Youtube comments of vk2ig (@vk2ig).

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  229.  @vanstry  I agree with you regarding the potential for interference by a mobile phone transmitter. As a professional radiocommunications engineer with a few decades of experience, it used to surprise me that people don't recognise the potential interference issues of mobile phones in aircraft. Nowadays, noting the lack of experience most people in the electronics industry have with anything related to radio (for example, look at how much radio frequency interference pours out of a typical solar panel inverter or a switch-mode power supply), it doesn't surprise me at all. I've seen plenty of engineers come unstuck, and companies and governments lose lots of money, because people didn't understand the mechanisms by which interference from radio transmitters occurs. Anyway, to further to the points you made: - Just because a receiver is designed to operate at 117, 330, 1500 MHz or some other frequency doesn't mean a nearby transmitter operating at 800 or 1900 MHz won't cause problems. It depends on how susceptible the receiver is to strong out-of-band signals - there are a number of mechanisms by which receivers can suffer interference from non-co-frequency interferers, e.g. poor front-end bandpass filtering, poor IF image rejection, etc. It also depends on how spectrally "dirty" the mobile phone transmitter is - poor output stage filtering can allow appreciable energy on other frequencies to be "unintentionally" emitted by the phone, and increasing the number of phones in the cabin increases the radio frequency noise on a given frequency. - Signals emitted by a mobile phone transmitter can couple into cables within an aircraft. Whether the circuits at each end of the cable can operate properly in the presence of such signals is another issue. That depends on whether EMI/EMC principles were employed when designing the circuit - the designers may have operated on the assumption that there would be no strong radio signals inside the aircraft - put one or more mobile phones in the cabin and that assumption doesn't hold. MIL-STD-461 (in whatever revision it currently is - I used "E" last) is a suitable standard. - Radiation of signals internal to the mobile phone receiver (e.g. heterodyne oscillator, etc) is "a thing". One of the terms for it is "backwave", which comes from the earlier days of radiocommunications. This too can cause problems with radio receivers and other equipment, although arguably often it's not as impactful as the transmitter signal. (This is the principle underlying how the radiofrequency regulator in the UK can track down people who are using TV sets without a licence ... they can even tell whether it's colour or monochrome receiver due to unintentional radiation of the colour-burst signal.) With regard to aircraft accidents, it may be that there have been none due to mobile phones. But airline pilots have reported navigation issues when mobile phones have been used by passengers. I guess those who think mobile phones aren't a problem are willing to tolerate that sort of event ... an event which might just be one of the Swiss cheese holes needing to line up one fateful day.
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  283.  @banditkeef3864  That's an excellent question, and I'd be interested to read an answer which disproves your statement. But I suspect such an answer won't be clear cut. The Korean War and Vietnam War were fought to stop the spread of communism (and thus the influence of China and the USSR) in the Far East. Some argue that this was to protect the USA, but given no ICBMs were installed in North Korea, Vietnam, Laos, or Cambodia it's arguable that there was no real threat to the USA. (The USSR learnt its lesson from the Cuban Missile Crisis that deploying ICBMs outside its territory was a ticket to a lot of trouble.) The Invasion of Iraq was dressed up as protecting freedom ("We have to get those WMDs!") but in reality it was to fought to secure the oil supply for the USA - American presidents know that they don't survive long if the cost of filling a SUV's gas tank rises. Securing the oil supply could be construed as protecting the USA's way of life, and (by a somewhat dubious extension of that) its freedom. Afghanistan was arguably intended to get Osama Bin Laden. But the likelihood of him (and Al Qaeda) being able to launch more attacks on US soil after 9/11 were vanishingly small due to heightened security, awareness, etc. The war achieved the zapping of OBL, but it didn't eliminate Al Qaeda, so that threat - in its post 9/11 context of reduced effectiveness - remains. Finally; it can be easily and successfully argued that maintaining a standing military force is the means of protecting freedom. However; that force doesn't need to go to war to achieve its aims - it just needs to exist and be demonstrably competent.
