Your question is kind of like asking "How long is a road and what's the best road to drive on".
Hams, (or amateur radio operators) are people who have obtained a license which allows them to use many frequencies. There are radios designed specifically for those frequencies. They are referred to as ham radios. But, hams can use commercial radios as well.
Some ham radios can decode digital signals, and some can't. -- Some commercial radios that hams use can decode digital signals and some can't.
Also consider that all digital signals aren't all the same. As a quick guess, there have to be at least 100 different modulation schemes in use. Most of them are created using a sound card.
So.. What digital signals do you want to copy and which frequencies do you want to use. (That will narrow things down).