Hacker News Reader

Comment by sippeangelo | Hacker News Reader

The theory that they broadcast communication on a band near GPS in order to discourage jamming of their early warning system sounds likely. Flexing the ability to jam GPS is pointless, since it's obvious that any state actor who has military satellites in orbit has considered this option or have the capability already. Therefore, the disruptions must either be regular tests of the capability, or just actual communication. Right?

View on HN

> The theory that they broadcast communication on a band near GPS in order to discourage jamming of their early warning system sounds likely.

Is it? If it is an early warning system, could it be jammed briefly so it would fail to warn, couldn't it? It will be a global disruption of GPS, but a brief one and I'm sure people wouldn't be concerned of it due to other news.

> Flexing the ability to jam GPS is pointless

Do you believe that cutting sea cables is a sensible action? Or sending drones to neighbors? It is what they call "hybrid asymmetric warfare", I'm not sure how it is supposed to work, but presumably it may let them take over the world or something.

Probably they just strive to normalize deviations, to boil frog slowly. When people become used to some stupid actions they widen their repertoire, until everything short of tanks crossing the borders became just normal news noise nobody reads twice.

AKA Salami Tactics, famously referred to in the UK sitcom "Yes, Prime Minister"

https://en.wikipedia.org/wiki/Salami_slicing_tactics

Presumably the missile needs GPS to hit the target so if you jam right when the missile is coming in the missile will miss so you can't really jam the warning

Also if you broadcast noise when your missile is about to hit then your own jamming signal acts as an early warning as well, although I guess it wouldn't provide location.

ICBMs don’t rely on GPS. They are typically self-guided and use a blend of their known launch location, inertial navigation using gyroscopes, celestial navigation (yes, looking at stars), and a few other techniques.

US weapon systems have never relied on GPS for guidance. Some will accept GPS corrections to the primary inertial guidance system but those corrections will be rejected if they deviate more than a few meters from the inertial guidance. US missiles in particular use precision terminal guidance which doesn't involve GPS at all; in these systems GPS would only be used to correct mid-course guidance.

There has been anecdotal evidence for years suggesting that the latest US inertial guidance technology is sufficiently precise and accurate that GPS correction no longer adds value.

I do not think that is correct. For example, Excalibur [1] relies on GPS and proved to be quite inefficient in Ukraine. Russia figured out how to jam them in a few months.

[1] https://en.wikipedia.org/wiki/M982_Excalibur

This isn't true for US made weapons. They explicitly do not use GPS because it is the first thing to go in a war

> Flexing the ability to jam GPS is pointless, since it's obvious that any state actor who has military satellites in orbit has considered this option or have the capability already.

Forget "state actors", truck drivers have taken out entire airports with GPS jammers:

* https://www.cnet.com/culture/truck-driver-has-gps-jammer-acc...

People like the Resilient Navigation and Timing Foundation have been trying for years to get some kind of GNSS backup accepted:

* https://rntfnd.org

China has certainly put their money into resiliency (both navigation and timing):

* https://www.gpsworld.com/china-completes-national-eloran-net...

* https://rntfnd.org//2026/03/19/china-has-built-a-triad-of-sa...

* https://rntfnd.org/2023/11/28/china-eloran-used-for-critical...

Some folks are certainly cluing in: South Korea has (e)Loran and the UK and France are joining up with them:

* https://rntfnd.org/2025/04/30/the-uks-system-of-systems-appr...

* https://rntfnd.org/2025/11/12/s-korea-leads-meeting-with-u-k...

The US still has a fairly robust network of VOR's / VOR with DME / VORTAC stations. Good for navigation, but there's no timing component, beyond what's inherent in how they operate.

Admittedly, that'll never be of use outside aviation as its line-of-sight only. But if the sun threw a Carrington event (or worse) at us, I think a lot of western aviation could carry on.

> The US still has a fairly robust network of VOR's / VOR with DME / VORTAC stations. Good for navigation, but there's no timing component, beyond what's inherent in how they operate. Admittedly, that'll never be of use outside aviation […]

I'm aware of the FAA's MON, Minimum Operating Network.

