The Weak Signal Propagation Report (WSPR) is based on a protocol invented by Joe Taylor. WSPR is a digital radio communication protocol designed for weak signal transmission. WSPR uses frequency-shift keying and forward error correction to reliably send data tens of thousands of miles with just a few milliwatts of power. WSPR was designed to test radio signal propagation.
Inmarsat is a British satellite telecommunications company, offering global mobile services. It provides telephone and data services to users worldwide, via portable or mobile terminals which communicate with ground stations through fourteen geostationary telecommunications satellites. Inmarsat’s network provides communications services to ships, aircraft and remote regions where there is no reliable terrestrial network. The SATCOM on MH370 was an Inmarsat satellite communication system.
Both systems were designed for another purpose other than the detection, identification and localisation of aircraft. However, together the two systems can be used to detect, identify and localise MH370 during its flight path into the Southern Indian Ocean (SIO). Neither system is perfect for this task, but together they can give a good result.
The paper can be downloaded here
(The paper has been updated on 14th April 2021 to correct an error in the numbering of the Figures.)
Richard: Amateur radio stations operating in the 10, 15 and 20 meter bands typically use high gain antennas (Yagi or quad). Some use a 1/4 wave vertical (omni directional) antennas, but most are directional. Do we know what kind of antennas are in use on these WSPR transmitters and receivers?
@ALSM
Many thanks for your excellent question. The type of antenna used is not included in the WSPRnet database, but most stations publish their antenna information.
There is a large variety of antenna used. Many radio stations use a number of different types of antenna and switch between them depending on what they are trying to achieve. Many radio stations experiment with different configurations of antenna and make changes in order to improve transmission and reception. A lot depends on the location of the antenna, proximity of metal fences, metal fuel tanks, electricity pylons, trees, buildings, highways, hills, mountains, ocean, airports, etc.
WSPR transmissions range from low frequency up to 144 MHz, but on 7th March 2014 78% were in either the 10 MHz, 14 MHz or 28 MHz bands.
Typical Tx and Rx antennas between 10 MHz to 20 MHz are 3-element Yagi at 10 meters above ground level.
Typical Tx antenna between 30 MHz to 80 MHz are 1/4 wave vertical above good ground.
Typical Rx antenna between 30 MHz to 80 MHz are dipole at 10 meters above ground level.
Some antenna are omni-directional, others are directional from a low to a high degree.
Between 7th March 2014 00:00 UTC and 8th March 2014 02:00 UTC there were 297,985 WSPR spots covering all bands, all distances (from the same Maidenhead grid cell to the other side of the world at a distance of 19,704 km) and all transmission power levels (0 dBm to 60 dBm). For long distance WSPR links where the transmission is at 37 dBm, the mean received SNR is typically between -14 dB and -22 dB and the standard deviation SNR is between 4 dB and 5 dB. I am looking for anomalies, over the period of the MH370 flight in 2 hour time slots, in the SNR for any particular WSPR DX link outside the standard deviation of the SNR and including a drift of greater than ± 2 Hz/minute. I am assuming that the antenna configuration of the Tx and Rx in each of the WSPR link does not change in the space of the 2 hour time slot.
Here is a list of common antennas used by radio stations:
Isotrope, 0 dBi gain (reference)
1/4 wavelength Vertical, with Average or Good Ground
3/2 wavelength Vertical, with Average Ground
5/8 wavelength Vertical, with Average Ground
Half-Wave Vertical Dipole, feed at 1/4 wavelength Above Ground Level
Horizontal Half-Wave Dipole at xx meters Above Ground Level (xx = 5m to 60m)
Horizontal 2-element Yagi at 10 meters Above Ground Level
Horizontal 3-element Yagi at xx meters Above Ground Level (xx = 10m to 60m)
Horizontal 5-element Yagi at xx meters Above Ground Level (xx = 10m to 60m)
Horizontal 8-element Yagi at xx meters Above Ground Level (xx = 10m to 60m)
20m Band Hexbeam at 10 meters Above Ground Level
7m whip antenna (vehicles)
15m backstay antenna (boats)
OH5Z 7 MHz, 14 MHz, 21 MHz, 28 MHz
@Richard. WSPR as an exclusion indicator is a useful addition.
