Here's an informal summary:

Flightradar24 is a free online service that allows users to track flight paths in real-time using GPS coordinates sent out by planes via radio signals on frequency 1090 MHz.

To explain how it works, let’s dive deeper into some of the technical aspects. Each plane has an ADS-B (Automatic Dependent Surveillance - Broadcast) transponder onboard which continuously sends various pieces of information such as its type, location, speed and direction to nearby receivers using a radio signal on frequency 1090 MHz.

These signals are then received by ground-based antennas called 'receivers' that can decode the data contained within. These decoded packets of information contain crucial details about every flight in range - including where they've been, where they're headed and even their current altitude!

Here's how it all comes together:

1. A plane takes off with its ADS-B transponder turned on (which is always unless there are specific reasons not to).

2. The transponder continuously sends out radio signals containing flight data every second or so via frequency 1090 MHz.

3. Nearby receivers pick up these signals using special antennas tuned into the correct frequency range and decode them.

Now, here's where things get really interesting - anyone can join in on this fun! All you need is an RTL-SDR (Software Defined Radio) stick which costs around $15 connected to a computer running some free software. Once set up correctly, your rig will be able to receive these same signals too!

But wait... there's more! With enough receivers spread out across different locations worldwide sharing their data with online platforms like Flightrader24 via the internet (which most people already have anyway), it becomes possible for anyone else who wants access to see exactly where every plane currently flying in range is at any given moment - all thanks to open-source software and cheap hardware!

And yes, even you can join this community of flight enthusiasts by simply following these simple steps:

1. Purchase an RTL-SDR stick online (costs around $15).

2. Connect it up with a PC or Mac running Linux/Windows/Mac OS X respectively.

3. Download & install the necessary software from websites like https://github.com/mkowitz/cfclient .

Once you've got everything set up and configured correctly, just sit back relax... because now whenever any plane within range turns its ADS-B transponder on (which they always do unless otherwise specified), your receiver will automatically pick up their signal decode it - giving YOU access to real-time flight tracking data directly from the source!

So there you have it folks! With a bit of technical know-how and some cheap off-the-shelf hardware, anyone can now join this fascinating world of amateur radio monitoring and contribute towards keeping skies safe & secure one plane at time...

Flight radar 24 beta