Timeline for Why would a time signal receiving watch have an airplane mode?
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 26, 2016 at 0:23 | comment | added | Aaron D. Marasco | This is also how radar detector detectors work in states like Virginia. | |
| Jul 25, 2016 at 18:49 | comment | added | Chris Stratton | Non-trivial transmitters typically also use heterodyne frequency conversion, yes, but the described incident however seems to not be about leakage from either, but rather about mixing. Likely, with both transmitters in close proximity to the receiver, their signals are strong enough to put parts of the receiver circuitry into a non-linear regime where mixing between input signals would occur. In contrast, in the usual case with transmitters attenuated by distance, linearity means it is possible to hear two transmitters at once - such an ability to interrupt is allegedly why ATC stuck with AM. | |
| Jul 25, 2016 at 16:22 | comment | added | David | It's called "heterodyne interference" because the effect is the same: when two transmitters are simultaneously operating on the same channel, their carrier frequencies usually don't match precisely. So the difference between the two carriers turns into a loud audible tone that drowns out the intended signal. | |
| Jul 25, 2016 at 16:18 | comment | added | Dmitry Grigoryev | @David It seems to blame "three-second-long whistling sound (or heterodyne)". Are heterodynes used in transmitters as well? | |
| Jul 25, 2016 at 16:16 | comment | added | David | @DmitryGrigoryev: According to the article, that crash was caused by interference from a simultaneous transmitter, not from a receiver. | |
| Jul 25, 2016 at 14:52 | vote | accept | Geier | ||
| Jul 25, 2016 at 11:47 | comment | added | Dmitry Grigoryev | Note that interference from receivers had actually contributed to the deadliest airplane crash in history by masking the stand by for takeoff command with heterodyne whistle. | |
| Jul 25, 2016 at 9:08 | comment | added | Oscar Bravo | This is the correct answer. For an example of how useful local oscillator emissions can be, this was the method used by Spycatcher Peter Wright and his team of MI5 boffins to search for KGB illegals listening in to Moscow in Cold War London. It is also, reputedly, the basis of the notorious TV detector vans in the UK. | |
| Jul 24, 2016 at 17:44 | history | answered | Chris Stratton | CC BY-SA 3.0 |