Exactly: that doesn't help boats. Or people in cars. Or farmers:

* https://www.deere.com/en/technology-products/precision-ag-te...

It doesn't help those that use GNSS for precise timing (TCXOes can only 'free run' for a finite amount of time before drift compounds 'too much').

A lot of these were getting dismantled until quite recently, but given recent developments they should obviously be kept

> A lot of these were getting dismantled until quite recently, but given recent developments they should obviously be kept

The FAA has always planned for keeping a non-GNSS-based infrastructure:

* https://www.faa.gov/air_traffic/flight_info/aeronav/acf/medi...

* https://www.federalregister.gov/documents/2012/08/21/2012-20...

* https://download.aopa.org/epilot/2012/120112VOR-MON-White-Pa...

* https://flighttrainingcentral.com/2017/03/legacy-navigation-...

Iridium has launched its own alternative positioning and timing system now https://www.iridium.com/iridium-pnt

It's wild how far Motorola has fallen.

GPS L1 is at 1575 MHz, Iridium is (AFACIT) at 1626 MHz: that's 50 MHz over.

* https://gssc.esa.int/navipedia/index.php/GNSS_signal

* https://insidegnss.com/something-old-something-new/

* https://en.wikipedia.org/wiki/Iridium_satellite_constellatio...

If you're jamming on L1 I don't think it's that much more difficult to jam a little bit over as well.

Celestial Navigation is also doable even in daylight nowadays, e.g. https://sodern.com/en/ranges/astradia

It's been doable since the 1940's.

https://patents.google.com/patent/US2981843A/en

Will that come as an option for my RAV4 or F-150? How about my Cessna?

Will it help keep my NTP/PTP masters sync'd?

There is definitely value in having a demonstrated as opposed a simply supposed capability, though. And actions that are 'almost-certainly-but-not-completely-provably-us' is very much something Russia likes to do.

(One question I would have about the comms theory is whether the amount of power being used would be reasonable for that use-case. Jamming tends to be much higher power than just communicating, but also GNSS signals are very low bandwidth as comms channels go)

> One question I would have about the comms theory is whether the amount of power being used would be reasonable for that use-case. Jamming tends to be much higher power than just communicating, but also GNSS signals are very low bandwidth as comms channels go

GPS is suprisingly low power. I believe the satellites themselves transmit between 20W and 50W, and in general the signal is quieter than the background noise threshold. It's only by correlating with the PRNG stream [1] that the data signal can be detected at all [2].

[1] The PRNG stream is 1023 bits at 1.023Mbps, so repeats every 1ms, and only autocorrelates with the correct stream when they are aligned. When the streams are not aligned, the data looks like random noise, and each transmitter has a different LFSR configuration to provide a different sequence such that each stream has a low level of correlation with another.

[2] The PRNG stream bits at 1.023Mbps are exclusive-or'd with the data stream at 50bps, so when the decoder is using the correct PRNG and sequence offset, exclusive-or'ing with that produces detectable long pulses at the expected 50bps.

FWIW this is how almost every communication system works. They're all weaker than background noise (e.g. sunlight) but you extract them by correlating with some kind of carrier signal (often but not always a sine wave)

Err what?

No, conventional radio broadcasts can be received with a low noise amplifier and a tuned filter.

The received GPS signal, at ground level, is lower than the thermal noise floor. And the 1.023MHz code is modulated on the RF carrier anyway.

> and a tuned filter

So correlating it with a sine wavelet?

No? Old AM radio required only rectification. You can receive it with accidental diodes.

You do generally need a tuned filter before the rectification, unless you have an extremely large signal dominating the local airwaves. Which is precisely the parent poster's point: with RF you are almost always doing something to demodulate the signal. Whether you are doing it with a sine wave or something more complicated is not that fundamentally different. (and if you're looking at a spectrum analysis, that is looking at the radio signal from the point of view of that sinusoidal modulation scheme, so you will see such signals 'above' the noise floor more readily than something using a different modulation).