@David
A single WSPR link is a possible inclusion or exclusion indicator.
Multiple WSPR links at the same time are much more likely inclusion or exclusion indicators.
Richard,
I’ve only given your recent paper a first pass skim – it’s certainly up to your usual standard of scholarship.
One question springs to mind regarding the SLDMB drop possible detections, how effective would WSPR be with low altitude targets?
Those SLDMB drops and the associated on-task flying would have been be at relatively low altitudes. Would it be reasonable to expect a WSPR detection for such a low flying target at such extreme ranges?
To flip things around a bit, the P3s and P8s would have been ingressing and egressing the search zones at higher altitudes and their transit routes would have been well removed from commercial routes. Is there any evidence WSPR detections on the transit corridors?
@Mick Gilbert
Many thanks for your compliment and questions.
Low Altitude WSPR Detections.
@RobW previously reported (my comments on drift analysis 1st March 2021 15:06 and 2nd March 2021 11:45) that he detected two Airbus H125 helicopters at the Australian Davis Station way East of DP0GVN. There were receptions from Tx DP0GVN in Antarctica in New Zealand by Rx ZL2005SWL, a distance of more than 7,500 km. There had not been any receptions for the previous 10 days, due to lower solar flux index (SFI) and geomagnetic storms. Quite probably also because there were no targets, but propagation conditions improved. So the propagation conditions make a big difference, but MH370 flew in very good propagation conditions. If helicopters can be detected, then altitude would appear not to be an issue to detect a low flying search aircraft or MH370.
The flight of two Airbus H125 helicopters near Davis Station in the Antartica on 27th February 2021 between 07:45 UTC and 09:07 UTC detected by WSPR link between Tx DP0GVN and Rx ZL2005SWL at 08:24 UTC changed my view on low altitude detections. The Airbus H125 helicopter is small compared to a B777 and according to FlightRadar24 was only at an altitude of 2,150 feet. Although the propagation conditions were good, I was surprised that a small target at low altitude could be detected.
Evidence of WSPR detections on the transit corridors
There is substantial evidence of aircraft departing from Pearce RAAF Base near Perth for the SIO Search Area and following transit corridors outside the usual commercial flight routes and later returning to Pearce during the AMSA search. It appears that aircraft departed in two shifts. The first shift departed before dawn mainly between 3:00 and 6:00 Local Time to arrive in the search area at first light or just after. The second shift departed mainly between 11:00 and 13:00 Local Time. The first wave of aircraft returned between 11:00 and 18:00 Local Time. The second wave of aircraft returned between 19:00 and 02:00 Local Time. You can even detect aircraft arriving at Pearce on 17th March 2014, the day before the AMSA aerial search started.
As far as the usual commercial flight routes are concerned, the WSPR links between Tx HB9CZF at JN47CH near Zurich, Switzerland on 7th March 2014 at 22:46 UTC and 22:56 UTC and Rx VK6ZRY at OF78VD near Perth, Australia appear to have picked up flight EK425 from Perth to Dubai on flight route L894 between waypoint BONGS and waypoint SAKEG (my comment on drift analysis 12th March 2021 11:35).
@Richard
Thanks for those clarifications, Richard. I should have joined the dots on the Antarctic helo detections and efficacy against low altitudes targets myself, having read about those in Rob’s earlier paper.
That’s a very impressive capacity for detection, well beyond what I thought might be achievable when Rob first started commenting on the topic.
@All
The MH370 Families have posted the following on their FaceBook page:
“Mr Richard Godfrey, one of many researchers who has devoted much effort and time to solving the mystery of MH370 has put forth a new credible method that can be utilised to identify possible MH370 Flight Paths using WSPRnet [Weak Signal Propagation Report (WSPR)] and Inmarsat Satellite data.
This is a new approach that requires interpreting existing data collected and made available on WSPRNet
We are hoping further research and refinement of possible flight paths using this methodology will help in further validating/narrowing the potential splash point of MH370.”
https://www.facebook.com/MH370Families/posts/4023561147703577
Keep up the good work Richard. Let’s help restart the search and find the rest of the plane and the truth about what happened to it.
