so there could be more openings on 50 MHz from Europe to Australia.

10-milliwatt WSPR signal on 28 MHz heard in Ireland - 28th May 2021

Friday 28th May 2021: I left the radio monitoring the WSPR frequency on 28 MHz for whole day and I heard signals from all over Europe including DP0POL on the German Icebreaker ship near the north of Norway.

At the end of the day, I got an interesting e-mail from Andreas, DL2KCL about my reception of his very low power WSPR beacon during the day.

Andreas wrote... "You received a transmission from my homemade WSPR-TX on 10m. The TX puts out 10 mW directly from a Si5351A-chip. No PA. It runs from a single rechargeable D-cell with a DC/DC-converter (85 mA).

The antenna is a piece of about 2.5 m thin wire wound on a 18 cm PVC tube in resonance on 28.2 MHz. There is no additional counterpoise."

I checked back through the WSPR logs and amazingly, I had heard the 10-milliwatt signal from DL2KCL a total of 77 times during the day. The weakest signal was -27dB which is buried way in the noise. The strongest signal was -12dB which would have been just about audible to the human ear.

The photo above shows the transmit antenna which is just a quarter wave of wire wound on an 18cm PVC pipe. To hear such a low power system 77 times during the way just goes to show how good conditions must have been.

On my side, I was just using a simple CB type half wave vertical so there was no additional gain to pull in weak signals.

Analysis: The one crucial part of equation is the distance... 1075kms. During the Sporadic-E season, signals in the 1000 to 1500km range are a bit like the sweet spot on 28 MHz. 

There are a lot more openings on 28 MHz compared to the higher bands like 50 MHz and signals around 1100kms are at the very least 6dB stronger than those out around 2200kms just due to the fact they are closer.

The signals at 1100kms are also coming in around 8 degrees above the horizon which allows it to clear local obstructions at either end of the path. 

Antennas on 28 MHz will probably have more gain at 8 degrees above the horizon in comparison to say 1 or 2 degrees and a 2000km skip distance.

It just goes to show how good the 28 MHz band can be when the conditions are right.

D4VHF on Cape Verde not active on 144 MHz due to antenna damage - May 2021

In response to a recent query, one of the D4VHF team has confirmed that their 144 MHz VHF station is off air at present.

Andrea, HB9DUR writes... “I am sorry to disappoint you re. D4VHF but the station is not fully operative, especially on 2m.

Monteverde has been suffering from non stop high winds from Christmas last year till some weeks ago.

So the yagi to west is heavily damaged by strong winds, the towers as well are not in a good shape. Moreover no power amplifier is available until somebody can travel there….“

The D4VHF station on Cape Verde off the west coast of Africa has in recent years has been responsible for some of the most spectacular contacts on 144 MHz and 432 MHz to Europe and across the Atlantic to the Caribbean.

For the moment (May 2021), they are still active on 50 MHz and the QO-100 satellite.

First 9A to 9A contact on 40 MHz - 25th May 2021

25th May 2021: A little bit of history was made on the 40 MHz band on the 25th of May when the first contact between two stations in Croatia took place.

At 06:00 UTC, Patrik, 9A5CW and Zeljko, 9A2EY completed a successful FT8 contact on 40.680 MHz.

The distance was 24.5kms between the two stations over an obstructed path and both stations were using vertical non-resonant HF antennas.

One of the antennas was a vertical for the 60m HF band without a tuner and the radio was an ICOM IC706 Mk2.

Hopefully this will encourage more 9A stations to experiment with the band.

3000km opening on 144 MHz between Israel and Germany - 25th May 2021

Tuesday 25th May 2021: During the major Sporadic-E opening on the 25th, many European stations made multiple contacts on the 144 MHz band. While the vast majority were in the one-hop range (<2300kms), there were a few exceptional contacts.

Jan, 4X/OM2IB in Israel (KM72JC) managed to complete two FT8 contacts with two stations in Germany during a short opening.

The two German stations were DJ9MG (08:18UTC - JO52TC - 2909kms) and DG6JF/P (08:31 - JO33QN - 3234kms).

The FT8 screen from 4X/OM2IB is shown below...

It clearly shows the two FT8 contacts as well as reception of PA0O and DL7TY. The time range of the reports is from 07:53 to 08:36 UTC, a span of roughly 43 minutes.

