[H8crilA]

Basic receive-only SDR is for example the famous RTL-SDR, which you can get for ~$50 with a dipole antenna. It's a USB dongle, and it will get you to surprisingly many interesting places despite the low price tag.

In order to transmit you need some slightly better hardware, such as the HackRF. Replaying a signal with a HackRF is really easy. Note that technically you're not allowed to transmit without a license, whereas reception is generally lawful, with very few exceptions (looking at your legal scar tissue, UK). The author of HackRF published a nice, though not yet completed, tutorial series on YouTube.

There's a lot of activity in the spectrum, if you like to tinker with things then definitely get an SDR, some of the best entertainment value per dollar for a hacker :)