@All
Another great article by Geoffrey Thomas:
https://www.airlineratings.com/news/mh370-set-off-radio-tripwires-confirming-location-says-new-report/
“A fascinating technology, Weak Signal Propagation, which is a digital radio communication protocol is proving a new tool to confirm the location of MH370 which disappeared just over seven years ago with 239 souls on board.”
“Put simply, imagine you had to hike across a prairie and every 2 minutes there were a bunch of tripwires that you could not see, that set off an alarm or put another way imagine you broke into a high-security bank and to reach the vault you had to cross a room full of laser beams (link below) that you could not see and any one interruption of a laser beam would set off an alarm.”
https://www.dropbox.com/s/itvfh6fedkwqez1/Laser%20Beams.jpeg?dl=0
“Well, that is what aircraft do – they trip off invisible radio waves and Richard Godfrey one of the leading experts in the hunt for MH370 has just concluded a new study which finds that MH370 tripped off a series of radio transmission detections which confirm it is in the location that satellite studies and drift modeling have suggested.”
Thank you Richard and Geoffrey Thomas. Well explained in language even I can understand.
Richard- Thank you for this.
I was struggling with the statement that the MH370 likely did not go below the Great Circle Johannesburg to Perth. I seem to show that circle crossing Arc7 at around 37.5 South. I currently agree with you that I do not feel MH370 went that far west, but I think you saying if we are both wrong about that, we would not have that WSPR signal to help find MH370?
The debris and drift analysis make it highly unlikely that 370 crashed south of 36°S. When I flew from Johannesburg to Perth my SAA flight did not fly that far south, so I may have flown over or near the crash site.
@TBill, @BG370
The drift analysis and the WSPR analysis make it very unlikely that MH370 went further south than 37°S.
The great circle path from Johannesburg to Perth crosses the 7th Arc at 37.0257°S 93.7876°E. This point is 6217.0 km from Johannesburg and 2108.5 km from Perth.
Here is a link to a map with a wide view:
https://www.dropbox.com/s/lihyck31jwbodma/SIO%20WSPR%20DX%20Links%20and%20lower%20limit%200f%2037.0257%C2%B0S.png?dl=0
Here is a link to a map with a close up view:
https://www.dropbox.com/s/zv077zp988hsvj8/SIO%20WSPR%20DX%20Links%20and%20lower%20limit%200f%2037.0257%C2%B0S%20Zoom.png?dl=0
@Richard,
You write in your comment: “The great circle path from Johannesburg to Perth crosses the 7th Arc at 37.0257°S 93.7876°E.”
This point is shown in your map with a close up view. South of the 7th Arc.
Pity to leave it that way, with such a productive analysis.
@George G
Welcome to the blog!
Rest assured that I am continuing the WSPR analysis.
First up, fascinating work Richard, I hope this new line of inquiry produces some fruit !
I have always thought that Z may have had a specific endpoint (target) in mind, one that was easy to remember, and available in the FMC. Two waypoints seem too close to your proposed route to be discounted.
Waypoint OLPUS (37.115000°S 95.000000°E) is on the Great Circle Perth/Johannesburg.
Waypoint EKUTA (39.843334°S 95.000000°E) is on the Great Circle Perth/Capetown.
These old air routes were used “back in the day” but have fallen into disuse. The main reason for them being abandoned being that modern weather forecasting and the introduction of FANS allows flights to use the jet steams eastbound (and avoid them westbound). Even pre-covid, there were very few flights following those old routes into and out of Perth, even approximately. Indeed, Qantas dropped Perth a long time ago in lieu of Sydney for the Johannesburg route when the 744’s came in. A daughter of a friend of mine, was a Qantas FA (pre-covid) on the 744’s operating Sydney/Johannesburg return. She is now working in a local warehouse, and considers herself lucky to have got that job.
@ventus45
Welcome to the blog!
Interesting research and background.
I agree that ZS had an ultimate waypoint in mind, the big question is, if so, which waypoint. The UGIB paper comes down firmly on the geographic South Pole as the ultimate waypoint and it is easy to remember and entered as 99SP, S90EXXXXX, or S90WXXXXX (see separate post on MH370 Flight Path Analysis by UGIB). Previously I had proposed NZPG together with Victor Iannello in a paper on McMurdo station in the Antarctica, which we wrote in 2016 (see Archive section on Flight Path Analysis 25th August 2016). More recently @TBill provided some interesting insights from the ZS home flight simulator about the magnetic South Pole (see separate Guest Paper by Bill Tracy).