Propagation Mode: As outlined already, the normal maximum distance for one-hop Sporadic-E is about 2300kms. There are probably two choices to help explain how 144 MHz signals from Germany traveled the approximately 3000kms to Israel.

Theory 1) Sp-E & Tropo: In this scenario, there was one hop Sporadic-E from Germany to Turkey and then the last few hundred kms by tropo ducting over the sea to Israel. The tropo prediction map below from F5LEN certainly suggests that this might be possible.

The distance from 4X/OM2IB to the coast of Turkey is about 700kms. 

In this scenario, it's not hard to imagine a Sporadic-E hop of 2200kms going from DJ9MG is the eastern half of Germany to the southern coast of Turkey and from there via a tropo duct of about 700kms to Israel.

The problem however comes with DG6JF/P who is an additional 300kms further away at 3234kms. That can't be easily explained by a tropo extension at the eastern end of the circuit as that would require the duct to cross over a large part of the landmass of Turkey.  . 

It's possible that the Sporadic-E ionised region was higher than usual which sometime happens near the start of an opening but it seems a bit of a stretch.

Theory 2) Chordal Hop: The other possibility is that there were two active Sporadic-E regions involved and the signal bounced from one to the other before returning to the ground. This resulted in a range in excess of 3000kms.

The problem with the Chordal Hop theory is that it requires two Sporadic-E clouds to line up correctly. It would seem that it does happen at 144 MHz but how often and for how long?

In conclusion: In his Sporadic-E report, 4X/OM2IB noted..."Random and very short openings. Probably sea TROPO + Es for this distance. Doesn't look like a double Es hop."

Sometimes when you can look back at an opening, you can examine the evidence and you can determine the most likely scenario. In this 144 MHz opening between Germany and Israel, it's hard to know for sure which propagation mode was responsible. I think without further evidence, we just have to put a question mark next to it.

It does however show yet again that contacts in the region of 3000 kms are possible at 144 MHz, the same distance across the North Atlantic from Newfoundland to Ireland.

Addendum: 

1) PA0O in his blog post says he worked Istanbul in Turkey at 2150kms. This gives some additional credence to the Sp-E & Tropo theory. Link HERE

5900km+ opening on 70 MHz from the Canary Islands to Kazakhstan - 25th May 2021

Tuesday 25th May 2021: There was an extensive Sporadic-E opening on the VHF bands with openings all of the way up to 144 MHz. On 70 MHz, there was evidence of plenty of multi-hop Sporadic-E including the one shown above from EA8JF in the Canary Islands to UN3M in Kazakhstan, a distance of 5946kms.

The map above from the PSK Reporter website clearly shows the 3 hop zones. First hop to Spain & Portugal, second hop to the centre of Europe and the one lone triple hop to Kazakhstan.

While double hop Sporadic-E at 70 MHz is rarer than 50 MHz, it is unusual to see triple hop on the band. Sometimes this can be as much to the limited number of countries with access to the band as much as the difficultly of getting three hops at 70 MHz.

These are the reports from the PSK Reporter website for distances over 4000kms.

Txmtr Rcvr Band Mode Distance Time (UTC)

UN3M EA8JF 4m FT8 5946 km 09:49:14

SP2CHY EA8WU 4m FT8 4014 km 11:53:42

YL2CP EA8/DF4UE 4m FT8 4399 km 11:40:44

YL2CA EA8/DF4UE 4m FT8 4208 km 12:24:59

It was interesting to see that EA8/DF4UE managed to hear Latvia as well.

From the Kazakhstan point of view, this is the map for UN3M...

...and for UN7MBH...

These are the combined reports for distances over 4000kms from Kazakhstan...

Txmtr Rcvr Band Mode Distance Time (UTC)

UN3M EA8JF 4m FT8 5946 km 09:49:14

EA4T UN3M 4m FT8 4462 km 10:11:59

EC4TR UN3M 4m FT8 4414 km 10:12:29

UN3M EA3KE 4m FT8 4114 km 09:54:42

EA1YV UN7MBH 4m FT8 4566 km 13:53:56

UN7MBH EA1YV 4m FT8 4566 km 13:46:44

UN7MBH EA1UR 4m FT8 4468 km 07:10:12

UN7MBH EA1AF 4m FT8 4279 km 13:46:14

DX Cluster: Some of  the double hop Sporadic-E spots for 70 MHz from the day are shown below. Note the spot for EA8BPX to ES1II/8, a distance of 4537ms which is close to the maximum for double hop Sporadic-E.

