# Any engineers on the boards here?



## Driver_1 (May 22, 2009)

What does your TV transmit?

So this morning I'm reading a blog about OnStar and FBI lawsuit, and the blogger says he's not worried that his TV can do the same things as his OnStar-equipped vehicle.

Then I remembered a story I read many years ago:



> Strange News - October 19, 2004
> 
> Ore. Man's TV Emits Int'l Distress Signal *
> *
> ...


This transmitter was not in this TV by design; it's just a tumor. Right???

...and this morning I found this:


> Originally Posted by Some /. nerd
> 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.
> 
> [Redacted due to copyright violation - original story can be found here]


Can anyone elaborate on this just a little here?

One morning about '96 or so, I was chatting some guy up in my apartment parking lot while I was in college. He said he was a sub-contractor for the local cable company, and he was reading a device that showed if any apartment had satellite AND cable. He was IN HIS TRUCK.

What info DOES get transmitted by our TV - or other media devices?


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## dirtyblueshirt (Dec 7, 2008)

Driver_1 said:


> What does your TV transmit?
> 
> So this morning I'm reading a blog about OnStar and FBI lawsuit, and the blogger says he's not worried that his TV can do the same things as his OnStar-equipped vehicle.
> 
> ...


As far as the cable issue, if there's some improperly shielded (and older) cable, there is a measurable RF signal "leakage" readable at short ranges. Modern digital signals and cables shouldn't have this issue.

As far as the TV, it's quite possible a capacitor or other component in the TV was malfunctioning. Due to the nature of mass production, these instances, although certainly very rare, can occur from time to time if a component isn't precisely tuned.

One time I was at an Army-Navy Surplus store and the guy behind the counter swore up and down the government uses the speakers in out TVs as reverse microphones to monitor all of our in-home conversations. I'm sure he had a tinfoil hat somewhere, too.

Besides, there's much more effective ways to conduct surveillance.


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## SayWhat? (Jun 7, 2009)

> but came back when they narrowed the location of the signal to a wall in van Rossman's hallway,


I seriously doubt that part. Within a few hundred foot radius maybe, but not to a specific wall in a house.


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## dmspen (Dec 1, 2006)

The emergency beacons used by boats, planes ets, are 121.5, 243, and 406.5 Mhz. If the TV is putting out a signal at 121.5, it could get picked up. The NOAA POES (TIROS) satellites have very sensitive receivers. The distress beacons have to be low power so they can run for an extended period on battery power.
I worked as a Test Engineer on a TIROS satellite. When we checked out the receivers on the satellite while it was on the ground, we could identify all kinds of emergency beacons since there was a Coast Guard Search and Rescue Center close by. They also contacted us when we turned our test set on because they picked up our beacon. Oddly enough, we also picked up a local TV station!

Why a TV would spit out those particular frequencies is the real mystery here.


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## kenglish (Oct 2, 2004)

The digital clock oscillator (which "clocks" all the microprocessor functions) is usually the culprit in most electronics.

I have a couple of FTA satellite receivers, and once "fox hunted" one of them right back to my own living room, when I discovered a signal on the 121.5 and 243 MHz International Distress Frequencies. It was a warbling tone, much like an ELT would put out.


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## peano (Feb 1, 2004)

Perhaps van Rossman was using an illegal device in his satellite receiver.

http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf05757.html


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