I did try to fit flight paths only using waypoints to the satellite data, but I missed OLPUS and EKUTA. SkyVector no longer shows waypoints OLPUS and EKUTA (see Archive section on Flight Path Analysis 1st February 2016).
Do you have a flight path analysis to OLPUS or EKUTA that matches the satellite data?
Hi Richard, I’m VK7JJ, an avid user of WSPR. I’m not sure how you are accessing your data but if it would assist I have built some web tools that directly access historic data.
Dragging markers on the map interface let’s you fetch spots between arbitrary locators which seems to be what you need.
Regards, Phil
@Phil
Welcome to the blog!
Greetings to VK7JJ and to Tasmania, especially QE38LR.
You are in my database, which I built from the WSPRnet downloads in the February to April 2014 timeframe. Where you recording on the night of 7th/8th March 2014?
I use VOACAP to run initial checks and have a number of Matlab scripts for the database analysis.
You are also in the paper from Dr. Robert Westphal in his guest post on this web site.
I would be very interested in your web tools.
You can contact me at richard@mh370search.com
Many thanks!
Richard- There is a discussion thread for this posted on Reddit MH370, and someone posted this pretty cool YouTube time lapse video of the global flights for 72 hours in 2016:
https://www.youtube.com/watch?v=8hedw5jKgzw&list=TLGG6XKrWgHZgwIwOTA0MjAyMQ
I think it is possible to pick out EK425 departing Perth and crossing Arc7 as the sunrise terminator approaches each morning. Which reminds me that could be a good base case to check on.
I now see the flight data is from 2008
@TBill
Many thanks for the link to the great video. It makes it all come to life.
As you say, EK425 is a very good base case.
I ask to forgive. I do not speak in English.
I use from automatic language translator.
I search for to Richard Godfrey the contact, the author of publication about WSPR.
Would like to pass on one graphic file, which deciding confirms
the ride of flight MH370 passed by mister.
Also important conclusions with this graphic arts result. I would want it mister to pass on.
My email: gw20@wp.pl
From respect
Grzegorz
@Grzegorz
Witaj na blogu! (Welcome to the blog!)
Wysłałem Ci wiadomość e-mail. (I have sent you an email.)
Proszę o przesłanie mi pliku, o którym wspominasz w komentarzu na moim blogu. (Please send me the file that you mention in your comment on my blog.)
Thank you Google Translate!
@TBill. “Pretty cool” as you say, even so.
@Richard. Below, your hope that the French will take an interest in WSPR.
(I suggest by-passing the interview with Byron Bailey as both out of date and just fill).
https://www.dailystar.co.uk/news/world-news/mh370-breakthrough-plane-set-radio-23876317
@David
A nice idea that the French authorities searching for MH370 will take an interest in WSPR.
Unfortunately (like so often) I never said, what I am quoted as saying in the article.
@Richard:
Thanks for the initial WSPR analysis. I don’t think WSPR data alone is sufficient to determine the flight path of MH370, mostly because we have no way to determine which one of the many planes near the propagation path is responsible for the reflections, or even if the detected WSPR anomalies are reflections off aircraft in the first place. They could also be related to weather, space weather, meteor trails, etc. Nevertheless, the WSPR anomalies could add credibility to conclusions made from other data like BTO/BFO or ocean drift results if they coincide with the predicted flight path.
@Phil:
The really interesting data would be the spectrograms of the detected 2 minute WSPR signals that night. Aircraft reflections appear to be clearly visible in the spectrogram as a weaker component with relatively steep Doppler slope from higher to lower frequency around the main signal. The presence of these Doppler components would allow us not only to determine if the detected anomalies really are aircraft reflections of something else, but also estimate the reflecting object’s speed component perpendicular to the great circle path between Tx and Rx. For example if the anomaly detected at 22:46 UTC was caused by flight EK425, the doppler slope would be relatively shallow since that plane’s flight path was almost parallel to the signal (short) path. If that anomaly was instead caused by MH370, the Doppler slope would be much steeper. Unfortunately these spectrograms are not stored in the WSPR database and probably not stored at all.
