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If anyone doesn't understand something, don't guess, just buy a book on it (above), attend a lecture, or better still visit somewhere relevant and ask the people who work in that field. Conspiracy supporters mostly just sit at home on a computer, then guess, assume, imagine, perform no experiments and try to convince you they are right. Which method of research would you take notice of?
Some people may say that the small antennae on the Apollo craft and Lunar Rover are too small and feeble to communicate with Earth. It may make sense at first until you take into account that the largest radio telescopes in the world were used along with the finest radio engineers. The voice transmissions were received by amateur Radio HAMS from the Apollo missions as well as the modern day flights too. But complex coded telemetry required decoding software and more sensitive receivers were required for it.
If you want more detail on how such systems work and how they amplify the signal millions of times, squeeze out background noise etc, just turn up at any of these places, take the free tour and ask them; we have. None of it is a secret.