I'd argue that "correlation" is an accurate description of what you're doing with Gold codes - you're testing the known sequence of the output of a PRNG against the received signal, and only accepting it when the data correlates, otherwise you're adjusting the offset and trying again until you find a high correlation (strong +ve and -ve spikes) or you give up and assume there's no transmission. There's nothing in the received signal that tells you there is a real signal there at all, without correlating against every possible offset.

If you compare that to the majority of radio transmissions modulated on a sine wave carrier, there is a clear signal there and you don't need to correlate anything to tell you that, and you don't need to keep trying different offsets - you can just demodulate using a carrier of the correct frequency and the result is correct, just with a slight phase shift relative to the local carrier and which probably isn't even relevant in the frequency domain of the signal.

The key point to me is the trying repeated offsets to try to pick out a signal well below the noise floor, and choosing the offset that provides the best correlation, compared to demodulating a very strong signal that's obviously there by just adding a carrier. The latter could be done using "correlation" if you're implementing an SDR, but it doesn't have to be, and most radio hams would prefer to think of it as a simple analogue operation instead.

A strong signal 'that's obviously there' is only obviously there after you've already filtered it to some extent. If you were to look at the raw broadband RF environment on a scope you very much would not see the vast majority of signals there. And when you're demodulating you do often need to tune the phase and frequency of the carrier you're demodulating with, as well. GNSS signals are just generally quite low bandwidth and so that process takes a while.

Not to say that such codes aren't a neat trick, but it's useful to consider that these are in many ways the same thing.

By "obviously there", I meant take some old analogue receiver and twiddle the tuning knob. The vast majority of radio transmissions are many orders of magnitude louder than the noise floor. They are very obviously there.

Tune your SDR radio down to 1.023MHz, you'll see nothing there at all. The signal is about 20dB below the noise floor. The only way you can pick out anything at all is by correlating it against the PRNG with the correct offset in the sequence.

The GP post (to be fair, I should have replied to the post 2 higher up) was arguing that all signals are weaker than the noise floor and demodulating using a carrier was exactly the same thing. It is in one way, but also not in another - in that you need to keep trying different offsets in the PRNG sequence until you find a correlation. That's why I think "correlation" is a sensible term for Gold Codes, but "demodulation" is better for signals modulated by a sine wave carrier.

What you're describing is correlating the received signal with complex sine wavelets of various frequencies.

You also need an accidental antenna. A tuned one that preferentially receives certain sines. Or else you are receiving sunlight with a solar panel.

>Flexing the ability to jam GPS is pointless

No, Russia does these "tests" all the time to see and gauge the reactions. Ex flying just a bit into EU airspace.

https://euromaidanpress.com/2026/06/05/nato-fighters-interce...

Unless the actor happens to be a state that puts a great deal of emphasis on flexing & appearances regardless of how pointless it is

Even if that's for communication, repurposing it for mass jamming shouldn't be that hard. It already has this effect. Unless it's low power satellites that wouldn't be able to sustain radio signal in anything longer than short bursts.

Why these capabilities, if they exist, were not used to send Iranian drones to a wrong target? Maybe because they do not exist. Israel definitely would be happy if thousands of drones were rerouted to a neighbour country or into the sea.

Are there any credible reports of Iran hitting any intended target smaller than a city? Because the drone doesn't need to have GPS for that.

American AWACS bombed on the ground, that is smaller than a city.

The flexing seems stupid, but also if it's a communication channel, they have given themselves away (just as if they were flexing with the jamming).

Or actual jamming mistargeted for some reason, or used because it was deemed necessary.

Repeatedly, over years, only for 2 to 5 seconds at a time? Seems unlikely

yeah, I have to admit I was commenting on possibilities here without having gone into the article yet -- having now looked for real, I agree that the disruptions don't seem very useful for actual jamming and repeatedly like this for years across satellites and bands in this specific way doesn't make sense for some mistaken targeting either.

There is a very good reason to do this. Suppose you had a device that would make the shoplifting detectors at stores go off. The first time you did it everyone would get hassled. And the second time and so forth. But if you kept doing it eventually the employees would stop caring. Then you just walk out the door with your stuff.

Reply on news.ycombinator.com