@ Arto:
Yes, appreciated and the tech is understood. Would have offered it if that was possible. I can confirm that no data is uploaded to WSPRnet other than that described in CSV values itemised a little way down this page
http://wsprnet.org/drupal/downloads
I can say that a very small number of hams from time to time do save the raw audio from their receivers usually SDR based (I have) to feed to other wspr decoder software but the chance of that being relevant and available is improbable. That is only worth mentioning because there is nothing else kept anywhere that I’m aware of and I’m part of a group that has spent a lot of time and effort on wspr data storage and analysis, I do a web front end for it.
The only other thing worth mentioning is transmissions by WSPR balloons, their data is often poorly understood and their telemetry spots are normally excluded by default by most wspr db systems. They typically transmit normal wspr spots on 20m followed by telemetry spots in a defined 2 minute time slot shortly afterwards, those transmissions do not have normal wspr callsign or locator data but that can be derived. I’ve not had a chance to see what if any balloons were around at the relevant date and time but I will.
For anyone else interested in wspr generally here is what I’m talking about … http://wspr.rocks
It is a fascinating endeavour that you’ve undertaken both technically and forensically, those involved have my absolute admiration.
Regards, Phil
@Arto L
I agree “I don’t think WSPR data alone is sufficient to determine the flight path of MH370”. That is why my paper is entitled “Using the WSPRnet and Inmarsat Satellite data in the search for MH370”.
In some areas the skies are full of aircraft and in other areas such as the SIO the skies are pretty empty.
My point is that WSPRnet data is available every 2 minutes, whereas in the SIO we only have BTO data every hour.
For aircraft other than MH370 we also have Flight Plans and ADS-B data to help distinguish which aircraft may be being detected.
If you get 3 or more WSPR anomalies on a location, where there is no recorded aircraft, then it is a possible detection. If it also fits the Inmarsat satellite data, then you are building a case for a MH370 detection.
It looks like there were two balloons around at the following UTC times, I would have to refer to another ham in Canada who would likely know whose balloons they were and what timeslots they were on in order to be able to search for their normal spots and their actual locations.
The data from spotnum 186401483 indicates it was at an altitude of 5,500m at the time.
The spotnum is generated by WSPRnet on upload of the data and is an absolute reference to the transmissions.
Regards, Phil
spotnum date (y-m-d) UTC
186734476 2014-03-09 21:46:00
186557554 2014-03-09 07:42:00
186401483 2014-03-08 16:54:00
186195591 2014-03-07 23:12:00
186002927 2014-03-07 08:46:00
185996169 2014-03-07 08:16:00
Prima facie the telemetry spotnum 186734476 came from this balloon, VE3KCL. The actual locator and other data below is normal wspr values and not telemetry though that would have to be confirmed.
I’m probably wasting your time but at least you know now that if you have that data already it did not come from a ground station but a balloon at a much higher altitude. Dave VE3KCL is a prolific balloonist and the Canadian I was referring to, he would have stored the data from the entire track of that balloon along with the telemetry for the entire flight, flight durations are often several earth circumnavigations.
Cheers, Phil
spotnum date (y-m-d) txCall txGrid rxCall rxGrid MHz Watts SNR drft km
186733216 2014-03-09 21:38:00 VE3KCL FN03iq VE1MDO FN84aq 14.097107 0.5 -22 -1 1226
Hi Richard, sorry I missed your first reply, the page scrolled to the newer posts, my apologies! Thanks for the welcome and other info, happy to correspond via phil@perite.com if I can help rather than me bother you just for a chat. Sadly I have no saved audio. I’ll stop posting here and taking up space unless something crops up.
Best regards to you and others.
Phil VK7JJ
@Phil
Fascinating information about balloons!
