WSPR & MH370: Facts against Fake News

How Aircraft Scatter generally works. This adaption from Gary S. Sales’ paper “OTH-B Radar System” (University of Masschusetts, Lowell/USA, 1992) should add to some other entries on my website. Double-click the picture to enlarge it.

Furthermore, there are people who claim against all facts and reason that they can prove aircraft movements with aircraft scattering of WSPR signals from their log data. Surprisingly or not, they find enthusiastic approval in the popular press, but also in technical-scientific organizations like many ham radio associations, first and foremost the notorious German DARC. Whether one deals with supporters of “conspiracy theories” at all (Nobel laureate Joe Taylor, K1JT, said having too little time for such obvious and non-scienctific nonsense), or whether one meets their convoluted theories with technical-scientific arguments, is quite controversial and a topic more of social psychology than one of physics.

Nevertheless, “Never Give a Sucker an Even Break” as the great comedian and juggler, W.C. Fields stated 1941. And that is why I would like to deal with some “arguments”, which would not be difficult because of the subject matter, but because of how these people “argue”. For the sake of clarity and brevity, let’s do this in the form of a question and answer game.

Do aircraft affect RF signals?
Certainly. HF signals are scattered on the electrically conductive metallic hull of aircraft.

How does Aircraft Scatter work at all?
The drawing at the top explains it: Radio waves from a transmitter reach the receiver directly on the one hand, and via aicraft scatter on the other. On the receiver side, both signals add up. Thanks to the Doppler effect, which the signal part scattered by the aircraft has, both signals can be separated from each other again with a method called FFT; see my website for a couple of examples. However, this is not possible with WSPR log data, here only the total signal is noted.

How big are these influences?
They mainly affect the signal strength and are around 35 to 50dB+ below the original signal. There are exceptions. Downward, there are far more cases than the exceedingly rare constellations where the scattered signal may be larger than the original signal. Above 30 MHz this occurs more often, below 30 MHz I have never observed it as there always was at least some backscatter of the original signal.
Signals or field strength can be measured and calculated. Generally speaking, a suitable form of the “Radar Equation” will do the calculation, see here. They largely match the values being measured by the method “separate original signal and scattered signal”.

Facts, please – how big … ?
Sorry, yes. Say, a booming signal by a broadcaster in the 19 meter band hits your antenna with a level of -40 dBm. Then a Boeing 747, flying over your house to touch down at your airport nearby (“in your backyard”, as they say) at a distance of 500m only, this will peak at -86dBm.
Not bad, and easily visible by FFT analysis.

How much does this scattered signal adds to the original signal?
Good, with this you steer to the central point, because WSPR measures only this total signal. You just have to add -40dBm and -86dBm and with this most favorable constellation you get a total signal of -39.999890911528446dBm.
Believe me: you cannot distinguish it from the level of the original signal, being -40dBm.

Oh, that’s disappointing … but they tell they can identfy aircraft not only 500m, but some/many 1000km away?
First, physiscs may be disappointing. Secondly, I took a most favourable case – booming broadcaster, short distance. The effective power of a stronger WSPR transmitter may reach 40dBm, compared to 100dBm+ of many broadcasters. The difference of 60dBm and more is whopping.

“Whopping” – what do you exactly mean by this?
Take the example of the broadcaster, reading -40dBm on my S-Meter. If the transmitter were an even above-average WSPR transmitter it reading of the S-Meter would be -100dBm. Still readable, and WSPR would give a decode.

So, it works?
Wait a moment, for introducing the scattered signal, also 60dB down. It will peak at -160dBm, and it reliably is eaten by noise which will start between -130 and -140dBm.
By this, the orginal signal of -100dBm will be enhanced and strengthed to -99.999995657057354dBm. Quite an achievement!

I understand, it cannot work. Does a greater distance improve things?!
By no means. A greater distance worsens things even exponentially.

OK, but what the hell are they measuring to come up with such far-reaching results?
They are measuring indeed fluctuations of the signal but without knowing the reason. And there are much more and of stronger influence to the received signal level than aircraft scatter. Prevailing is multi-path leading to near-normally distributed changes of the signal level of around ±8dB from second to second, and often more than 30dB within just a few seconds!

But – they mention “drift” … and “Doppler” means “drift”?!
Yes, but the “moon shapes” of a few signals surely have other reasons, much more obvious – just think of bad power supplies, meteor scatter (stronger and more often seen compared to aircraft scatter) and travelling waves within the ionosphere itself. Have you ever asked yourself, why in the presented cases the whole signal is shifted, instead of seeing a Doppler signal branching out from the original signal? „They don‘t know what they do“, says K1JT into their direction.

How much can I rely on the quality of WSPR signals?
Look yourself at the screenshot below, showing three hours of WSPR signals, showing drift, over-modulation, noisy signals. All fine for decoding WSPR but on only very few you consider those rocks where you want to build your church on (Mathew 16-18). You see instabilities at many scales, and also the duly repeating (!) half-moon footprints which for some ghostseers are the evidence of aircraft.