Reception of the German Polar Research Ship Polarstern in the North Sea - 25th & 26th May 2021

26th May 2021: I left the radio monitoring the 28 MHz WSPR frequency for the last 24 hours and heard just over 50 stations from around Europe via Sporadic-E. One station that caught my eye was DP0POL out in the North Sea.

DP0POL is a maritime mobile station on the German research icebreaker 'Polarstern'. While the WSPR station on board is often spotted on the various HF bands, it was just unusual for me to hear it on 28 MHz.

As the map shows above, I heard it in the North Sea as it was sailing past the coast of Norway.

UTC (y-m-d) TX         txGrid RX rxGrid         MHz W SNR drift km
2021-05-25 08:16 DP0POL JO26sw EI7GL IO51tu 28.12601 5 -28 2 1061
2021-05-25 23:56 DP0POL JO19um EI7GL IO51tu 28.126065 5 -19 0 1137
2021-05-26 00:16 DP0POL JO19un EI7GL IO51tu 28.126064 5 -7 0 1140
2021-05-26 00:36 DP0POL JO19to EI7GL IO51tu 28.126064 5 -5 0 1140
2021-05-26 00:56 DP0POL JO19tq EI7GL IO51tu 28.126063 5 -4 0 1146
2021-05-26 01:16 DP0POL JO19tr EI7GL IO51tu 28.126063 5 -7 0 1150
2021-05-26 01:36 DP0POL JO19st EI7GL IO51tu 28.126063 5 -11 0 1153
2021-05-26 01:56 DP0POL JO19su EI7GL IO51tu 28.126063 5 -9 0 1156
2021-05-26 02:16 DP0POL JO19sv EI7GL IO51tu 28.126062 5 -16 0 1159

Twitter account is 1-year old & has 500 followers

My Twitter amateur radio account is one-year old today! Even though I've been on Twitter since 2009, it was almost impossible for me to follow all of the various radio related Twitter accounts as well as following other non-radio material. 

I started the Twitter 'EI7GL' account on the 25th of May 2020 and one year later, it has recently passed the 500 followers mark!

I find that the account not only makes it easier for me to follow other radio related accounts and keep up with news but it allows me to notifies others about new posts here on the blog.

If you're on Twitter then you can follow me here... https://twitter.com/ei7gl

Solar Noise detected at 40 MHz - 22nd May 2021

Early on the morning of the 22nd of May 2021, I was listening for some aircraft scatter signals on the 40 MHz band when I noticed a sudden onset of solar noise as shown above.

This sounds just like a hissing sound but the intensity comes in waves. It's not like say interference you might get from an electrical source which is very much on or off. Solar noise is a gentle hiss that rises and falls in intensity, a bit like waves would do as they crash on a beach.

The waterfall display above shows the event starting around 06:48 UTC and finishing at 06:54 UTC. As soon as I was sure it had finished, I checked the Space Weather Prediction Center website and sure enough, there was a solar flare that matched what I had heard.

I later heard the same effect on 28 MHz while I was listening for WSPR signals and my Twitter feed had lots of tweets about solar flares and solar storms.

It seems to me that the 40 MHz band is a good choice for monitoring noise from the sun. It's high enough in frequency that it's above all of the usual F2 layer propagation and the antennas can be large enough to capture a lot of noise.

Aircraft Scatter on the 40 MHz band

 A few days ago during the Sporadic-E backscatter tests on the 40 MHz band, I noticed some curious little ticks on the waterfall display. These short lines were moving slowly downwards in frequency and lasted for about 30 seconds, a tell tale signature of aircraft scatter.

On the 21st of May, the band seemed to be quieter with less Sporadic-E about so I tried some aircraft scatter tests with both of the Irish 40 MHz beacons (EI1KNH 40.013 MHz & EI1CAH 40.016 MHz).

Both beacons are about 200kms from my location and I used the FlightRadar24 website to track the various flights. This was the strongest signal that I got...

The image above shows the carrier & CW portion of the signal appearing at about 11:06 UTC (12:06 Summer time). As the aircraft was moving at several hundred kph, there was some doppler shift in the received signal and this can be seen in the signal slowly drifting downwards in frequency.

