This article is currently an experimental machine translation and may contain errors. If anything is unclear, please refer to the original Chinese version. I am continuously working to improve the translation.
Introduction
My first encounter with Software Defined Radio (SDR) was during a research project on GPS spoofing, where I came across the HackRF One. As the name suggests, SDR allows software to control radio hardware for receiving and transmitting wireless signals across various frequency bands.
It looked super cool, but back then the HackRF was nearly a thousand yuan — way too expensive for me as a high school student. So I shelved the idea.
Much later, I had a sudden idea: what if I could set up a physical network between my two homes, roughly 2–3 km apart, without relying on telecom providers? Since all the power lines in my area are buried underground, pulling fiber myself didn’t seem feasible. That’s when I revisited my interest in SDR.
Hardware
Although the HackRF covers a wide frequency range (1MHz–6GHz), supports half-duplex transmission, and now costs around 500 RMB, I decided to start cheap — with the RTL2832U TV tuner dongle. You can get one on Taobao for under 100 RMB (just search RTL SDR).
(As for choosing SDR hardware, I mostly gathered info from random online sources and hearsay. I’m not really a radio enthusiast and don’t have deep knowledge, so I won’t go into comparisons here.)
This TV dongle was originally designed for receiving TV and FM radio broadcasts. But someone discovered that its RTL2832U chip can actually capture signals from 24MHz to 1700MHz, making it usable as an SDR device.
Original USB receiver + antenna
There’s also a product called “RTL-SDR” — essentially a custom board using the same chip but improved design. It costs around 200 RMB. But by that price point, you’ve got more SDR options, so there’s not much incentive to buy it. (Still, the software and drivers are compatible with the cheap TV dongle, so RTL-SDR guides are perfectly usable.)
Practical Signal Reception
Right away, I hit a snag: although the device theoretically receives everything from 24MHz to 1700MHz — including many decodable signals — many of these signals are extremely weak (like those from satellites) and easily drowned out by background noise. You often need DIY or specialized antennas for different bands, and ideally place them in good locations — like open rooftops. Some signals only appear at specific times and locations, requiring patience (and mobility) to catch.
No wonder amateur radio operators (Hams) who build huge antennas and chase signals have such dedication.
Also, shipping in Nanjing is so slow — life would be easier if I moved to Shenzhen.
Living in a dorm, I can’t set up outdoor antennas or drive around with gear. Plus, Nanjing’s dense high-rises block the view. So my success rate has been pretty low.
FM Radio
This is the classic “Hello World” of SDR. Almost anywhere, you can easily pick up local FM stations using the stock antenna — after all, that’s what it was made for. It’s a great way to verify your setup is working.
First, set up the environment. Once you’ve installed SDR# as described, you can start scanning for signals.
In the FM band (88–108MHz), signals are easy to spot visually — just look for clear peaks. Tune in, and you’ll hear local radio.
FM signals received in Gulou, Nanjing. Each peak is a station — taller peaks mean stronger signals
ATC Band
Right after FM comes the 108–136 MHz aviation band, used for communication between pilots and air traffic control (ATC). You can look up frequencies used by nearby airports and listen in on pilot chatter. (In fact, some enthusiasts even share recordings or live streams.)
Unfortunately, I’m about 40km from Nanjing Lukou Airport, so I can’t pick up anything. If you live near an airport, though, this is definitely worth a try.
ADS-B
Commercial aircraft broadcast their position, altitude, speed, etc. using ADS-B. This data powers flight tracking sites like FlightRadar24. To decode it, you’ll need extra software like dump1090.
Like ATC, this works best near airports with heavy air traffic. Since ADS-B operates at 1090MHz, the stock antenna won’t cut it — you’ll need a dedicated 1090MHz antenna.
433MHz Band
Many consumer devices operate at 433MHz — for example, car key fobs. If you press your key fob near the SDR antenna, you can easily catch its signal around 433MHz, and even record and replay it with other equipment (foreshadowing?). Of course, modern cars are immune to simple replay attacks.
The 433MHz band is surprisingly busy
NOAA Weather Satellites
NOAA operates weather satellites that take images of Earth and beam them back via radio.
Setup guide: https://www.bilibili.com/video/BV1zb4y1X7qT/
I tried tracking a satellite pass over Nanjing, cranked the gain to max, but still couldn’t detect a clear signal. Probably due to a poor antenna and surrounding buildings blocking the view. With a larger antenna and a clear open spot, receiving NOAA signals shouldn’t be too hard.
More Ideas
The RTL-SDR website has tons of articles on receiving and decoding various signals — definitely worth checking out. There are also many online posts (and antenna flexing) sharing detailed walkthroughs and experiences.
Summary
Sorry this blog post might feel a bit shallow — but it’s laying groundwork for future posts.
I bought this RTL TV dongle mainly as a handy tool for capturing and analyzing radio signals across bands. Who knows — it might just come in handy for my mesh networking project, or something else down the road?
This article is licensed under the CC BY-NC-SA 4.0 license.
Author: lyc8503, Article link: https://blog.lyc8503.net/en/post/rtl-sdr-explore/
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