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GPS antenna mods make Starlink terminal immune to jammers

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Re: GPS antenna mods make Starlink terminal immune to jammers

#41

Post by kayodelycaon »

dylan604 wrote: post #15
EA-3167 wrote: post #10

Earlier quoted context omitted.

Right, look at the US' current jammer suite, the AN/ALQ-99, while it has issues it's unbelievably powerful. One of the downsides is that it jams the AESA radars of friendlies in the area, including the plane using the jammer itself. The next gen replacement sounds like an absolute monster too, but without some of the donwsides like the need for a ram air turbine to power it.

> One of the downsides is that it jams the AESA radars of friendlies in the area, including the plane using the jammer itself. So you just lob in a heat seeker at the middle of the noise, and hope. Then again, if you have an airborne source of jamming, you know you have bigger problems following. How much effort do you spend trying to knock out the jamming vs preparing for what is inevitably following? Flying in jamm…

It's even easier than that. You use a missile (or bomb) programmed to lock onto the source of the jamming.

Re: GPS antenna mods make Starlink terminal immune to jammers

#42

Post by mmh0000 »

jandrese wrote: post #26
mezeek wrote: post #11

Question: How come aircraft can so easily get jammed then? They use GPS for precise positioning in flight, so I'm guessing they have the very best antennas...

GPS jamming defense in the US is mostly provided by the FCC bringing the hammer of God down on people who run GPS jammers. The penalties for interfering with navigation signals are severe.

HAMMER OF GOD[1][2][3][4][5]

[1] https://www.fcc.gov/general/jammer-enforcement

[2] https://www.fcc.gov/document/fcc-fines-florida-driver-48k-ja...

[3] https://www.cnet.com/culture/truck-driver-has-gps-jammer-acc...

[4] https://www.fcc.gov/document/fcc-upholds-fine-jammer-used-bl...

[5] https://docs.fcc.gov/public/attachments/DOC-339560A1.pdf

Re: GPS antenna mods make Starlink terminal immune to jammers

#43

Post by cesarb »

kbknapp wrote: post #18
dwighttk wrote: post #12

Earlier quoted context omitted.

Wait, starlink is one way? How does it know what to send?

GPS satellites don't "send" your coordinates to your receiver. Your receiver is just listening to the broadcast signal from several (usually 4+) satellites and based on the strength of that signal determining how far it is from each of those satellites. Which means the receiver is able to triangulate it's own position.

> Your receiver is just listening to the broadcast signal from several (usually 4+) satellites and based on the strength of that signal determining how far it is from each of those satellites.

GPS doesn't use the strength of the signal at all. Instead, each signal contains precise information about the current time at the highly-accurate atomic clocks onboard the corresponding satellite (plus some important metadata about each satellite, including things like their orbit parameters). If the receiver already knew the precise time, it could calculate the distance to each satellite from the difference between the true time and the received time (and the speed of the light), and 3 satellites would be enough to triangulate its position. Since the receiver usually doesn't know the precise time, it needs an extra satellite because there are now 4 unknowns (3 for its position plus 1 for the current time).

(Obviously, that's a very simplified explanation, there are plenty of other things which complicate the calculations.)

Re: GPS antenna mods make Starlink terminal immune to jammers

#44

Post by euler_angles »

nixgeek wrote: post #22
meindnoch wrote: post #20

Earlier quoted context omitted.

>and based on the strength of that signal Wrong. Utterly wrong.

Would you explain why?

By the time the signal reaches your GPS receiver, it is below the thermal noise floor of even amazing receivers. But each GPS satellite has a unique pseudo-random code (called a PRN) that is within the signal. Receivers that listen long enough can pick out the PRN and thus the GPS signal.

I'm no GPS expert, I've read some of the theory had enough of a working understanding to deal with tactical navigation systems, but that was in my past. I remember using El-Rabbany's "Introduction to GPS" text.

Re: GPS antenna mods make Starlink terminal immune to jammers

#46

Post by godelski »

baq wrote: post #9
sandworm101 wrote: post #5

>> IMMUNE TO JAMMERS No. That is not a thing. At most, one can make equipment less susceptible to jamming. Jamming is not like hacking, it isn't a matter of whether an attack works or does not. It cannot be fixed via a patch. Pump out enough energy close enough to the target and even a hyper-directional antenna can be jammed. Have a look at military GPS jammers. They aren't the little dongles that you can buy online…

But how do these jammers work? They can't point at the sky to blind the satellite because there's no receiver; they broadcast from above ground, so in theory putting your receiver in a metal box with the top removed solves the problem?

