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Launch window
2010-Feb-12, 09:10 AM
Seems to be a few rumors floating around the net that the Iranians have somehow stopped satellites from broadcasting into the Middle East.
How would they go about this? Did they do it net style hacking or is it a matter of getting one of their big dishes, pointing it into space, blasting up the wattage and jamming a certain frequency?

and please remember the rules * no politics on baut *
I know it might be tempting to say something on this topic but lets not get this one locked

Any more info on this?
How would low tech nation like Iran go about jamming/blocking a satellite

NEOWatcher
2010-Feb-12, 01:37 PM
Seems to be a few rumors floating around the net that the Iranians have somehow stopped satellites from broadcasting into the Middle East.
Rumors. :rolleyes:
If that had happened, I would think that there would be plenty of civilians that would experience the issue. And; being that there are many reporters among those civilians that rely on satellite communication, it would be all over the news. (Using other methods of communication of course)

As far as the technology, I don't know, but it's an interesting question.

Launch window
2010-Feb-12, 02:20 PM
Iran condemned by BBC, VoiceOfAmerica and Deutsche Welle (http://www.businessweek.com/news/2010-02-12/iran-condemned-by-bbc-voa-for-blocking-broadcasts-update1-.html)


The “deliberate act of jamming” contravenes international broadcasting agreements, the three media organizations said in a joint statement sent by e-mail today....
...The three broadcasters said their services across Europe and the Middle East are being affected as Iran interferes with their signal through the Hotbird satellite.

NEOWatcher
2010-Feb-12, 02:34 PM
Iran condemned by BBC, VoiceOfAmerica and Deutsche Welle (http://www.businessweek.com/news/2010-02-12/iran-condemned-by-bbc-voa-for-blocking-broadcasts-update1-.html)
Interesting, I guess it's not a big deal in our hemisphere.
And, it seems it's been going on a while.
June '09 BBC press release (http://www.bbc.co.uk/pressoffice/pressreleases/stories/2009/06_june/19/persian.shtml)

korjik
2010-Feb-12, 05:50 PM
Seems to be a few rumors floating around the net that the Iranians have somehow stopped satellites from broadcasting into the Middle East.
How would they go about this? Did they do it net style hacking or is it a matter of getting one of their big dishes, pointing it into space, blasting up the wattage and jamming a certain frequency?

and please remember the rules * no politics on baut *
I know it might be tempting to say something on this topic but lets not get this one locked

Any more info on this?
How would low tech nation like Iran go about jamming/blocking a satellite

All you need is a transmitter on that same frequency. Even a relatively modest transmitter with a good line of sight can jam a pretty bit area. The comm sat has to transmit from geosync orbit, while the jammer only needs to go 10s of miles.

Heck, it is even easier, since all the satt dishes are pointing in the same direction. One decent sized transmitter on a cell tower and BAM, no satt signal.

Larry Jacks
2010-Feb-12, 09:22 PM
All you need is a transmitter on that same frequency. Even a relatively modest transmitter with a good line of sight can jam a pretty bit area. The comm sat has to transmit from geosync orbit, while the jammer only needs to go 10s of miles.

Heck, it is even easier, since all the satt dishes are pointing in the same direction. One decent sized transmitter on a cell tower and BAM, no satt signal.

Actually, that wouldn't work very well. Those satellite antennas pointing up in the sky are very directional, typically with a beamwidth of a few degrees. It wouldn't be all that easy to jam them with ground antennas because the signal is coming in from the wrong direction. You might be able to get some signal in via a sidelobe but that isn't very easy.

A more effective approach is to point a ground antenna at the satellite and jam the uplink frequency.

korjik
2010-Feb-12, 10:16 PM
All you need is a transmitter on that same frequency. Even a relatively modest transmitter with a good line of sight can jam a pretty bit area. The comm sat has to transmit from geosync orbit, while the jammer only needs to go 10s of miles.

Heck, it is even easier, since all the satt dishes are pointing in the same direction. One decent sized transmitter on a cell tower and BAM, no satt signal.

Actually, that wouldn't work very well. Those satellite antennas pointing up in the sky are very directional, typically with a beamwidth of a few degrees. It wouldn't be all that easy to jam them with ground antennas because the signal is coming in from the wrong direction. You might be able to get some signal in via a sidelobe but that isn't very easy.

A more effective approach is to point a ground antenna at the satellite and jam the uplink frequency.

You do get around an effective 10^8 power boost cause of range, so even with a low efficiency you should be able to get something.

On the other hand, that is a pretty passive system. If people are complaining about jamming, you are prolly right. Tho, why do you need an uplink for a commercial broadcast?

kleindoofy
2010-Feb-12, 10:36 PM
If I recall correctly, the large majority of Iranians live in or around Teheran, so they won't need to block the entire country to be effective.

