The sky and space have always been a kind of last frontier for humanity — an obsession carried since the first curious mind wondered whether something might be out there, and whether we could ever communicate with it.

I remember spending hours during my teenage years reading forum posts where amateur radio operators described how they managed to intercept Earth images sent by weather satellites, or how they cloned car key frequencies using RF to unlock vehicles — all by tinkering with technologies that were never meant for the average citizen.

For a sixteen-year-old kid, those «stunts» felt like something straight out of science fiction. Adulthood, however, taught me that curiosity is capable of overcoming any initially unreachable goal. And so, over the years, I found myself pulled into the world of radio frequency (RF) and physical hacking, picking up my first RTL-SDR receiver and a patch antenna recommended by various YouTube and Reddit users.

That was the moment a routine began: researching, watching videos, taking notes, testing things, and reading — especially reading. Among those reads, Practical SDR: Getting Started with Software-Defined Radio by David Clark and Paul Clark was one of the books that helped me ground certain concepts and understand that in this world nothing comes quickly. Pretty much mandatory reading, in my opinion.

«This can’t be that hard… right?»

Getting started is fun, but it puts you in your place fast. Even now, some time later, I’ll admit there are aspects I still don’t fully understand that others probably consider basic — though I suppose that curious willingness to accept we can’t know everything is the spirit that makes us human, and above all, hackers.

Thanks to some knowledge picked up during my first year of telecommunications (yes, I only did one year of the degree, lol), I knew that systems like television, commercial radio, UHF, IoT devices, or even aviation operated within well-defined frequency bands. IoT is messier, but it tends to move in known ranges.

That made me assume that listening to radio, taxi drivers, other amateur operators, or even aviation communications would simply be a matter of scrolling through the spectrum and knowing where to look. I even managed to hear a pilot talking to air traffic control at some point, so my confidence was growing.

The expectation was clear. Reality, not so much.

I had no idea about satellites. Not about the bands and sub-bands they operated in, not about the fact that weather satellites, polar-orbit satellites, those from private companies like the famous Starlink constellation, telecommunications satellites, small university CubeSats — let alone military satellites — share neither objectives, nor transmission power, nor modulation schemes, even if they sometimes operate within similar frequency ranges.

If you have no background, you’re probably asking yourself right now what kind of mess you’re getting into — just like I did at the time.

In my case, the research eventually pulled me in by a guy from Milwaukee with a five-hectare field, an antenna larger than the one on a Boeing E-3 Sentry — note the irony — and a waterfall so clean it looked computer-rendered.

Obviously, this guy owned a pristine spectrum with no interference, no urban noise, and no neighbor’s TV remote sneaking in at four in the morning during a channel-surfing session.

Moving away from flashy cases like that one, I found that more modest operators were using patch antennas or even telescopic antennas — clearly more affordable options. But they all had something I didn’t: space, lots of space. And that was a problem, because a clean, open terrain helps considerably more than YouTube tends to admit.

Still, ignoring my situation, I decided to give it a go from my fantastic six-square-meter rectangular balcony. Because really, what could go wrong? Spoiler: a lot of things. But at least I was about to learn some valuable lessons.

First contact

The first thing that caught my attention when I plugged in the RTL-SDR for the first time — after the software recognized it (SDR++ in my case) — was a perfectly centered white line in the waterfall display, which was also the first thing that made me wonder whether I was doing something wrong.

That’s how I discovered it was being caused by a DC offset and small imbalances between the I (In-Phase) and Q (Quadrature) components of the signal, introduced during the analog-to-digital conversion inside the hardware itself. Nothing particularly serious — in most software it can be removed easily with a filter.

The next thing I had to deal with were strange spikes that appeared and disappeared without me being able to clearly see or hear them. That led me to intuitively poke at filters and settings, making things sometimes appear to improve and other times get worse.

All of that was enough to make me realize that this wasn’t as simple as «plug in and listen.» Instead, it taught me that before I could even hunt for a satellite signal, I needed to learn to interpret what I was seeing — before searching for signals, I had to understand the noise.

Satellites don’t wait

Windows and orbits

In case it isn’t clear yet: satellites are not like an IoT device, a Wi-Fi network, or any other piece of hardware that stays in one place. The satellite is far away, it moves, and you only have certain windows each day to try to receive anything. Outside those windows, communication is impossible. This is a domain ruled by physics and geometry, not software.