> But how do these jammers work?

Pretend you're having a conversation. Now pretend you're having a conversation at a concert/club/any loud place. So like this[0]

> so in theory putting your receiver in a metal box with the top removed solves the problem?

You'd think so, but not actually. Think about it this way: you're trying to toss a ball into a cup (or box).

Is it easier or harder if that cup has a wide mouth or a narrow one? Make it V shaped for easier visualization and we'd be talking about the angle of that cone. Obviously the wider one right? The extreme other end of this is like a carnival ball tossing game where the cup is just as big (or they cheat and its smaller) than the ball you're trying to throw in. Now pretend you're trying to make that shot from a moving car. You come from far away and drive right past it and you get more points in this game the more shots you score.

That's analogous to what then satellite is doing. Remember it comes from over the horizon and then passes to the other horizon. You want to maximize your viewing angle because that gives the satellites more chances to make contact. This is more complicated because you need to kinda do this in parallel as you're handing off data collection to the next satellite coming through so the better viewing angle the more chances you have to smoothly negotiate that pass over.

Then there's the whole issue that we're talking about waves instead of particles but I'll let someone else handle that. You can actually find some cool visualizations on the internet about these. See knife edge diffraction.

[0] https://youtu.be/m-YSPHib-kg?t=89

Re: GPS antenna mods make Starlink terminal immune to jammers

#47

Post by exar0815 »

kayodelycaon wrote: post #41
dylan604 wrote: post #15

Earlier quoted context omitted.

> One of the downsides is that it jams the AESA radars of friendlies in the area, including the plane using the jammer itself. So you just lob in a heat seeker at the middle of the noise, and hope. Then again, if you have an airborne source of jamming, you know you have bigger problems following. How much effort do you spend trying to knock out the jamming vs preparing for what is inevitably following? Flying in jamm…

It's even easier than that. You use a missile (or bomb) programmed to lock onto the source of the jamming.

Except the jammer oversaturates your receiver or even burns it out. Or causes it to see ghost targets.

Re: GPS antenna mods make Starlink terminal immune to jammers

#48

Post by dylan604 »

kayodelycaon wrote: post #41
dylan604 wrote: post #15

Earlier quoted context omitted.

> One of the downsides is that it jams the AESA radars of friendlies in the area, including the plane using the jammer itself. So you just lob in a heat seeker at the middle of the noise, and hope. Then again, if you have an airborne source of jamming, you know you have bigger problems following. How much effort do you spend trying to knock out the jamming vs preparing for what is inevitably following? Flying in jamm…

It's even easier than that. You use a missile (or bomb) programmed to lock onto the source of the jamming.

The heat seeker would have problems unless you launched from behind it, which would be problematic if you're launching from the ground, depending on the jamming plane. A steathly plane with the heat sources minimized might not be detected by a heat seeker if launched towards an oncoming source

Re: GPS antenna mods make Starlink terminal immune to jammers

#49

Post by exar0815 »

EA-3167 wrote: post #10
sandworm101 wrote: post #5

>> IMMUNE TO JAMMERS No. That is not a thing. At most, one can make equipment less susceptible to jamming. Jamming is not like hacking, it isn't a matter of whether an attack works or does not. It cannot be fixed via a patch. Pump out enough energy close enough to the target and even a hyper-directional antenna can be jammed. Have a look at military GPS jammers. They aren't the little dongles that you can buy online…

Right, look at the US' current jammer suite, the AN/ALQ-99, while it has issues it's unbelievably powerful. One of the downsides is that it jams the AESA radars of friendlies in the area, including the plane using the jammer itself. The next gen replacement sounds like an absolute monster too, but without some of the donwsides like the need for a ram air turbine to power it.

Fun fact: Airborne Jammers like these might be one of the last places of state of the art technology where the good old vacuum tube is still better than semiconductors.

For large power amplifiers, especially with power and power-density considerations, nothing beats a travelling wave tube.

And on the ground with "unlimited" power and cooling? Well, there's always the Klystron...

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