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Distress Signal Emitted By Flat-Screen TV
pinqkandi writes "CNN is a running a story on an Oregon college student's flat-screen Toshiba TV which was releasing the 121.5 MHz international distress signal. He was unaware of the issue until local police, search and rescue, and civil air patrol members showed up at his apartment's door. Apparently the signal was strong enough to be picked up by satellite and then routed to the Air Force Rescue Center in Virginia. Quite impressive - luckily Toshiba is offering him a free replacement."
It turns out it got stuck on the Lifetime network, so it really was in a state of distress.
I'd originally read this on CNet a while ago.
And the (CNet) article points out something of relevance - with so many new devices and what not, our radio spectrum is increasingly becoming very muddled and interference a lot more commonplace. I wonder if existing regulations would do, or if new ones be required.
Something to think about.
And I wonder how powerful that signal must have been to have caused such interference. Either that, or the receiving satellites must be having one hell of a resolution capability.
The latter also provides some food for thought - if their satellite equipment is sensitive enough to find out interfering signals from a Television set, wonder what else they can (and do) eavesdrop
What kind of Tempest attacks do take place, I wonder. Satellite Van Eck Phreaking?
~adjusts tinfoil hat~
"So if you need to transmit an international distress signal then stop by any local store and turn on a Toshiba flat-screen TV. We should be able to locate you in a matter of minutes."
. . . this is the last time that guy is a smartass to the salesman at Best Buy when buying a TV, though!
The TV probably gained sentience and realized the crap that was being fed to it. It responded in the only way it knew how.
Yeah, this gives me an idea for a new TV feature. Whenever you lose the remote control, it sends out a destress signal until a search team shows up to find it. Now that's service!
The Dude abides.
You've gotta wonder what that guy was doing to that poor TV. (and whether the teletubbies were involved...)
It's well known that certain hardware hacks for Dishnetwork receivers emit this same frequency.
What a coincidence that a college student (no money) would be doing something technical (education) to get TV for free.
If you could be told what you can see or read, then it follows that you could be told what to say or think - BoC
"Please Help! My plasma is burning out! I'll need to be replaced in 2 years!"
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It scares me that it took them almost a year to get the distress signal. Remind me never to get lost at sea.
Free Flat Screen
You'll be waiting ~ 3-4 hours before somebody comes and finds you, if they are really good at it.
First, wait for a satellite pass will notify the Air Force. They will then verify it if they can, contact the FAA for missing flights, etc. The next call goes out to the Civil Air Patrol wing that is responsible for that area. They in turn will normally notify the local authorities who are in charge of S&R. Of course, when you broadcast on 121.5, that sound is audible in every Airtraffic Control center that it can reach.
Once they have done this, they will organize a ground based S&R party and try get a general area of where the signal is coming from. Remember, this is non-directional, so they have to go to a few different places, measure the direction and approx. strength of the signal, and then they will know about where it is. Triangulation sucks, esp. with trees and mountains.
Once they have done this, they'll start their search. Oh, if it's at night and it's not somewhere near them, they'll wait until the morning. Hope you don't keel over at night.
Finally, once they triangulate it, they home in on it. In this case, they homed it to an apartment. Questioned the guy, and went back out into the hallway and confirmed it was coming from there.
So, do you REALLY want a 121.5 ELT locator? I would get one of the new 406mhz ones which are digitally encoded with your information. In addition, some models offer GPS in them that will transmit your GPS coordinates when it sends it. Much nicer and easier to find.
Oh, and I'm not a CAP member any more. But, it was fun while I did it. Not enough time now, but, maybe after I'm done building my airplane I'll have time.
On October 2, the 20 year-old college student was visited at his apartment in the small university town by a contingent of local police, civil air patrol and search and rescue personnel.
[...]
Authorities had expected to find a boat or small plane with a malfunctioning transponder, the usual culprit in such incidents, emitting the 121.5 MHz frequency of the distress signal used internationally.
Why did they expect to find a boat/plane in a apartment building?
^^
The frequency of the NTSC color subcarrier (the TV color system used in analog video standards in North America and Japan) is defined as exactly 5 MHz times 63/88. That works out to 3.579545454.... (infinitely repeating 54's) MHz. The horizontal scanning frequency is then defined as a 2/455 times the color subcarrier frequency. That works out to 15734.26573426.... (infinitely repeating 573426's) Hz (very nearly the original monochrome horizontal frequency of 15750 Hz). This is where the problem lies. 121.5 MHz divided by 7722 is exactly the same frequency as the horizontal in an NTSC color video signal.
The 7722nd harmonic shouldn't really be that strong, right? Usually not. But the harmonics can get to be very strong overall even at such high orders when dealing with modulating the high voltages needed for the horizontal sweep. There should be some low pass filters that prevent that from getting into the VHF range. But if the filters are absent, or were incorrectly installed, or were damaged somehow, and if some wires formed some resonance near 121.5 MHz (like wires going out to cable, speakers, etc) ... a wavelength of about 2.47 meters or 8.1 feet ... it is possible that harmonic, and a bunch of others near it, could be enhanced and radiated.
The local oscillator in the tuner is a remote possibility. But it would have to be tuned to be receiving a video carrier at 75.75 MHz based on the common satndard of 45.75 MHz for the IF stage in the tuner. But there is no TV broadcast on that frequency in the US ... though I could not rule out there being something on that frequency from a cable system. Still, it wouldn't be an expected place for a TV to tune to. But if the TV has a non-standard IF frequency, the local oscillator getting on 121.5 MHz by some expected channel could be possible. Those leak a lot and it's how the snoops can tell what channel you are tuned to by spying on the RF emitted from your house.
If just this one TV had the problem, then apparently it must be a manufacturing defect or shipping damage (or maybe user damage or tampering). If it were a design problem, I'd sure we'd hear more about it. That probably rules out the CPU clock frequency.
now we need to go OSS in diesel cars
Meanwhile... IT'S A FREAKING TELEVISION! "TV" and "crash" should not be sharing the same sentence.
Information wants to be free.
Entertainment wants to be paid.
You just want to be cheap.
If you want to do wiring yourself, here's what you should be looking for:
Hope that helps