An excellent upload from Chris [PyroElectro.com]! This time he made a very simple and easy to follow circuit of an RF receiver-transmitter pair. The transmitter sends bursts of 27MHz pulses to the antenna, with the help of a crystal oscillator for the 27MHz, and a 555 to control the burst duration and frequency.
Similarly simple is the receiver. The first stage is a regenerative circuit (autodyne) to filter and amplify the transmitted signal with an LC filter tuned at around 27MHz. Two stages of transistor amplifiers further amplify the received signal. A 555 chip connected as a comparator drives the red-green LEDs of the receiver.