Some ranges are set aside for GPS/GNSS: https://gssc.esa.int/navipedia/index.php?title=GNSS_signal
Some are monitored by the SMAP satellite: https://en.wikipedia.org/wiki/Soil_Moisture_Active_Passive
(Also in the L-band are all sorts of other things. A lot of cellular bands, known in the US as PCS and AWS, and more. Several different sat-phone systems. ADSB in 1090 is juuuust inside L-band. And more...)
All transmitters produce a bit of out-of-band interference, beyond where they meant to transmit. This is filtered to reduce it to a certain level below the intentional frequency, but filters aren't perfect. So when someone tries to jam GPS or other services, they inevitably bleed some energy into neighboring allocations too, some of which seems to be being picked up by SMAP.
Note that SMAP's passive radiometer doesn't have pinpoint spatial resolution, 36km is stated. This means it's listening to a pretty significant patch of ground at any given time, so for a source to be picked up among all that, it's got to be pretty loud. It also means that attributing the source is limited in precision, you can get to city level but not city-block level from this data.
There’s a reason that microwaves (the cooking instrument, named after the rough band of RF frequencies it uses) interfere with WiFi when improperly shielded: they run at approximately 2.4GHz. That’s a part of the band that’s free to use without licensing (ISM band, runs at 900MHz, 2.4GHz, 5Ghz, and so on). That’s because microwave manufacturers don’t want to license spectrum, and it’s the part of the ISM band closest to the ideal absorption frequency of water. The point of microwaves is to push energy into water molecules and make them move around faster, aka heat them. Water molecules do that well at 2.4GHz. This also means that water blocks RF at that frequency very well, because it absorbs it. Trying to shoot 2.4GHz WiFi through trees sucks because it gets blocked by the leaves.
So you want to control drones. You can’t be around 2.4GHz because rain would screw you up. You can’t go above that so you can get enough distance. You can’t go as low as 900MHz or other stuff on the ISM band might interfere with you.
Not that much left, given that 1.7GHz is a popular cell phone frequency, and so on - you can look at publicly available frequency charts to see what’s assigned for what where.
This glosses over a lot and is heavily simplified.
SMAP is in the 1.2 - 1.4 GHz range - so it overlaps with both GLONASS and GPS.
So jamming in that range will affect the nav systems of the drones. This is the reason you see drones tethered with fiber optic cables - control systems might be in the same range. The "why" has more to do that the machines are made to adapt to existing systems, and those systems were designed due to the physical properties they've made to serve / solve.
Both jamming and spoofing is pretty normal when you're close to Russia.
And this is the reason SMAP will pick up all this jamming, because it is sensing on the same band / range.
https://web.archive.org/web/20230517192717/https://aquarius....
for occupying armed forces.
So if you're looking for an intersting target, you could do worse than those lit up areas.
Normally ground transmitters in this band are using just a couple watts or less, so they don’t significantly impact the readings of a satellite looking at a large area on the earth, but a jammer uses a lot more power and can be noticed.
This band is extremely useful if you're stuck on a ship in the middle of a typhoon and need to get some help.
At a very high level handheld satellite communications devices work just like regular cellphones, except they also function in the middle of the ocean.
For instance, the bright spot to the north west of Moscow seems to fall somewhere in or close to Zavidovo National Park. Is there something important there? There's nearby air bases Migalovo and Klin, but both seem too far from the center.
But why? Because they have a bunch of major strategic airfields there.
In (and close) to Ukraine it could be anything. Airfields, base, ammo storage, radio towers, etc.
EDIT: 5 days ago they shot down Ukrainian drones there
https://www.thebarentsobserver.com/security/russian-war-mini...
Block III GPS satellites added a new feature, designed to help the military signals defeat jamming. They added a "spot beam" - a high gain directional antenna capable of covering an area about 200km wide with 20db extra power, to try and burn through jamming. This spot beam is only used for military signals, and it requires extra processing on the receiver to use (since the satellite still has the earth-wide antenna broadcasting the military signals, a military receiver inside the spot-beam area would see two different signals from the same satellite, absent jamming).
During the Biden administration, at least, USAF ISR assets spent a lot of time running race-tracks just at the edge of Ukrainian airspace, monitoring events in the country, and I would expect that would be something that would be a good use case for the spot beams, though I don't know about Ukraine ever getting any of those receivers, and I would not expect coordination with the USSF on pointing the high gain antenna to support UAF operations even under Biden, but all of that is my speculation, I haven't seen anything on where these high gains are pointing.
The amount of locations with GPS jam is impressive (compare march 2022 and may 2025).
Because i agree with you, nobody is jamming on a large/noticeable scale in New Zealand.
Hedge funds is the fun one: detecting economic activity and growth (independent of official government figures).
And there’s some info here: https://smap.jpl.nasa.gov/data/
Very cool stuff!
https://search.asf.alaska.edu/#/?maxResults=250&dataset=SMAP...
This lets you bulk download the .h5 files once you have an Earthdata account (https://urs.earthdata.nasa.gov/home )
or you can use the libraries if you'd like, https://github.com/nsidc/earthaccess or https://github.com/asfadmin/Discovery-asf_search
Sentinel 1, if I recall, is C band. But the technique would work for X-band as well, like TerraSAR-X and other commercial satellites.
The international treaties that say “don’t transmit here”? Those don’t matter much when you’re trying to survive a drone swarm.```
LLM prose, and it's not the only section that stands out. It's an informative article, so I don't mind it as much, but I think it's a shame people don't write things themselves anymore.
But it's more the "It's not x; it's y" and "that thing saying z? doesn't mean much" format.
That said, I just double checked with some of the online LLM checkers and none agreed with me. Maybe I had a false positive.
For example, water management districts can tell if the local soil can accommodate the water from an upcoming storm or if the water will stay on the surface and cause flooding.
giammaiot2 on twitter has a long history of trying to use science sensors to detect intentional RF interference, e.g. this post with a map from the Advanced Microwave Scanning Radiometer (AMSR) looking at 7 GHz: https://x.com/giammaiot2/status/1919493425100988490
Or this thread from 2023 looking at SMAP: https://x.com/giammaiot2/status/1770815247772729539
In the US, 1240 to 1400 MHz is allocated to radar. GNSS downlinks at 1240 to 1300 MHZ are not protected in the US.
o_1•9mo ago