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  576. The Forgotten Soldier is one hell of a book, to say the least. After I read it, I couldn't help but wonder what ever happened to ... The young German replacement who was left to his own devices wandering across the snow-covered Russian steppe looking for the unit he was supposed to join. Sajer says he, at least one other soldier joining Sajer's unit, and this replacement were behind German lines walking eastwards in the middle of nowhere trying to find their respective units. As dusk approached, some transport arrived that was heading towards Sajer's unit, so all but the replacement jumped on the vehicle and drove away. Sajer says he remembered seeing this young, lone soldier, looking very scared, trudging off into the dusk into the featureless terrain. One can only wonder if he ever did find his unit - Sajer and the others had difficulty finding his own unit as it had moved many times while he was away from it, and kept being given conflicting information regarding its whereabouts. Paula, the girl Sajer spent leave with in Berlin. The other young (Soviet?) soldier that Sajer saw through the window. Sajer's unit was moving inside a row of houses, and he looked through a window and saw across the way another young face looking through a window at him. They just looked at each other for a while, and might've even waved. The girl in the cellar with whom Sajer made love. Sajer's comrades - they (with Sajer) surrendered to the British and were being held in a POW camp. When Sajer was questioned, the British discovered he was from Alsace so they took him away to another part of the camp. He was treated more as an unfortunate French "draftee" than a former German combatant, so he wasn't able to see his comrades after the interview. (Sajer was repatriated to Alsace, and to "atone" for his crimes had to serve in the French Army for a period, and even had the ironic experience of marching in the victory parade in Paris!) I wonder if Sajer ever reconnected with any of his former comrades?
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  680. Some comments: 1. Very good of you to mention the coordinated attacks on the Far East on 8th December and the attack on Pearl Harbor [US spelling] on the 7th. Many people think the East Indies attacks occurred the day after Pearl Harbor, but they don't realise that the International Date Line separates these two regions - the 8th West of that line and the 7th East of that line are the same day. 2. Singapore was doomed because SS Automedon was captured by the German commerce raider Atlantis (a.k.a HSK 2, Schiff 16, and Raider-C. ) The boarding party of Atlantis were able to get into the Automedon's strong room, and unfortunately for the British the Automedon's crew hadn't destroyed the highly classified material there. This provided incredibly valuable information regarding the disposition of British forces in the Far East - information of which Japan was unaware. Captain Bernhard Rogge, master of Atlantis, recognised the value of this information and sent one of his prizes (captured ship) to Japan with the documents. The Japanese were so surprised by this information that initially they suspected it to be forged. 3. Some years ago the Wikipedia entry on the loss of Repulse and Prince Of Wales carried a quote from a British admiral in London, who upon hearing of the loss, expostulated something akin to "I knew [admiral's name] would make a balls-up of it, and he has!" However; the entry has been edited since then, and there's no mention of this outburst. Unfortunately, I cannot recall which admiral allegedly said this, or to which admiral he referred. 4. I had a great uncle who served with 8th Division 2nd AIF in Malaya and ended up being a "guest" of the Japanese for effectively the duration of the Pacific war. Not much was said about it in my family, but my father did say once that Uncle Bob was awfully thin when he finally returned home. Edit: grammar and clarity.
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  683.  @DieNibelungenliad  In hindsight it wasn't that big a feat to take Singapore. Documents detailing a pessimistic British assessment of their ability to defend their Far East possessions had been captured by the German Raider Atlantis from the British ship SS Automedon. Realising the importance of these documents, KZS Bernhardt Rogge, Captain of the Atlantis immediately sent them with one of his prize crews on a captured ship to Tokyo. The Japanese were so surprised by these documents that they initially suspected them to be fake. These documents helped inform Japanese plans for entering WW2. There were other factors which didn't help the British defence in the Far East. One was the British idea that somehow the "White Guns" of Singapore would defeat the IJN. What they didn't count on was the IJN landing IJN and IJA forces on the Malaya Peninsula, and marching down the coast to capture Singapore. Another was the British inability to provide a level of defence to the colonies which equalled that provided to the British Isles. There was no Chain Home radar system, there were no front line fighters: there wasn't a Spitfire or a Hurricane in the theatre, only outdated fighters like the Brewster Buffalo (the crews called it "The Flying Coffin"), and there weren't flotillas of destroyers. At the time, the British lacked an adequate appreciation of modern warfare, including the propensity of the Japanese land forces to engage in flanking manoeuvres (hence the march down the Peninsula), and the ability of aircraft to destroy capital ships (hence the loss of HMS Repulse and HMS Prince Of Wales in the space of hours).
