Ham radio encourages experimenting. One of the most challenging tasks is EME (Earth-Moon-Earth), commonly known as moonbounce. This involves bouncing VHF+ signals off the moon, using our cosmic neighbor as an RF reflector, enabling communication on frequencies that the ionosphere would not refract with skywave. This was the subject of Project Diana before hams took up the challenge.

EME is such a challenge because of the *massive* losses involved. Your signal has to exit the atmosphere, travel over 384,000km, with the moon reflecting less than 7% of that, and traveling another 384,000km. Even travelling at the speed of light, it takes our signals over 2.5 seconds to be heard. 

Depending on the frequency, you can expect a round trip path loss of >250dB!!! This means that if putting out 100W, the returning power would be measured in fractions of a nanowatt! With such incredible losses, just a couple dB is the difference between a successful and unsuccessful contact. This means using high-gain yagis, minimizing transmission line loss by using LMR400+ coax, extremely low noise LNAs and power amps, high quality N connectors, etc. Most EME folks also have extremely high power (>300kW ERP) stations producing >1kW PEP RF. 

I lead the CU Amateur Radio Club (W0YQ), and we've been working on using retrofitting our club's SATCOM ground station for a QRP (low power) EME. Instead of using specialized high power amps, we hope to minimize losses and tx signal degradation to make contacts on only 50W. We've made much progress, and hope to have our first QSO soon!