I was particularly interested in spotnum 186195591 on 7th March 2014 at 23:12 UTC, which is during the flight of MH370.
https://www.dropbox.com/s/acdfbffufb8cyq0/SIO%20WSPR%20DX%20Links%20and%20WSPR%20Balloon%20Detection%20at%202312%20UTC%20Data.png?dl=0
Here is a global view of the WSPR links during the flight of MH370. I have marked the Balloon spot in blue.
https://www.dropbox.com/s/ylxlo8kslxfj1f9/SIO%20WSPR%20DX%20Links%20and%20WSPR%20Balloon%20Detection%20at%202312%20UTC.png?dl=0
Here is a close up view of the Balloon spot and the hypothesised trajectory of MH370. The WSPR Balloon link crosses the MH370 trajectory at 26.4 °S 93.8°E at 23:12 UTC. The predicted position of MH370 from our hypothesis is 25.3°S 93.8°E. Could this be another MH370 WSPR detection? I would be interested in the Balloon trajectory data from Dave at VEKCL. Can you put me in contact with Dave please?
https://www.dropbox.com/s/eum4chrq3k982up/SIO%20WSPR%20DX%20Links%20and%20WSPR%20Balloon%20Detection%20at%202312%20UTC%20Zoom.png?dl=0
@ Richard, all good, email sent.
@Phil
Many thanks! I will contact Dave at VE3KCL.
@All
Another great article by Geoffrey Thomas:
It is time for the facts and nothing but the facts on the location of MH370.
https://www.airlineratings.com/news/mh370-time-facts-facts/
For seven long years, the relatives of those 239 lost have been subjected to a tsunami of misinformation and endless conspiracy theories not to mention an incredible 130 books written about the disappearance of the Boeing 777 on March 8, 2014, on a flight from Kuala Lumpur to Beijing.
Now it is time for hard facts, backed by science, not fantasy and bizarre speculation that is as stupid as it is cruel to the relatives.
@All
MH370 was diverted on 7th March 2014 shortly after 17:20 UTC.
For those who have downloaded the WSPRnet data and wish to track the other aircraft in the same region as MH370 following diversion, I have attached a link to a table (.pdf and .xlsx) of the 55 flights captured by ADS-B in the 4 hour period following the diversion. There were 33 departures from Kuala Lumpur (KUL) and Singapore (SIN) and 15 arrivals at both airports. 7 aircraft were in transit across this airspace. The area covered is from 1°N to 10°N and 99°E to 108°E, which totals 287,000 square nm. There were no domestic flights at Penang Airport (PEN), Langkawi Airport (LGK) or Kota Bharu Airport (KBR) during this timeframe. I have used the IATA short codes for airports in the table for the column marked “Route”. The column marked “Flight Route” which was used by the various aircraft for entry or departure from the airspace are noted in the table and can be viewed on SkyVector https://skyvector.com
https://www.dropbox.com/s/prpa65od6gp9jcu/Aircraft%20in%20the%20Vicinity%20of%20MH370%20at%20the%20time%20of%20the%20Diversion.pdf?dl=0
https://www.dropbox.com/s/pmbrcw7eyigw054/Aircraft%20in%20the%20Vicinity%20of%20MH370%20at%20the%20time%20of%20the%20Diversion.xlsx?dl=0
It is interesting that there were 7 flights using Flight Route N571 apart from MH370. Emirates UAE343 KUL-DXB FL340 was following just behind MH370 and Indigo IGO053 MAA-SIN FL330 was just in front of MH370. IGO053 was flying in the opposite direction on this bi-directional flight route. There was no other traffic on the flight routes to the south of MH370 towards the Indian Ocean in this timeframe. The nearest flight was Etihad ETD475 CGK-AUH on flight route M766 at FL380, but had already passed well before any final major turn southwards by MH370. CAPTIO have published a you tube video showing the traffic on N571:
http://mh370-captio.net/wp-content/uploads/Traffic-8-March-2014-uploadee.mp4
For those wishing to track aircraft on a global basis, I have attached a table of all 67,663 flights that were operating in 2014. The table uses the short IATA codes for airlines and airports as well as recording the aircraft type normally used on each route.
https://www.dropbox.com/s/6vl7h3dtgc4ngj1/Global%20Flight%20Routes%202014.xlsx?dl=0
Hi,
Just a precision, please, about your paper:
2nd paragraph page 2:
During the flight of MH370, the WSPR database contains 7,708 DX global links between 7th March 2014 16:42 UTC and 8th March 00:22 UTC at an average of 34 links every 2 minutes.
3rd paragraph page 6:
There are 91,895 WSPR links recorded during the flight of MH370 from 7th March 2014 16:42 UTC until 8th March 2014 00:22 UTC.
Does this mean that there were 7708 “anomalies” out 91895 recorded links?
