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How to Jam a Worldwide Satellite TV Broadcast
An anonymous reader submits: "According to an MSNBC article, 'it's simply a matter of aiming a strong signal at the uplink transponder on the satellite and overwhelming the...broadcaster's signals...You need a dish, some power, not too much. You put up a test pattern ... and do a sweep and find the transponder on the satellite you want to jam. It could even be smaller than the standard 6-meter dish. It could be a small dish with a lot of power.' This was apparently how an Iranian satellite television station was knocked off of Loral Skynet's TelStar-12 a few days ago. Loral contacted TLS, a company which specializes in satellite broadcast security, who quickly located the source of the jamming to Cuba."
Spread spectrum is essentially unjammable
Huh? By definition, spread spectrum bounces all over the given band of frequencies in some predetermined patern. It makes it a bit harder to jam, because you'd have to cover all of the frequencies with the jamming signal, but not impossible if the attacker can just jam the whole frequency range.
Furthermore, spread spectrum makes things a whole lot harder on the transmitters on the ground. Let's use a simple example, imagine a satellite with channel space for 6 upbound signals coming from 6 different TV networks that are located at 6 different studios. In simple frequency division, they'd each get 1 slot of bandwidth, and so long as nobody retunes their transmitter to somebody else's frequency it all works. But, in spread spectrum, they'd each be all over the band... unless coordination was very tight between the spreading patern, the 6 sources would keep jamming each other by being on the same frequency at the same moment... you'd need a ton of retransmitting and error correction to get around that.
A sophisticated antenna system will provide steerable nulls in its radiation pattern. Once the source of the interference is localized, the antenna can be adjusted to place the null over the source of interference.
Mea navis aericumbens anguillis abundat
According to company website they use radio interferometry. To do this they need another (relatively) nearby satellite with a similar transponder, which also sees some interference. Then they measure the arrival time difference between the signals bounced from the two satellites, using this they can then triangulate the position to within a few miles.
If you pay them lots of money they'll send out helicopter
(assuming its not in Cuba!) to find the exact antenna causing the problem.
Here's TLS's website. They talk about how they do it.
http://www.tls2000.com/Site/Equip.html
--PatThis isn't likely to happen, specifically.
:) ), unless you take precautions. tune it too low, however, and you encounter signal loss in bad weather.
:). You'd have to actually take control of the satellite (probably not as hard as it sounds, even with modern satellites, really) to get your own signal, and then you'd do it by making it receive a different frequency and you start broadcasting.
Your average satellite receiver is setup to deliberately receive and amplify a particular signal, to make it usable by a decoder.
The satellite LNB (the device at the focal point of a satellite dish) is tuned when installed, and is specifically set to give the decoder a signal of a particular strength. This is usually measured in the order of a particular number of decibells (dB).
Most receivers will actually shut down if you overload them with signal however. It's possible for you to encounter problems when you tune an LNB, and someone goes and jacks up the output level on the satellite for some reason (like, say, they need to use it to broadcast military signals
This means, that on the satellite that's receiving the uplink, you'll find that if you overload it, it'll just shut down the receiver instead of overriding the signal.
Don't let anyone fool you into thinking you can drive everyone nuts by replacing their favorite shows with reruns of the original odd couple
ashridah
"It seems more likely that jamming an Iranian satellite signal would come from the American dishes at the Guantanamo installation than from Cubans."
Armchair punditry at it's worst.
If you'd do some research about NITV The TV station is actually broadcasted from the US into Iran. That's right. National Iranian TV (NITV) is produced in the US. And no, I am not making this up.
NITV, not being state run, has government enemies in Iran for doing things like making fun of the leaders there. So the Mullahs in Iran call the Castro gang in Cuba and get them to do a favor for them.
This is something the US military would not want to block.
Hello there, I would like to clear some things up and shed some light on the matter. (excuse the bad English) Firstly, a satellite related history about Iran:
... anyways). Since the channels mostly show boring old films or even more boring documentaries, most pople have digital satellite receivers and just watch show and Iranian channels.
We have 6 channels. One is news, one is sport and the other four are mixed channels, showing anything from soccer to documentaries to dubbed American films and series (yeah, death to america baby!!) to English films in original language to japanese samurai black and white films to cartoons etc.. you name it. Ofcourse the news biased towards the evils of America and the poor Palestinians getting killed and so on (one interesting thing is that when 5 Palestinians get killed, they are Martyred (and if there are any kids / women in between the killed, they are mentioned loudly, but if a school bus of Jew kids are killed, then "20 zionists were killed"
Satellite Receivers and Dishes are 'illegal' in Iran and every now and then the media's attention is focused on the matter and so the local police bitches about and raids a few houses, taking away their equipment and fining them... then gives up. This has become the norm. Since Tehran (the capital city) has over 14 million in population, going round every house and taking away their equipments was not a feasable task. I have written (at the end of this post) what they have done NOW to get the channels jammed and it seems to be working... 90 cm dishes are the norm here. They're big enough to do the job and yet small enough to be concealed easily. 60 cm versions are also available but you need a *really* good LNB (such as Nokia) to get a good signal. Now on to the NITV matter:
The National Iranian TV station (NITV) is a station based in USA and it mostly broadcasts talk shows and documentaries AGAINST the current regime in Iran so they are America's friend and Iranian government's enemy. Currently, there are 6 or 7 Iranian language satellite channels that can be received in Iran. All are transmitted from "TelStar 12" satellite. About two years ago, the only Iranian satellite channels were NITV and another one I can't remember. Both used to be broadcasted from Hotbird satellite. That
was until their signals were jammed multiple times (after a few months of broadcasting) and at the end they made the decision of moving to TelStar 12. I remember they issued a statement that Hotbird has received jamming signal FROM IRAN that has worked against the Iranian channels and so on... the funny thing is that the Iranian gov. broadcasts 4 or 5 propaganda channels to the very same "hotbird" satellite and they continued to broadcast their programmes even after Hotbird had found about their dirty trick. Don't you think those hotbird guys should have stopped broadcasting their programmes as a result ?
Since then, everyone has had to either add a new satellite dish or just add another LNB to their dish (which is set to Hotbird to get those music shows) and receive the Iranian channels as well. Recently there was a lot of talk in the "Majles" which is parliament about jamming signals being broadcast locally to stop people receive the
channels. And there was debate on whether these signals could be cancerous or not. At the end, they started to send jamming signals while the case remained open in the parliament.
At first, I laughed at the idea because a satellite dish works by concentrating bounced microwaves to a point where the LNB receives them and converts them to electrical signal. But if the government broadcasts signals locally, then the point of concentration would not be at the LNB part and so it shouldn't really matter huh ? Well, I am wrong and they have been successful (up to a certain level) to annoy the hell out of people and in some areas people can't get a signal. The jamming they are using is sweep based. From what I experienced at a friend's house, the sweep signal was on *any* channel