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  913. It reminds me of a couple of the kids at school - they were always telling tall tales to impress or scare the rest of us ... still remember "Patrick R" telling us about how a particular sort of lightning bolt would crack the world in two, LOL! And one of the others saying the concrete structure in the middle of the school ground was a WW2 bunker (there used to be a bunker there, but that wasn't it). LOL. As I was saying in an earlier comment; recently I read an article in which researchers claimed we humans are wired to believe in the mysterious, which is why we're inclined to be religious. Religions are great mysteries. For an example, look no further than Christianity's book, The Bible. In the earlier part there's a great flood, a burning bush, a pillar of fire, an ark which gets carried around and from which the "Power" or "Voice" of God emanates, a sea that parts and lets people cross to safety, an entire city razed and a woman turned into a pillar of salt, a guy called Ezekiel who describes something akin to an aircraft - "I'll have some of whatever he was having, thanks!" - just to name a few instances. In the latter part it's just as good: there's walking on water, turning water into wine, raising people from the dead, feeding thousands with a few loaves and fishes, driving out demons, transfiguring into three entities (again, "I'll have some of whatever they're having, thanks!"), disappearing from a tomb, appearing on the road to Emmaus, tongues of fire, and ascending upstairs. We're so wired for believing the mysterious we can't help ourselves! In this modern age, we're only just starting to eclipse our ancestors as the biggest conspiracy theorists to have ever walked the Earth. What are the latest ones/ Virus escaped from a lab ... or engineered by a rich American philanthropist and a financial speculator to kill most of us off, a vaccine engineered to kill the rest of us off, stolen election and "Fed posting", chemtrails, child-molesting blood-drinking lizard men in human disguise ... they get better and better each day, LOL!
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  1195. "I'm happy to be corrected." Excellent. Talk to someone who really understands electronics and radio propagation. For starters, ask how the wavelength of the mobile phone signals (both intentional and unintentional) mobile phone compares to the circumference of an aircraft window (actually, you don't need to talk to an expert on this one ... after all, if the mobile phone signal from the tower on the ground can get in, then it's highly likely that the signal from the mobile phone in the aircraft can also get out!) Ask about receiver performance in the presence of strong out-of-band signals. Ask about out-of-band spectral components in the mobile phone output signal. Ask about effectiveness of radiofrequency decoupling and bypassing in non-radio frequency aircraft electronics inside the cabin. Ask about how the signals produced by a number of uncorrelated transmitters combine to increase power spectral density in a given frequency band. Ask about local oscillator radiation in receivers. Ask about why a laptop computer and power supply that comply with FCC regulations (at the consumer level) can cause interference to a radio receiver that also complies with its applicable FCC regulations. Ask about the radiofrequency shielding effectiveness of a modern airframe made of composite materials. Ask about intermodulation in the power amplifier stage of a transmitter due to mixing of external radio signals picked up by the antenna. And they're just some of the issues you could ask about.