Drifting away: Three hours of WSPR signals on 20m. Their quality works for decoding WSPR, but it is difficult to use them as reference …

They work with the concept of “tripwire”. Any comment on this?
Well, they seem to consider propagation working by distinctive, laser-like “rays”, not fields of energy. (This is just a guess from this blog entry.) Each object crossing this ray causes a-normal propagation which they fail to precisely specify. This is a fundamental misconcept of how HF propagation works plus an incomprehensable application of PropLab Pro 3.1, the propagation software, which they seem not to understand. Propagation doesn’t produce “tripwires”. And if you need some parallel, you should more think of a booby trap, thanks to which not only signals are pulverized, but with them all the dream fantasies that this or that plane may have caused them to go off.
They must use “Broadcast Coverage Map” with PropLab Pro to get a realistic view of electromagnetic fields and their propagation, see secreenshot below.

No “tripwire”: HF propagation doesn’t work by laser-like rays, but by electromagnetic fields. This PropLab 3.1 Broadcasting Coverage Map screenshot gives a general impression of this – transmitter Tiganesti/Romania, simulated a sector of ±30° of the antenna’s direction. And you can try to get your own impression for free with e.g., VOACAP online.

Can I understand your assertions?
Absolutely! In theory, as well as in practice. You can find many examples on my website. A SDR and software are all you need. Oh, and, last but not least: and unbiased view not on the possibly desirable, but on the physically possible!

But why do they still spread their charlanteries with great success?
Look around you. The world is full of castles in the air. That’s actually not so bad. Here, however, they are built by those who could know better and they are spread with enthusiasm by those who know better. Or at least should know better.
But that is the usual pattern of Fake News. Only that it undermines the technical-scientific competence of the radio amateurs and makes them look ridiculous.


  • Thanks for explaining the gut-instinct-obvious again and again!

    This matter is somehow reminding me of an OM from in the late 90s, who – besides real merits – also had a maniac facet: he claimed it is possible to DX-communicate via earth rays, and he arranged a public demonstration supervised by a notary in order to prove it. Two randomly selected morse letters were “sent” via his bizarre self made apparatus very slowly, and an involved friend 1500 km away on the faroe islands tried to “receive” them — with a divining rod! But little surprising, the friend was not able to recognize the letters, while the initiator unflinchingly considered it still a success anyway…

    No matter where the black box might be perhaps found one day – people who are boastfully calling their method “GDTAAA” (Global Detection and Tracking of Any Aircraft Anywhere) will surely have known it beforehand and will count that as their success, just like the earth ray man, I guess… 😉

    It’s embarrassing that some DARC officials seemingly couldn’t resist the temptation to bask in the glory of a supposedly brilliant idea rather than deal with it straight and factually first.

    73, Manfred, DL7AWL

  • Friedhelm DK9JZ

    Die Gründe für das “Fehlen” kritischer Leserbriefe in der CQ-DL ist mir Dank dieser Webseite schlagartig klar geworden.

    Der neuen “Satzung” sei Dank reicht eine harmlose Bemerkung, die ein DARC-Mitglied in den falschen Hals “kriegt”, oder auch ein kritischer Leserbrief (deren hätte ich mehrere), um `rausgeschmissen zu werden. Weitere Gründe aber sind mangelnde Kompetenz der Redakteusen (Zwar mit akademischem Grad, aber was will ein Dipl. -Soz.-Wiss. von Technik wissen?) . Der Umgang mit WSPR und MH370 zeigt zwanglos die mangelnde HF-Kompetenz.

    Waren das Zeiten, als wir Wissenschaftler, Ingenieure und Techniker im Stab hatten. By the the way, das Wiss.steht nicht für Wissen, sondern für Wissenschaftler hi! Obwohl: das ist nicht zum Lachen!
    Mir ist nicht klar, weshalb Geisteswissenschaftler die wenigen Ingenieure im Stab unterbuttern dürfen, was sich auch im laienhaften Layout der CQ-DL spiegelt: Da ist z. B. von Aufmacherbild die Rede ( an Stelle von Bild 1). Das ist und war Setzer- Jargon.
    Weiters werden white old men in der CD-DL als technisch gestrige bezeichnet. Und das nur, weil selbige die Restlebenszeit Funken und nicht tagelang programmieren wollen um dann in einer Sprachqualität zu Funken, die zu Zeiten Bells und Reis gängig war. Ich werde hierauf antworten: Ich und technisch gestriger? Ich bin auf dem neuesten technischen Stand: Ich werde auf E-QSL umstellen. Dann aber brauche ich keinen DARC mehr.

    Geben wir der CQ-DL vier Chancen zur Veröffentlichung von vier Leserbriefen, bevor ich austrete:
    1) Fragen zum verworrenen pseudomodernen Layout und der unwissenschaftlichen Titelei der CQ-DL
    2) Wehalb gibt es nur noch anbiedernde Pille-Palle-Leserbriefe?
    3) Juristische Fragen zum Jugendschutz und zur angeblichen Genderproblematik
    4) Da fällt mir bestimmt noch etwas ein, aber bis Nummer drei bin ich vermutlich längst rausgeschmissen worden…

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