Geometry and elevation

On top of that, orbital passes are not all equal. Depending on the elevation angle, where the satellite passes relative to the receiver’s location, the surrounding environment, and your antenna, you might simply receive nothing — because knowing when it passes is not enough.

Even if you spend an hour or two waiting for a window with everything set up, if the geometry and elevation aren’t optimal, the signal will travel through more atmosphere or get attenuated by urban obstacles. In a city environment, this translates to receiving very little or nothing at all.

Power and distance

It can also come down to power and distance: a satellite’s transmission power is limited and the distance is enormous. To counter this, a key component is the LNA — Low Noise Amplifier. Its purpose, briefly explained, is to amplify the weak signal. A good LNA is characterized by adding very little noise of its own during that amplification.

However, it doesn’t work miracles — it amplifies both the desired signal and all the noise and interference already present in your environment.

Bursts and short transmissions

Another key concept is that not all transmissions are continuous. Some satellites send data in short bursts: they transmit for a few seconds — sometimes less — and then go silent. If you’re not watching at exactly that moment, it looks like there’s no signal.

Doppler

Because they move so fast, satellites produce a frequency shift throughout the pass. The signal doesn’t sit still at one point in the spectrum — it drifts gradually. Various applications handle Doppler correction automatically, but it should be clear that this is not a configuration problem: it’s pure physics.

Duty cycle

Another detail to keep in mind is that not all satellites are always «on» (duty cycle). Some weather satellites, like the NOAA series, don’t transmit constantly or randomly.

What they do is transmit only when bathed in sunlight, because their solar panels need to generate enough surplus energy to power their radio transmitter. When they enter Earth’s shadow, the transmitter shuts off to conserve battery.

This means you can have a perfect pass directly overhead, but if the NOAA satellite is crossing Earth’s shadow at that moment, its transmitter will be off and you’ll receive nothing.

That’s where prediction tools become your best ally. A program like Gpredict — free and very popular — not only tells you when and where the satellite will pass, but also calculates whether it will be sunlit or in eclipse during the flyover.

The theory is nice, but where’s the ‘pip’?

By now I imagine you’re expecting a photo of Earth, captured from my balcony and decoded on the computer I’m writing this on. Unfortunately, I have bad news: there is no image.

What I have managed to see — or rather hear — has been things like taxi drivers asking for help finding an address, a pilot apparently talking to control, and devices exchanging data with each other. Basically machines talking to machines: the «urban» world of the radio spectrum.

Simply put, I haven’t managed to intercept a satellite yet. You might think you’ve wasted your time reading all of this — but not entirely. Even without a «PIP,» we’ve understood some very important things to keep in mind for next time. We’ve understood the medium through which these communications travel.

And yes, here’s the promised reward. It’s not mine, but it serves as a reminder of why I started looking at the sky in the first place.

This isn’t a hobby — it’s the prelude

If you’ve read this far, you probably share that itch: the feeling that you’re playing with something bigger than a pastime.

The reality is that «satellite hacking,» as a serious field, is not a future possibility. It’s already here. A 2025 study demonstrated this, where researchers using equipment worth just $800 intercepted calls, SMS messages, and even military communications traveling unencrypted through satellites — all from a rooftop.

In my opinion, over the next five years, all of this RF satellite analysis work — which is already happening within the security research community — will stop being a niche for radio amateurs and hobbyists and become a critical domain of cybersecurity.

Think about it:

Massive constellations like Starlink and Kuiper are deploying a globally accessible network, while university and commercial CubeSats are being launched by the dozen, often with hardware and communications security as an afterthought — in a context where modern warfare already incorporates GPS jamming and targeted attacks against satellites.

Most security planning in these environments relies on security by obscurity. Basically: since they’re up there, most people assume they’re out of reach. The researchers themselves summed it up in the title of their study: «Don’t Look Up» — because the strategy seemed to be hoping nobody would.

The problem isn’t that everything is hackable. It’s that for too long, people counted on nobody looking up.

The step from listening to intercepting, and from intercepting to understanding, is the same step that actors with far worse intentions will eventually take. The space frontier is being digitized, and with it, its vulnerabilities.

My balcony full of cables and my failed passes aren’t just a whim — they’re the first clumsy steps into a field that will soon be fundamental.

We are at the exact moment — and perhaps the last one — when this is still accessible enough to learn out of curiosity, before it becomes a discipline exclusive to nation-states and large corporations.

See you, space cowboy.