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  1196.  @BlackEpyon  Sounds like you've had some interesting experience with radio frequency devices for networking, and your tale of investigations does credit - it appears that you've looked into it more than the average IT person would have. A few points in response to your post: 1. Interference to out-of-line-of-sight antennas. Whenever an electromagnetic wave at radio frequencies encounters a conductor (whether it be a good or poor conductor), it will induce currents in the surface of that conductor. (The currents flow just under the surface too, and the depth to which they will flow below the surface is called "skin depth", and is inversely proportional to frequency.) These currents will flow along the surfaces of the conductor, and they will themselves radiate electromagnetic waves. This is what happened when you saw reflection of WiFi signals from metal lockers: the electromagnetic wave induced currents in the surface of the locker door, and those currents caused another electromagnetic wave to be radiated from the surface of the door. (Incidentally, it so happens that for good conductors the electric field component of the radiated wave is anti-phase to that of the incident wave, as the tangential electric field value at the conductor must be zero, so this gives rise to a 180 degree phase shift between the incident and reflected waves.) If the conductor is curved, e.g. like the outer metal skin of an aircraft, those currents will flow along the surface around the curve. The currents will flow in every direction possible along the surface, radiating as they go. (Obviously the current density drops off as the distance from the incident wave increases.) So it's possible for electromagnetic waves to be radiated by a surface current and affect an antenna which is not line-of-sight to the antenna which gave rise to the incident electromagnetic wave. A classic example of this effect is a conical horn antenna used at microwave frequencies (and by that I don't mean "microwave oven" frequencies): make the bicone angle too acute and currents will flow on the outside surface of the horn (and electromagnetic waves will be radiated from the outside surface of the horn), even though there is no external electromagnetic wave arriving from elsewhere to excite those currents. (Incidentally, that's not how you want a horn antenna to operate - you want to restrict the currents to the inside surface of the horn so that it launches a plane wave along the axis of the horn.) 2. Frequencies used by mobile phones. These aren't restricted to the 2.5 GHz ISM (or "hash") band where WiFi often operates. Google "LTE frequency bands" and look at all the frequencies! 3. Non-linear effects. With regard to surface currents; to compound matters, if the surface is not continuous, but is made of overlapping sheets (quite typical of aluminium-skinned aircraft), then the thin oxide layer between the sheets acts as an insulator, implementing a form of diode through which these currents will flow. This will give rise to some form of rectification. A basic rule is whenever a waveform is changed non-linearly (e.g. by rectification), then the frequency spectrum of that waveform will also change. So, you can get frequency multiplication, e.g. doubling, tripling, etc; and also intermodulation where two currents at different signals give rise to currents at sum and difference frequencies, or three frequencies give to even more complex sum and difference frequencies, and so on. Some of these spurious frequencies (as they're referred to) could be at the input frequency ranges of certain aircraft radio systems. Consider this in terms of all the LTE frequencies in 2 above, and a number of phones operating on different frequencies inside an aircraft cabin. 4. Is a short circuit always a short circuit? Aircraft metal structures are electrically bonded together, but this is not necessarily effective at radio frequencies. The bonding is mainly for static dissipation. The aircraft accumulates static charge as it moves through the air, and this shouldn't be allowed to build up differentially on separate parts of the aircraft and then discharge suddenly in the form or an arc, causing possible damage or disruption to electrical and electronic systems. Also, bonding helps ensure that lightning currents are passed around sensitive components such as bearings supporting moveable flight surfaces, etc. But the bonding straps have a finite length, and these will not look like electrical short circuits at radio frequencies. Consider a transmission line consisting of two parallel conductors which are not connected to anything at one end and connected to a radio frequency source at the other - if this is an odd multiple of 1/4 wavelength long, then the radio frequency source will see a short circuit, whereas if it is any multiple of 1/2 wavelength long then it will see an open circuit. So similarly with a single wire - the electrical length (in wavelengths) of a bonding wire can make a direct current or low frequency short circuit look like an open circuit at certain radio frequencies. Thus two pieces of metal bonded by a wire strap might actually act as two separate conductors at radio frequencies, i.e one piece of aluminium acts like a patch antenna even though it's part of the aircraft skin. 5. Out of band response of radio receivers. Yes, aircraft electronics are not designed to receive energy from mobile devices (operating at any of the LTE frequencies discussed in 2 above). But how good is the front-end filtering of the receivers based on the designer's assumptions of the proximity of nearby transmitters operating on other frequencies? Here are some examples