The 21 MHz antenna array of ES5RY in Estonia is reputed to be the largest in the world for that band.
The array is made up of eight 5-element Yagi's for 15m mounted on a 70-metre tower. It has a gain of 16dBd in free space with a beamwidth of less than 30 degrees.
It has a phasing system which allows the selection of five different take-off angles.... 4, 7, 10, 15 and 30 degrees.
Here is a video of ES5RY hearing a signal coming back from the moon on 21 MHz!
This next video shows the construction of the array...