Radio enthusiasts share QSL cards as a way to confirm their radio communication with other radio operators or stations. A QSL card is a postcard-sized confirmation card that includes details about the contact, such as the date, time, frequency, and mode of the communication. It also typically includes information about the station and its operator, such as their call sign and location. By exchanging QSL cards, radio enthusiasts can confirm that they have made contact with each other and can use these cards to apply for various awards and certificates.

As for why radio enthusiasts use clusterdx, it is a tool that allows them to track and share information about active radio frequencies, modes, and stations in real-time. Clusterdx is essentially a network of amateur radio operators who share information about the current state of the radio bands. By using clusterdx, radio enthusiasts can quickly and easily find active frequencies and stations to communicate with, making it an invaluable tool for ham radio operators who want to make the most out of their radio communications.
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