I've seen: - 14 GHz transmitter completely "flattening" a 12 GHz receiver. This was due out-of-band emissions from the transmitter being high enough in level to swamp the input circuits of the receiver. Solution: install a bandpass filter on the transmitter output which limited the signals at 12 GHz. - A receiver designed for 7 GHz kept failing when a nearby 8 GHz transmitter was operated. The receiver had a very good lowpass filter at its front end designed to reject the 8 GHz signal. The problem was that the 8 GHz transmitter generated some broadband, very low level, spurious emissions all the way down to below 6 GHz. And the receiver designers hadn't counted on energy at that level down to 6 GHz and below coupling into the receiver - their lowpass filter was completely ineffective at 6 GHz. Solution: install bandpass filters (for the respective operating frequencies) on both transmitter output and receiver inputs. - Transmitter on an orbiting satellite caused surface currents to flow in one of the metal panels forming the skin of the satellite body. The joint in the panel caused frequency multiplication which overloaded a receiver operating at a frequency five times higher than the transmitter output frequency! That's a very expensive mistake to make ... None of these transmitters were bad transmitters - all transmitters generate some form of out-of-band spurious emissions, and often the transmitter designer has no control over the nearby environment (e.g. metal structures featuring joints). And the filters on consumer grade electronics are designed to be just good enough to meet the specification ... if the filters are over-designed, then that costs more money, increases the required transmitter power or level of the minimum received signal (all filters exhibit loss, and tighter filters are lossier), etc. In summary, getting into trouble with radio frequency interference is pretty easy to do if all factors aren't considered - especially in multi-transmitter and multi-receiver environments.
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  1342.  @capusvacans  "[Religious adherents] are free to think whatever you want, as long as it doesn't diminish the freedom of others." And herein lies the danger to many in society from those who claim the moral high ground based on their religion. Look at what's happening in the USA nowadays as an example. I have trod a similar path to yours. And I cannot reconcile the professed faith of many members of a Church whose daily actions appear not to reflect the worldly actions of the deity they worship (as recorded some 2,000 years ago). My observations over the years have led me to two conclusions: 1. If Jesus Christ came to Earth today, many Christians wouldn't recognise him - and would reject him outright as a false prophet. Why? Because many Christians - especially in the West - live privileged lives and don't mix with the sort of people Mr. J. Christ would mix with. Christ mixed with the sinners and outcasts of his day, viz. prostitutes, tax collectors, etc - not the privileged, the Romans, Pharisees and Sadducees, etc. 2. The only differences between Western Christians and other theocrats such as the Taliban are their God, their Book, their language, and dress code. (And the weaponry I guess - M4 Carbine vs AK-47.) Otherwise, they share the common goal of a burning desire (no pun intended) to tell other people what to do based on their "enlightened", guided-by-God interpretations of the readings from their particular Book. And both groups seem quite happy with subjugating women, minorities, and adherents of other religions.
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  1578.  @NicolaW72  I recommend that you don't fly on anything anywhere, as there are plenty of "single switches that would kill everyone" on every modern airliner. That's why there's pilot training, checklists, an annunciator that indicates the pressurisation system is operating in manual mode, and then a warning sound that operates when the cabin altitude exceeds the danger level. Let's say you redesigned the aircraft and took this switch away ... how would you have the maintenance personnel conduct pressurisation runs on the ground to check for leaks? Note that these are done after maintenance work on any door (including cargo doors) and emergency exit, and whenever faults are reported, e.g. cabin leaks - so these activities cannot be eliminated if you want the aircraft to be maintained. There would need to be some other "manual" intervention required which allows the outflow valve(s) to be manually operated on the ground ... a different "single switch that would kill everyone" somewhere in the aircraft, maybe this time in the E&E bay where it can't be accessed in flight, so the crew know the switch is there but can't do anything with it during an emergency - that emergency might be failure of the pressurisation controller (i.e. the controller fails, or the sensors feeding it fail, or the wiring connected to the controller fails, etc), which means the aircraft lands pressurised and no-one can open the doors. On one occasion I remember that happening, the crew conducted an emergency landing due to a fire, but the rescue teams couldn't open the doors - the "single switch that would kill everyone" could have been moved to the alleged "kill everyone" position which would've dumped the cabin air back to ambient and - ironically - saved lives. I'd really be interested to know how you would design the aircraft to operate differently so that it can be flown - with and without pressurisation controller faults (faults which can occur while in the air) - as well as maintained on the ground.
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