There is a gap at around 11:07 UTC when the beacon was sending out PI4 signals and it then returns again.

This was one of the longest signals I got as the vast majority last maybe 20-30 seconds.

The image below shows what happened....

The EI1KNH beacon is about 200kms from my location. A Delta Airlines plane heading from London to Seattle crossed over the mountains to the south-west of the beacon and it reflected the signal.

While the beacon has an excellent take off to the East, it is badly blocked to the West by the local mountains. I have a pretty good take off in that direction which means I am probably close to line of sight to planes at an altitude of 35000-40000 feet (7-8kms) over the mountains near the beacon.

Despite the doppler shift, I managed to get a successful PI4 decode during this crossing and a small number of other ones.

Using the FlightRadar24 site as a reference, I could correlate a lot of the doppler tracks seen with passing aircraft near both of the beacons. Nearly all of the signals were incredibly weak and were not audible to the ear. Most of the tracks were also about 10-30 seconds in duration. 

It's also worth noting that not all passing aircraft resulted in me hearing a signal. One large airplane went right over the EI1KNH beacon and I saw nothing. Obviously the orientation of the aircraft with respect to the beacon and my location are a factor here. It needs to be close but not too close.

I also got some reflections from aircraft that were on the far side of the beacon. I got one trail from a Ryanair flight just off the coast of Wicklow and heading north for Dublin as well as tracks from trans-Atlantic aircraft passing just north of the EI1CAH beacon in the west of Ireland.

FT8: Considering how often I was seeing these little doppler tracks at 40 MHz, I suspect a lot of people are getting FT8 decodes on the 28 MHz and 50 MHz bands from stations in the 100km to 250km range via aircraft scatter without even really realising it. I often see this, I get one FT8 decode from a station and get nothing else.

Other bands: Needless to say, aircraft scatter isn't confined to the 40 MHz band. If you or a distant beacon or station are blocked by a local hill then you might see aircraft scatter on 28 MHz or any of the VHF and UHF bands.

In the tests that I carried out above, I was 200kms away from the distant beacons and aircraft and the signals were weak as a result. If you try this and the distance are much shorter then you may experience much stronger reflections and signals.

3980km path opens up between Sweden & the Canary Islands on 144 MHz - 19th May 2021

During the Sporadic-E opening on 144 MHz on the 19th of May, many stations in western Europe made contacts in the region of 1200 to 2300kms... a pretty standard distance for one hop Sporadic-E.

One path that stood out however was that between SM6VTZ in Sweden and EA8CXN in the Canary Islands.

Although a full contact wasn't completed on this occasion, it was still a remarkable distance at approximately 3980 kms. This is the screen from SM6VTZ showing the attempted FT8 contact...

As you can see, the signal was quite weak at -18dB which is at a level below what is audible to the human ear.

Analysis: How did this happen? During the Sporadic-E opening, Chris SM6VTZ managed to work several stations in the north-west of Spain at a distance of about 2300kms. This is close to the maximum distance for one-hop Sporadic-E.

10:36 EB1B IN73DM FT8 

10:41 EA1NL IN52PJ FT8
10;44 EA8CXN IL18SK FT8 lost in QSB, 3978km
11:07 EB1DJ IN52MO SSB
11:56 EA1M IN53TI SSB

12:05 EB1A IN53TF SSB

It's very likely that the Sporadic-E signal then coupled into a tropo duct for the rest of the journey to the Canary Islands.

As the prediction mapt from F5LEN above shows, there was some good tropo from EA8CXN on the island of Tenerife to the north-west coast of Spain, a distance of about 1400 kms.

A similar combined Sporadic-E / Tropo ducting path was seen back in August of 2020 when there was an opening from the Canary Islands to Denmark, a distance of 3710kms. See previous post.

Just one observation / question. This area of ducting often occurs off the west coast of Africa and Portugal. If a combined Sporadic-E & Tropo signal can get from Sweden to the Canary Islands (3980kms), then why can't a combined Sporadic-E & Tropo signal get across the North Atlantic from Newfoundland to the north-west of Spain (~3500kms)???

Some more examples of long distance 144 MHz signals can be found on my 144 MHz page.