I'm no engineer and have no idea what it would take to make reception difficult in a major city, but if it's possible, just blocking out Teheran would be enough to virtually keep the majority of the population in the dark.

HenrikOlsen
2010-Feb-13, 12:10 AM
You do get around an effective 10^8 power boost cause of range, so even with a low efficiency you should be able to get something.

On the other hand, that is a pretty passive system. If people are complaining about jamming, you are prolly right. Tho, why do you need an uplink for a commercial broadcast?
The satellite needs to receive what it's broadcasting from somewhere:)
But that's probably also received by a rather directional antenna.

Locomotion
2010-Feb-13, 12:32 AM
If I recall correctly, the large majority of Iranians live in or around Teheran, so they won't need to block the entire country to be effective.

I'm no engineer and have no idea what it would take to make reception difficult in a major city, but if it's possible, just blocking out Teheran would be enough to virtually keep the majority of the population in the dark.

I would call the 20% or so living in or near Tehran a small minority, rather than a large majority.

Larry Jacks
2010-Feb-13, 01:10 AM
You do get around an effective 10^8 power boost cause of range, so even with a low efficiency you should be able to get something.

On the other hand, that is a pretty passive system. If people are complaining about jamming, you are prolly right.

Parabolic antenna feeds are designed to receive the signal from a specific direction. Even with a fairly powerful transmitter on the ground, if you want area coverage, you have to go with an antenna that probably has an omni-directional radiation pattern, meaning it has little or no gain. I don't know if a signal coming in from the side would be powerful enough to do the job.

Tho, why do you need an uplink for a commercial broadcast?

To overpower the signal that the satellite is supposed to relay. Satellites don't originate the programming, they receive the programming, amplify it, and retransmit it back down. If you overpower the original signal with a jamming signal, the people on the ground don't get to see what was intended. This has happened before.

John Jaksich
2010-Feb-13, 01:20 AM
Despite who or what (has or hasn't been) jammed---operatives of the West are most certainly aware of it--- I am sure we will definitely hear more of it in the coming days if it is true? However, is it not the case that some transmissions are encrypted (?) or broadcast at frequencies that are not so readily jammed by off- the - table technology. Putting a rocket into space is hard--but to possess the capability of jamming the right frequency is (IMHO) a completely different ball of wax. I don't always like to speculate about Mid-East policy--that part of the world has proved to be too pivotal to raise one'e ire about.

John Jaksich
2010-Feb-13, 01:24 AM
Thanks for the information, Larry....

korjik
2010-Feb-13, 08:21 AM
You do get around an effective 10^8 power boost cause of range, so even with a low efficiency you should be able to get something.

On the other hand, that is a pretty passive system. If people are complaining about jamming, you are prolly right.

Parabolic antenna feeds are designed to receive the signal from a specific direction. Even with a fairly powerful transmitter on the ground, if you want area coverage, you have to go with an antenna that probably has an omni-directional radiation pattern, meaning it has little or no gain. I don't know if a signal coming in from the side would be powerful enough to do the job.

Tho, why do you need an uplink for a commercial broadcast?

To overpower the signal that the satellite is supposed to relay. Satellites don't originate the programming, they receive the programming, amplify it, and retransmit it back down. If you overpower the original signal with a jamming signal, the people on the ground don't get to see what was intended. This has happened before.

I see now. Hitting the satt receiver is going to be a much smaller angle difference than trying to hit the ground receivers from the ground.

I was thinking that the uplink would be more directional, and it very well could be, but the angle difference from opposite sides of the planet is probably less than the angle difference of trying to hit a ground reciever from the ground.

Delvo
2010-Feb-13, 01:02 PM
A powerful enough radio/radar (or even raser) blast would be able to not merely jam a receiving radio system, but even damage it. Then the effect is permanent, instead of only lasting until you turn off your jamming machine.

Larry Jacks
2010-Feb-13, 07:02 PM
Most communications satellites that I'm familiary with have limiters to prevent any permanent damage from a too-powerful uplink. Keep in mind that the RF power level at the satellites is on the order of -90 to -110 dBm. Even if they blasted an extremely powerful uplink signal, it's still likely on the order of microwatts or less. All you have to do is to saturate the receiver to overwhelm the original signal.

captain swoop
2010-Feb-13, 09:01 PM
A powerful enough radio/radar (or even raser) blast would be able to not merely jam a receiving radio system, but even damage it. Then the effect is permanent, instead of only lasting until you turn off your jamming machine.

To paraphrase Black Adder. 'Know you of such a Radio or Laser?'