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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

#51

Post by netsharc »

sandworm101 wrote: post #25
kbknapp wrote: post #18

Earlier quoted context omitted.

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.

Strength of signal isn't used because strength is an unreliable measure of distance. The amount of atmosphere the signal passes through, reflection/refraction and all manner of weather effects will modify a signal's strength. So the sats transmit a pulse at a pre-agreed time and the receivers use the timing that they receive the signal as the measure of distance.

Pre-agreed time? Don't the satellites pulse a "The current time is x" signal?

With signals from 4 satellites one can triangulate oneself in 3D space, with 5 signals, in 4D! (3D + time). I once did the math and astounded myself that it worked.

Re: GPS antenna mods make Starlink terminal immune to jammers

#52

Post by [deleted] »

cesarb wrote: post #43
kbknapp wrote: post #18

Earlier quoted context omitted.

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…

[deleted]

Re: GPS antenna mods make Starlink terminal immune to jammers

#54

Post by Terr_ »

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…

> So you just lob in a heat seeker at the middle of the noise, and hope.

There's already another category of missile for that:

https://en.wikipedia.org/wiki/Anti-radiation_missile

Re: GPS antenna mods make Starlink terminal immune to jammers

#55

Post by [deleted] »

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…

[deleted]

Re: GPS antenna mods make Starlink terminal immune to jammers

#56

Post by TaylorAlexander »

auspiv wrote: post #27
thrtythreeforty wrote: post #23

Does Starlink have a mode where you can manually tell it its lat/long? For a semi-stationary receiver, surely that would be a better way to bootstrap a connection.

I'm currently messing around with a u-blox timing chip, the LEA-6T. It (and many other slightly-above-consumer grade u-blox chip) has a "survey-in" mode, where you tell it "yes, you are stationary" and it essentially averages into a fixed location. This was a $30 chip from China and it gets to 4cm accuracy in 10 min with a $10 antenna. Do that once and you have a location. If the chip reboots, you can either survey-i…

Survey-in won’t help if your system is being jammed.

Re: GPS antenna mods make Starlink terminal immune to jammers

#57

Post by sandworm101 »

netsharc wrote: post #51
sandworm101 wrote: post #25

Earlier quoted context omitted.

Strength of signal isn't used because strength is an unreliable measure of distance. The amount of atmosphere the signal passes through, reflection/refraction and all manner of weather effects will modify a signal's strength. So the sats transmit a pulse at a pre-agreed time and the receivers use the timing that they receive the signal as the measure of distance.

Pre-agreed time? Don't the satellites pulse a "The current time is x" signal? With signals from 4 satellites one can triangulate oneself in 3D space, with 5 signals, in 4D! (3D + time). I once did the math and astounded myself that it worked.

If there is no agreed time then you don't know when the signals were sent and cannot make any sense out of the signal. They all have to send either in unison or according to a predetermined schedule. The synced clocks set that schedule.

Re: GPS antenna mods make Starlink terminal immune to jammers

#58

Post by sandworm101 »

looofooo0 wrote: post #29
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…

Atomic clock and hard coded GPS Location for the win?!

Good luck syncing a clock at a random location on the ground with one in orbit. In a warzone. Without a connection to the sat with which you are trying to sync.

Re: GPS antenna mods make Starlink terminal immune to jammers

#59

Post by lazide »

BHSPitMonkey wrote: post #53
CrzyLngPwd wrote: post #45

Surely, a satellite in orbit could easily jam Starlink boxes on the ground.

Maybe, but unless your goal was to deny service to a small, fast-moving window of the earth's surface you would need quite a lot of these.

If I was a nation state adversary, I’d put pretty high on my TODO list getting a handful of jamming satellites with a decent power supply at geostationary locations above all my adversaries.

Since a single geostationary satellite has line of sight covering about 1/3 of the planets surface, I bet if they had a decent sized reactor onboard and a well thought out transmitter/antenna array, the ROI would look pretty good.

And I’m just some random punter.

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