Backscatter on 40 MHz - 19th May 2021

Wednesday 19th May 2021: The day started with a comment by Joe, EI3IX on a Facebook post that he wasn't hearing the new EI1CAH 40 MHz beacon even though he is only 64kms from it. That set me off checking why that was the case and I ended going down a rabbit hole that saw me on the 8-metre band for most of the day!

Both the EI1CAH (40.016 MHz) and the EI1KNH (40.013 MHz) beacons are about 200kms from my location with plenty of hills and mountains in the way. I listened early on the morning of the 19th and I couldn't hear either beacon although I did get a meteor burst from EI1CAH so I knew that it was still operational.

A few hours later, I tried listening again and I found I could now hear EI1CAH all of the time! What had changed? As the signal was buried in the noise with a Signal to Noise ratio of -26dB, my initial thought was that it might be tropo? However, I couldn't rule out that it may have been to Sporadic-E backscatter either.

It was only later when I saw the signal improve to -6dB over the space of a few minutes then I knew it was Sporadic-E related. While there are no doubt slight tropo enhancements at 40 MHz, large changes like this are almost certainly due to Sp-E.

Later when I checked the EI1KNH beacon near Dublin, I could that as well. At that stage, I was 100% sure it was backscatter. Lloyd, EI7HBB reports hearing both beacons by backscatter as well.

Backscatter Sporadic-E: What is it? Refer to the diagram below...

The signal from the EI1CAH beacon (TX) is being propagated forward by an intense Sporadic-E region about 100-110kms above the Earth. The signal is then being reflected off something maybe 500kms or so away... maybe a range or mountains? The signal then returns by pretty much the same path and I hear it at my location (RX).

I've heard backscatter via Sporadic-E several times before on 10m and 6m. Back in the 'old days' when everyone was on either on SSB or CW, I remember beaming South to work stations in the UK on 50 MHz.

The signals seem to have a certain characteristic in that they are pretty constant but just at a very low level. This is what I was hearing... EI1CAH was a weak but constant signal for most of the time with the occasional jump.

The truth is that backscatter is probably there all of the time during Sporadic-E openings but we're not aware of it as the signals are so weak. When there is an intense Sporadic-E with the skip distances much shorter (e.g. <700kms), signals get a LOT stronger.

Imagine a signal being reflected off a distant mountain range which is 1500kms away which is a pretty normal skip distance for Sporadic-E at 40 MHz. Now imagine the range reduces to 500kms under intense Sporadic-E like there was on the 19th of May. Obeying the inverse square law, the transmitted signal at the mountain range would appear 9.5dB stronger. But crucially, this also applies to the reflected path resulting in an additional 9.5dB enhancement. This adds up to a 19dB improvement overall in signal which is a really big jump. 

Back in the 'old days' with SSB/CW, backscatter via Sporadic-E was something that was observed on an occasional basis. Now that we have digital modes like FT8 and PI4, we are 'hearing' signals that are much much weaker.

Assumptions about Propagation: It is for me a reminder that we should always question our assumptions about a propagation mode when we hear a weak signal. Is a weak signal from someone say 200-400kms away on 28/40/50 MHz really tropo, short skip Sporadic-E or via Sporadic-E backscatter?

When we look at those FT8 or WSPR maps at the end of the day, how were we hearing all of those stations in the 200km-500km skip zone? Meteor Scatter? Tropo? Back-Scatter? I think the real picture is a lot more complicated than we assume.

Practical Application: It's all very well wondering about the propagation mode but most people will want to know what is the practical application? Imagine say you are a serious 50 MHz station and you want to work a new country which is only 400kms away and there are mountains in the way. You should never assume that just pointing your beam at a wanted station will always result in a stronger signal. If the signal is weak but constant then it may be via backscatter and you'll have to look for the direction which gives the strongest signals.

Addendum

For Reference: This map from DXMaps shows the suggested maximum usable frequency (MUF) at around 12:00 UTC on the 19th of  May.

It clearly shows one area over the south of England. Note however that this map is generated by users reports and areas of Sporadic-E out over the ocean are not shown. There could be an intense area to the west of Ireland and it would go unreported.

This was the Jet Stream at the time...

Changes in the direction of the Jet Stream are associated with Sporadic-E openings.

Data: Just for my own benefit, I've kept a list of the PI4 decodes below.