Anyway, many thanks for your work!
PL
@PaxLambda
Many thanks for your good question! I will try and clarify.
During the flight of MH370 there were a total of 91,895 WSPR links between any two points globally and over any distance, from between neighbouring antenna pairs to between antenna on the other side of the world.
Out of these 91,895 there were 7,708 WSPR DX links over a distance greater than 8,000 km. A DX link is a communication over large or relatively uncommon distances. In the case of MH370 we are looking for WSPR DX links that cross the Southern Indian Ocean (SIO).
Out of these 7,708 WSPR DX links there were only 17 WSPR DX links that crossed the SIO on the short path or direct path between the transmitter and receiver. Out of these 17 WSPR DX SIO links there was only one anomaly on the short path, which is shown in Figure 15 and Figure 16 in the paper.
However on the long path around the globe using WSPR DX SIO links there were eight anomalies and they are listed in Table 2 on page 16 of the paper and shown in Figure 17 and Figure 18.
There are more WSPR links in the earlier part of the flight before reaching the SIO and I am currently analysing the WSPR links during the final major turn (FMT). This is more complicated because of the much larger number of other aircraft operating in the area around Malaysia, Singapore, Thailand and Indonesia.
I also note that I had two figures called Figure 18, my apologies for the confusion and I have now corrected this mistake.
Hi Richard, thank you very much for your clear and complete answer.
Just a last question: how the RX station “knows” that the signal traveled the short or the long path?
PL
@PaxLambda
The Rx station does not “know” whether the WSPR signal travelled the short path or long path or both paths, unless it has a highly directional antenna. In any case this is not recorded in the WSPRnet database, although many operators publish which antenna they use on the internet. WSPR spots are detected by radio stations all over the world on every possible azimuth from 0° to 359°. The azimuth between the Tx and Rx station is recorded in the WSPRnet database, but the reverse azimuth could equally be true.
Some antenna are omni-directional, others are directional from a low to a high degree.
If a Tx station uses an omni-directional or isotropic antenna or an antenna with directional lobes both say North-South or East-West, then the signal will travel both the short path and the long path. The majority of Tx stations want to be received by as many Rx stations as possible.
The majority of Rx stations like to be able to receive from every direction. A typical Rx antenna for frequencies between 30 MHz to 80 MHz is a dipole at 10 meters above ground level. A typical Rx antennas for frequencies between 10 MHz to 20 MHz is a 3-element Yagi at 10 meters above ground level.
Thanks again for your answer… but it brings another question!
If the database doesn’t contain any info about the path(es), how have you concluded that the 8 “long pathes” of the figure 17 were, effectively, long pathes? From the TX antenna? Or because there is no cause along the short one?
PL
@PaxLambda
Simply because each path should be considered both as a short path and a long path.
There are always two ways to reach the same point on the other side of the globe, the short route and the long route.
Yes, I understand that. My question was very badly formulated: Sorry to bother you this way, I try to reforformulate!
The caption of your figure 17 is “Anomalous Long Path WSPR DX links during the MH370 Flight”
What I wanted to ask was: How, in this figure, have you concluded that the “anomaly” was somewhere along the long path? Because there is no cause along the short one? Or from the TX antenna caracteristics?
@PaxLambda
For every WSPR link between a Tx station and a Rx station there are usually multiple examples across a 2 hour period in time. I calculate the mean and the standard deviation of the signal to noise ratio (SNR) of the received signal over a 2 hour time period and look for changes in the SNR by more than the standard deviation. In the FMT tables that I am currently working on, I include both these values. I also compare the SNR with other days at the same time. Hence the reason that I built a database of WSPR links from 28th February 2014 to 21st April 2014.
The Rx station also measures the drift of the received signal compared to the actual frequency of the Tx station, which is digitally encoded and sent in the WSPR protocol to the Rx station. The drift is normally 0 Hz/min but can be up to ± 4 Hz/min.
An anomaly is defined by either a sudden change in the SNR or a non-zero drift or both.
A single anomaly is not significant, but multiple anomalies can be a clue to an aircraft detection. Multiple anomalies can be both from the same WSPR link pair over time when tracking an aircraft from a known start point with a known speed and direction or from multiple WSPR link pairs at the same time that intersect at a specific point.